Volume 19,Issue 3,2021 Table of Contents
2021, 19(3):417-426.
Abstract:
The water inflow of Hanjiang River basin (HRB) continues to decline in recent years.The imbalance between supply and demand of water resources becomes more acute.Hence,it is necessary to study the middle and longterm water inflow prediction of HRB.If the annual and monthly runoff of the Danjiangkou reservoir can be predicted accurately,it would may ensure water supply safety of the Middle Route of the South-to-North Water Transfer Project for the northern region.Meanwhile,it can also provide technical support for making an annual water regulation plan of the Middle Route of the South-to-North Water Transfer Project. The basin above the Danjiangkou reservoir was selected as a research object.Water inflow of the Danjiangkou reservoir was predicted from qualitative and quantitative perspectives,respectively.The trend and periodicity characteristics of annual runoff were analyzed based on the monthly runoff data from 1956 to 2016.Characteristics of the annual water inflow were analyzed from qualitative perspectives in the Danjiangkou reservoir.The predictive factors which closely related to the runoff were selected based on hundredterm climate system indices set and sunspot number.The multiple linear regression model and random forest model were constructed for the monthly runoff prediction.The monthly runoff was also predicted from quantitative perspective. The results showed that the annual runoff exhibited a significant decreasing trend,with periodic oscillation characteristics of 6-8 years and 18-21 years.The monthly runoff of 2017 was predicted with a passing rate of 83.3% and 75.0% for the random forest model and multiple linear regression model,respectively.The high prediction accuracies indicated that they can be applied for the monthly runoff prediction in the Danjiangkou reservoir.By contrast,the random forest model was better. Presently,the runoff of the Danjiangkou reservoir is low.It is also predicted that water inflow less than normal runoff is expected in the near future.The multiple linear regression model and random forest model were constructed.Both simulation precisions were good based on calibration and validation results.They can be applied for the runoff prediction of the Danjiangkou reservoir.By contrast,the simulation performance of the random forest model is slightly better.Besides,the prediction precision of runoff in dry seasons is poor.The main reason is that prediction permissible error depends on the variation range of annual runoff.
The water inflow of Hanjiang River basin (HRB) continues to decline in recent years.The imbalance between supply and demand of water resources becomes more acute.Hence,it is necessary to study the middle and longterm water inflow prediction of HRB.If the annual and monthly runoff of the Danjiangkou reservoir can be predicted accurately,it would may ensure water supply safety of the Middle Route of the South-to-North Water Transfer Project for the northern region.Meanwhile,it can also provide technical support for making an annual water regulation plan of the Middle Route of the South-to-North Water Transfer Project. The basin above the Danjiangkou reservoir was selected as a research object.Water inflow of the Danjiangkou reservoir was predicted from qualitative and quantitative perspectives,respectively.The trend and periodicity characteristics of annual runoff were analyzed based on the monthly runoff data from 1956 to 2016.Characteristics of the annual water inflow were analyzed from qualitative perspectives in the Danjiangkou reservoir.The predictive factors which closely related to the runoff were selected based on hundredterm climate system indices set and sunspot number.The multiple linear regression model and random forest model were constructed for the monthly runoff prediction.The monthly runoff was also predicted from quantitative perspective. The results showed that the annual runoff exhibited a significant decreasing trend,with periodic oscillation characteristics of 6-8 years and 18-21 years.The monthly runoff of 2017 was predicted with a passing rate of 83.3% and 75.0% for the random forest model and multiple linear regression model,respectively.The high prediction accuracies indicated that they can be applied for the monthly runoff prediction in the Danjiangkou reservoir.By contrast,the random forest model was better. Presently,the runoff of the Danjiangkou reservoir is low.It is also predicted that water inflow less than normal runoff is expected in the near future.The multiple linear regression model and random forest model were constructed.Both simulation precisions were good based on calibration and validation results.They can be applied for the runoff prediction of the Danjiangkou reservoir.By contrast,the simulation performance of the random forest model is slightly better.Besides,the prediction precision of runoff in dry seasons is poor.The main reason is that prediction permissible error depends on the variation range of annual runoff.
2021, 19(3):427-436,445.
Abstract:
Accurate understanding of groundwater balance in karst area can provide technical guarantee for scientific evaluation of groundwater resources.To study the water balance in karst area,it is necessary to clarify the boundary conditions and hydrogeological properties of karst water system.However,due to the high complexity of geological structures and karstic development in the karstic area,it has become one of the difficult problems in current research.The Baotu Spring basin is a typical karst basin in northern China.At present,there are two different views on the east and west boundaries of the Baotu Spring basin.If the boundary of the Baotu Spring basin is unclear and its hydrogeological property is unknown,the calculation of water balance in the Baotu Spring basin can not be correctly carried out.The research on the boundary conditions and the water balance of Baotu Spring basin under two kinds of boundary conditions were carried out. The main difference between the east and west boundaries is the area surrounded by the fault and the watershed,and the main recharge is the infiltration from precipitation.According to the actual hydrogeological conditions in the study area,a numerical model is established to simulate the conversion from precipitation to different types of runoff in the faultwatershed area to obtain its water exchange law.According to the obtained conversion law,the water balance method is used to calculate the replenishment and discharge in the study basin,and the water balance results of the two boundary conditions are obtained.On the other hand,based on the same law of water exchange,combining with the exploration data and drilling data of the Baotu Spring basin,the numerical simulation models of faultboundary spring basin and faultwatershed boundary spring basin are established by the FEFLOW software,and the water balance of the two kinds of boundary conditions is calculated.The calculation results provided by the waterbalance method and numerical simulation model are compared and analyzed. Based on the numerical model of the fault-watershed area,the relationship between the precipitation and the proportion of surface runoff (SR/P),the proportion of porous subsurface runoff (PSSR/P),the proportion of karstic subsurface runoff(KSSR/P) can be established.The results provided by the numerical simulation model show that the relation between the proportion of surface runoff and precipitation is RSR=33.967lnP-14.728,the relation between the proportion of karstic subsurface runoff and precipitation is RKSSR=-30.52lnP+59.941,and the proportion of porous subsurface runoff is about 0.50.Applying this law to the waterbalance method,it is found that the replenishment,discharge and balance difference of the faultboundary spring basin are respectively 9.022 million m3/a,3.376 million m3/a and 5.646 million m3/a larger than that of the fault-watershed boundary spring basin.Applying this law to the numerical simulation method,it is found that the replenishment,discharge and balance difference of the fault-boundary spring basin are all greater than that of the fault-watershed spring basin,and the difference values are 12.108 million m3/a,4.433 million m3/a and 7.675 million m3/a,respectively.The precipitation in the fault-watershed region is converted into surface runoff(SR),porous subsurface runoff(PSSR) and karstic subsurface runoff (KSSR) runoff in a certain proportion.Therefore,when the fault-watershed is used as the boundary of the Baotu Spring basin,it is necessary to consider the close hydraulic relationship between surface water and groundwater as well as the transformation relationship between them.Reasonable conversion of the water volume of each part can improve the accuracy of water balance calculation results.Combining with the law of water exchange in the fault-watershed region,the water balance in the spring basin is calculated by the traditional water balance method and the numerical simulation method.The calculation results of the two methods show that the replenishment,discharge and balance difference of the fault boundary spring basin are greater than that of the fault-watershed boundary spring basin.There are some differences in spring water balance under different boundary conditions,but the difference is small.
Accurate understanding of groundwater balance in karst area can provide technical guarantee for scientific evaluation of groundwater resources.To study the water balance in karst area,it is necessary to clarify the boundary conditions and hydrogeological properties of karst water system.However,due to the high complexity of geological structures and karstic development in the karstic area,it has become one of the difficult problems in current research.The Baotu Spring basin is a typical karst basin in northern China.At present,there are two different views on the east and west boundaries of the Baotu Spring basin.If the boundary of the Baotu Spring basin is unclear and its hydrogeological property is unknown,the calculation of water balance in the Baotu Spring basin can not be correctly carried out.The research on the boundary conditions and the water balance of Baotu Spring basin under two kinds of boundary conditions were carried out. The main difference between the east and west boundaries is the area surrounded by the fault and the watershed,and the main recharge is the infiltration from precipitation.According to the actual hydrogeological conditions in the study area,a numerical model is established to simulate the conversion from precipitation to different types of runoff in the faultwatershed area to obtain its water exchange law.According to the obtained conversion law,the water balance method is used to calculate the replenishment and discharge in the study basin,and the water balance results of the two boundary conditions are obtained.On the other hand,based on the same law of water exchange,combining with the exploration data and drilling data of the Baotu Spring basin,the numerical simulation models of faultboundary spring basin and faultwatershed boundary spring basin are established by the FEFLOW software,and the water balance of the two kinds of boundary conditions is calculated.The calculation results provided by the waterbalance method and numerical simulation model are compared and analyzed. Based on the numerical model of the fault-watershed area,the relationship between the precipitation and the proportion of surface runoff (SR/P),the proportion of porous subsurface runoff (PSSR/P),the proportion of karstic subsurface runoff(KSSR/P) can be established.The results provided by the numerical simulation model show that the relation between the proportion of surface runoff and precipitation is RSR=33.967lnP-14.728,the relation between the proportion of karstic subsurface runoff and precipitation is RKSSR=-30.52lnP+59.941,and the proportion of porous subsurface runoff is about 0.50.Applying this law to the waterbalance method,it is found that the replenishment,discharge and balance difference of the faultboundary spring basin are respectively 9.022 million m3/a,3.376 million m3/a and 5.646 million m3/a larger than that of the fault-watershed boundary spring basin.Applying this law to the numerical simulation method,it is found that the replenishment,discharge and balance difference of the fault-boundary spring basin are all greater than that of the fault-watershed spring basin,and the difference values are 12.108 million m3/a,4.433 million m3/a and 7.675 million m3/a,respectively.The precipitation in the fault-watershed region is converted into surface runoff(SR),porous subsurface runoff(PSSR) and karstic subsurface runoff (KSSR) runoff in a certain proportion.Therefore,when the fault-watershed is used as the boundary of the Baotu Spring basin,it is necessary to consider the close hydraulic relationship between surface water and groundwater as well as the transformation relationship between them.Reasonable conversion of the water volume of each part can improve the accuracy of water balance calculation results.Combining with the law of water exchange in the fault-watershed region,the water balance in the spring basin is calculated by the traditional water balance method and the numerical simulation method.The calculation results of the two methods show that the replenishment,discharge and balance difference of the fault boundary spring basin are greater than that of the fault-watershed boundary spring basin.There are some differences in spring water balance under different boundary conditions,but the difference is small.
2021, 19(3):437-445.
Abstract:
The rapid development of regional economy has brought great pressure on water resource,energy,and food system.Evaluation of water resource,energy,and food is the key to promoting harmonious and sustainable development among the three systems.Chinese consumption of water resource,energy,and food ranks among the top in the world.Still,there are some problems,such as small per capita water resource and large water consumption in food production and energy exploitation.However,the issue of water resource shortage is becoming more and more serious.To promote the sustainable development of resource,it is of practical significance to carry out the harmonious evaluation of water-energy-food coupling system and to study its changing relationship. To evaluate the multidimensional coupling system harmoniously,and to reduce the uncertainty of each index from the incomplete data and the subjectivity of evaluation index selection,a comprehensive evaluation index system of water resource,energy,and food based on the harmonious quantification model is proposed.It couples the fuzzy multi-attribute decisionmaking method with the harmonious quantization method,and the harmonious degree of the waterenergyfood coupling system is determined according to the weight of fuzzy language and the harmonious quantification.In addition,the data of Henan Province from 2011 to 2018 are selected to analyze the development level and harmony degree of water-energy-food coupling system,and explore the spatio-temporal variation characteristics of each subsystem and the coupling system. During the study years,the harmony degree of water-energy-food coupling system in the whole province increases annually.In the study years,the improvement of harmony degree in the early stage is mainly affected by the energy system,while the later stage is related to the food system and water resource system.The development characteristics of each subsystem are different,but the whole system presents an upward trend.Due to the improvement of water use efficiency,and the remarkable effect of pollution control,the harmony degree of water resource system fluctuates,which indicates that the state of water resource in Henan Province continues to improve.The harmony degree of the energy system reached the maximum in 2015,and the harmony degree is the best.However,with the change of industrial structure,the total power of rural machinery decreased,and with the increase of urban electricity consumption,the harmony degree of the system become worse,and the overall trend of change is upward,fluctuating,and downward.Because of the upgrading of agricultural technology,the increase of effective irrigation area and other factors,the harmony degree of food system shows a gradual upward trend,and reach the maximum value in 2018. In general,the harmony degree of water resource system in Henan Province is the highest,followed by the food system and the energy system.The food subsystem has a relatively high development level and stable performance,while the energy subsystem has a fluctuating development and poor stability.The harmonious quantization method based on fuzzy multiattribute decisionmaking can solve the uncertainty problem in index quantization.Meanwhile,the results can account for complex information and recognize the subtle differences between the indicators,making it easier for decision makers to identify the adverse development factors.The harmonious evaluation of the comprehensive system can support the management of water resource,energy and food system.
The rapid development of regional economy has brought great pressure on water resource,energy,and food system.Evaluation of water resource,energy,and food is the key to promoting harmonious and sustainable development among the three systems.Chinese consumption of water resource,energy,and food ranks among the top in the world.Still,there are some problems,such as small per capita water resource and large water consumption in food production and energy exploitation.However,the issue of water resource shortage is becoming more and more serious.To promote the sustainable development of resource,it is of practical significance to carry out the harmonious evaluation of water-energy-food coupling system and to study its changing relationship. To evaluate the multidimensional coupling system harmoniously,and to reduce the uncertainty of each index from the incomplete data and the subjectivity of evaluation index selection,a comprehensive evaluation index system of water resource,energy,and food based on the harmonious quantification model is proposed.It couples the fuzzy multi-attribute decisionmaking method with the harmonious quantization method,and the harmonious degree of the waterenergyfood coupling system is determined according to the weight of fuzzy language and the harmonious quantification.In addition,the data of Henan Province from 2011 to 2018 are selected to analyze the development level and harmony degree of water-energy-food coupling system,and explore the spatio-temporal variation characteristics of each subsystem and the coupling system. During the study years,the harmony degree of water-energy-food coupling system in the whole province increases annually.In the study years,the improvement of harmony degree in the early stage is mainly affected by the energy system,while the later stage is related to the food system and water resource system.The development characteristics of each subsystem are different,but the whole system presents an upward trend.Due to the improvement of water use efficiency,and the remarkable effect of pollution control,the harmony degree of water resource system fluctuates,which indicates that the state of water resource in Henan Province continues to improve.The harmony degree of the energy system reached the maximum in 2015,and the harmony degree is the best.However,with the change of industrial structure,the total power of rural machinery decreased,and with the increase of urban electricity consumption,the harmony degree of the system become worse,and the overall trend of change is upward,fluctuating,and downward.Because of the upgrading of agricultural technology,the increase of effective irrigation area and other factors,the harmony degree of food system shows a gradual upward trend,and reach the maximum value in 2018. In general,the harmony degree of water resource system in Henan Province is the highest,followed by the food system and the energy system.The food subsystem has a relatively high development level and stable performance,while the energy subsystem has a fluctuating development and poor stability.The harmonious quantization method based on fuzzy multiattribute decisionmaking can solve the uncertainty problem in index quantization.Meanwhile,the results can account for complex information and recognize the subtle differences between the indicators,making it easier for decision makers to identify the adverse development factors.The harmonious evaluation of the comprehensive system can support the management of water resource,energy and food system.
2021, 19(3):446-458.
Abstract:
Global warming has a profound impact on the hydrological process,which leads to serious problems of regional water shortage.In order to increase the efficient use of available water，it is necessary to predict the impacts of climate change on water resources.Analyzing the spatial and temporal variations of BLUE and GREEN water resources can provide a more reliable basis for regional water resources management and protection. Daily precipitation and temperature data of Shanmei reservoir watershed from two CMIP5 models（HadGEM2-ES and NoerESM1-M）and two representative concentration pathways（RCP4.5 and RCP8.5）for the periods of 2031-2050,2051-2070 and 2071-2090 were statistically downscaling by quantile mapping method based on the measured climate data from 1991 to 2010.Then,to assess the impact of climate change on BLUE and GREEN water resources for the next 60 years,SWAT model was applied to simulate the spatial and temporal distribution of BLUE water and GREEN water during the baseline period (1991-2010) and three future periods. (1)Under the scene of RCP45,the annual average precipitation in the future will change by -0.43% to 1.93% compared to the baseline period,and the average temperature will increase by 1.72 ℃ to 3.90 ℃.Under the scene of RCP8.5,the estimated annual average precipitation will vary by -0.43% to 1.93%,and the average temperature will increase by 1.72℃ to 3.90℃.With the increasing of RCP concentration path,the magnitude of change in temperature and precipitation become lager as well.(2)The annual average BLUE and GREEN water resource were 1 334.90 mm and 717.18 mm,respectively,in Shanmei reservoir watershed from 1991 to 2010.Compared with the baseline period,the amount of BLUE water resources in the RCP45 scenario will decrease by 1281% to 3341%,and the amount of GREEN water resources will increase by 28.45% to [JP2]33.33% from 2031 to 2090.While the amount of BLUE water resources will decrease by 14.17% to 35.28%,the amount of GREEN water resources will increase by 32.21% to 36.12% under the RCP8.5 scenario.(3)The distribution of BLUE and GREEN water resources in Shanmei reservoir watershed were similar to some degree,with the water resources quantities in upstream subbasins larger than that in downstream subbasins.In different climate scenarios,compared with the baseline period,the BLUE water resources in 38 subbasins decreased by 7% to 43% and the GREEN water resources increased by 15% to 49%. From the perspective of time,the future climate change has a significant impact on BLUE and GREEN water resources in Shanmei reservoir watershed and the precipitation BLUE water resources,while GREEN water resources are directly related to temperature.In the next 60 years,the daily minimum temperature in the basin of Shanmei reservoir watershed will increase between 10.19% and 31.94%,and the precipitation will increase in the range of -4.56% to 9.48% which will lead to a significant decrease in BLUE water resources and a significant increase in GREEN water resources.From a spatial perspective,precipitation was the main factor to influence the distribution of BLUE water resources,while the proportion of agricultural land use in subbasins had a significant effect on the distribution of GREEN water resources.The spatial variation of BLUE water quantity is related to the climatic characteristics,and the difference of land use types leads to the spatial differentiation of GREEN water resources.
Global warming has a profound impact on the hydrological process,which leads to serious problems of regional water shortage.In order to increase the efficient use of available water，it is necessary to predict the impacts of climate change on water resources.Analyzing the spatial and temporal variations of BLUE and GREEN water resources can provide a more reliable basis for regional water resources management and protection. Daily precipitation and temperature data of Shanmei reservoir watershed from two CMIP5 models（HadGEM2-ES and NoerESM1-M）and two representative concentration pathways（RCP4.5 and RCP8.5）for the periods of 2031-2050,2051-2070 and 2071-2090 were statistically downscaling by quantile mapping method based on the measured climate data from 1991 to 2010.Then,to assess the impact of climate change on BLUE and GREEN water resources for the next 60 years,SWAT model was applied to simulate the spatial and temporal distribution of BLUE water and GREEN water during the baseline period (1991-2010) and three future periods. (1)Under the scene of RCP45,the annual average precipitation in the future will change by -0.43% to 1.93% compared to the baseline period,and the average temperature will increase by 1.72 ℃ to 3.90 ℃.Under the scene of RCP8.5,the estimated annual average precipitation will vary by -0.43% to 1.93%,and the average temperature will increase by 1.72℃ to 3.90℃.With the increasing of RCP concentration path,the magnitude of change in temperature and precipitation become lager as well.(2)The annual average BLUE and GREEN water resource were 1 334.90 mm and 717.18 mm,respectively,in Shanmei reservoir watershed from 1991 to 2010.Compared with the baseline period,the amount of BLUE water resources in the RCP45 scenario will decrease by 1281% to 3341%,and the amount of GREEN water resources will increase by 28.45% to [JP2]33.33% from 2031 to 2090.While the amount of BLUE water resources will decrease by 14.17% to 35.28%,the amount of GREEN water resources will increase by 32.21% to 36.12% under the RCP8.5 scenario.(3)The distribution of BLUE and GREEN water resources in Shanmei reservoir watershed were similar to some degree,with the water resources quantities in upstream subbasins larger than that in downstream subbasins.In different climate scenarios,compared with the baseline period,the BLUE water resources in 38 subbasins decreased by 7% to 43% and the GREEN water resources increased by 15% to 49%. From the perspective of time,the future climate change has a significant impact on BLUE and GREEN water resources in Shanmei reservoir watershed and the precipitation BLUE water resources,while GREEN water resources are directly related to temperature.In the next 60 years,the daily minimum temperature in the basin of Shanmei reservoir watershed will increase between 10.19% and 31.94%,and the precipitation will increase in the range of -4.56% to 9.48% which will lead to a significant decrease in BLUE water resources and a significant increase in GREEN water resources.From a spatial perspective,precipitation was the main factor to influence the distribution of BLUE water resources,while the proportion of agricultural land use in subbasins had a significant effect on the distribution of GREEN water resources.The spatial variation of BLUE water quantity is related to the climatic characteristics,and the difference of land use types leads to the spatial differentiation of GREEN water resources.
2021, 19(3):459-468.
Abstract:
Soil moisture (SM) is significant in hydrological cycle with its frequent interaction between surface water and groundwater.Recently,there are two major methods of field measurement and remote sensingbased retrieval for monitoring SM.Although field SM measurement is widely used in practical applications,it fails to work in large scale areas with complex terrain for its inability to reflect spatial heterogeneity of SM.Moreover,the soil structure would be destructed due to its soil desiccation process.Remote sensingbased retrieval from optical or radar imagery is another major way to acquire SM at a large scale in space.The obstacle to the development and application of this technology is its limited maximum detection depth of 1-5 cm.SM levels affect a range of soil and plant dynamics.Surface SM is the water that is in the upper 10 cm of soil,whereas root zone SM is the water that is available to plantsgenerally considered to be in the upper 200 cm of soil.Consequently,one new method to obtain SM should be developed to overcome the problems above. Based on the principle of water balance,changes in terrestrial water storage (TWS) include three main parts:changes in surface water storage,SM,and groundwater storage.Detailly,changes in surface water storage are dominated by changes in snow depth and surface runoff.Changes in TWS were obtained from downscaled GRACE data,and changes in surface runoff and snow depth were from GLDAS NOAH data.Changes in groundwater from measured groundwater level were used to construct the water balance equation to calculate changes in SM.Then the SM change product was compared with other seven SM products of AMSR-E,ASCAT,ERA-Interim,MERRA2,GLDAS NOAH,GLDAS Mosaic,and GLDAS Catchment.All SM products were resampled to the same spatial resolution of 0.25°×0.25° for comparative analysis.Due to the inconsistent units of the various SM products,all data were normalized to the same range between 0 and 1.Furthermore,five statistical indicators were applied to validate the SM change product proposed.(1) Pearson correlation coefficient was used to verify the correlation of estimated SM change with other SM products in a time series.(2) Spatial auto-correlation coefficients (univariate Moran′s I) was used to verify how well the estimated SM change variability matches the spatial distribution of other SM change products.(3) The bivariate Moran′s I was used to reflect the correlation between the changes of estimated SM and other SM products in each grid point.(4) The root mean square error (RMSE) of the estimated SM change was compared to that of other SM products to assess the dispersion degree of all products.(5) The Mann-Kendall trend test was used to assess the trend of the time series of various SM change products and to verify the consistency of the trends for the estimated SM change with that of other products. Through the research,the following findings were made.Generally,the estimated SM changes showed a good temporal agreementwith each SM product in research area except the Yellow River basin and the Haihe River basin.This may be caused by the significant difference in the soil discrepancy characters during the permafrost and nonpermafrost periods in these basins,which affected the SM changes detected using microwaves such as AMSR-E and ASCAT.This discrepancy may amplified to some extent by the different methods of the discrepancy correction in different SM products.In terms of spatial distribution,a drying process was showed from the upper and middle reaches of the Yangtze River basin to the Huaihe River basin in spring;in summer,SM showed a south-wet,north-dry state;in autumn,the extent area of SM reduction gradually expanded southwards to the Pearl River basin;in winter,SM increased significantly in the upper reaches of the Yangtze River basin,and showed a slight increase in the lower reaches of the Yellow River basin and the Haihe River basin,while the rest of the research area were in the process of drying out.By analyzing the validation indicators,it is found that the estimated SM variation performed best agreementwith other products in the Pearl River basin,witch Pearson correlation coefficients are 0.70,0.79,0.86,0.85,0.81,0.50,and 0.51 with AMSR-E,ASCAT,ERA-Interim,MERRA2,GLDAS NOAH,GLDAS Mosaic,and GLDAS Catchment.The RMSE with other products is low,mostly controlled between 0.25 and 0.30.And the univariate Moran′s I was similar with [JP2]MERRA2,ASCAT,and GLDASCatchment (0.67,0.80,and 0.74),the bivariate Moran′s I was also[JP] similar with ERA-Interim,MERRA2,and ASCAT (0.70,0.70,and 0.77).The estimated SM changes showed poor consistency in the Yellow River basin,with Pearson correlation coefficients are all below 0.41,and the MK tests all show a near opposite trend to the other products,whitch may be the combined effect of retrieval errors in GRACE data due to the mountainous terrain in the western part of the Yellow River basin,the difficulty of land surface model data to accurately describe SM transport in loess soils,and the underrepresentation of measured groundwater data. The following main conclusions are made:(1) One method for estimating SM based on GRACE TWS was proposed.The SM obtained could keep more agreement with the connotation of SM in hydrology.It can overcome the limitations of field observations due to topography and number of stations,which may reflect spatial heterogeneity of SM of the whole study area.In addition,traditional remote sensing observation techniques can only detect the surface SM changes,while the proposed method can estimate SM of all soil layers above groundwater level.However,the estimation method does not consider the changes of biological water and the influence of human activities,which may introduce some uncertainty.(2) The estimated SM changes showed high spatial and temporal correlation with all other products in the Pearl River basin,which indicated that the estimation method is highly applicable in this basin.But in the Yellow River basin,the consistency of SM variation between the estimated SM changes and that of others products are not so good,which indicates that there are many other factors influencing SM variation in this basin and the uncertainty is high.Herewith,the research on SM estimation in the Yellow River basin needs to be strengthened in the future.
Soil moisture (SM) is significant in hydrological cycle with its frequent interaction between surface water and groundwater.Recently,there are two major methods of field measurement and remote sensingbased retrieval for monitoring SM.Although field SM measurement is widely used in practical applications,it fails to work in large scale areas with complex terrain for its inability to reflect spatial heterogeneity of SM.Moreover,the soil structure would be destructed due to its soil desiccation process.Remote sensingbased retrieval from optical or radar imagery is another major way to acquire SM at a large scale in space.The obstacle to the development and application of this technology is its limited maximum detection depth of 1-5 cm.SM levels affect a range of soil and plant dynamics.Surface SM is the water that is in the upper 10 cm of soil,whereas root zone SM is the water that is available to plantsgenerally considered to be in the upper 200 cm of soil.Consequently,one new method to obtain SM should be developed to overcome the problems above. Based on the principle of water balance,changes in terrestrial water storage (TWS) include three main parts:changes in surface water storage,SM,and groundwater storage.Detailly,changes in surface water storage are dominated by changes in snow depth and surface runoff.Changes in TWS were obtained from downscaled GRACE data,and changes in surface runoff and snow depth were from GLDAS NOAH data.Changes in groundwater from measured groundwater level were used to construct the water balance equation to calculate changes in SM.Then the SM change product was compared with other seven SM products of AMSR-E,ASCAT,ERA-Interim,MERRA2,GLDAS NOAH,GLDAS Mosaic,and GLDAS Catchment.All SM products were resampled to the same spatial resolution of 0.25°×0.25° for comparative analysis.Due to the inconsistent units of the various SM products,all data were normalized to the same range between 0 and 1.Furthermore,five statistical indicators were applied to validate the SM change product proposed.(1) Pearson correlation coefficient was used to verify the correlation of estimated SM change with other SM products in a time series.(2) Spatial auto-correlation coefficients (univariate Moran′s I) was used to verify how well the estimated SM change variability matches the spatial distribution of other SM change products.(3) The bivariate Moran′s I was used to reflect the correlation between the changes of estimated SM and other SM products in each grid point.(4) The root mean square error (RMSE) of the estimated SM change was compared to that of other SM products to assess the dispersion degree of all products.(5) The Mann-Kendall trend test was used to assess the trend of the time series of various SM change products and to verify the consistency of the trends for the estimated SM change with that of other products. Through the research,the following findings were made.Generally,the estimated SM changes showed a good temporal agreementwith each SM product in research area except the Yellow River basin and the Haihe River basin.This may be caused by the significant difference in the soil discrepancy characters during the permafrost and nonpermafrost periods in these basins,which affected the SM changes detected using microwaves such as AMSR-E and ASCAT.This discrepancy may amplified to some extent by the different methods of the discrepancy correction in different SM products.In terms of spatial distribution,a drying process was showed from the upper and middle reaches of the Yangtze River basin to the Huaihe River basin in spring;in summer,SM showed a south-wet,north-dry state;in autumn,the extent area of SM reduction gradually expanded southwards to the Pearl River basin;in winter,SM increased significantly in the upper reaches of the Yangtze River basin,and showed a slight increase in the lower reaches of the Yellow River basin and the Haihe River basin,while the rest of the research area were in the process of drying out.By analyzing the validation indicators,it is found that the estimated SM variation performed best agreementwith other products in the Pearl River basin,witch Pearson correlation coefficients are 0.70,0.79,0.86,0.85,0.81,0.50,and 0.51 with AMSR-E,ASCAT,ERA-Interim,MERRA2,GLDAS NOAH,GLDAS Mosaic,and GLDAS Catchment.The RMSE with other products is low,mostly controlled between 0.25 and 0.30.And the univariate Moran′s I was similar with [JP2]MERRA2,ASCAT,and GLDASCatchment (0.67,0.80,and 0.74),the bivariate Moran′s I was also[JP] similar with ERA-Interim,MERRA2,and ASCAT (0.70,0.70,and 0.77).The estimated SM changes showed poor consistency in the Yellow River basin,with Pearson correlation coefficients are all below 0.41,and the MK tests all show a near opposite trend to the other products,whitch may be the combined effect of retrieval errors in GRACE data due to the mountainous terrain in the western part of the Yellow River basin,the difficulty of land surface model data to accurately describe SM transport in loess soils,and the underrepresentation of measured groundwater data. The following main conclusions are made:(1) One method for estimating SM based on GRACE TWS was proposed.The SM obtained could keep more agreement with the connotation of SM in hydrology.It can overcome the limitations of field observations due to topography and number of stations,which may reflect spatial heterogeneity of SM of the whole study area.In addition,traditional remote sensing observation techniques can only detect the surface SM changes,while the proposed method can estimate SM of all soil layers above groundwater level.However,the estimation method does not consider the changes of biological water and the influence of human activities,which may introduce some uncertainty.(2) The estimated SM changes showed high spatial and temporal correlation with all other products in the Pearl River basin,which indicated that the estimation method is highly applicable in this basin.But in the Yellow River basin,the consistency of SM variation between the estimated SM changes and that of others products are not so good,which indicates that there are many other factors influencing SM variation in this basin and the uncertainty is high.Herewith,the research on SM estimation in the Yellow River basin needs to be strengthened in the future.
2021, 19(3):469-476.
Abstract:
Hydrometeorological forecasting is a major measure to improve the accuracy and extend the lead time of runoff prediction for a large watershed,and remains a challenge to hydrosciences.Although much progress has been made in the research of hydrological forecasting based on the combination of meteorology and hydrology in China,the results are mainly focused on theoretical methods,and there are relatively few highlights on the application level,especially for operational forecasts.Dadu River basin has the characteristics of complex topography,great height change and vertical climate variations,which brings extra difficulties for the hydrometeorological forecasting.Therefore,the Dadu River basin is taken as the research object,aiming to serve the scientific decision-making of flood control and power generation for the basin through scale conversion and the connection of meteorological and hydrological elements,and establishes a runoff forecast model for operational purpose based on the meteorologichydrologic coupling. A four-layer nested grid WRF model was used to solve the difficulties of microclimate simulation caused by the large changes in topography and severe vertical variability of the Dadu River basin.Assimilation technologies including four-dimensional variational (4DVAR) and Ensemble Kalman filter (EnKF) hybrid were used to reduce the initial meteorological field error.The statistical optimal combination was employed to determine the model parameters of WRF in different periods of the year.The Xin′anjiang model was employed as the catchment-scale hydrological model since the Dadu River basin is a wet region (although there is a small part of the semihumid area in the upper reaches).The outputs of future rainfall from WRF were used as the inputs of the Xin′anjiang model.Therefore,a WRF-Xin′anjiang model was established for runoff prediction for the Dadu River basin. The constructed WRF model based on the four-layer nested grid for Dadu River basin can forecast rainfall in the next 7 days,and the overall forecast accuracy (qualification rate) reached over 80%.For the Xin′anjiang model,the qualified rates in flood season and non-flood season were 100% and 86%,respectively,and the average determination coefficients were 090 and 086,respectively.In the verification period,the qualified rates in flood season and nonflood season were both 100%,and the average determination coefficients were 089 and 086,respectively.For the WRF-Xin′anjiang model,20 flood events were chosen in flood season and 10 flood events in nonflood season from 2010 to 2017 to verify the model.Results showed that the qualified rates of flood peak and flood volume in flood season both reached 100%,and the qualified rates of flood peak and flood volume in nonflood season reached 100% and 90%,respectively.It is indicated that with an extension of the lead time to extra 7 days,the WRFXin′anjiang model established could still guarantee a higher forecast accuracy. The WRF-Xin′anjiang model established can provide a reference for hydrological forecasting of the basin with complex terrain,wide height difference and significant vertical climate change,and provide technical support for hydropower generation and flood control decisionmaking of Dadu River basin.At the same time,with the accumulation of hydrometeorological data in the future,it is necessary to do indepth research on more refined WRF and hydrological model for the basin.
Hydrometeorological forecasting is a major measure to improve the accuracy and extend the lead time of runoff prediction for a large watershed,and remains a challenge to hydrosciences.Although much progress has been made in the research of hydrological forecasting based on the combination of meteorology and hydrology in China,the results are mainly focused on theoretical methods,and there are relatively few highlights on the application level,especially for operational forecasts.Dadu River basin has the characteristics of complex topography,great height change and vertical climate variations,which brings extra difficulties for the hydrometeorological forecasting.Therefore,the Dadu River basin is taken as the research object,aiming to serve the scientific decision-making of flood control and power generation for the basin through scale conversion and the connection of meteorological and hydrological elements,and establishes a runoff forecast model for operational purpose based on the meteorologichydrologic coupling. A four-layer nested grid WRF model was used to solve the difficulties of microclimate simulation caused by the large changes in topography and severe vertical variability of the Dadu River basin.Assimilation technologies including four-dimensional variational (4DVAR) and Ensemble Kalman filter (EnKF) hybrid were used to reduce the initial meteorological field error.The statistical optimal combination was employed to determine the model parameters of WRF in different periods of the year.The Xin′anjiang model was employed as the catchment-scale hydrological model since the Dadu River basin is a wet region (although there is a small part of the semihumid area in the upper reaches).The outputs of future rainfall from WRF were used as the inputs of the Xin′anjiang model.Therefore,a WRF-Xin′anjiang model was established for runoff prediction for the Dadu River basin. The constructed WRF model based on the four-layer nested grid for Dadu River basin can forecast rainfall in the next 7 days,and the overall forecast accuracy (qualification rate) reached over 80%.For the Xin′anjiang model,the qualified rates in flood season and non-flood season were 100% and 86%,respectively,and the average determination coefficients were 090 and 086,respectively.In the verification period,the qualified rates in flood season and nonflood season were both 100%,and the average determination coefficients were 089 and 086,respectively.For the WRF-Xin′anjiang model,20 flood events were chosen in flood season and 10 flood events in nonflood season from 2010 to 2017 to verify the model.Results showed that the qualified rates of flood peak and flood volume in flood season both reached 100%,and the qualified rates of flood peak and flood volume in nonflood season reached 100% and 90%,respectively.It is indicated that with an extension of the lead time to extra 7 days,the WRFXin′anjiang model established could still guarantee a higher forecast accuracy. The WRF-Xin′anjiang model established can provide a reference for hydrological forecasting of the basin with complex terrain,wide height difference and significant vertical climate change,and provide technical support for hydropower generation and flood control decisionmaking of Dadu River basin.At the same time,with the accumulation of hydrometeorological data in the future,it is necessary to do indepth research on more refined WRF and hydrological model for the basin.
2021, 19(3):477-486,495.
Abstract:
With only 7% of the global water resources available to feed 22% of the world′s population,China is facing significant challenges from water scarcity.Since 2000,China has entered a stage of rapid development,however,the extensive utilization of water resources has led to low water use efficiency (WUE) which seriously hinders the sustainable development of economy,society and ecological environment.Guangdong,as a developed province in China,has ranked the first in economic aggregate for the last twentyeight years.However,the regional inequality development is still prominent,among which the uneven of water resources exploitation and utilization can not be ignored.Thus,the improvement of spatial equilibrium in WUE is highly needed for solving the problem of uneven spatial distribution of water resources. Time series of panel data were obtained from Guangdong Province from 2004 to 2018,and this dataset is comprised of 21 prefecturelevel cities.The spatiotemporal characteristic of the regional WUE and its spatial correlation degree were explored using constructing gravity model and spatial analysis technique.The multiple regression models were further used to identify the main influencing factors. The water consumption per tenthousandyuan of Gross Domestic Product (GDP) and the average water consumption per mu for farmland irrigation had relatively strong spatial correlations in Guangdong Province in terms of WUE.The area of high WUE (cold spot) was located in the Pearl River Delta (PRD) while the area of low WUE (hot spot) was located in the north,east and west of Guangdong.Meanwhile,an increasing trend was observed in correlation degree of WUE,among which the highest correlation degree was found in the PRD(with Shenzhen and Dongguan as the core),followed by the east of the province (with Shantou as the core) and the north and west of the province.For the driving factors,it is found that the research and experimental development funds(R&D),urbanization rate,the proportion of secondary and tertiary industry have positive effect on the potential correlation degree of WUE.Furthermore,R&D was found the major driving factor for the increase of the potential correlation degree of WUE over time,while per capita water resources,per capita GDP and the proportion of primary industry performed negative effect on the potential correlation degree of WUE. The spatiotemporal distribution of WUE is uneven in the Guangdong Province.The correlation degree of WUE showed an increasing trend over time,yet spatial variation of the correlation degree of WUE was obvious.Multi-factor interactions are essential for the potential correlation degree of WUE,however,the R&D was found the dominant factor for the changes of the potential correlation degree of WUE
With only 7% of the global water resources available to feed 22% of the world′s population,China is facing significant challenges from water scarcity.Since 2000,China has entered a stage of rapid development,however,the extensive utilization of water resources has led to low water use efficiency (WUE) which seriously hinders the sustainable development of economy,society and ecological environment.Guangdong,as a developed province in China,has ranked the first in economic aggregate for the last twentyeight years.However,the regional inequality development is still prominent,among which the uneven of water resources exploitation and utilization can not be ignored.Thus,the improvement of spatial equilibrium in WUE is highly needed for solving the problem of uneven spatial distribution of water resources. Time series of panel data were obtained from Guangdong Province from 2004 to 2018,and this dataset is comprised of 21 prefecturelevel cities.The spatiotemporal characteristic of the regional WUE and its spatial correlation degree were explored using constructing gravity model and spatial analysis technique.The multiple regression models were further used to identify the main influencing factors. The water consumption per tenthousandyuan of Gross Domestic Product (GDP) and the average water consumption per mu for farmland irrigation had relatively strong spatial correlations in Guangdong Province in terms of WUE.The area of high WUE (cold spot) was located in the Pearl River Delta (PRD) while the area of low WUE (hot spot) was located in the north,east and west of Guangdong.Meanwhile,an increasing trend was observed in correlation degree of WUE,among which the highest correlation degree was found in the PRD(with Shenzhen and Dongguan as the core),followed by the east of the province (with Shantou as the core) and the north and west of the province.For the driving factors,it is found that the research and experimental development funds(R&D),urbanization rate,the proportion of secondary and tertiary industry have positive effect on the potential correlation degree of WUE.Furthermore,R&D was found the major driving factor for the increase of the potential correlation degree of WUE over time,while per capita water resources,per capita GDP and the proportion of primary industry performed negative effect on the potential correlation degree of WUE. The spatiotemporal distribution of WUE is uneven in the Guangdong Province.The correlation degree of WUE showed an increasing trend over time,yet spatial variation of the correlation degree of WUE was obvious.Multi-factor interactions are essential for the potential correlation degree of WUE,however,the R&D was found the dominant factor for the changes of the potential correlation degree of WUE
2021, 19(3):487-495.
Abstract:
In recent years,the spatial and temporal distribution of water resources in China does not match the scale of economic and social development,which seriously restricts the efficient utilization of water resources and the sustainable development of sociometric development.Therefore,it is of great significance to clarify the matching degree of regional water resources utilization and sociometric development.Shaying River is one of the main water sources in Henan Province that carries several cities′ water utilization in agricultural irrigation and urban life,while significant differences existed in water resources endowments and economic development.Discussing the temporal and spatial evolution trend and influencing factors of the matching relationship between water resources utilization and sociometric development in the Shaying River basin is of great significance for promoting the high-quality development. The representative matching elements from two aspects of water resources and economic society are selected,and the Henan section of Shaying River basin is selected as the research object to study the matching characteristics of water resources and sociometric development from the spatial and temporal dimensions.According to the actual situation of Henan section of Shaying River basin,inverted calculations and groundwater extraction coefficient methods are used to determine the available water resources in each city.The matching relationship between the water resources utilization and the economic development of 10 cities in Henan section of the Shaying River basin from 2014 to 2018 is studied,based on the calculation method of data sequence.Finally,the matching degree among water consumption,the available water resources and the GDP of each city is analyzed. Results show that there is a large gap in available water resources due to climatic conditions and other factors,among which Luohe and Zhoukou have more available water resources.During the study period,the matching relationship between available water resources and water consumption of various cities differed greatly.Although Zhumadian is rich in water resources and has many rivers in its territory,while its water consumption ranks low among the cities,so the matching degree of water resources availability and water consumption in Zhumadian is poor.In the time dimension,the matching degree between water consumption and GDP of various cities was good;while in the spatial dimension,the matching situation of Kaifeng was the worst,and other cities such as Luohe were better.Meanwhile,the matching degree was at a higher level or above,indicating that the water resources consumed by cities in the Henan section of the Shaying River basin can produce corresponding economic benefits.In terms of time and space,the matching relationship between the available water resources and GDP in various cities had significant differences.The matching degree of Shaying River basin was the best in 2016,and the matching degree in Pingdingshan,Ruzhou,Nanyang，and Zhumadian were relatively better. In general,the matching degree of water consumption and GDP of different cities in Henan around Shaying River basin has little difference over time,and the matching degree of different cities is similar.However,the matching degree of available water resources and GDP varies greatly between different cities.Therefore,it is necessary to use water transfer or other ways to improve the local water resources endowment conditions.Results are helpful to reveal the temporal and spatial evolution law of water resources utilization and economic development in various cities of Shaying River basin,clarify its influencing factors,and provide decision supports for realizing the optimal allocation and efficient utilization of water resources,and coordinated sociometric development among regions.
In recent years,the spatial and temporal distribution of water resources in China does not match the scale of economic and social development,which seriously restricts the efficient utilization of water resources and the sustainable development of sociometric development.Therefore,it is of great significance to clarify the matching degree of regional water resources utilization and sociometric development.Shaying River is one of the main water sources in Henan Province that carries several cities′ water utilization in agricultural irrigation and urban life,while significant differences existed in water resources endowments and economic development.Discussing the temporal and spatial evolution trend and influencing factors of the matching relationship between water resources utilization and sociometric development in the Shaying River basin is of great significance for promoting the high-quality development. The representative matching elements from two aspects of water resources and economic society are selected,and the Henan section of Shaying River basin is selected as the research object to study the matching characteristics of water resources and sociometric development from the spatial and temporal dimensions.According to the actual situation of Henan section of Shaying River basin,inverted calculations and groundwater extraction coefficient methods are used to determine the available water resources in each city.The matching relationship between the water resources utilization and the economic development of 10 cities in Henan section of the Shaying River basin from 2014 to 2018 is studied,based on the calculation method of data sequence.Finally,the matching degree among water consumption,the available water resources and the GDP of each city is analyzed. Results show that there is a large gap in available water resources due to climatic conditions and other factors,among which Luohe and Zhoukou have more available water resources.During the study period,the matching relationship between available water resources and water consumption of various cities differed greatly.Although Zhumadian is rich in water resources and has many rivers in its territory,while its water consumption ranks low among the cities,so the matching degree of water resources availability and water consumption in Zhumadian is poor.In the time dimension,the matching degree between water consumption and GDP of various cities was good;while in the spatial dimension,the matching situation of Kaifeng was the worst,and other cities such as Luohe were better.Meanwhile,the matching degree was at a higher level or above,indicating that the water resources consumed by cities in the Henan section of the Shaying River basin can produce corresponding economic benefits.In terms of time and space,the matching relationship between the available water resources and GDP in various cities had significant differences.The matching degree of Shaying River basin was the best in 2016,and the matching degree in Pingdingshan,Ruzhou,Nanyang，and Zhumadian were relatively better. In general,the matching degree of water consumption and GDP of different cities in Henan around Shaying River basin has little difference over time,and the matching degree of different cities is similar.However,the matching degree of available water resources and GDP varies greatly between different cities.Therefore,it is necessary to use water transfer or other ways to improve the local water resources endowment conditions.Results are helpful to reveal the temporal and spatial evolution law of water resources utilization and economic development in various cities of Shaying River basin,clarify its influencing factors,and provide decision supports for realizing the optimal allocation and efficient utilization of water resources,and coordinated sociometric development among regions.
2021, 19(3):496-510.
Abstract:
In order to explore the climate change in the Dawen River basin,based on the data of six weather stations in the Dawen River basin from 1966 to 2017,MannKendall test and wavelet analysis were used to study the temperature and precipitation trends,mutations and cycles in the region.In addition,based on the three scenarios of RCP2.6,RCP4.5,and RCP8.5 under the CanESM2 model,SDSM was used to compare and analyze the future climate change of the Dawen River basin.The results revealed that:the annual mean temperature of the Dawen River basin had increased significantly since 1966 (p<0.01);in different scenarios,the spatial distribution of the projected maximum temperature,minimum temperature and precipitation will hardly change compared with that in history;the temperature and precipitation in the Dawen River basin will generally increase in the future.The rising trend of maximum and minimum temperature under the three scenarios is in the EP
In order to explore the climate change in the Dawen River basin,based on the data of six weather stations in the Dawen River basin from 1966 to 2017,MannKendall test and wavelet analysis were used to study the temperature and precipitation trends,mutations and cycles in the region.In addition,based on the three scenarios of RCP2.6,RCP4.5,and RCP8.5 under the CanESM2 model,SDSM was used to compare and analyze the future climate change of the Dawen River basin.The results revealed that:the annual mean temperature of the Dawen River basin had increased significantly since 1966 (p<0.01);in different scenarios,the spatial distribution of the projected maximum temperature,minimum temperature and precipitation will hardly change compared with that in history;the temperature and precipitation in the Dawen River basin will generally increase in the future.The rising trend of maximum and minimum temperature under the three scenarios is in the EP
2021, 19(3):511-519.
Abstract:
With the development of social economy,the demand for water resources of the Yellow River basin is increasing.And most areas of the Yellow River basin are in arid and semiarid areas and the ecological environment is fragile,aggravating the sensitivity of the water resources system to climate change.Although many researches have been conducted on the impact of climate factors on hydrological phenomena,the causality and the probability of interaction between climate factors and runoff are still very vague.Besides,in the study of hydrological forecast,the water balance model,the wavelet analysis,the neural network,and the fuzzy inference method can merely provide a deterministic forecast of hydrological process,while they can not quantitatively describe the uncertainty of forecast results.Based on the correlation and uncertainty of climate and hydrological systems,Bayesian network (BN) is then used to quantify the impact of climate factors on runoff and forecast the future runoff in the Yellow River basin. Based on expert knowledge bases and other scholars′ research results on the relationship between climate and runoff in the Yellow River basin,six climate factors including temperature,pressure,wind speed,specific humidity,evaporation,and precipitation were determined to form the variable node of BN with runoff,and the BN model of climate runoff was constructed by the Netica.The ChiMerge method was used to discretize the ERAInterim reanalysis of climate and hydrological data from 1979 to 2018 into three sections.After the determination of network structure and training data set,the conditional probability table of each node can be obtained by the maximum likelihood estimation,and the Bayesian influence probability between variables can be calculated by the variable elimination method.In the BN model for predicting runoff,all the data in the prediction model is divided into twelve intervals to improve the prediction accuracy.The ERA reanalysis data in years of 1979-2018 is used as the training set.The history climatic data of CMIP5 ten climate models in years of 1979-2005 is used as a validation set.The reliability verification of the model is established by comparing the predicted range and trend of runoff in years of 1979-2005 with ERA runoff data over the same period.Finally,the future runoff data of the Yellow River basin is predicted by the climate variables of several typical concentration emission scenarios (RCP 2.6,RCP 45,and RCP 8.5) in years of 2006-2080. From the climate runoff Bayesian network,it is found that any change in the state of any variable can cause other variables to change.For example,as the temperature state from low to high,the probability of high state evaporation and precipitation can increase,and the probability of high state runoff can also increase,indicating temperature,evaporation,and precipitation are positively correlated with runoff.The relationship among other climatic factors and runoff can also be found that specific humidity is positively correlated,pressure and wind speed are negatively correlated,and precipitation has the closest relationship with runoff.From years of 1979-2018,the natural runoff of the Yellow River showed a decreasing trend,and the runoff based on the probability prediction from BN also showed a decreasing trend.In the RCP26 scenario,the Yellow River basin′s runoff in the next twenty and sixty years will be reached 58.55 billion m3 and 58.857 billion m3.While in the RCP4.5 scenario,the Yellow River basin′s runoff in the next twenty and sixty years will be reached 58.542 billion m3 and 58.753 billion m3;and in the RCP8.5 scenario,the associated values will be reached 59.35 billion m3 and 58.511 billion m3. Climate change is of great significance to the change of surface runoff.The climaterunoff BN constructed in this paper is a network of uncertain relationships between climate and hydrological elements.It explores the climatic reasons for the reduction of runoff and conducts midand longterm predictions of future runoff.It is concluded that the main reason for the decrease in runoff is the decrease in precipitation,and the specific humidity is a key climatic element affecting precipitation.The future runoff forecast of the Yellow River in the next sixty years is estimated to be around 58.7 billion m3 by BN.
With the development of social economy,the demand for water resources of the Yellow River basin is increasing.And most areas of the Yellow River basin are in arid and semiarid areas and the ecological environment is fragile,aggravating the sensitivity of the water resources system to climate change.Although many researches have been conducted on the impact of climate factors on hydrological phenomena,the causality and the probability of interaction between climate factors and runoff are still very vague.Besides,in the study of hydrological forecast,the water balance model,the wavelet analysis,the neural network,and the fuzzy inference method can merely provide a deterministic forecast of hydrological process,while they can not quantitatively describe the uncertainty of forecast results.Based on the correlation and uncertainty of climate and hydrological systems,Bayesian network (BN) is then used to quantify the impact of climate factors on runoff and forecast the future runoff in the Yellow River basin. Based on expert knowledge bases and other scholars′ research results on the relationship between climate and runoff in the Yellow River basin,six climate factors including temperature,pressure,wind speed,specific humidity,evaporation,and precipitation were determined to form the variable node of BN with runoff,and the BN model of climate runoff was constructed by the Netica.The ChiMerge method was used to discretize the ERAInterim reanalysis of climate and hydrological data from 1979 to 2018 into three sections.After the determination of network structure and training data set,the conditional probability table of each node can be obtained by the maximum likelihood estimation,and the Bayesian influence probability between variables can be calculated by the variable elimination method.In the BN model for predicting runoff,all the data in the prediction model is divided into twelve intervals to improve the prediction accuracy.The ERA reanalysis data in years of 1979-2018 is used as the training set.The history climatic data of CMIP5 ten climate models in years of 1979-2005 is used as a validation set.The reliability verification of the model is established by comparing the predicted range and trend of runoff in years of 1979-2005 with ERA runoff data over the same period.Finally,the future runoff data of the Yellow River basin is predicted by the climate variables of several typical concentration emission scenarios (RCP 2.6,RCP 45,and RCP 8.5) in years of 2006-2080. From the climate runoff Bayesian network,it is found that any change in the state of any variable can cause other variables to change.For example,as the temperature state from low to high,the probability of high state evaporation and precipitation can increase,and the probability of high state runoff can also increase,indicating temperature,evaporation,and precipitation are positively correlated with runoff.The relationship among other climatic factors and runoff can also be found that specific humidity is positively correlated,pressure and wind speed are negatively correlated,and precipitation has the closest relationship with runoff.From years of 1979-2018,the natural runoff of the Yellow River showed a decreasing trend,and the runoff based on the probability prediction from BN also showed a decreasing trend.In the RCP26 scenario,the Yellow River basin′s runoff in the next twenty and sixty years will be reached 58.55 billion m3 and 58.857 billion m3.While in the RCP4.5 scenario,the Yellow River basin′s runoff in the next twenty and sixty years will be reached 58.542 billion m3 and 58.753 billion m3;and in the RCP8.5 scenario,the associated values will be reached 59.35 billion m3 and 58.511 billion m3. Climate change is of great significance to the change of surface runoff.The climaterunoff BN constructed in this paper is a network of uncertain relationships between climate and hydrological elements.It explores the climatic reasons for the reduction of runoff and conducts midand longterm predictions of future runoff.It is concluded that the main reason for the decrease in runoff is the decrease in precipitation,and the specific humidity is a key climatic element affecting precipitation.The future runoff forecast of the Yellow River in the next sixty years is estimated to be around 58.7 billion m3 by BN.
2021, 19(3):520-527.
Abstract:
Precipitable water vapor(PWV) is an important parameter for the study of regional water vapor distribution and formation mechanism of precipitation,which is a quantified indicator to describe water vapor.In QinghaiTibet Plateau,the PWV is hard to be acquired for the low spatial and temporal resolution of water vapor detection due to the large variation in altitude as well as the scarcity and uneven distribution of surface radiosonde stations.While the water vapor data with high precision and high spatiotemporal resolution is the premise to improve accuracy of regional precipitation prediction,herewith the PWV with high precision is needed.Water vapor detection by groundbased Global Positioning System (GPS) is an effective supplement to radiosonde.To analyze the accuracy and influencing factors of PWV detected by GPS,5 typical GPS and radiosonde stations were selected in QinghaiTibet Plateau as the source of the data for further research. GPS data of the Chinese constructed environmental monitoring network,and sounding data of the website of Wyoming University (http://weather.uwyo.edu/wyoming/)were applied.The international highprecision GPS data processing software GAMIT based on the double difference method has been used to calculate the total zenith delay,which contributes to the obtainment of the millimeter scale zenith wet delay.And then the PWV in zenith direction is accordingly gained by the proportional relationship between zenith wet delay and PWV.The GPT2 tropospheric delay model is utilized for the calculation with cutoff height angle setting at 10 degrees.In order to eliminate the systematic error caused by correlation,3 IGS reference stations with a distance of more than 500 km from the point to be measured are introduced.Retrival calculation is an integration of total zenith delay calculation,tropospheric delay calculation as well as PWV calculation.The GPS retrival accuracy evaluated and verified by the near radiosonde data (approximate true value) is used to the analysis on the daily and monthly accuracy of PWV measured by GPS as well as on the impact of the retrival accuracy exerted by PWV and surface temperature. The results show that the daily variation of PWV retrieved by GPS is consistent with radiosonde data with the correlation coefficients from 0.87 to 0.93.The RMSE and ARE of each station at UTC0 are less than UTC12,and the correlation coefficient at UTC0 time is higher than the value at UTC12 time.By analyzing the monthly deviation of the stations,it is found that the MAE from June to September is relatively large,about 2.0-5.5 mm;the value in November,January and February is relatively small,about 0.5~2.0 mm.Among the 5 stations,XNIN Station has the largest MAD,while QHDL Station and QHGE Station are relatively stable.The RMSE and MAD of all stations have the same trend.The RMSE of all stations reaches the maximum in August,and the value of XNIN Station is the largest,which is 5.05 mm at UTC0 and 6.04 mm at UTC12,respectively.The minimum value of RMSE appears in January or February,which area about 1.1 mm for each station.The MAD,RMSE,and ARE at UTC12 are significantly higher than those at UTC0,and the MAD and RMSE at UTC0 and UTC12 from May to September are larger than those in other months.In addition,the influence of PWV and surface temperature was analyzed on the accuracy of PWV retrival.It is found that the PWV and the MAD,the ground temperature and the MAD all have a moderate correlation.Apparently,both the PWV and the surface temperature have a certain effect on the accuracy of GPS detection of PWV. In conclusion,the detection accuracy of each GPS station is equivalent to that of nearby radiosonde stations with RMSE of 2~3 mm and the correlation coefficient of 0.88~0.93,which satisfies the accuracy requirements.In this circumstance,the retrival results can be put into use on the study of PWV on representative areas.In the future,the research on water vapor retrival may dependent on the information combined radiosonde with GPS,and thus provides data support on water vapor conditions and precipitation forecasts in QinghaiTibet Plateau.Based on PWV retrival of GPS,the detection accuracy at UTC0 is more exquisite than that at UTC0,and more exquisite in winter than in summer.It is found that PWV detected by GPS is susceptible to the change of surface temperature and PWV.Hence,the errors caused by the variation should be considered on the application of GPS detection data in QinghaiTibet Plateau.
Precipitable water vapor(PWV) is an important parameter for the study of regional water vapor distribution and formation mechanism of precipitation,which is a quantified indicator to describe water vapor.In QinghaiTibet Plateau,the PWV is hard to be acquired for the low spatial and temporal resolution of water vapor detection due to the large variation in altitude as well as the scarcity and uneven distribution of surface radiosonde stations.While the water vapor data with high precision and high spatiotemporal resolution is the premise to improve accuracy of regional precipitation prediction,herewith the PWV with high precision is needed.Water vapor detection by groundbased Global Positioning System (GPS) is an effective supplement to radiosonde.To analyze the accuracy and influencing factors of PWV detected by GPS,5 typical GPS and radiosonde stations were selected in QinghaiTibet Plateau as the source of the data for further research. GPS data of the Chinese constructed environmental monitoring network,and sounding data of the website of Wyoming University (http://weather.uwyo.edu/wyoming/)were applied.The international highprecision GPS data processing software GAMIT based on the double difference method has been used to calculate the total zenith delay,which contributes to the obtainment of the millimeter scale zenith wet delay.And then the PWV in zenith direction is accordingly gained by the proportional relationship between zenith wet delay and PWV.The GPT2 tropospheric delay model is utilized for the calculation with cutoff height angle setting at 10 degrees.In order to eliminate the systematic error caused by correlation,3 IGS reference stations with a distance of more than 500 km from the point to be measured are introduced.Retrival calculation is an integration of total zenith delay calculation,tropospheric delay calculation as well as PWV calculation.The GPS retrival accuracy evaluated and verified by the near radiosonde data (approximate true value) is used to the analysis on the daily and monthly accuracy of PWV measured by GPS as well as on the impact of the retrival accuracy exerted by PWV and surface temperature. The results show that the daily variation of PWV retrieved by GPS is consistent with radiosonde data with the correlation coefficients from 0.87 to 0.93.The RMSE and ARE of each station at UTC0 are less than UTC12,and the correlation coefficient at UTC0 time is higher than the value at UTC12 time.By analyzing the monthly deviation of the stations,it is found that the MAE from June to September is relatively large,about 2.0-5.5 mm;the value in November,January and February is relatively small,about 0.5~2.0 mm.Among the 5 stations,XNIN Station has the largest MAD,while QHDL Station and QHGE Station are relatively stable.The RMSE and MAD of all stations have the same trend.The RMSE of all stations reaches the maximum in August,and the value of XNIN Station is the largest,which is 5.05 mm at UTC0 and 6.04 mm at UTC12,respectively.The minimum value of RMSE appears in January or February,which area about 1.1 mm for each station.The MAD,RMSE,and ARE at UTC12 are significantly higher than those at UTC0,and the MAD and RMSE at UTC0 and UTC12 from May to September are larger than those in other months.In addition,the influence of PWV and surface temperature was analyzed on the accuracy of PWV retrival.It is found that the PWV and the MAD,the ground temperature and the MAD all have a moderate correlation.Apparently,both the PWV and the surface temperature have a certain effect on the accuracy of GPS detection of PWV. In conclusion,the detection accuracy of each GPS station is equivalent to that of nearby radiosonde stations with RMSE of 2~3 mm and the correlation coefficient of 0.88~0.93,which satisfies the accuracy requirements.In this circumstance,the retrival results can be put into use on the study of PWV on representative areas.In the future,the research on water vapor retrival may dependent on the information combined radiosonde with GPS,and thus provides data support on water vapor conditions and precipitation forecasts in QinghaiTibet Plateau.Based on PWV retrival of GPS,the detection accuracy at UTC0 is more exquisite than that at UTC0,and more exquisite in winter than in summer.It is found that PWV detected by GPS is susceptible to the change of surface temperature and PWV.Hence,the errors caused by the variation should be considered on the application of GPS detection data in QinghaiTibet Plateau.
2021, 19(3):528-538.
Abstract:
Under the background of global warming,drought has become the foremost disaster endangering agricultural and animal husbandry production,thus it has an increasingly negative impact on human life.Ningxia is in the arid and semiarid area,and has limited water resources and fragile ecology due to its unique climate.At present,studies on drought are mainly conducted in southwest China,the Yangtze River and Yellow River basins,and many provinces in China,while few in Ningxia,which has been threatened by water shortage and drought for decades.Therefore,it is of great significance to clarify the spatiotemporal variation characteristics of drought in Ningxia. The standardized precipitation index (SPI) was used as the drought index,and the drought frequency and the drought intensity were used to evaluate the drought characteristics.Based on the distribution probability of precipitation during a certain period,SPI carries out the normal standardization processing.Then,the cumulative frequency distribution of standardized precipitation is used to divide the drought grade of the northern Yellow River irrigation area,the central arid zone and the southern mountainous area.The drought frequency is the frequency of drought occurring during the study period,while the drought intensity is an important index to evaluate the severity of drought.The drought frequency and the drought intensity were analyzed and evaluated at seasonal and annual scales in each study area of Ningxia. The results show that the variation trend of temperature and rainfall of different regions in spring,summer,autumn,and winter from 1960 to 2016 is almost the same;the interannual variation difference of temperature is not obvious,the distribution of temperature is not uniform,but the overall trend of warming and drying appears.In the autumn of 2004,a drought event happened in the Yellow River irrigation area,where the SPI index reached 243 and the frequency is 172%;in the winter of 1998,a drought event happened in the arid zone,where the SPI is 298 and the frequency is 1.72%.In the spring of 1994,the summer of 1981,the 1971,the autumn of 1985,and the winter of 1998,drought events happened in the southern mountain area,with the SPI value of 2.17,2.11,2.61,220,3.25,and the frequency of occurrence of 77.59%,10.34%,5.17%,5.17% and 1.72%,respectively.For the SPI in the regional scale during the study period,the count of excessive drought events in the Yellow River irrigation area,the arid zone and the southern mountainous area increased.For the SPI value in the time scale,the frequency of excessive drought events decreased in recent years.According to the analysis and calculation of the annual and quarterly drought intensity in each region,the annual drought intensity fluctuated between 0.68 and 1.47.The times of drought intensity greater than 0.5 were 28,29,and 27 times,respectively;the average drought occurred in 2.07 years,2 years,and 2.1 years.From the perspective of seasonal scale,there are certain differences in different regions and different seasons. The spatial and temporal distribution of rainfall and temperature in Ningxia was uneven and the interannual difference was obvious.The annual rainfall had a significant decreasing trend;the seasonal rainfall had an overall decreasing trend but a rising trend in winter and autumn of the irrigated area along the Yellow River.The average annual temperature and seasonal temperature showed an increasing trend.The annual drought was more frequent and lasted longer in the northern Yellow River irrigation area,the central arid zone,and the southern mountainous area;the drought intensity showed a decreasing trend.The years with the highest intensity were 2004,1981,and 1981,respectively.In the three regions,the seasonal scale drought showed a decreasing trend in summer,autumn of the arid zone and southern mountainous area,while the rest showed an increasing trend.The decreasing degree of drought in summer and autumn was attributed to the fact that most of the rainfall was concentrated in summer and autumn,and the rainfall frequency was more frequent in recent years.The seasons with the greatest drought intensity in the three regions were the summer of 2007,spring of 1994,and winter of 1998.
Under the background of global warming,drought has become the foremost disaster endangering agricultural and animal husbandry production,thus it has an increasingly negative impact on human life.Ningxia is in the arid and semiarid area,and has limited water resources and fragile ecology due to its unique climate.At present,studies on drought are mainly conducted in southwest China,the Yangtze River and Yellow River basins,and many provinces in China,while few in Ningxia,which has been threatened by water shortage and drought for decades.Therefore,it is of great significance to clarify the spatiotemporal variation characteristics of drought in Ningxia. The standardized precipitation index (SPI) was used as the drought index,and the drought frequency and the drought intensity were used to evaluate the drought characteristics.Based on the distribution probability of precipitation during a certain period,SPI carries out the normal standardization processing.Then,the cumulative frequency distribution of standardized precipitation is used to divide the drought grade of the northern Yellow River irrigation area,the central arid zone and the southern mountainous area.The drought frequency is the frequency of drought occurring during the study period,while the drought intensity is an important index to evaluate the severity of drought.The drought frequency and the drought intensity were analyzed and evaluated at seasonal and annual scales in each study area of Ningxia. The results show that the variation trend of temperature and rainfall of different regions in spring,summer,autumn,and winter from 1960 to 2016 is almost the same;the interannual variation difference of temperature is not obvious,the distribution of temperature is not uniform,but the overall trend of warming and drying appears.In the autumn of 2004,a drought event happened in the Yellow River irrigation area,where the SPI index reached 243 and the frequency is 172%;in the winter of 1998,a drought event happened in the arid zone,where the SPI is 298 and the frequency is 1.72%.In the spring of 1994,the summer of 1981,the 1971,the autumn of 1985,and the winter of 1998,drought events happened in the southern mountain area,with the SPI value of 2.17,2.11,2.61,220,3.25,and the frequency of occurrence of 77.59%,10.34%,5.17%,5.17% and 1.72%,respectively.For the SPI in the regional scale during the study period,the count of excessive drought events in the Yellow River irrigation area,the arid zone and the southern mountainous area increased.For the SPI value in the time scale,the frequency of excessive drought events decreased in recent years.According to the analysis and calculation of the annual and quarterly drought intensity in each region,the annual drought intensity fluctuated between 0.68 and 1.47.The times of drought intensity greater than 0.5 were 28,29,and 27 times,respectively;the average drought occurred in 2.07 years,2 years,and 2.1 years.From the perspective of seasonal scale,there are certain differences in different regions and different seasons. The spatial and temporal distribution of rainfall and temperature in Ningxia was uneven and the interannual difference was obvious.The annual rainfall had a significant decreasing trend;the seasonal rainfall had an overall decreasing trend but a rising trend in winter and autumn of the irrigated area along the Yellow River.The average annual temperature and seasonal temperature showed an increasing trend.The annual drought was more frequent and lasted longer in the northern Yellow River irrigation area,the central arid zone,and the southern mountainous area;the drought intensity showed a decreasing trend.The years with the highest intensity were 2004,1981,and 1981,respectively.In the three regions,the seasonal scale drought showed a decreasing trend in summer,autumn of the arid zone and southern mountainous area,while the rest showed an increasing trend.The decreasing degree of drought in summer and autumn was attributed to the fact that most of the rainfall was concentrated in summer and autumn,and the rainfall frequency was more frequent in recent years.The seasons with the greatest drought intensity in the three regions were the summer of 2007,spring of 1994,and winter of 1998.
MENG Qingbo
,
LIU Yanli
,
JU Qin
,
LIU Ji
,
WANG Guoqing
,
JIN Junliang
,
GUAN Tiesheng
,
LIU Cuishan
,
BAO Zhenxin
2021, 19(3):539-550.
Abstract:
Climate change is a hot topic in recent decades,and the global ecosystem has already been affected by it.Climate warming has a significant impact on the vegetation change process in country.Vegetation is an important part of the terrestrial ecosystem.It not only affects the hydrology,climate,and energy balance of the ecosystem,but also is subject to change the hydrological,climatological process.Therefore,by monitoring the vegetation status,analyzing the characteristics of temporal and spatial changes of vegetation cover and the correlation of climate factors,soil and other factors with the vegetation changes are of great significance for revealing the intrinsic relationship between climate change and vegetation changes. Firstly,based on MODIS NDVI data,DEM data,and 1∶1 million Chinese vegetation type map,the MannKendall trend and mutation point test method were used to analyze the temporal change characteristics of NDVI at different altitude gradients and vegetation types from 2001 to 2018 in the basin.Slope value of MODIS NDVI for each pixel and the characteristics of the vegetation NDVI spatial change were calculated from 2001 to 2018 in the Yarlung Zangbo River basin.Secondly,spatial distribution characteristics of the correlation coefficient between NDVI and monthly precipitation and monthly average temperature under the four lag time conditions of the current month,the previous month,the first two months,and the first three months were analyzed to explore the lag of climate factors on NDVI.Finally,the response time corresponding to different vegetations was calculated based on precipitation and temperature change and then correlation between NDVI changes of different vegetation types and climate factors were analyzed. (1) From 2001 to 2018,NDVI showed an increasing trend in 80% of the Yarlung Zangbo River basin.Among them,the downstream area showed the most significant increase in NDVI.The 6 types of altitude gradients showed a gradual increase in NDVI.Vegetation NDVI in areas with an altitude greater than 4,500 m has a significant growth trend.From the perspective of vegetation types,the results are similar to those of different altitude gradients,and both show a gradual significant increase trend;(2)The area where the vegetation NDVI is moderately correlated with precipitation and temperature is 80 % of the Yarlung Zangbo River basin,and it is found that the correlation between vegetation NDVI and precipitation in 5296% area of the basin is weaker than that of temperature,but 3369% area is highly correlated with precipitation than that of area highly correlated with temperature;(3) From the perspective of the same planting type in the Yarlung Zangbo River,except for grassland and meadow,the correlation coefficients of vegetation NDVI with temperature are all higher than precipitation.The response time of grassland,meadow,and alpine vegetation to temperature is longer than precipitation,and the response time of other vegetation to the changes of the two climatic factors shows that precipitation response time is greater than temperature. (1)Vegetation growth in the Yarlung Zangbo River basin has improved in the past 18 years.The vegetation NDVI at different altitude gradients and vegetation types has shown an increasing trend in 2015.It may be related to the state′s environmental protection and ecological construction policies in Tibet during the "Twelfth FiveYear Plan" period after 2013.(2) The NDVI of the vegetation in the Yarlung Zangbo River basin is greatly affected by precipitation and temperature.The correlation of vegetation with precipitation and temperature displayed that temperature is slightly stronger than precipitation;(3)The temperature in the Yarlung Zangbo River basin has a stronger impact on vegetation than precipitation,and the vegetation has a shorter response time to temperature changes.
Climate change is a hot topic in recent decades,and the global ecosystem has already been affected by it.Climate warming has a significant impact on the vegetation change process in country.Vegetation is an important part of the terrestrial ecosystem.It not only affects the hydrology,climate,and energy balance of the ecosystem,but also is subject to change the hydrological,climatological process.Therefore,by monitoring the vegetation status,analyzing the characteristics of temporal and spatial changes of vegetation cover and the correlation of climate factors,soil and other factors with the vegetation changes are of great significance for revealing the intrinsic relationship between climate change and vegetation changes. Firstly,based on MODIS NDVI data,DEM data,and 1∶1 million Chinese vegetation type map,the MannKendall trend and mutation point test method were used to analyze the temporal change characteristics of NDVI at different altitude gradients and vegetation types from 2001 to 2018 in the basin.Slope value of MODIS NDVI for each pixel and the characteristics of the vegetation NDVI spatial change were calculated from 2001 to 2018 in the Yarlung Zangbo River basin.Secondly,spatial distribution characteristics of the correlation coefficient between NDVI and monthly precipitation and monthly average temperature under the four lag time conditions of the current month,the previous month,the first two months,and the first three months were analyzed to explore the lag of climate factors on NDVI.Finally,the response time corresponding to different vegetations was calculated based on precipitation and temperature change and then correlation between NDVI changes of different vegetation types and climate factors were analyzed. (1) From 2001 to 2018,NDVI showed an increasing trend in 80% of the Yarlung Zangbo River basin.Among them,the downstream area showed the most significant increase in NDVI.The 6 types of altitude gradients showed a gradual increase in NDVI.Vegetation NDVI in areas with an altitude greater than 4,500 m has a significant growth trend.From the perspective of vegetation types,the results are similar to those of different altitude gradients,and both show a gradual significant increase trend;(2)The area where the vegetation NDVI is moderately correlated with precipitation and temperature is 80 % of the Yarlung Zangbo River basin,and it is found that the correlation between vegetation NDVI and precipitation in 5296% area of the basin is weaker than that of temperature,but 3369% area is highly correlated with precipitation than that of area highly correlated with temperature;(3) From the perspective of the same planting type in the Yarlung Zangbo River,except for grassland and meadow,the correlation coefficients of vegetation NDVI with temperature are all higher than precipitation.The response time of grassland,meadow,and alpine vegetation to temperature is longer than precipitation,and the response time of other vegetation to the changes of the two climatic factors shows that precipitation response time is greater than temperature. (1)Vegetation growth in the Yarlung Zangbo River basin has improved in the past 18 years.The vegetation NDVI at different altitude gradients and vegetation types has shown an increasing trend in 2015.It may be related to the state′s environmental protection and ecological construction policies in Tibet during the "Twelfth FiveYear Plan" period after 2013.(2) The NDVI of the vegetation in the Yarlung Zangbo River basin is greatly affected by precipitation and temperature.The correlation of vegetation with precipitation and temperature displayed that temperature is slightly stronger than precipitation;(3)The temperature in the Yarlung Zangbo River basin has a stronger impact on vegetation than precipitation,and the vegetation has a shorter response time to temperature changes.
2021, 19(3):551-560.
Abstract:
Changji City is the capital of Changji Hui Autonomous Prefecture, Xinjiang, and the increasingly serious quality problem of groundwater resources seriously restricts the local economic and social development. Based on the detection data of 42 groups of groundwater samples in Changji plain in 2016 (including 27 groups of unconfined groundwater samples and 15 groups of confined groundwater samples), the chemical characteristics of groundwater in this area are studied comprehensively by various means and its influencing factors are analyzed.At the same time, the detection data of nine groups of groundwater insitu samples in 2011 (including eight groups of unconfined groundwater samples and one group of confined groundwater sample) were used to reveal the law of spatial and temporal variation of groundwater quality in this area,in order to provide theoretical basis for the utilization and protection of groundwater resources. The mathematical statistics method is used to analyze the chemical composition content characteristics of groundwater Changji City,Piper diagram is used to analyze the chemical [JP2]types of groundwater, Gibbs figures are used to analyze[JP] the influencing factors of chemical characteristics of groundwater,ion ratio method is used to analyze the main sources of chemical composition of groundwater in the current year,F value evaluation method is used to evaluate the groundwater quality category,and quality comparison method is used to analyze the changes of groundwater quality insitu in 2011 and 2016. The [JP2]relationship between the average content of cations and anions [JP]in unconfined groundwater is Ca2+>Na+>Mg2+>K+ and HCO3->SO42->Cl-. The confined groundwater is Na+>Ca2+>Mg2+>K+ and Cl->HCO3->SO42-.The currentyear groundwater hydrochemical types were obtained by Piper diagram, with HCO3·SO4-Na·Ca and HCO3·SO4-Na·Ca·Mg types dominating in unconfined groundwater and HCO3Na·Ca and HCO3·SO4-Na·Ca types dominating in confined groundwater.The chemical characteristics of groundwater in current year were analyzed by Gibbs figures.The TDS range of unconfined groundwater and confined groundwater was mostly between 020 and 110 g/L. In unconfined groundwater, γ(Na+)/γ(Na++Ca2+) is more than 0.5 and γ(Cl-)/γ(Cl-+HCO3-) is less than 0.5. In confined groundwater,γ(Na+)/γ(Na++Ca2+) and γ(Cl-)/γ(Cl-+HCO3-) are mostly less than 0.5.The statistical results evaluated by Fvalue evaluation method show that the samples of groundwater quality in the current year of unconfined groundwater are 16 groups,6 groups,0 groups,3 groups,and 2 groups for Class Ⅰ,Class Ⅱ,Class Ⅲ,Class Ⅳ,and Class Ⅴ groundwater,respectively. The samples of groundwater quality in the current year of unconfined groundwater are 10 groups,2 groups,0 groups,2 groups,and 1 group. Compared with 9 groups of groundwater insitu points in 2011 and 2016,the quality category of samples C1,C22,and C40 in unconfined groundwater did not change,the quality category of samples C4,C34,and C39 improved from Class Ⅱ to Class Ⅰ,C41deteriorated from Class Ⅰ to Class Ⅱ,and C42deteriorated from Class Ⅰ to Class Ⅳ.The quality category of C2 in confined groundwater sample did not change. Both unconfined groundwater and confined groundwater in the plain area of Changji City are characterized by neutral to weakly alkaline,the highest Na+ overstandard rate and high TDS content.The spatial variation of Cl- and Ca2+ in unconfined groundwater is quite different,while the spatial variation of Cl- and Mg2+in confined groundwater is quite different.The hydrochemical types of unconfined groundwater are mainly HCO3·SO4-Na·Ca and HCO3·SO4Na·Ca·Mg, while the confined groundwater are mainly HCO3-Na·Ca and HCO3·SO4-Na·Ca. The chemical composition of unconfined groundwater in the study area is mainly affected by the combined effect of evaporation concentration and rock weathering,and the confined groundwater is mainly affected by the effect of rock weathering.The overall quality of groundwater in the study area was better in 2016,mainly Class Ⅰ.The samples of Class Ⅰ,Class Ⅱ,Class Ⅳ,and Class Ⅴ in unconfined groundwater accounted for 59.3%,22.2%,11.3%,and 7.4% of the total, respectively.While the samples of Class Ⅰ,Class Ⅱ,Class Ⅳ,and Class Ⅴ in confined groundwater accounted for 66.7%,13.3%,13.3%,and 6.7% of the total,respectively.Compared with the groundwater insitu samples in 2011 and 2016, it was found that the quality category of three groups of unconfined groundwater sampling sites remained unchanged,three groups improved,two groups deteriorated,and the quality category of one group of the confined groundwater sampling sites had no change.The main factors that affect the chemical characteristics and the spatial and temporal distribution of groundwater quality are natural factors and human factors.
Changji City is the capital of Changji Hui Autonomous Prefecture, Xinjiang, and the increasingly serious quality problem of groundwater resources seriously restricts the local economic and social development. Based on the detection data of 42 groups of groundwater samples in Changji plain in 2016 (including 27 groups of unconfined groundwater samples and 15 groups of confined groundwater samples), the chemical characteristics of groundwater in this area are studied comprehensively by various means and its influencing factors are analyzed.At the same time, the detection data of nine groups of groundwater insitu samples in 2011 (including eight groups of unconfined groundwater samples and one group of confined groundwater sample) were used to reveal the law of spatial and temporal variation of groundwater quality in this area,in order to provide theoretical basis for the utilization and protection of groundwater resources. The mathematical statistics method is used to analyze the chemical composition content characteristics of groundwater Changji City,Piper diagram is used to analyze the chemical [JP2]types of groundwater, Gibbs figures are used to analyze[JP] the influencing factors of chemical characteristics of groundwater,ion ratio method is used to analyze the main sources of chemical composition of groundwater in the current year,F value evaluation method is used to evaluate the groundwater quality category,and quality comparison method is used to analyze the changes of groundwater quality insitu in 2011 and 2016. The [JP2]relationship between the average content of cations and anions [JP]in unconfined groundwater is Ca2+>Na+>Mg2+>K+ and HCO3->SO42->Cl-. The confined groundwater is Na+>Ca2+>Mg2+>K+ and Cl->HCO3->SO42-.The currentyear groundwater hydrochemical types were obtained by Piper diagram, with HCO3·SO4-Na·Ca and HCO3·SO4-Na·Ca·Mg types dominating in unconfined groundwater and HCO3Na·Ca and HCO3·SO4-Na·Ca types dominating in confined groundwater.The chemical characteristics of groundwater in current year were analyzed by Gibbs figures.The TDS range of unconfined groundwater and confined groundwater was mostly between 020 and 110 g/L. In unconfined groundwater, γ(Na+)/γ(Na++Ca2+) is more than 0.5 and γ(Cl-)/γ(Cl-+HCO3-) is less than 0.5. In confined groundwater,γ(Na+)/γ(Na++Ca2+) and γ(Cl-)/γ(Cl-+HCO3-) are mostly less than 0.5.The statistical results evaluated by Fvalue evaluation method show that the samples of groundwater quality in the current year of unconfined groundwater are 16 groups,6 groups,0 groups,3 groups,and 2 groups for Class Ⅰ,Class Ⅱ,Class Ⅲ,Class Ⅳ,and Class Ⅴ groundwater,respectively. The samples of groundwater quality in the current year of unconfined groundwater are 10 groups,2 groups,0 groups,2 groups,and 1 group. Compared with 9 groups of groundwater insitu points in 2011 and 2016,the quality category of samples C1,C22,and C40 in unconfined groundwater did not change,the quality category of samples C4,C34,and C39 improved from Class Ⅱ to Class Ⅰ,C41deteriorated from Class Ⅰ to Class Ⅱ,and C42deteriorated from Class Ⅰ to Class Ⅳ.The quality category of C2 in confined groundwater sample did not change. Both unconfined groundwater and confined groundwater in the plain area of Changji City are characterized by neutral to weakly alkaline,the highest Na+ overstandard rate and high TDS content.The spatial variation of Cl- and Ca2+ in unconfined groundwater is quite different,while the spatial variation of Cl- and Mg2+in confined groundwater is quite different.The hydrochemical types of unconfined groundwater are mainly HCO3·SO4-Na·Ca and HCO3·SO4Na·Ca·Mg, while the confined groundwater are mainly HCO3-Na·Ca and HCO3·SO4-Na·Ca. The chemical composition of unconfined groundwater in the study area is mainly affected by the combined effect of evaporation concentration and rock weathering,and the confined groundwater is mainly affected by the effect of rock weathering.The overall quality of groundwater in the study area was better in 2016,mainly Class Ⅰ.The samples of Class Ⅰ,Class Ⅱ,Class Ⅳ,and Class Ⅴ in unconfined groundwater accounted for 59.3%,22.2%,11.3%,and 7.4% of the total, respectively.While the samples of Class Ⅰ,Class Ⅱ,Class Ⅳ,and Class Ⅴ in confined groundwater accounted for 66.7%,13.3%,13.3%,and 6.7% of the total,respectively.Compared with the groundwater insitu samples in 2011 and 2016, it was found that the quality category of three groups of unconfined groundwater sampling sites remained unchanged,three groups improved,two groups deteriorated,and the quality category of one group of the confined groundwater sampling sites had no change.The main factors that affect the chemical characteristics and the spatial and temporal distribution of groundwater quality are natural factors and human factors.
2021, 19(3):561-571,589.
Abstract:
The Jungar coalfield is one of the major coal resource mining sites in northwest China.Water damage at the bottom of the coal seam has become an important factor that is limiting the development of the local economy and society.Therefore,it is important to identify the recharge relationship and circulation characteristics between atmospheric precipitation,surface water,and groundwater in the Jungar coalfield to provide a theoretical basis for the scientific development of coal resources and the effective restoration of groundwater resources in the area. Environmental isotope method,water chemistry analysis methods,and HYSPLIT applied to the groundwater of the Jungar coalfield.Through historical data collection,field survey sampling,and indoor analysis,the water chemistry composition and environmental isotope characteristics of atmospheric precipitation,surface water and groundwater,the main sources of atmospheric precipitation,surface water and groundwater transformation relationships were analyzed.The results show that:(1) Surface water has low mineralization and is weakly alkaline,and the water chemistry type is mainly HCO3·SO4·Cl-Ca type water.The overall mineralization of groundwater is low and weakly alkaline,and the water chemistry type is mainly HCO3-Na·Ca type,ClNa type,HCO3-Ca·Mg type,and HCO3·Cl-Na type water.(2) The average value of δ（D）of Yellow River water is -79.6‰,and the δ（18.O） is -10.7‰,respectively.The average value of δ（D） of Quaternary water is -66.25‰,and the δ（18.O） is -9.1‰,respectively.The average value of δ（D） of Cretaceous water is -70.6‰,and theδ（18.O） is -9.3‰,respectively.The average value of δ（D） of CarboniferousPermian water is -77.07‰,and the δ（18.O） is -9.9‰,respectively.The average value of CambrianOrdovician water δ（D） average value is -75.73‰,δ（18.O） is -10.06‰.Atmospheric precipitation is influenced by polar air masses and southeastern monsoons,and the principal sources are westerly water vapor,surface water,and groundwater vapor evaporation recirculation.(3) The fourth system water has high tritium content,the presence of nuclear explosive tritium,and excellent groundwater runoff conditions.The Cretaceous water has low tritium content and is a mixture of groundwater recharged before 1952 and recently recharged water.The CarboniferousPermian water contains a wide range of tritium content,including groundwater recharged before 1952 and modern water.The CambrianOrdovician water contains a wide range of tritium content,including groundwater recharged before 1952,modern water,and mixed water.(4) The recharge ratio of atmospheric precipitation to CambrianAustralian water ranges from 0.98% to 91.7%,with an average recharge rate of 61.2%.The recharge ratio of surface water (referred to as Yellow River water) to CambrianOrdovician water ranges from 0.83% to 90.2%,with an average recharge rate of 38.8%.Among them,the recharge ratio of Yellow River water to CambrianOrdovician water is larger in Longwanggou,Suancigou,and Huangyuchuan well field,which is influenced by the development of geological structures. The fault zone and the fracture zone of the fold axis are the main waterconducting channels between different aquifers.Atmospheric precipitation and the Yellow River are the principal sources of groundwater recharge.The precipitation vapor sources are mainly westerly water vapor,surface water,and groundwater vapor evaporation recirculation.Highly pressurized head CambrianOrdovician karst fracture water crossflow recharges the Fourth Series and sandstone fracture water.The pore water of the Fourth Series recharges the fracture water of the CarboniferousPermian sandstone downward through the fracture development zone of the unconformity contact surface between the strata.The recharge ratio of the Yellow River to Cambrian-Australian water is influenced by the development of geological structures.In Longwanggou,Suancigou,and Huangyuchuan well field,the proportion of recharge of the Yellow River water to CambrianOrdovician water is larger.
The Jungar coalfield is one of the major coal resource mining sites in northwest China.Water damage at the bottom of the coal seam has become an important factor that is limiting the development of the local economy and society.Therefore,it is important to identify the recharge relationship and circulation characteristics between atmospheric precipitation,surface water,and groundwater in the Jungar coalfield to provide a theoretical basis for the scientific development of coal resources and the effective restoration of groundwater resources in the area. Environmental isotope method,water chemistry analysis methods,and HYSPLIT applied to the groundwater of the Jungar coalfield.Through historical data collection,field survey sampling,and indoor analysis,the water chemistry composition and environmental isotope characteristics of atmospheric precipitation,surface water and groundwater,the main sources of atmospheric precipitation,surface water and groundwater transformation relationships were analyzed.The results show that:(1) Surface water has low mineralization and is weakly alkaline,and the water chemistry type is mainly HCO3·SO4·Cl-Ca type water.The overall mineralization of groundwater is low and weakly alkaline,and the water chemistry type is mainly HCO3-Na·Ca type,ClNa type,HCO3-Ca·Mg type,and HCO3·Cl-Na type water.(2) The average value of δ（D）of Yellow River water is -79.6‰,and the δ（18.O） is -10.7‰,respectively.The average value of δ（D） of Quaternary water is -66.25‰,and the δ（18.O） is -9.1‰,respectively.The average value of δ（D） of Cretaceous water is -70.6‰,and theδ（18.O） is -9.3‰,respectively.The average value of δ（D） of CarboniferousPermian water is -77.07‰,and the δ（18.O） is -9.9‰,respectively.The average value of CambrianOrdovician water δ（D） average value is -75.73‰,δ（18.O） is -10.06‰.Atmospheric precipitation is influenced by polar air masses and southeastern monsoons,and the principal sources are westerly water vapor,surface water,and groundwater vapor evaporation recirculation.(3) The fourth system water has high tritium content,the presence of nuclear explosive tritium,and excellent groundwater runoff conditions.The Cretaceous water has low tritium content and is a mixture of groundwater recharged before 1952 and recently recharged water.The CarboniferousPermian water contains a wide range of tritium content,including groundwater recharged before 1952 and modern water.The CambrianOrdovician water contains a wide range of tritium content,including groundwater recharged before 1952,modern water,and mixed water.(4) The recharge ratio of atmospheric precipitation to CambrianAustralian water ranges from 0.98% to 91.7%,with an average recharge rate of 61.2%.The recharge ratio of surface water (referred to as Yellow River water) to CambrianOrdovician water ranges from 0.83% to 90.2%,with an average recharge rate of 38.8%.Among them,the recharge ratio of Yellow River water to CambrianOrdovician water is larger in Longwanggou,Suancigou,and Huangyuchuan well field,which is influenced by the development of geological structures. The fault zone and the fracture zone of the fold axis are the main waterconducting channels between different aquifers.Atmospheric precipitation and the Yellow River are the principal sources of groundwater recharge.The precipitation vapor sources are mainly westerly water vapor,surface water,and groundwater vapor evaporation recirculation.Highly pressurized head CambrianOrdovician karst fracture water crossflow recharges the Fourth Series and sandstone fracture water.The pore water of the Fourth Series recharges the fracture water of the CarboniferousPermian sandstone downward through the fracture development zone of the unconformity contact surface between the strata.The recharge ratio of the Yellow River to Cambrian-Australian water is influenced by the development of geological structures.In Longwanggou,Suancigou,and Huangyuchuan well field,the proportion of recharge of the Yellow River water to CambrianOrdovician water is larger.
2021, 19(3):572-580,605.
Abstract:
China is facing with water shortages,and the per capita water resources of China are below the global average.Therefore,to solve the problem of water shortages in the northern region,the Chinese government launched the SouthtoNorth Water Diversion Project (SNDP) in 2002.The Eastern Route Project (SNWD-ERP) is an integral part of the SouthtoNorth Water Diversion Project.The SNWD-ERP diverts water from the lower reaches of the Yangtze River to Shandong and Hebei Provinces,and Tianjin municipality with a complex hydraulic system of interconnected lakes,rivers,and canals,which provides important guarantees for the socioeconomic development of the northern region.Nansi Lake (NSL)which is located in Shandong Province,China,is an important storage hub for the SNWD-ERP.Since the SNWD-ERP has officially been in operation,it was found that the concentrations of sulfate rapidly increased after water transfer from Jiangsu Province to Shandong Province,especially in NSL,where the sulfate concentrations reached 400 mg/L.This was a huge impact on the water quality of the SNWDERP.After sulfate was dissolved in the water,it was stable and easy to accumulate in the water body.Excessive sulfate concentration not only limited the use of water transfer but also had adverse effects on the human body.Therefore,accurately identifying the source of sulfate in lakes and channels and related biogeochemical processes are important conditions for protecting and managing water resources.To ascertain the source of sulfate pollution during the water diversion period in the SNWDERP in Shandong province,monitoring points in NSL and its surrounding rivers and groundwater distribution were sampled to analyze the characteristics of hydrochemical and sulfate concentration distribution in NSL.The δ(34SSO4) value was used to calculate the contribution rate of each direct source in the diversion water period,and combining with the δ(18OSO4) value to explore the sources of sulfate in NSL and the major sources of sulfate in inflowing rivers in the diversion water period.The variety rules of sulfate sources in NSL are analyzed to search for the potential sources of sulfate pollution and appropriate treatment techniques were investigaled to reduce sulfate concentration and ensure the safety of water supply,and provide data support in the SNWD-ERP. The main result were as follows:(1) in the diversion water period,the pH of NSL and its inflowing rivers was alkalescence,and groundwater was neutral.The sulfate concentration in NSL gradually increased from south-to-north,even as high as 631。50 mg/L in the Nanyang sub lake (NE).The main water types of NSL were Na+SO42-Cl- and Na+SO42-HCO3,which was mainly affected by carbonate weathering.But the water types in groundwater were Ca2+SO42-Cl-,which was mainly affected by the dissolution of evaporite salt and the weathering of silicate.(2) Evaporite dissolution has the largest sulfate contribution rate in NSL,reaching 52.18 %.But the direct source of sulfate in Nanyang sub lake was mainly carried by rivers,especially Zhuzhaoxin River,Old Canal,and Wanfu River.The contribution rate to Nanyang Lake sulfate was much higher than that of evaporite dissolution,and contribution rate of water transfer in NSL from Jiangsu was only 5.34 %.(3) For the inflowing river,sewage inflow was the main source of sulfate in the Baima River,Chengguo River,Panlong River,and Dongyu River,and the main sulfate source in Zhuzhaoxin River,Wanfu River,Old Wanfu River,Guangfu River,and Old Canal were evaporite dissolution,while the Zhushui River sulfate was affected by both sewage and evaporite dissolution.(4) Based on the analysis of the source of sulfate in the Nansi Lake basin during the water transfer period,a reasonable sulfate prevention and control system was constructed.For rivers with a high contribution rate,the "river chief system" should be adopted to assign responsibility to people,and reasonable treatment measures should be taken before the water is transferred and used.
China is facing with water shortages,and the per capita water resources of China are below the global average.Therefore,to solve the problem of water shortages in the northern region,the Chinese government launched the SouthtoNorth Water Diversion Project (SNDP) in 2002.The Eastern Route Project (SNWD-ERP) is an integral part of the SouthtoNorth Water Diversion Project.The SNWD-ERP diverts water from the lower reaches of the Yangtze River to Shandong and Hebei Provinces,and Tianjin municipality with a complex hydraulic system of interconnected lakes,rivers,and canals,which provides important guarantees for the socioeconomic development of the northern region.Nansi Lake (NSL)which is located in Shandong Province,China,is an important storage hub for the SNWD-ERP.Since the SNWD-ERP has officially been in operation,it was found that the concentrations of sulfate rapidly increased after water transfer from Jiangsu Province to Shandong Province,especially in NSL,where the sulfate concentrations reached 400 mg/L.This was a huge impact on the water quality of the SNWDERP.After sulfate was dissolved in the water,it was stable and easy to accumulate in the water body.Excessive sulfate concentration not only limited the use of water transfer but also had adverse effects on the human body.Therefore,accurately identifying the source of sulfate in lakes and channels and related biogeochemical processes are important conditions for protecting and managing water resources.To ascertain the source of sulfate pollution during the water diversion period in the SNWDERP in Shandong province,monitoring points in NSL and its surrounding rivers and groundwater distribution were sampled to analyze the characteristics of hydrochemical and sulfate concentration distribution in NSL.The δ(34SSO4) value was used to calculate the contribution rate of each direct source in the diversion water period,and combining with the δ(18OSO4) value to explore the sources of sulfate in NSL and the major sources of sulfate in inflowing rivers in the diversion water period.The variety rules of sulfate sources in NSL are analyzed to search for the potential sources of sulfate pollution and appropriate treatment techniques were investigaled to reduce sulfate concentration and ensure the safety of water supply,and provide data support in the SNWD-ERP. The main result were as follows:(1) in the diversion water period,the pH of NSL and its inflowing rivers was alkalescence,and groundwater was neutral.The sulfate concentration in NSL gradually increased from south-to-north,even as high as 631。50 mg/L in the Nanyang sub lake (NE).The main water types of NSL were Na+SO42-Cl- and Na+SO42-HCO3,which was mainly affected by carbonate weathering.But the water types in groundwater were Ca2+SO42-Cl-,which was mainly affected by the dissolution of evaporite salt and the weathering of silicate.(2) Evaporite dissolution has the largest sulfate contribution rate in NSL,reaching 52.18 %.But the direct source of sulfate in Nanyang sub lake was mainly carried by rivers,especially Zhuzhaoxin River,Old Canal,and Wanfu River.The contribution rate to Nanyang Lake sulfate was much higher than that of evaporite dissolution,and contribution rate of water transfer in NSL from Jiangsu was only 5.34 %.(3) For the inflowing river,sewage inflow was the main source of sulfate in the Baima River,Chengguo River,Panlong River,and Dongyu River,and the main sulfate source in Zhuzhaoxin River,Wanfu River,Old Wanfu River,Guangfu River,and Old Canal were evaporite dissolution,while the Zhushui River sulfate was affected by both sewage and evaporite dissolution.(4) Based on the analysis of the source of sulfate in the Nansi Lake basin during the water transfer period,a reasonable sulfate prevention and control system was constructed.For rivers with a high contribution rate,the "river chief system" should be adopted to assign responsibility to people,and reasonable treatment measures should be taken before the water is transferred and used.
2021, 19(3):581-589.
Abstract:
The power generation efficiency problem and hydropower stations turbine abrasion overwhelmed water conservancy engineers,especially during the flood season,when heavy rains,and the inflow and sediment concentration have reached their peaks.The power generation efficiency of hydropower stations is the best during this period,while the flow components of the turbine are also subject to abrasion.The Xiangjiaba Hydropower Station is located in the lower reaches of the Jinsha River.After its completion,it exerts tremendous flood control and power generation benefits.As the core equipment of the power station,the performance of the hydraulic turbine and the reliability of its operation are some of the keys to whether it can exert engineering benefits.To understand the rules of damage to hydraulic turbines by sediment in time,and to study various protective measures to reduce the abrasion damage to the surface of the turbine′s flowpassing parts by the sand-containing water flow,it is necessary to carry out the medium– and long–term monitoring of the sediment of the typical units on the left and right banks of the Xiangjiaba Hydropower Station to provide data support for the subsequent development of hydraulic turbine protection measures. The Xiangjiaba Hydropower Station flood season from June to September is taken as the research object.The maximum sediment concentration is selected twice a month by taking into account the time difference of the sediment particle size distribution during the flood season.The silt is sampled by the machine.For each sample,the left and right bank typical units are selected and enter the designated water intake inside the turbine volute for water sample collection.A total of 8 samples were taken during the entire flood season.After sampling the laser particle size analyzer was used to analyze the volume percentage of the machinesilt particle size gradation.The characteristic law of particle size distribution was studied using multifractal analysis. The results show that the particle size of the machined sediment has good multifractal characteristics.Combined with the multifractal theory,the overall average inhomogeneity of the particle size distribution is D1（B2）＞D1（C1）＞D1（C2）＞D1（A2）＞D1（B1）＞D1（A1）＞D1（D2）＞D1（D1）.There is a certain threshold,so that when,the uneven size of the largest subset particle size distribution is D≥5(B2)＞D≥5(B1)＞D≥5(D2)＞D≥5(C2)＞D≥5(A2)＞D≥5(C1)＞D≥5(A1)＞D≥(D1),at that time,the unevensize of the smallest subset particle size distribution isD≤-7，D≤-7(C1)＞D≤-7(B2)＞D≤-7(A1)＞D≤-7(D1)＞D≤-7(C2)＞D≤-7(A2)＞D≤-7(D2)＞D≤-7(B1)(A1,B1,C1,D1 are the sediment sample numbers of the left bank unit,and A2,B2,C2,D2 is the sediment sample number of the right bank unit).Combined with the generalized dimensional spectrum,the nonuniform distribution of the largest subset and the smallest subset of the sediment size of the Xiangjiaba Hydropower Station can not be effectively compared.Combined with the multifractal singularity,the spectrum width is Δα1 and Δα2,and the uneven size of the largest subset particle size distribution is Δα1 (B2)>Δα1 (B1)>Δα1(D2)>Δα1 (C2)>Δα1 (A2)>Δα1 (C1)>Δα1 (A1)>Δα1 (D1).The smallest subset particle size distribution is Δα2 (C1)>Δα2 (B2)>Δα2 (A1)>Δα2 (D1)>Δα2 (C2)>Δα2 (A2)>Δα2 (D2)>Δα2 (B1). Combining the generalized dimensional spectrum and the multifractal singular spectrum,the two conclusions are the same regarding the local unevenness of the particle size distribution.Combined with the correlation analysis,the sediment refinement and the maximum subset distribution unevenness show good results.The negative correlation of the silt refinement has nothing to do with the uneven size of the smallest subset distribution.
The power generation efficiency problem and hydropower stations turbine abrasion overwhelmed water conservancy engineers,especially during the flood season,when heavy rains,and the inflow and sediment concentration have reached their peaks.The power generation efficiency of hydropower stations is the best during this period,while the flow components of the turbine are also subject to abrasion.The Xiangjiaba Hydropower Station is located in the lower reaches of the Jinsha River.After its completion,it exerts tremendous flood control and power generation benefits.As the core equipment of the power station,the performance of the hydraulic turbine and the reliability of its operation are some of the keys to whether it can exert engineering benefits.To understand the rules of damage to hydraulic turbines by sediment in time,and to study various protective measures to reduce the abrasion damage to the surface of the turbine′s flowpassing parts by the sand-containing water flow,it is necessary to carry out the medium– and long–term monitoring of the sediment of the typical units on the left and right banks of the Xiangjiaba Hydropower Station to provide data support for the subsequent development of hydraulic turbine protection measures. The Xiangjiaba Hydropower Station flood season from June to September is taken as the research object.The maximum sediment concentration is selected twice a month by taking into account the time difference of the sediment particle size distribution during the flood season.The silt is sampled by the machine.For each sample,the left and right bank typical units are selected and enter the designated water intake inside the turbine volute for water sample collection.A total of 8 samples were taken during the entire flood season.After sampling the laser particle size analyzer was used to analyze the volume percentage of the machinesilt particle size gradation.The characteristic law of particle size distribution was studied using multifractal analysis. The results show that the particle size of the machined sediment has good multifractal characteristics.Combined with the multifractal theory,the overall average inhomogeneity of the particle size distribution is D1（B2）＞D1（C1）＞D1（C2）＞D1（A2）＞D1（B1）＞D1（A1）＞D1（D2）＞D1（D1）.There is a certain threshold,so that when,the uneven size of the largest subset particle size distribution is D≥5(B2)＞D≥5(B1)＞D≥5(D2)＞D≥5(C2)＞D≥5(A2)＞D≥5(C1)＞D≥5(A1)＞D≥(D1),at that time,the unevensize of the smallest subset particle size distribution isD≤-7，D≤-7(C1)＞D≤-7(B2)＞D≤-7(A1)＞D≤-7(D1)＞D≤-7(C2)＞D≤-7(A2)＞D≤-7(D2)＞D≤-7(B1)(A1,B1,C1,D1 are the sediment sample numbers of the left bank unit,and A2,B2,C2,D2 is the sediment sample number of the right bank unit).Combined with the generalized dimensional spectrum,the nonuniform distribution of the largest subset and the smallest subset of the sediment size of the Xiangjiaba Hydropower Station can not be effectively compared.Combined with the multifractal singularity,the spectrum width is Δα1 and Δα2,and the uneven size of the largest subset particle size distribution is Δα1 (B2)>Δα1 (B1)>Δα1(D2)>Δα1 (C2)>Δα1 (A2)>Δα1 (C1)>Δα1 (A1)>Δα1 (D1).The smallest subset particle size distribution is Δα2 (C1)>Δα2 (B2)>Δα2 (A1)>Δα2 (D1)>Δα2 (C2)>Δα2 (A2)>Δα2 (D2)>Δα2 (B1). Combining the generalized dimensional spectrum and the multifractal singular spectrum,the two conclusions are the same regarding the local unevenness of the particle size distribution.Combined with the correlation analysis,the sediment refinement and the maximum subset distribution unevenness show good results.The negative correlation of the silt refinement has nothing to do with the uneven size of the smallest subset distribution.
ZHANG Rongxuan
,
LEI Xiaohui
,
LU Longbin
,
JING Xiang
,
ZHANG Zhao
,
KONG Lingzhong
,
LIU Xiaolian
,
LI Yueqiang
2021, 19(3):590-597.
Abstract:
With the rapid development of industry,agriculture, and the improvement of residents′ living standards,the demand of regional water resources has also increased.The water delivery project of series cascade pumping stations has played a huge role in realizing the rational allocation and scientific dispatch of water resources in different regions.The research on the optimal dispatching of water delivery project of series cascade pumping station has always been a common concern in the field of water conservancy system optimization because it has the characteristics of long distance along the line,large water flows,large head change,and large energy consumption.Most researches at home and abroad usually use optimization algorithms such as linearnonlinear programming,dynamic programming,ant colony algorithm,particle swarm optimization,and large-scale system decomposition.These traditional optimization algorithms are used in solving relatively complex mathematical models.Each has its advantages,but at the same time,it is easy to fall into the "dimensionality disaster",which leads to a huge amount of calculation and is not helpful to the generation of results. At present,most researches on the head optimization distribution of cascade pumping stations are carried out based on design conditions or certain specific operating conditions,and little attention is paid to the optimal operation of the pumping station group systems under nondesign conditions.The water delivery system of the cascade pumping station group is often operating under undesigned conditions,affected by factors such as changes in water load,fluctuations in the incoming water process,and adjustment of pumping station units.Taking the water transfer section from the north to the Huaijiang River as the research area,using a genetic algorithmbased model for the optimization of the head distribution of the series cascade pumping station,a study on the head optimization distribution of the water delivery system of the series cascade pumping station is carried out.The efficient operation plan of the water delivery system of the river water north section is analyzed and calculated.In this project,genetic algorithm is used to solve the problem.The modelling first determines the objective function,decision variables,and constraint conditions,and then performs preprocessing on the flow operation interval and discrete step length,to determine the set of operating conditions of the pumping station.The flow individuals are generated randomly by coding to solve the problem in the next step. (1) Based on the optimized efficiency of the Xifeihe,Kantuanan,Xifeihebei,Zhuji,and Longde single-stage pumping stations and the hydraulic calculation results between the five stages of the Xifeihe-Longde pumping station section,the head optimization of the series cascade pumping station was constructed,and then the distribution model is calculated for the optimal head distribution in each station under the design conditions and different cascade net head conditions of the water delivery system of the river water north section.The result shows that the total efficiency of the cascade pumping station is increased by 286% after the calculation of the optimized model.(2) Simultaneously,the optimal head distribution scheme,the optimal water level combination between the cascades,and the optimal efficiency of the water conveyance system are calculated for any net head corresponding to different water conveyance flow conditions under the off-design condition.Comprehensive analysis and optimization of the calculation results can provide a basis for the operation of the water transfer system of the cascade pumping station under different working conditions. This paper constructs a head optimization distribution model for series cascade pumping stations is constructed based on the genetic algorithm,which is applied to the economic operation of the water transfer section of the water diversion from the Yangtze River to the Huaijiang River to achieve the purpose of efficient operation and has high application value.Therefore,it is suitable for medium and large cascade pumping station projects.The study of the economic operation has an important significance,and this article is aimed at maximizing efficiency,and the results can be applied to the optimization research of time-of-use electricity rates so that the entire system can obtain the best comprehensive benefits.
With the rapid development of industry,agriculture, and the improvement of residents′ living standards,the demand of regional water resources has also increased.The water delivery project of series cascade pumping stations has played a huge role in realizing the rational allocation and scientific dispatch of water resources in different regions.The research on the optimal dispatching of water delivery project of series cascade pumping station has always been a common concern in the field of water conservancy system optimization because it has the characteristics of long distance along the line,large water flows,large head change,and large energy consumption.Most researches at home and abroad usually use optimization algorithms such as linearnonlinear programming,dynamic programming,ant colony algorithm,particle swarm optimization,and large-scale system decomposition.These traditional optimization algorithms are used in solving relatively complex mathematical models.Each has its advantages,but at the same time,it is easy to fall into the "dimensionality disaster",which leads to a huge amount of calculation and is not helpful to the generation of results. At present,most researches on the head optimization distribution of cascade pumping stations are carried out based on design conditions or certain specific operating conditions,and little attention is paid to the optimal operation of the pumping station group systems under nondesign conditions.The water delivery system of the cascade pumping station group is often operating under undesigned conditions,affected by factors such as changes in water load,fluctuations in the incoming water process,and adjustment of pumping station units.Taking the water transfer section from the north to the Huaijiang River as the research area,using a genetic algorithmbased model for the optimization of the head distribution of the series cascade pumping station,a study on the head optimization distribution of the water delivery system of the series cascade pumping station is carried out.The efficient operation plan of the water delivery system of the river water north section is analyzed and calculated.In this project,genetic algorithm is used to solve the problem.The modelling first determines the objective function,decision variables,and constraint conditions,and then performs preprocessing on the flow operation interval and discrete step length,to determine the set of operating conditions of the pumping station.The flow individuals are generated randomly by coding to solve the problem in the next step. (1) Based on the optimized efficiency of the Xifeihe,Kantuanan,Xifeihebei,Zhuji,and Longde single-stage pumping stations and the hydraulic calculation results between the five stages of the Xifeihe-Longde pumping station section,the head optimization of the series cascade pumping station was constructed,and then the distribution model is calculated for the optimal head distribution in each station under the design conditions and different cascade net head conditions of the water delivery system of the river water north section.The result shows that the total efficiency of the cascade pumping station is increased by 286% after the calculation of the optimized model.(2) Simultaneously,the optimal head distribution scheme,the optimal water level combination between the cascades,and the optimal efficiency of the water conveyance system are calculated for any net head corresponding to different water conveyance flow conditions under the off-design condition.Comprehensive analysis and optimization of the calculation results can provide a basis for the operation of the water transfer system of the cascade pumping station under different working conditions. This paper constructs a head optimization distribution model for series cascade pumping stations is constructed based on the genetic algorithm,which is applied to the economic operation of the water transfer section of the water diversion from the Yangtze River to the Huaijiang River to achieve the purpose of efficient operation and has high application value.Therefore,it is suitable for medium and large cascade pumping station projects.The study of the economic operation has an important significance,and this article is aimed at maximizing efficiency,and the results can be applied to the optimization research of time-of-use electricity rates so that the entire system can obtain the best comprehensive benefits.
2021, 19(3):598-605.
Abstract:
The storage of a reservoir with low regulation capacity is often small,and the reservoir water level is sensitive to changes in the outflow process.In flood control optimization process operation,small changes in outflows may lead to large variations in the reservoir water level,resulting in the reservoir water level frequently approaches the upper and lower controlled boundaries.To meet the maximum and minimum water level constraints,it will cause severe fluctuations of the reservoir outflow process and affect the operability of the optimal solution. The maximum peak-reduction criterion is taken as the objective function,considering the constraint conditions such as the mass balance,the maximum and minimum water levels,the discharge capacity,the fluctuation of the outflow period,and the return storage level at the end of the operation horizon.The optimized dispatching model is developed for reservoir flood control.Based on the operation process of the realtime flood control operation of the reservoir and the mechanism that the reservoir water levels frequently approach the upper and lower controlled boundaries in the flood control operation,the improved stagewise trialanderror method with low regulation capacity is proposed.The maximization of real-time flood regulation capacity and the operability of the optimal operation solutions is taking into account in this method and proposes the principle of "conceptual" segment.The whole operation period is divided into five stages including the predischarge stage,maintenance stage,flood storage stage,safety drawdown stage,and final drawdown stage.Based on the principle of segmented mass balance,with the principle of homogenizing the outflow process,a segmented trial calculation strategy and implementation process for dynamically determining the start and end times of each stage are proposed using the realtime flooding process of the storage.Furthermore,the uniform outflow process iterative optimization method is proposed. Taking the Fuchunjiang Reservoir as the research subject,the simulation operation of the improved stagewise trialanderror method was carried out.The results were compared with the original stage-wise trial-and-error method and reveal the following: (1) It was found that with the improved stagewise trialanderror method,various constraints are strictly met.However,the original stagewise trialanderror method had a certain deviation from the given water level control conditions.The lowest water level was 0.38 m higher,and the highest water level was lower by 0.2 m,and the adjustable flood control storage capacity was not fully used. (2) From the perspective of the outflow process,the improved stagewise trialanderror method had a regular outflow process with clear stages,and the outflow process at each stage conformed to preexpectations,with reasonable results and strong operability.The "sawtooth" in the outflow process of the original stagewise trialanderror method operation results was more serious,especially in the prerelease stage,where the prerelease period was short and large. (3) Due to the "precision" water level control of the improved stage-wise trial-and-error method and the full utilization of the adjustable flood control storage capacity,the peak reduction rate was 16.2%,which was better than the 14.3% peak reduction rate produced by the original stagewise trialanderror method,and the peak reduction rate was increased by 13.3%. To address the poor performance of the original stagewise trialanderror method applied to reservoirs with low regulation capacity under weekly regulation,an improved stagewise trialanderror method was proposed,which had the following advantages compared with the original one: (1) It could better adapt to the characteristics of reservoirs with small storage and low regulation capacity.It may overcome the shortcoming that the upper and lower limits of reservoir storage capacity and discharge capacity were frequently broken in the original one,which brought a good stability performance to the algorithm. (2) The calculation principle of the improved stagewise trialanderror method was simple,and the segmentation iteration process was complete and clear.A reasonable and operability operation solution could be easily obtained. (3) The case study in Fuchunjiang Reservoir proved that the improved stagewise trialanderror method achieved good application results in the flood control operation.
The storage of a reservoir with low regulation capacity is often small,and the reservoir water level is sensitive to changes in the outflow process.In flood control optimization process operation,small changes in outflows may lead to large variations in the reservoir water level,resulting in the reservoir water level frequently approaches the upper and lower controlled boundaries.To meet the maximum and minimum water level constraints,it will cause severe fluctuations of the reservoir outflow process and affect the operability of the optimal solution. The maximum peak-reduction criterion is taken as the objective function,considering the constraint conditions such as the mass balance,the maximum and minimum water levels,the discharge capacity,the fluctuation of the outflow period,and the return storage level at the end of the operation horizon.The optimized dispatching model is developed for reservoir flood control.Based on the operation process of the realtime flood control operation of the reservoir and the mechanism that the reservoir water levels frequently approach the upper and lower controlled boundaries in the flood control operation,the improved stagewise trialanderror method with low regulation capacity is proposed.The maximization of real-time flood regulation capacity and the operability of the optimal operation solutions is taking into account in this method and proposes the principle of "conceptual" segment.The whole operation period is divided into five stages including the predischarge stage,maintenance stage,flood storage stage,safety drawdown stage,and final drawdown stage.Based on the principle of segmented mass balance,with the principle of homogenizing the outflow process,a segmented trial calculation strategy and implementation process for dynamically determining the start and end times of each stage are proposed using the realtime flooding process of the storage.Furthermore,the uniform outflow process iterative optimization method is proposed. Taking the Fuchunjiang Reservoir as the research subject,the simulation operation of the improved stagewise trialanderror method was carried out.The results were compared with the original stage-wise trial-and-error method and reveal the following: (1) It was found that with the improved stagewise trialanderror method,various constraints are strictly met.However,the original stagewise trialanderror method had a certain deviation from the given water level control conditions.The lowest water level was 0.38 m higher,and the highest water level was lower by 0.2 m,and the adjustable flood control storage capacity was not fully used. (2) From the perspective of the outflow process,the improved stagewise trialanderror method had a regular outflow process with clear stages,and the outflow process at each stage conformed to preexpectations,with reasonable results and strong operability.The "sawtooth" in the outflow process of the original stagewise trialanderror method operation results was more serious,especially in the prerelease stage,where the prerelease period was short and large. (3) Due to the "precision" water level control of the improved stage-wise trial-and-error method and the full utilization of the adjustable flood control storage capacity,the peak reduction rate was 16.2%,which was better than the 14.3% peak reduction rate produced by the original stagewise trialanderror method,and the peak reduction rate was increased by 13.3%. To address the poor performance of the original stagewise trialanderror method applied to reservoirs with low regulation capacity under weekly regulation,an improved stagewise trialanderror method was proposed,which had the following advantages compared with the original one: (1) It could better adapt to the characteristics of reservoirs with small storage and low regulation capacity.It may overcome the shortcoming that the upper and lower limits of reservoir storage capacity and discharge capacity were frequently broken in the original one,which brought a good stability performance to the algorithm. (2) The calculation principle of the improved stagewise trialanderror method was simple,and the segmentation iteration process was complete and clear.A reasonable and operability operation solution could be easily obtained. (3) The case study in Fuchunjiang Reservoir proved that the improved stagewise trialanderror method achieved good application results in the flood control operation.
2021, 19(3):606-613,624.
Abstract:
Sand ripple movement widely exists in the impinged river and coastal zone,and the ripple shape leads to the obvious change of bed surface roughness,which has a significant influence on the total resistance of the bottom bed.For ripple height and ripple length calculation methods,many scholars did comprehensive research,but due to the diversity of each factor affect the ripple scale and the complexity of interconnected,the different research methods,and the differences between the source and water features,lead to the existing formula of ripple shape structure that is diversiform,and the calculation formula lack universality due to an error in the formula under different hydraulic conditions. The general expression for calculating ripple height and ripple length was established based on adapting wave conditions to ripple shape.A total of 385 groups of field measured data and flume experimental data were used for fitting analysis from 1957 to 2018,and the calculation formula for ripple height and ripple length based on the mobility number of near-bottom wave water quality point was obtained.Compared with the existing ripple calculation models,the influence rules of the mobility number on the ripple shape and the advantages and disadvantages of each model were analyzed and demonstrated.Two statistical error parameters RMSE and MAE were used to evaluate the degree of concordance [JP3]between the predicted ripple height and ripple length of each prediction model and the actual value,and the accuracy of the formula was measured according to the calculation error.At the same time,the calculation formulas of ripple height and ripple length were applied to calculate the bottom rough height of the bed.The variation characteristics of ripple surface roughness under wave action and the rationality of the ripple formula were discussed by comparing with the existing models,and the parameters in the formula were calibrated using measured data.The formula of ripple shape and bottom roughness were introduced into the calculation of the bottom friction coefficient of waves,and the influence of the calculation method on the calculation result of the bottom friction coefficient was discussed. The Eq.(12) and Eq.(13) for the ripple height and the ripple length were obtained by fitting analysis of measured data.The analysis showed that the dimensionless ripple height and ripple length were related to the mobility number,and decrease with the increase of the mobility number.Based on measured data,compared with Ni81 regular wave model,Ni81 irregular wave model,VR89 model,and GK04 model,the calculated values of Eq.(12) and Eq.(13) had higher accuracy,which could be applied to the prediction of the ripple height and the ripple length in both field flow and flume experiment,and the expression form of the formula was more general.The bottom roughness had a high sensitivity to wave parameters.According to the measured value,the parameter α in the bottom roughness formula was calibrated,and α was set as 245.The ripple scale formula was substituted into the bottom friction coefficient under wave action,and the calculated results were in good agreement with the representative experimental data,indicating that the newly obtained ripple scale formula could be applied for bottom friction coefficient calculation.The shape of the bed surface and the ripple scale affect the energy dissipation and flow state of the wave bottom boundary layer,and the ripple scale had a significant effect on the roughness of the bed surface.However,there were some differences in the calculation methods of the ripple height and the ripple length.The new formula for calculating the shape of the ripple was more accurate and could better reflect the influence of the ripple scale on the friction coefficient of wave bottom.The new formula is more general in expression form and easy to be applied in engineering.This paper provides an effective basis for analyzing the shape resistance of bed surface under wave action and also provides a reference for further studying the total resistance of bed surface and sediment transport.
Sand ripple movement widely exists in the impinged river and coastal zone,and the ripple shape leads to the obvious change of bed surface roughness,which has a significant influence on the total resistance of the bottom bed.For ripple height and ripple length calculation methods,many scholars did comprehensive research,but due to the diversity of each factor affect the ripple scale and the complexity of interconnected,the different research methods,and the differences between the source and water features,lead to the existing formula of ripple shape structure that is diversiform,and the calculation formula lack universality due to an error in the formula under different hydraulic conditions. The general expression for calculating ripple height and ripple length was established based on adapting wave conditions to ripple shape.A total of 385 groups of field measured data and flume experimental data were used for fitting analysis from 1957 to 2018,and the calculation formula for ripple height and ripple length based on the mobility number of near-bottom wave water quality point was obtained.Compared with the existing ripple calculation models,the influence rules of the mobility number on the ripple shape and the advantages and disadvantages of each model were analyzed and demonstrated.Two statistical error parameters RMSE and MAE were used to evaluate the degree of concordance [JP3]between the predicted ripple height and ripple length of each prediction model and the actual value,and the accuracy of the formula was measured according to the calculation error.At the same time,the calculation formulas of ripple height and ripple length were applied to calculate the bottom rough height of the bed.The variation characteristics of ripple surface roughness under wave action and the rationality of the ripple formula were discussed by comparing with the existing models,and the parameters in the formula were calibrated using measured data.The formula of ripple shape and bottom roughness were introduced into the calculation of the bottom friction coefficient of waves,and the influence of the calculation method on the calculation result of the bottom friction coefficient was discussed. The Eq.(12) and Eq.(13) for the ripple height and the ripple length were obtained by fitting analysis of measured data.The analysis showed that the dimensionless ripple height and ripple length were related to the mobility number,and decrease with the increase of the mobility number.Based on measured data,compared with Ni81 regular wave model,Ni81 irregular wave model,VR89 model,and GK04 model,the calculated values of Eq.(12) and Eq.(13) had higher accuracy,which could be applied to the prediction of the ripple height and the ripple length in both field flow and flume experiment,and the expression form of the formula was more general.The bottom roughness had a high sensitivity to wave parameters.According to the measured value,the parameter α in the bottom roughness formula was calibrated,and α was set as 245.The ripple scale formula was substituted into the bottom friction coefficient under wave action,and the calculated results were in good agreement with the representative experimental data,indicating that the newly obtained ripple scale formula could be applied for bottom friction coefficient calculation.The shape of the bed surface and the ripple scale affect the energy dissipation and flow state of the wave bottom boundary layer,and the ripple scale had a significant effect on the roughness of the bed surface.However,there were some differences in the calculation methods of the ripple height and the ripple length.The new formula for calculating the shape of the ripple was more accurate and could better reflect the influence of the ripple scale on the friction coefficient of wave bottom.The new formula is more general in expression form and easy to be applied in engineering.This paper provides an effective basis for analyzing the shape resistance of bed surface under wave action and also provides a reference for further studying the total resistance of bed surface and sediment transport.
2021, 19(3):614-624.
Abstract:
The construction of reinforced concrete levees damaged the resilience of the riparian zone to resist flood.It was also unable to cope with extreme flood disasters that exceeded the planned flood control standards under climate change conditions.Therefore,the traditional flood-control strategy by increasing the elevation of concrete floodcontrol levee was not the most effective way to solve the problem of urban flood control safety.It was urgent to establish an elevation optimization model of flood control levee considering ecological resilience of riparian zone,so as to provide decision support for the formulation of urban levee safety optimization scheme in the context of climate change. Aiming at the uncertainty in the elevation optimization model of flood control levee,an interval mixedinteger stochastic robust optimization model was established.The model could not only regulate the ecological resilience of riparian zone to resist flood,but also deal with the uncertainty of parameters in the optimal design of levee elevation.These uncertain parameters included the flood peak level in the form of the probability distribution function and the economic cost in the form of interval value.Besides,considering the dynamic change of riparian ecosystem resilience to flood due to the impact of climate change,binary variables were introduced into the model to indicate whether the restoration and reconstruction of the ecological riparian zone were necessary.Moreover,decision-makers could also make a quantitative tradeoff between system stability and economy by setting different risk parameters. The developed model was applied to three planned areas located on both sides of the urban river.Under the condition of the different flood peak levels and riparian ecological resilience,the optimal design elevation of the flood control levee was obtained.The result showed that when the value of the risk parameter was 0.5,the system cost was ［4.872,6.552］ million yuan.Before ecological reconstruction,the designed elevations of the flood control levees in the three areas were 118,［13.0,13.8］,13.9 meters,respectively.It could be seen that the impact of uncertain factors caused by climate change on the second region was more obvious.Affected by extreme flood disasters,ecological reconstruction was needed in the first area to increase the resilience of the riparian zone against floods when the flood level ranges from mediumhigh to veryhigh.Correspondingly,the levee needed to be raised ［2.8,3.5］,［3.5,4.0］ ，and ［2.8,3.5］ meters respectively.The situation in the second area seemed to be different.It only carried out ecological reconstruction at very-high flood level,and after the reconstruction,the floodcontrol levee in this area increased ［3.0,4.0］ meters.In addition,when the flood level was medium,high,and veryhigh,the flood overflowed the levee and submerged the third area.Furthermore,when the value of the risk parameter increased from 0 to 1,the system cost increased from ［4.809,6.437］ million yuan to ［4.926,6.656］ million yuan.At the same time,the stability of the model result was improved. It could be seen from the results that when the overall flood control capacity of the region was not enough to resist the intrusion of the extreme flood,the model would prioritize the allocation of excessive flood to subareas where the cost of flood damage was lower.Also,it must be recognized that there was a trade-off between system stability and economy.Therefore,in practical application,decisionmakers should comprehensively consider the extreme flood risk caused by climate change and the system′s resilience to resist extreme floods.Based on this,appropriate risk parameter values should be selected to control the proportionality of the optimization results,so as to obtain a better decisionmaking scheme.The results of the case showed that the model could provide decisionmakers with a reasonable flood control optimization strategy that considered the ecological resilience of riparian zones,and could provide a reference for the study of urban levee safety strategy under climate change.
The construction of reinforced concrete levees damaged the resilience of the riparian zone to resist flood.It was also unable to cope with extreme flood disasters that exceeded the planned flood control standards under climate change conditions.Therefore,the traditional flood-control strategy by increasing the elevation of concrete floodcontrol levee was not the most effective way to solve the problem of urban flood control safety.It was urgent to establish an elevation optimization model of flood control levee considering ecological resilience of riparian zone,so as to provide decision support for the formulation of urban levee safety optimization scheme in the context of climate change. Aiming at the uncertainty in the elevation optimization model of flood control levee,an interval mixedinteger stochastic robust optimization model was established.The model could not only regulate the ecological resilience of riparian zone to resist flood,but also deal with the uncertainty of parameters in the optimal design of levee elevation.These uncertain parameters included the flood peak level in the form of the probability distribution function and the economic cost in the form of interval value.Besides,considering the dynamic change of riparian ecosystem resilience to flood due to the impact of climate change,binary variables were introduced into the model to indicate whether the restoration and reconstruction of the ecological riparian zone were necessary.Moreover,decision-makers could also make a quantitative tradeoff between system stability and economy by setting different risk parameters. The developed model was applied to three planned areas located on both sides of the urban river.Under the condition of the different flood peak levels and riparian ecological resilience,the optimal design elevation of the flood control levee was obtained.The result showed that when the value of the risk parameter was 0.5,the system cost was ［4.872,6.552］ million yuan.Before ecological reconstruction,the designed elevations of the flood control levees in the three areas were 118,［13.0,13.8］,13.9 meters,respectively.It could be seen that the impact of uncertain factors caused by climate change on the second region was more obvious.Affected by extreme flood disasters,ecological reconstruction was needed in the first area to increase the resilience of the riparian zone against floods when the flood level ranges from mediumhigh to veryhigh.Correspondingly,the levee needed to be raised ［2.8,3.5］,［3.5,4.0］ ，and ［2.8,3.5］ meters respectively.The situation in the second area seemed to be different.It only carried out ecological reconstruction at very-high flood level,and after the reconstruction,the floodcontrol levee in this area increased ［3.0,4.0］ meters.In addition,when the flood level was medium,high,and veryhigh,the flood overflowed the levee and submerged the third area.Furthermore,when the value of the risk parameter increased from 0 to 1,the system cost increased from ［4.809,6.437］ million yuan to ［4.926,6.656］ million yuan.At the same time,the stability of the model result was improved. It could be seen from the results that when the overall flood control capacity of the region was not enough to resist the intrusion of the extreme flood,the model would prioritize the allocation of excessive flood to subareas where the cost of flood damage was lower.Also,it must be recognized that there was a trade-off between system stability and economy.Therefore,in practical application,decisionmakers should comprehensively consider the extreme flood risk caused by climate change and the system′s resilience to resist extreme floods.Based on this,appropriate risk parameter values should be selected to control the proportionality of the optimization results,so as to obtain a better decisionmaking scheme.The results of the case showed that the model could provide decisionmakers with a reasonable flood control optimization strategy that considered the ecological resilience of riparian zones,and could provide a reference for the study of urban levee safety strategy under climate change.
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