Volume 20,Issue 2,2022 Table of Contents
2022, 20(2):209-217.
Abstract:
In the context of the prominent contradiction between supply and demand in China and the rapid growth of urban domestic water,reasonable control of the excessive growth of urban domestic water is the key to regulating economic and social water use and promoting sustainable social development.The tiered water pricing system can alleviate the trend of water stress through price leverage.However,the current domestic water quota standards for urban residents are generally too high,which can not effectively guide the implementation of the tiered water pricing system.The current water quota is determined concerning the relevant national and local quota standards.Although it has wide applicability,it is not typical and representative.How to determine a reasonable quota standard based on fully complying with regional differences is worthy of in-depth consideration. Through the combination of qualitative analysis and quantitative calculation,the strong correlation factors are explored that affect the domestic water quota.Pearson correlation analysis can explore the correlation between indicators from cross-sectional data.In addition,qualitative analysis can help for in-depth study of the law of urban domestic water use.Based on the full consideration of regional climatic conditions and economic development level,the model selected factors such as water price,per capita disposable income,and temperature as explanatory variables for urban household water quotas.The 2017 data of 293 prefecture-level cities across the country are used as a sample to construct a water demand function model.To better seek regional common features,the seven geographical regions of China were modeled separately.During data processing,the obvious centrifugal data and marginal data are excluded,and the number of valid samples accounts for about 98% of the total data volume.Then,a significant test on the constructed water demand function model is conducted to predict a reasonable water quota. The results show that the fit of the national and regional models is good,the coefficient of determination R2 of the model is above 0.5,and the corresponding significance level is much less than 0.05.The model is effective through the significance test.The model-fitting results are good.Cities with a model fitting deviation rate of less than 10% account for 61.5% of the effective samples,and cities with a deviation rate of less than 20% account for 86.5%.From the perspective of the zoning fitting effect,the deviation rate of north China and southwest region is mainly controlled below 10%,and the deviation rate of some cities in south China and east China region exceeds 20%.Among the three explanatory variables of the model,although the income variable conforms to a certain trend of change,with the increase of instability and uncertainty in the current international environment,the difficulty of income forecasting increases.The temperature variable has obvious regional characteristics.Although the fluctuation is small in a short period,as the risk of climate change intensifies.The temperature prediction method should be improved accordingly.Water price variables are affected by unpredictable policy factors,with the highest degree of uncertainty.The prediction model constructed according to geographical divisions reflects the common characteristics of the region.It is foreseeable that some cities have a large deviation rate when using the model to predict,but the model is still effective from the perspective of the region as a whole.In addition,it is found that the cities with high current per capita domestic water quotas are mostly located in the high water areas of southern China and the middle of China or near the water source areas.This part of the city has great water-saving potential.Under the guidance of water-saving awareness and policy pressure,the water-saving potential can be gradually released as a water-saving effect.By analyzing the elasticity coefficient of the model,it is found that in the era of rapid economic development in the country,although water prices and income are increasing at the same time,the impact of income on water demand is much greater than that of prices.Income growth will have a significant effect on living standards and water demand,but the price increase policy assisted by effective policies is still an important means to restrict water use.Finally,by setting the water consumption quota under the expected water fee expenditure and the water price under the expected quota standard,it can be found that,in 2025,the domestic water quota for residents in cities lacking water in the north will maintain the current level or slightly decline.However,the domestic water quota of cities with abundant water in the south has shown a significant downward trend,which means that the increase in prices in southern cities has a more obvious inhibitory effect on the domestic water quota of residents. To a certain extent,this shows that the rigid water consumption of residents in northern cities accounts for a relatively high proportion,while the enjoyment and luxury water consumption in southern cities accounts for a relatively large proportion.The results showed that:At annual scale,TRMM and CMORPH show higher detection accuracy than CHIRPS and PERSIANN_CDR,and terms of the spatial distribution characteristics of annual precipitation,only TRMM,CMORPH and CHIRPS could reflect its spatial distribution to varying degrees;At a monthly scale，TRMM and CMORPH still have high accuracy in precipitation estimation,and TRMM,CMORPH,and CHIRPS have different advantages in describing the spatial distribution of precipitation in different regions in YRB;At daily scale,the four satellite-based precipitation products have a strong ability to capture weak precipitation but have a poor ability to detect heavy precipitation;At spatial scale,the accuracy of the four types of satellite-based precipitation data is higher in high-altitude areas at daily and monthly scales,and there is no obvious change law at the annual scale. In general,among the four types of satellite-based precipitation products,TRMM and CMORPH have more advantages in different time scales in YRB,but the spatial distribution of the four types of products is significantly different in different regions and different time scales.This conclusion lays the foundation for the further development of high-temporal-resolution precipitation fusion products suitable for YRB.
In the context of the prominent contradiction between supply and demand in China and the rapid growth of urban domestic water,reasonable control of the excessive growth of urban domestic water is the key to regulating economic and social water use and promoting sustainable social development.The tiered water pricing system can alleviate the trend of water stress through price leverage.However,the current domestic water quota standards for urban residents are generally too high,which can not effectively guide the implementation of the tiered water pricing system.The current water quota is determined concerning the relevant national and local quota standards.Although it has wide applicability,it is not typical and representative.How to determine a reasonable quota standard based on fully complying with regional differences is worthy of in-depth consideration. Through the combination of qualitative analysis and quantitative calculation,the strong correlation factors are explored that affect the domestic water quota.Pearson correlation analysis can explore the correlation between indicators from cross-sectional data.In addition,qualitative analysis can help for in-depth study of the law of urban domestic water use.Based on the full consideration of regional climatic conditions and economic development level,the model selected factors such as water price,per capita disposable income,and temperature as explanatory variables for urban household water quotas.The 2017 data of 293 prefecture-level cities across the country are used as a sample to construct a water demand function model.To better seek regional common features,the seven geographical regions of China were modeled separately.During data processing,the obvious centrifugal data and marginal data are excluded,and the number of valid samples accounts for about 98% of the total data volume.Then,a significant test on the constructed water demand function model is conducted to predict a reasonable water quota. The results show that the fit of the national and regional models is good,the coefficient of determination R2 of the model is above 0.5,and the corresponding significance level is much less than 0.05.The model is effective through the significance test.The model-fitting results are good.Cities with a model fitting deviation rate of less than 10% account for 61.5% of the effective samples,and cities with a deviation rate of less than 20% account for 86.5%.From the perspective of the zoning fitting effect,the deviation rate of north China and southwest region is mainly controlled below 10%,and the deviation rate of some cities in south China and east China region exceeds 20%.Among the three explanatory variables of the model,although the income variable conforms to a certain trend of change,with the increase of instability and uncertainty in the current international environment,the difficulty of income forecasting increases.The temperature variable has obvious regional characteristics.Although the fluctuation is small in a short period,as the risk of climate change intensifies.The temperature prediction method should be improved accordingly.Water price variables are affected by unpredictable policy factors,with the highest degree of uncertainty.The prediction model constructed according to geographical divisions reflects the common characteristics of the region.It is foreseeable that some cities have a large deviation rate when using the model to predict,but the model is still effective from the perspective of the region as a whole.In addition,it is found that the cities with high current per capita domestic water quotas are mostly located in the high water areas of southern China and the middle of China or near the water source areas.This part of the city has great water-saving potential.Under the guidance of water-saving awareness and policy pressure,the water-saving potential can be gradually released as a water-saving effect.By analyzing the elasticity coefficient of the model,it is found that in the era of rapid economic development in the country,although water prices and income are increasing at the same time,the impact of income on water demand is much greater than that of prices.Income growth will have a significant effect on living standards and water demand,but the price increase policy assisted by effective policies is still an important means to restrict water use.Finally,by setting the water consumption quota under the expected water fee expenditure and the water price under the expected quota standard,it can be found that,in 2025,the domestic water quota for residents in cities lacking water in the north will maintain the current level or slightly decline.However,the domestic water quota of cities with abundant water in the south has shown a significant downward trend,which means that the increase in prices in southern cities has a more obvious inhibitory effect on the domestic water quota of residents. To a certain extent,this shows that the rigid water consumption of residents in northern cities accounts for a relatively high proportion,while the enjoyment and luxury water consumption in southern cities accounts for a relatively large proportion.The results showed that:At annual scale,TRMM and CMORPH show higher detection accuracy than CHIRPS and PERSIANN_CDR,and terms of the spatial distribution characteristics of annual precipitation,only TRMM,CMORPH and CHIRPS could reflect its spatial distribution to varying degrees;At a monthly scale，TRMM and CMORPH still have high accuracy in precipitation estimation,and TRMM,CMORPH,and CHIRPS have different advantages in describing the spatial distribution of precipitation in different regions in YRB;At daily scale,the four satellite-based precipitation products have a strong ability to capture weak precipitation but have a poor ability to detect heavy precipitation;At spatial scale,the accuracy of the four types of satellite-based precipitation data is higher in high-altitude areas at daily and monthly scales,and there is no obvious change law at the annual scale. In general,among the four types of satellite-based precipitation products,TRMM and CMORPH have more advantages in different time scales in YRB,but the spatial distribution of the four types of products is significantly different in different regions and different time scales.This conclusion lays the foundation for the further development of high-temporal-resolution precipitation fusion products suitable for YRB.
2022, 20(2):218-229.
Abstract:
The complex interaction between surface water and groundwater interferes with the hydrological cycle affect the ecological status of the basin.Engineering measures for artificial collection of surface water and groundwater not only play a key role in solving the uneven distribution of water resources and the contradiction between water supply and demand,but also cause a series of ecological problems.Therefore,it is particularly important to explore the relevant mechanism of the interaction between surface water and groundwater.Through bibliometric analysis,it helps researchers grasp the current research status and hotspots in this field,which provides references for related research. Based on the Web of Science (WoS) data sources from 1985 to 2020,CiteSpace bibliometric software is used to quantitatively analyze the literature on the interaction of surface water and groundwater.By analyzing the cited documents,authors,research organizations,key words,and other elements,combined with the knowledge map,it displays the current research status,frontiers,and hotspots of this field. From 1985 to 2020,the total amount of scientific research papers in this field can be divided into three stages:slow growth-fluctuating,growth-steady growth and the increase in the number of published articles.The number of articles published in Journal of Hydrology,Environmental Earth Science,Hydrological Processes ranks top three.Research forces in this field are mainly concentrated in the United States,China,Australia.The author who published the most in the research period is Chunmiao Zheng.Chinese Academy of Sciences,U.S.Geological Survey,and Flinders Univ S Australia are the most influential institutions in the world.The knowledge graphs show the top ten cited documents in this field and the top 5% key words of the literature frequency.The keywords generate six cluster tags:hyporheic zone,hydrogeochemistry,climate change,soil moisture,riparian,and submarine groundwater discharge. More scholars are paying attention to this field,which contains several interdisciplinary subjects,providing a wide range of ideas and methods for research.The changing trend of research in this field is single groundwater research→groundwater-surface water interaction research→errestrial-aquatic ecosystem water interaction research on the response to influencing factors.The research hotspots in this field in recent years are exploring the water flux,permeability and discharge of groundwater-surface water interaction through heat tracing,developing and improving numerical models to improve the fit of the model to the interaction interface and the interaction of water bodies in different research areas,analyzing the response of water interactions to the biological,physical and chemical processes of human activities and the climate system under the concept of biogeochemical cycles.In the future,the multi-scale interdisciplinary research of surface water-groundwater interaction and enhance cooperation among teams should be focused on.
The complex interaction between surface water and groundwater interferes with the hydrological cycle affect the ecological status of the basin.Engineering measures for artificial collection of surface water and groundwater not only play a key role in solving the uneven distribution of water resources and the contradiction between water supply and demand,but also cause a series of ecological problems.Therefore,it is particularly important to explore the relevant mechanism of the interaction between surface water and groundwater.Through bibliometric analysis,it helps researchers grasp the current research status and hotspots in this field,which provides references for related research. Based on the Web of Science (WoS) data sources from 1985 to 2020,CiteSpace bibliometric software is used to quantitatively analyze the literature on the interaction of surface water and groundwater.By analyzing the cited documents,authors,research organizations,key words,and other elements,combined with the knowledge map,it displays the current research status,frontiers,and hotspots of this field. From 1985 to 2020,the total amount of scientific research papers in this field can be divided into three stages:slow growth-fluctuating,growth-steady growth and the increase in the number of published articles.The number of articles published in Journal of Hydrology,Environmental Earth Science,Hydrological Processes ranks top three.Research forces in this field are mainly concentrated in the United States,China,Australia.The author who published the most in the research period is Chunmiao Zheng.Chinese Academy of Sciences,U.S.Geological Survey,and Flinders Univ S Australia are the most influential institutions in the world.The knowledge graphs show the top ten cited documents in this field and the top 5% key words of the literature frequency.The keywords generate six cluster tags:hyporheic zone,hydrogeochemistry,climate change,soil moisture,riparian,and submarine groundwater discharge. More scholars are paying attention to this field,which contains several interdisciplinary subjects,providing a wide range of ideas and methods for research.The changing trend of research in this field is single groundwater research→groundwater-surface water interaction research→errestrial-aquatic ecosystem water interaction research on the response to influencing factors.The research hotspots in this field in recent years are exploring the water flux,permeability and discharge of groundwater-surface water interaction through heat tracing,developing and improving numerical models to improve the fit of the model to the interaction interface and the interaction of water bodies in different research areas,analyzing the response of water interactions to the biological,physical and chemical processes of human activities and the climate system under the concept of biogeochemical cycles.In the future,the multi-scale interdisciplinary research of surface water-groundwater interaction and enhance cooperation among teams should be focused on.
2022, 20(2):230-242,252.
Abstract:
Accurately assessing the temporal and spatial accuracy characteristics of existing multi-source satellite-based precipitation products can lay a solid meteorological data foundation for the efficient development and utilization of water resources in the Yangtze River basin (YRB). The daily precipitation data of 191 meteorological gauges in YRB from 1999 to 2019 and four types of satellite-based products of TRMM(Tropical Rainfall Measuring Mission),CMORPH(CPC MORPHing technique),CHIRPS(Climate Hazards Group Infrared Precipitation with Station data) and PERSIANN_CDR(Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Climate Data Record)were used.The indicators (e.g.R,ERMS and ENS)were used to evaluate the detection accuracy of four satellite-based precipitation products related to gauge based precipitation at temporal and spatial scales.POD,RFA and TS classification evaluation indicators are used to measure the ability of four satellite-based precipitation products of different magnitudes.
Accurately assessing the temporal and spatial accuracy characteristics of existing multi-source satellite-based precipitation products can lay a solid meteorological data foundation for the efficient development and utilization of water resources in the Yangtze River basin (YRB). The daily precipitation data of 191 meteorological gauges in YRB from 1999 to 2019 and four types of satellite-based products of TRMM(Tropical Rainfall Measuring Mission),CMORPH(CPC MORPHing technique),CHIRPS(Climate Hazards Group Infrared Precipitation with Station data) and PERSIANN_CDR(Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Climate Data Record)were used.The indicators (e.g.R,ERMS and ENS)were used to evaluate the detection accuracy of four satellite-based precipitation products related to gauge based precipitation at temporal and spatial scales.POD,RFA and TS classification evaluation indicators are used to measure the ability of four satellite-based precipitation products of different magnitudes.
2022, 20(2):243-252.
Abstract:
In 2011,the water-energy-food nexus was proposed in Bonn and it was summarized that the water-energy-food nexus can help humans to better understand the relationship between the three and solve global resource problems.In the same year,Stockholm International Environment Institute proposed the conceptual framework of water-energy-food nexus,including influencing factors such as population growth and climate change.In 2013,the UN Economic and Social Council of Asia-Pacific issued the Report on Water-Energy-Food Link in Asia-Pacific Region.In 2014,FAO expounded on the water-energy-food relationship from the perspective of food security.The relationship between the three is particularly important in the shortage of global resources,population growth,climate change,and environmental deterioration. The spatial correlation of water resources system development index,energy system development index,food system development index,water-energy-grain system comprehensive development index,and waterenergygrain coupling coordination are calculated,and the water-energy-food coupling coordination from 2003 to 2017,and the influence of working population,fixed asset investment,GDP per capita and total population are analyzed. The water resources system development index is lower than the energy system development index and the food system development index.The water-energy-food system comprehensive development index shows a rising trend,and low levels of coordination of water-energy-grain coupling,most are at the level of forced and primary coordination.The results of the spatial autocorrelation test showed that the Moran′s I index varies greatly in the time series,except for the following 2004,2005,outside of 2013,all passed the significance test at the 10% level,with the spatial aggregation characteristics,spatially interrelated and dependent.When performing the influence factor analysis using the spatial Dubin model,the number of the employed population,fixed asset investment,and urbanization have passed the significance test.It promotes the improved coordination of water-energy-grain coupling.The per capita GDP,population,and industrial pollution passed the significance test,which was negative,suppressed the improved coordination of water-energy-grain coupling. According to the above studies,the water-energy-food coordination is weak at the primary level,but in the current development trend,in the future,increase working population,increase investment in fixed assets,accelerate urbanization,strictly control industrial enterprises,reduce industrial pollution emissions,reasonably control population quantity and coordinate the relationship between economic development and resource environment can enhance water-energy-food coordination.
In 2011,the water-energy-food nexus was proposed in Bonn and it was summarized that the water-energy-food nexus can help humans to better understand the relationship between the three and solve global resource problems.In the same year,Stockholm International Environment Institute proposed the conceptual framework of water-energy-food nexus,including influencing factors such as population growth and climate change.In 2013,the UN Economic and Social Council of Asia-Pacific issued the Report on Water-Energy-Food Link in Asia-Pacific Region.In 2014,FAO expounded on the water-energy-food relationship from the perspective of food security.The relationship between the three is particularly important in the shortage of global resources,population growth,climate change,and environmental deterioration. The spatial correlation of water resources system development index,energy system development index,food system development index,water-energy-grain system comprehensive development index,and waterenergygrain coupling coordination are calculated,and the water-energy-food coupling coordination from 2003 to 2017,and the influence of working population,fixed asset investment,GDP per capita and total population are analyzed. The water resources system development index is lower than the energy system development index and the food system development index.The water-energy-food system comprehensive development index shows a rising trend,and low levels of coordination of water-energy-grain coupling,most are at the level of forced and primary coordination.The results of the spatial autocorrelation test showed that the Moran′s I index varies greatly in the time series,except for the following 2004,2005,outside of 2013,all passed the significance test at the 10% level,with the spatial aggregation characteristics,spatially interrelated and dependent.When performing the influence factor analysis using the spatial Dubin model,the number of the employed population,fixed asset investment,and urbanization have passed the significance test.It promotes the improved coordination of water-energy-grain coupling.The per capita GDP,population,and industrial pollution passed the significance test,which was negative,suppressed the improved coordination of water-energy-grain coupling. According to the above studies,the water-energy-food coordination is weak at the primary level,but in the current development trend,in the future,increase working population,increase investment in fixed assets,accelerate urbanization,strictly control industrial enterprises,reduce industrial pollution emissions,reasonably control population quantity and coordinate the relationship between economic development and resource environment can enhance water-energy-food coordination.
2022, 20(2):253-262,296.
Abstract:
A large number of major coal energy bases of national energy strategic planning are distributed in the Yellow River basin,which occupy an important position in China′s social and economic development.In recent years,the ecological problems of the Yellow River basin have gradually attracted the attention of all sectors of society,and its fragile ecological environment has seriously restricted the social and economic development of the basin.The changes in land water reserves caused by climate change and human activities are investigated,and the errors caused by coal mining in the calculation process of land water reserve changes in the Yellow River basin are investigated. The GRACE gravity satellite data is processed using MATLAB programming to obtain the surface gravity disturbance from 2005 to 2015.Since the gravitational change of the surface is basically caused by the change of land water reserves,the gravitational disturbance is converted to the equivalent water height to express the change of land water reserves and analyze its temporal and spatial changes.The GLDAS data was used to calculate the change value of surface water reserves .In the process of treatment,the same filtering method as the GRACE gravity satellite data was adopted,and the change value of land water reserves was subtracted from the change value of surface water reserves to the change value of groundwater reserves.The precipitation data was cross-interpolated to obtain the spatial distribution of the average annual precipitation in the Yellow River basin from 2005 to 2015.The temporal and spatial changes of land water reserves in the Yellow River basin were obtained.The change trend of land water reserves in the Yellow River basin from 2005 to 2015 was -5.20 mm/a,and the change trend of land water reserves in 2005-2006 reached -0.91 mm/month,and only July-September showed a surplus state in each year.In order to significantly reflect the spatial change characteristics of the change trend of land water reserves in the Yellow River basin from 2005 to 2015,combined Theil-Sen median trend analysis and Mann-Kendall test were used and it was found that 51.2% of the regional terrestrial water reserves had decreased significantly,33.3% of the regional terrestrial water reserves had increased significantly,and the proportion of flat areas was small.The final results showed that the western part of the basin was in a surplus state,and the eastern part of the basin was in a state of loss.The coal mining data of various provinces and cities in the Yellow River basin were counted and converted into equivalent water height,and the change trend was -1.95 mm/a,and the change trend of land water reserves was -3.25 mm/a,which was more accurate after deducting the trend.Through correlation analysis,it was obtained that the change of inland water reserves and the precipitation level have a certain degree of correlation (correlation coefficient r=0.33,ρ<0.01).It can be seen that precipitation was one of the reasons affecting the change of land water reserves in the Yellow River basin,and the precipitation increased sharply in July,August and September every year,resulting in an increase in the runoff of the Yellow River,which was an important reason for the obvious temporal characteristics of the change of land water reserves in the Yellow River basin. Through the above calculation and analysis,it was proved that the influence of coal mining on the accuracy of the inversion result of traditional land water reserves could not be ignored.In addition,precipitation and groundwater changes were important factors that lead to changes in terrestrial water reserves in the upstream and downstream regions,respectively.The influence of coal mining volume was comprehensively considered,which helps to improve the accuracy of the traditional inversion method of land water reserves.
A large number of major coal energy bases of national energy strategic planning are distributed in the Yellow River basin,which occupy an important position in China′s social and economic development.In recent years,the ecological problems of the Yellow River basin have gradually attracted the attention of all sectors of society,and its fragile ecological environment has seriously restricted the social and economic development of the basin.The changes in land water reserves caused by climate change and human activities are investigated,and the errors caused by coal mining in the calculation process of land water reserve changes in the Yellow River basin are investigated. The GRACE gravity satellite data is processed using MATLAB programming to obtain the surface gravity disturbance from 2005 to 2015.Since the gravitational change of the surface is basically caused by the change of land water reserves,the gravitational disturbance is converted to the equivalent water height to express the change of land water reserves and analyze its temporal and spatial changes.The GLDAS data was used to calculate the change value of surface water reserves .In the process of treatment,the same filtering method as the GRACE gravity satellite data was adopted,and the change value of land water reserves was subtracted from the change value of surface water reserves to the change value of groundwater reserves.The precipitation data was cross-interpolated to obtain the spatial distribution of the average annual precipitation in the Yellow River basin from 2005 to 2015.The temporal and spatial changes of land water reserves in the Yellow River basin were obtained.The change trend of land water reserves in the Yellow River basin from 2005 to 2015 was -5.20 mm/a,and the change trend of land water reserves in 2005-2006 reached -0.91 mm/month,and only July-September showed a surplus state in each year.In order to significantly reflect the spatial change characteristics of the change trend of land water reserves in the Yellow River basin from 2005 to 2015,combined Theil-Sen median trend analysis and Mann-Kendall test were used and it was found that 51.2% of the regional terrestrial water reserves had decreased significantly,33.3% of the regional terrestrial water reserves had increased significantly,and the proportion of flat areas was small.The final results showed that the western part of the basin was in a surplus state,and the eastern part of the basin was in a state of loss.The coal mining data of various provinces and cities in the Yellow River basin were counted and converted into equivalent water height,and the change trend was -1.95 mm/a,and the change trend of land water reserves was -3.25 mm/a,which was more accurate after deducting the trend.Through correlation analysis,it was obtained that the change of inland water reserves and the precipitation level have a certain degree of correlation (correlation coefficient r=0.33,ρ<0.01).It can be seen that precipitation was one of the reasons affecting the change of land water reserves in the Yellow River basin,and the precipitation increased sharply in July,August and September every year,resulting in an increase in the runoff of the Yellow River,which was an important reason for the obvious temporal characteristics of the change of land water reserves in the Yellow River basin. Through the above calculation and analysis,it was proved that the influence of coal mining on the accuracy of the inversion result of traditional land water reserves could not be ignored.In addition,precipitation and groundwater changes were important factors that lead to changes in terrestrial water reserves in the upstream and downstream regions,respectively.The influence of coal mining volume was comprehensively considered,which helps to improve the accuracy of the traditional inversion method of land water reserves.
2022, 20(2):263-270.
Abstract:
With the continuous development of China′s economy,society,and utilization of water resources,the contradiction between water supply and demand has become increasingly prominent,especially in arid areas.Many river basins are facing ecological and environmental problems such as over-exploitation,ecological degradation,and wetland shrinking.To realize the sustainable development of water resources and the ecological protection of river basins,over-exploitation of water resources have formulated and implemented river basin rehabilitation and water resources restoration planning.To solves the ecological and environmental problems in the Shule River basin,the ′Dunhuang Comprehensive Plan for Rational Utilization of Water Resources and Ecological Protection (2011-2020)′ was approved in 2011 by the State Council.The effect of the implementation of the planning became an issue of concern to all walks of life.Therefore,how to evaluate the implementation effects of river basin rehabilitation planning has become a brand-new subject to be studied and resolved. Focusing on the assessment of the effect of water resources restoration of basin rehabilitation planning on the Shule River basin and based on the principles of scientificity,typicality,comprehensiveness,and accessibility,the evaluation index system of water resources restoration effect was constructed through two dimensions of consistency evaluation and substantive evaluation.The in-position rate,investment completion rate,project completion rate,and evaluation index completion rate were selected to evaluate the consistency of the planned indicators.Furtheromre,the amount of water saving in the basin,the amount of river runoff restoration,and the extent of groundwater level recovery were considered to assess the substantial effect of water resources restoration. In the consistency evaluation,the project fund in-position rate and completion rate are between 79.97% and 100%.The completion rate of all projects is almost 100%.As of 2018,the proportion of agricultural water used in Dunhuang City has not reached the short-term target,the water consumption per ten thousand yuan of industrial added value did not reach the recent target except for Subei County,and the remaining targets were all completed at 100%.In the substantive evaluation,the amount of water saved in the irrigation area increased and the total annual water consumption decreased.The amount of water in the reservoir increased,and the ecological discharge of the reservoir and the river channel showed an inter-annual tortuous upward trend.Through water saving,the project has improved the efficiency of water use.The groundwater level in the plain area and the Dunhuang basin showed an inter-annual upward trend,mainly due to the increase in the ecological discharge of the Danghe reservoir and the Shuangta reservoir.With the increase of water inflow,the ecology of the West Lake Nature Reserve was improved. The implementation of the Shule River basin rehabilitation planning was relatively smooth,the completion rate of the planning evaluation index is close to 100%.The effect of water resources restoration such as water saving,water use reduction,restoration of river ecological flow,restoration and raising of the water level of crescent spring is remarkable.However,the lag in the implementation of the water and soil conservation and ecological construction project has a certain impact on the deployment and implementation of the next phase of the project.The results show that it is more realistic to evaluate the effect of water resources restoration based on consistency evaluation and substantive evaluation.
With the continuous development of China′s economy,society,and utilization of water resources,the contradiction between water supply and demand has become increasingly prominent,especially in arid areas.Many river basins are facing ecological and environmental problems such as over-exploitation,ecological degradation,and wetland shrinking.To realize the sustainable development of water resources and the ecological protection of river basins,over-exploitation of water resources have formulated and implemented river basin rehabilitation and water resources restoration planning.To solves the ecological and environmental problems in the Shule River basin,the ′Dunhuang Comprehensive Plan for Rational Utilization of Water Resources and Ecological Protection (2011-2020)′ was approved in 2011 by the State Council.The effect of the implementation of the planning became an issue of concern to all walks of life.Therefore,how to evaluate the implementation effects of river basin rehabilitation planning has become a brand-new subject to be studied and resolved. Focusing on the assessment of the effect of water resources restoration of basin rehabilitation planning on the Shule River basin and based on the principles of scientificity,typicality,comprehensiveness,and accessibility,the evaluation index system of water resources restoration effect was constructed through two dimensions of consistency evaluation and substantive evaluation.The in-position rate,investment completion rate,project completion rate,and evaluation index completion rate were selected to evaluate the consistency of the planned indicators.Furtheromre,the amount of water saving in the basin,the amount of river runoff restoration,and the extent of groundwater level recovery were considered to assess the substantial effect of water resources restoration. In the consistency evaluation,the project fund in-position rate and completion rate are between 79.97% and 100%.The completion rate of all projects is almost 100%.As of 2018,the proportion of agricultural water used in Dunhuang City has not reached the short-term target,the water consumption per ten thousand yuan of industrial added value did not reach the recent target except for Subei County,and the remaining targets were all completed at 100%.In the substantive evaluation,the amount of water saved in the irrigation area increased and the total annual water consumption decreased.The amount of water in the reservoir increased,and the ecological discharge of the reservoir and the river channel showed an inter-annual tortuous upward trend.Through water saving,the project has improved the efficiency of water use.The groundwater level in the plain area and the Dunhuang basin showed an inter-annual upward trend,mainly due to the increase in the ecological discharge of the Danghe reservoir and the Shuangta reservoir.With the increase of water inflow,the ecology of the West Lake Nature Reserve was improved. The implementation of the Shule River basin rehabilitation planning was relatively smooth,the completion rate of the planning evaluation index is close to 100%.The effect of water resources restoration such as water saving,water use reduction,restoration of river ecological flow,restoration and raising of the water level of crescent spring is remarkable.However,the lag in the implementation of the water and soil conservation and ecological construction project has a certain impact on the deployment and implementation of the next phase of the project.The results show that it is more realistic to evaluate the effect of water resources restoration based on consistency evaluation and substantive evaluation.
2022, 20(2):271-280.
Abstract:
Under the joint influence of climate change and rapid urbanization,China's cities are facing increasingly severe flood problems.SWMM（storm water management model） is an important tool for calculating and analyzing the urban rainstorm,which has been widely used in urban drainage analysis,urban flood simulation,evaluation of sponge city building,water quality change,etc.Although lots of work have been done in this domain,the analysis of the whole process of pipe network drainage at the scale of the urban community still needs to be further improved. Based on the measured rainfall data and measured pipeline water level data,the main parameters of the SWMM are optimized and cablibrated through a genetic algorithm,and the Morris method is used to analyze the sensitivity of each parameter.On this basis,using rainfall-driven models with different return periods,the drainage capacity of community drainage networks under different scenarios is compared and analyzed. The results show that the parameter calibration of the SWMM based on a genetic algorithm has obtained good results.The Nash efficiency coefficient(ENS) calculated for 20180531 rainfall event is 0.82,and for the 20180620 rainfall event is 0.81,respectively.The errors of measured maximum water level,peak time,and other parameters are within 2%.Through the Morris sensitivity analysis of the parameters,the maximum infiltration rate,minimum infiltration rate,decay constant,and pipeline roughness of the SWMM of the residential area are more sensitive model parameters. Using different combined scenarios to drive the SWMM,taking a typical drainage community in Jin′an District,Fuzhou as [JP2]an example,a relatively complete urban drainage waterlogging analysis system is proposed.Based on analysis of the drainage capacity of the drainage pipe network under the rainfall scenarios of different return[JP] periods,when the rainfall duration increases,the flow,average overload duration of nodes,overflow number of nodes,full pipe time,and other indicators are greatly affected by the rainfall return period,and the overload number of nodes and full flow pipes are relatively less affected by the rainfall duration.Some reference can be provided for the simulation and evaluation of pipe network drainage systems at urban community scale.
Under the joint influence of climate change and rapid urbanization,China's cities are facing increasingly severe flood problems.SWMM（storm water management model） is an important tool for calculating and analyzing the urban rainstorm,which has been widely used in urban drainage analysis,urban flood simulation,evaluation of sponge city building,water quality change,etc.Although lots of work have been done in this domain,the analysis of the whole process of pipe network drainage at the scale of the urban community still needs to be further improved. Based on the measured rainfall data and measured pipeline water level data,the main parameters of the SWMM are optimized and cablibrated through a genetic algorithm,and the Morris method is used to analyze the sensitivity of each parameter.On this basis,using rainfall-driven models with different return periods,the drainage capacity of community drainage networks under different scenarios is compared and analyzed. The results show that the parameter calibration of the SWMM based on a genetic algorithm has obtained good results.The Nash efficiency coefficient(ENS) calculated for 20180531 rainfall event is 0.82,and for the 20180620 rainfall event is 0.81,respectively.The errors of measured maximum water level,peak time,and other parameters are within 2%.Through the Morris sensitivity analysis of the parameters,the maximum infiltration rate,minimum infiltration rate,decay constant,and pipeline roughness of the SWMM of the residential area are more sensitive model parameters. Using different combined scenarios to drive the SWMM,taking a typical drainage community in Jin′an District,Fuzhou as [JP2]an example,a relatively complete urban drainage waterlogging analysis system is proposed.Based on analysis of the drainage capacity of the drainage pipe network under the rainfall scenarios of different return[JP] periods,when the rainfall duration increases,the flow,average overload duration of nodes,overflow number of nodes,full pipe time,and other indicators are greatly affected by the rainfall return period,and the overload number of nodes and full flow pipes are relatively less affected by the rainfall duration.Some reference can be provided for the simulation and evaluation of pipe network drainage systems at urban community scale.
2022, 20(2):281-296.
Abstract:
The ensemble method can efficiently reduce the uncertainty of rainfall forecast.The ensemble rainfall forecast is established through random disturbance of the initial field.Different numerical weather prediction models are used to form the forecasting ensemble.The ensemble rainfall forecast is build based on a combination of different physical parameterization schemes,which is regularly used for rainfall forecasting under unknown weather conditions.The selection of the physical parameterization scheme has a significant impact on forecasting results.A single physical parameterization scheme is difficult to adapt to different rainfall processes,which brings great uncertainty in the forecast.Ensemble forecast based on physical parameterization scheme can effectively reduce the uncertainty of rainfall forecast,which can provide reliable rainfall information for flood forecast. Thirty-six physical parameterization schemes based on the WRF model are used to establish the ensemble rainfall forecast.The relative error (ER),critical success index (ICS),and the root mean square error (ERMS) are used to comprehensively evaluate the rainfall forecast.Meixi distributed hydrological model is constructed based on China flash flood hydrological model (CNFF-HM).The peak flood discharge error,peak present time error,and Nash efficiency coefficient are used to evaluate the flood forecast.The coupled meteorological and hydrological system is formed by the WRF model and Meixi distributed hydrological model.The research also uses a statistical model that is developed based on the heteroscedastic extended Logistic algorithm to postprocess the rainfall ensemble forecast results. For rainfall storms caused by Saola typhoon,the ERs based on 36 schemes are between 0.88% and 21.00%.In spatial dimension,the ICSs are between 0.736 8 and 0.758 2,and the ERMSs are between 0.133 1 and 0.221 6.In the time dimension,the ICSs are both 0.687 5 and the ERMSs are between 0.592 4 and 0.760 0,respectively.The error of peak flow discharge based on coupled meteorological and hydrological systems is 11.3%.With rainfall forecasting postprocess,the error of peak flow discharge is 3.97%.Likewise,for rainfall storms caused by Hagibis typhoon,the ERs based on 36 schemes are between 24.32% and 68.51%.In spatial dimension,the ICSs are between 0.347 0 and 0.487 9,and the ERMSs are between 0.521 6 and 0.845 1.In the time dimension,the ICSs are between 0.329 2 and 0.435 6,and the ERMSs are between 1.300 1 and 1.634 9,respectively.The error of peak flow discharge based on coupled [JP2]meteorological and hydrological systems is -86.89%.With rainfallforecasting post-process,the error of peak flow discharge is -48.95%. Forecasted rainfall in spatial dimension performs better than that in time dimension with different physical parameterizations schemes.The ensemble rainfall forecast is appropriately used for flood forecast with the coupled meteorological and hydrological system,which can efficiently reduce the forecasting uncertainty.Reasonable postprocessing methods should be used to process the numerical rainfall forecast.For the rainfall with even spatiotemporal distribution,flood forecast with the coupled meteorological and hydrological system has certain advantages compared to flood forecast based on observed rainfall.For the rainfall with uneven spatiotemporal distribution,the forecast still has room for improvement.
The ensemble method can efficiently reduce the uncertainty of rainfall forecast.The ensemble rainfall forecast is established through random disturbance of the initial field.Different numerical weather prediction models are used to form the forecasting ensemble.The ensemble rainfall forecast is build based on a combination of different physical parameterization schemes,which is regularly used for rainfall forecasting under unknown weather conditions.The selection of the physical parameterization scheme has a significant impact on forecasting results.A single physical parameterization scheme is difficult to adapt to different rainfall processes,which brings great uncertainty in the forecast.Ensemble forecast based on physical parameterization scheme can effectively reduce the uncertainty of rainfall forecast,which can provide reliable rainfall information for flood forecast. Thirty-six physical parameterization schemes based on the WRF model are used to establish the ensemble rainfall forecast.The relative error (ER),critical success index (ICS),and the root mean square error (ERMS) are used to comprehensively evaluate the rainfall forecast.Meixi distributed hydrological model is constructed based on China flash flood hydrological model (CNFF-HM).The peak flood discharge error,peak present time error,and Nash efficiency coefficient are used to evaluate the flood forecast.The coupled meteorological and hydrological system is formed by the WRF model and Meixi distributed hydrological model.The research also uses a statistical model that is developed based on the heteroscedastic extended Logistic algorithm to postprocess the rainfall ensemble forecast results. For rainfall storms caused by Saola typhoon,the ERs based on 36 schemes are between 0.88% and 21.00%.In spatial dimension,the ICSs are between 0.736 8 and 0.758 2,and the ERMSs are between 0.133 1 and 0.221 6.In the time dimension,the ICSs are both 0.687 5 and the ERMSs are between 0.592 4 and 0.760 0,respectively.The error of peak flow discharge based on coupled meteorological and hydrological systems is 11.3%.With rainfall forecasting postprocess,the error of peak flow discharge is 3.97%.Likewise,for rainfall storms caused by Hagibis typhoon,the ERs based on 36 schemes are between 24.32% and 68.51%.In spatial dimension,the ICSs are between 0.347 0 and 0.487 9,and the ERMSs are between 0.521 6 and 0.845 1.In the time dimension,the ICSs are between 0.329 2 and 0.435 6,and the ERMSs are between 1.300 1 and 1.634 9,respectively.The error of peak flow discharge based on coupled [JP2]meteorological and hydrological systems is -86.89%.With rainfallforecasting post-process,the error of peak flow discharge is -48.95%. Forecasted rainfall in spatial dimension performs better than that in time dimension with different physical parameterizations schemes.The ensemble rainfall forecast is appropriately used for flood forecast with the coupled meteorological and hydrological system,which can efficiently reduce the forecasting uncertainty.Reasonable postprocessing methods should be used to process the numerical rainfall forecast.For the rainfall with even spatiotemporal distribution,flood forecast with the coupled meteorological and hydrological system has certain advantages compared to flood forecast based on observed rainfall.For the rainfall with uneven spatiotemporal distribution,the forecast still has room for improvement.
2022, 20(2):297-307.
Abstract:
Mountain torrents are recognized as one of the most harmful natural disasters in the world,which often cause serious casualties,public facilities damage,and environmental disasters because of their sudden occurrence,quick disaster,and great destructive power.In recent years,due to the increase of locally heavy rainfall and the change of underlying surface,frequent flood disasters occur in China.Critical rainfall is an important index of early warning of mountain torrents,and the temporal and spatial distribution of rainfall has an important influence on it.In the process of critical rainfall calculation,the regional design rainfall pattern is often used to generalize the rainfall process,or only one of the temporal and spatial distribution of rainfall is considered,which is lack of simultaneous consideration of both uncertainties.However,for the actual early warning of mountain torrents,the temporal and spatial distribution of each rainfall is different,which leads to the deviation of critical rainfall. To improve the early warning accuracy of mountain torrent disaster,Luanchuan basin was taken as an example.Using the Gini coefficient and the position coefficient of peak rainfall intensity,nine characteristic rainfall patterns,including partial front uniformity and partial concentration were generalized,and the Copula joint probability distribution of total rainfall and peak rainfall intensity was constructed,and the peak relationship under the risk combination probability of 5 return periods of total rainfall and 7 conditional probabilities of peak rainfall intensity was calculated.Five kinds of rainfall spatial distribution scenarios were set up in which the rainfall center of gravity shifts from upstream to downstream.HEC-HMS mode was taken as a rainfall-runoff model,and the critical rainfall under different conditions was determined by trial method.The influence of the uncertainty of temporal and spatial distribution of rainfall on the critical rainfall was discussed.The critical rainfall data set was established,and the three-level critical rainfall early warning model was constructed and verified. The results show that:When the soil water content is less before rainfall,the rainfall center is in the middle reaches,and the rainfall pattern is uniform,the critical rainfall corresponding to the rainfall process in which the position of the rain peak is in front of it is 23.87% larger than that corresponding to the rainfall process wherein the position of the rain peak is in back of it.When the peak is in the back of rainfall,the rainfall process with uniform distribution of rainfall is 6.53% larger than that with the concentrated distribution of rainfall.At the same time,the critical rainfall corresponding to the rainfall process with the rainfall center in the upstream is 31.61%~48.94% higher than that corresponding to the rainfall process with the downstream rainfall center .The conditional probability of the peak rainfall intensity increases when the probability of the total rainfall in the risk combination probability is constant.In the process of verification,the early warning is carried out according to the third-level critical rainfall early warning model of mountain torrents,all four floods can be warned before the flow in the river near the warning object reaches the disaster causing flow. It is shown that the temporal and spatial distribution of rainfall in the basin has a significant impact on the early warning of mountain torrents,and the critical rainfall values under the different temporal and spatial distributions of rainfall are quite different.So the critical rainfall should be properly modified according to the actual rainfall process in the practice of early warning of mountain torrents.The threelevel early warning model considering the uncertainty of rainfall is reasonable and reliable,which can provide technical reference for the early warning of mountain torrents in other small and medium-sized watersheds.
Mountain torrents are recognized as one of the most harmful natural disasters in the world,which often cause serious casualties,public facilities damage,and environmental disasters because of their sudden occurrence,quick disaster,and great destructive power.In recent years,due to the increase of locally heavy rainfall and the change of underlying surface,frequent flood disasters occur in China.Critical rainfall is an important index of early warning of mountain torrents,and the temporal and spatial distribution of rainfall has an important influence on it.In the process of critical rainfall calculation,the regional design rainfall pattern is often used to generalize the rainfall process,or only one of the temporal and spatial distribution of rainfall is considered,which is lack of simultaneous consideration of both uncertainties.However,for the actual early warning of mountain torrents,the temporal and spatial distribution of each rainfall is different,which leads to the deviation of critical rainfall. To improve the early warning accuracy of mountain torrent disaster,Luanchuan basin was taken as an example.Using the Gini coefficient and the position coefficient of peak rainfall intensity,nine characteristic rainfall patterns,including partial front uniformity and partial concentration were generalized,and the Copula joint probability distribution of total rainfall and peak rainfall intensity was constructed,and the peak relationship under the risk combination probability of 5 return periods of total rainfall and 7 conditional probabilities of peak rainfall intensity was calculated.Five kinds of rainfall spatial distribution scenarios were set up in which the rainfall center of gravity shifts from upstream to downstream.HEC-HMS mode was taken as a rainfall-runoff model,and the critical rainfall under different conditions was determined by trial method.The influence of the uncertainty of temporal and spatial distribution of rainfall on the critical rainfall was discussed.The critical rainfall data set was established,and the three-level critical rainfall early warning model was constructed and verified. The results show that:When the soil water content is less before rainfall,the rainfall center is in the middle reaches,and the rainfall pattern is uniform,the critical rainfall corresponding to the rainfall process in which the position of the rain peak is in front of it is 23.87% larger than that corresponding to the rainfall process wherein the position of the rain peak is in back of it.When the peak is in the back of rainfall,the rainfall process with uniform distribution of rainfall is 6.53% larger than that with the concentrated distribution of rainfall.At the same time,the critical rainfall corresponding to the rainfall process with the rainfall center in the upstream is 31.61%~48.94% higher than that corresponding to the rainfall process with the downstream rainfall center .The conditional probability of the peak rainfall intensity increases when the probability of the total rainfall in the risk combination probability is constant.In the process of verification,the early warning is carried out according to the third-level critical rainfall early warning model of mountain torrents,all four floods can be warned before the flow in the river near the warning object reaches the disaster causing flow. It is shown that the temporal and spatial distribution of rainfall in the basin has a significant impact on the early warning of mountain torrents,and the critical rainfall values under the different temporal and spatial distributions of rainfall are quite different.So the critical rainfall should be properly modified according to the actual rainfall process in the practice of early warning of mountain torrents.The threelevel early warning model considering the uncertainty of rainfall is reasonable and reliable,which can provide technical reference for the early warning of mountain torrents in other small and medium-sized watersheds.
10 Optimal application of SCS-CN model in runoff estimation in the southern mountainous area of Jinan
ZHAO Dengliang
,
CHEN Zhenjiang
,
LIU Jianhua
,
MENG Fanrong
,
XU Zhenghe
,
SANG Guoqing
,
BIAN Zhen
2022, 20(2):308-316.
Abstract:
Gushan watershed in the southern mountainous area of Jinan is located in the northern China.Soil erosion is a serious problem,dominated by hydraulic erosion and the ecological environment is fragile.Runoff carrying sediment are intuitive manifestations of soil erosion.The Gushan watershed is a key area for dynamic monitoring of water and soil erosion at the provincial level in Jinan.Complete rainfall and runoff datasets and the parameter optimization of the rainfall-runoff estimation model (runoff curve model (SCS-CN)) can improve the applicability of the model in the watershed and provide technical support and basis for the monitoring and forecasting of soil and water conservation in the region. Based on multi-source remote sensing technology and ArcGIS 10.7 platform,and according to the principle of the SCS-CN model,comprehensive consideration is given to the soil types in the watershed,the degree of early soil moisture,land use types,and topographic features.Measured rainfall and runoff data of five rainfall stations and one hydrological station in the basin for the past 10 years is selected,and goodness-fitting statistical analysis method and Nash-Sutcliffe efficiency coefficient verification method are used to determine the initial loss rate (λ) and the number of runoff curves of the model parameters (CN) to carry out optimization test.The rainfall-runoff estimation results of the standard SCS-CN model,Woodward model,and optimized SCS-CN model in the watershed are used to improve the estimation accuracy of rainfall-runoff of the SCS-CN model in the Gushan watershed. (1) When the value of the model parameter λ is less than 0.06,the runoff simulation result fits well with the measured value.After parameter optimization,λ is selected as 0.05.(2) The runoff curve model is greatly affected by topographical changes in the limestone mountain area.After using CN value slope conversion model,the accuracy of the model is further improved.(3) The optimized model has high accuracy with K=0.905 8,R2=0.812 7,ENS=0.796 9 which can be better applied to the rainfall-runoff estimation in the Gushan watershed.(4) The rainfall-runoff generation of 29 erosive rainfalls in 2019 is estimated in the Gushan watershed,and the cumulative calculations show that the annual runoff in the watershed is 0.53×10.8 m3,the annual runoff depth is between 34.15 mm and 371.52 mm,and the average annual runoff depth is 134.52 mm,respectively.The runoff generated by rainfall during the flood season accounts for 90.27% of the annual runoff. The optimized SCS-CN model has higher applicability in the study area.The model goodness of fit determination coefficient is increased by 17.68% compared with the Woodward model,and is increased by 113.08% compared with the standard SCS-CN model.The Nash efficiency coefficient (ENS) is compared with the Woodward model shows an increase of 48.81%,and 137.59% compared to the standard SCS-CN model.(2) The runoff generated by the various erosive rainfall events in the study area is affected by many factors such as the amount of rainfall and vegetation coverage.Based on research results,it can be determined that rainfall and runoff are positively correlated,and the degree of vegetation coverage and runoff has a negative correlation.(3) The annual runoff of the Gushan watershed was 0.53×10.8 m3 in 2019,and the spatial distribution showed a pattern of high in the north and low in the south,high in the east,and low in the west.The order of the average annual runoff depth of each administrative township in the basin is Guyunhu Sub-district>Zhangxia Sub-district>Wande Sub-district.(4) The optimization of the parameter CN value in the model optimization process is obtained based on the look-up table value.The soil type,the artificially cultivated tree species,natural tree species,and other vegetation types are staggered and complicated.The next research plan is to establish a runoff community and to further optimize the parameter values of the SCS-CN model and improve its application accuracy in the southern mountainous area of Jinan.
Gushan watershed in the southern mountainous area of Jinan is located in the northern China.Soil erosion is a serious problem,dominated by hydraulic erosion and the ecological environment is fragile.Runoff carrying sediment are intuitive manifestations of soil erosion.The Gushan watershed is a key area for dynamic monitoring of water and soil erosion at the provincial level in Jinan.Complete rainfall and runoff datasets and the parameter optimization of the rainfall-runoff estimation model (runoff curve model (SCS-CN)) can improve the applicability of the model in the watershed and provide technical support and basis for the monitoring and forecasting of soil and water conservation in the region. Based on multi-source remote sensing technology and ArcGIS 10.7 platform,and according to the principle of the SCS-CN model,comprehensive consideration is given to the soil types in the watershed,the degree of early soil moisture,land use types,and topographic features.Measured rainfall and runoff data of five rainfall stations and one hydrological station in the basin for the past 10 years is selected,and goodness-fitting statistical analysis method and Nash-Sutcliffe efficiency coefficient verification method are used to determine the initial loss rate (λ) and the number of runoff curves of the model parameters (CN) to carry out optimization test.The rainfall-runoff estimation results of the standard SCS-CN model,Woodward model,and optimized SCS-CN model in the watershed are used to improve the estimation accuracy of rainfall-runoff of the SCS-CN model in the Gushan watershed. (1) When the value of the model parameter λ is less than 0.06,the runoff simulation result fits well with the measured value.After parameter optimization,λ is selected as 0.05.(2) The runoff curve model is greatly affected by topographical changes in the limestone mountain area.After using CN value slope conversion model,the accuracy of the model is further improved.(3) The optimized model has high accuracy with K=0.905 8,R2=0.812 7,ENS=0.796 9 which can be better applied to the rainfall-runoff estimation in the Gushan watershed.(4) The rainfall-runoff generation of 29 erosive rainfalls in 2019 is estimated in the Gushan watershed,and the cumulative calculations show that the annual runoff in the watershed is 0.53×10.8 m3,the annual runoff depth is between 34.15 mm and 371.52 mm,and the average annual runoff depth is 134.52 mm,respectively.The runoff generated by rainfall during the flood season accounts for 90.27% of the annual runoff. The optimized SCS-CN model has higher applicability in the study area.The model goodness of fit determination coefficient is increased by 17.68% compared with the Woodward model,and is increased by 113.08% compared with the standard SCS-CN model.The Nash efficiency coefficient (ENS) is compared with the Woodward model shows an increase of 48.81%,and 137.59% compared to the standard SCS-CN model.(2) The runoff generated by the various erosive rainfall events in the study area is affected by many factors such as the amount of rainfall and vegetation coverage.Based on research results,it can be determined that rainfall and runoff are positively correlated,and the degree of vegetation coverage and runoff has a negative correlation.(3) The annual runoff of the Gushan watershed was 0.53×10.8 m3 in 2019,and the spatial distribution showed a pattern of high in the north and low in the south,high in the east,and low in the west.The order of the average annual runoff depth of each administrative township in the basin is Guyunhu Sub-district>Zhangxia Sub-district>Wande Sub-district.(4) The optimization of the parameter CN value in the model optimization process is obtained based on the look-up table value.The soil type,the artificially cultivated tree species,natural tree species,and other vegetation types are staggered and complicated.The next research plan is to establish a runoff community and to further optimize the parameter values of the SCS-CN model and improve its application accuracy in the southern mountainous area of Jinan.
2022, 20(2):317-326.
Abstract:
There is an increase of extreme rainfall events frequency in cities due to global climate change and rapid urbanization,which brings urban flood disasters.The temporal and spatial heterogeneity of extreme rainfall events in urban areas became more and more obvious in recent years,mainly manifested in the aggravation of spatial heterogeneity and more concentration temporally and spatially in the rainfall process.Owing to temporal and spatial heterogeneity,it is difficult to evaluate and predict the flooding process in urban areas,especially with sudden rainstorm events,which becomes an important issue for improving the accuracy of the urban flood model. Buji River basin is located in Shenzhen,China,which covers 40.59 square kilometers area,and the built-up area in the region exceeds 70%.To improve the urban flood model concerning temporal and spatial heterogeneity,116 heavy rainfalls events were extracted from the monitoring data of 5-minute intervals of meteorological stations from 2018 to 2020,and the discrete station monitoring data was interpolated into spatially continuously distributed grid data by a spatial interpolation algorithm.The spatial average rainfalls and rain peak synchronous rainfalls were constructed with spatial averaging and time synchronization method.The spatial averaging method was to average the rainfall data every 5-minute for the whole basin.The time synchronous method was realized by adjusting the phase of the rainfall process in each grid,to ensure that the rain peaks of each grid appear at the same time.A urban flood model was used to simulate the flooding process of the outlet section of the watershed caused by 116 monitoring rainfall and 232 rainfall processes after spatial averaging and time synchronization,and the flood peak change index of each rainfall was extracted.The rainfall center and rainfall movement direction of 116 rainfall events were counted,and their effects on peak discharge and flood process were analyzed. The results showed that after spatial averaging,the variation of flood peak was -43.9%~34.7%,with an average of -3.3% compared with the flood peak obtained from the original rainfall.The flood peak was varied due to the spatial relationship between the rainfall center and geometric center of the basin.The flood peak was mainly reduced with the rainfall center located upstream of the geometric center of the basin,after spatial averaging,and the flood peak was mainly reduced with the rainfall center located in the opposite position of the geometric center of the basin.For the 65 rainfalls in the northeast (upstream) of the geometric center,the average variation of flood peak was -15.1%,and for the 51 rainfalls in the southwest side of the geometric center,the average change of flood peak was 3.1%.Compared with the original rainfalls,the variation of flood peak obtained by the rainfall peak synchronous processing is -33.7%~20.0%,with an average of -3.0%.The variation of flood peak was related to the direction of rainfall movement,with the average variation of flood peak 14 rainfalls moving from northwest to the southeast was -7.3%.The average variation of 12 rainfalls moving from northeast to southwest was -2.2% and the average variation of 20 rainfalls moving from southwest to northeast was 2%.For the flooding process,when the flood peak increased,the flood peak duration was shortened.On the contrary,when the flood peak decreased,the flood peak duration increased. Under the same total rainfall,compared with the original rainfall,the variation of flood peak caused by spatial average was -43.9%~34.7%,and the variation of flood peak caused by synchronous rainfall was -33.7%~20.0%.The variation of flood peak with spatial averaging was mainly due to the spatial relationship between the center of original rainfall and the spatial center of the basin.The variation of flood peaks caused by the synchronization was related to the moving direction of rainfall.The flood peak was more likely to increase after synchronization with the moving direction of rainfall opposite to the confluence direction.The references can be provided for flood simulation calculation and flood risk assessment in an urban watershed.
There is an increase of extreme rainfall events frequency in cities due to global climate change and rapid urbanization,which brings urban flood disasters.The temporal and spatial heterogeneity of extreme rainfall events in urban areas became more and more obvious in recent years,mainly manifested in the aggravation of spatial heterogeneity and more concentration temporally and spatially in the rainfall process.Owing to temporal and spatial heterogeneity,it is difficult to evaluate and predict the flooding process in urban areas,especially with sudden rainstorm events,which becomes an important issue for improving the accuracy of the urban flood model. Buji River basin is located in Shenzhen,China,which covers 40.59 square kilometers area,and the built-up area in the region exceeds 70%.To improve the urban flood model concerning temporal and spatial heterogeneity,116 heavy rainfalls events were extracted from the monitoring data of 5-minute intervals of meteorological stations from 2018 to 2020,and the discrete station monitoring data was interpolated into spatially continuously distributed grid data by a spatial interpolation algorithm.The spatial average rainfalls and rain peak synchronous rainfalls were constructed with spatial averaging and time synchronization method.The spatial averaging method was to average the rainfall data every 5-minute for the whole basin.The time synchronous method was realized by adjusting the phase of the rainfall process in each grid,to ensure that the rain peaks of each grid appear at the same time.A urban flood model was used to simulate the flooding process of the outlet section of the watershed caused by 116 monitoring rainfall and 232 rainfall processes after spatial averaging and time synchronization,and the flood peak change index of each rainfall was extracted.The rainfall center and rainfall movement direction of 116 rainfall events were counted,and their effects on peak discharge and flood process were analyzed. The results showed that after spatial averaging,the variation of flood peak was -43.9%~34.7%,with an average of -3.3% compared with the flood peak obtained from the original rainfall.The flood peak was varied due to the spatial relationship between the rainfall center and geometric center of the basin.The flood peak was mainly reduced with the rainfall center located upstream of the geometric center of the basin,after spatial averaging,and the flood peak was mainly reduced with the rainfall center located in the opposite position of the geometric center of the basin.For the 65 rainfalls in the northeast (upstream) of the geometric center,the average variation of flood peak was -15.1%,and for the 51 rainfalls in the southwest side of the geometric center,the average change of flood peak was 3.1%.Compared with the original rainfalls,the variation of flood peak obtained by the rainfall peak synchronous processing is -33.7%~20.0%,with an average of -3.0%.The variation of flood peak was related to the direction of rainfall movement,with the average variation of flood peak 14 rainfalls moving from northwest to the southeast was -7.3%.The average variation of 12 rainfalls moving from northeast to southwest was -2.2% and the average variation of 20 rainfalls moving from southwest to northeast was 2%.For the flooding process,when the flood peak increased,the flood peak duration was shortened.On the contrary,when the flood peak decreased,the flood peak duration increased. Under the same total rainfall,compared with the original rainfall,the variation of flood peak caused by spatial average was -43.9%~34.7%,and the variation of flood peak caused by synchronous rainfall was -33.7%~20.0%.The variation of flood peak with spatial averaging was mainly due to the spatial relationship between the center of original rainfall and the spatial center of the basin.The variation of flood peaks caused by the synchronization was related to the moving direction of rainfall.The flood peak was more likely to increase after synchronization with the moving direction of rainfall opposite to the confluence direction.The references can be provided for flood simulation calculation and flood risk assessment in an urban watershed.
2022, 20(2):327-337,364.
Abstract:
The probability distribution of extreme precipitation in the Shanmei reservoir basin is expected to change due to the dual influence of global climate change and human activities,showing non-stationary characteristics.Therefore,investigating the temporal and spatial trend characteristics and the non-stationarity of the extreme precipitation are valuable for policy decisions. Based on the daily precipitation data of 8 meteorological stations in the Shanmei reservoir basin from 1972 to 2010,9 extreme precipitation indices including 6 intensity indices and 3 frequency indices were used to describe the extreme precipitation characteristics.The Pre-Whitening Mann-Kendall (P -WM-K) method was adopted to analyze the temporal and spatial trend changes of extreme precipitation,and the generalized additive models for location,scale,and shape (GAMLSS) was employed to characterize the non-stationarities in the 9 indices in the Shanmei reservoir basin. The number of moderate precipitation days (R10 mm) and the number of heavy rain days (R25mm) showed a downward trend while the number of very heavy rain days (R50mm) showed an upward trend with a 0.05 significant level.Except for the total precipitation (PRCPTOT),the other intensity indices (daily intensity (SDII),very wet day precipitation (R95P),extremely wet day precipitation (R99P),max 1-day precipitation (RX1day) and the max 5-day precipitation (RX5day) increased significantly.The linear trend rate of R95 reached 30.5 mm/（10 a）.The extreme precipitation indices had abrupt changes in the whole basin,and the mutation years mainly occurred in the late 1980s and early 1990s.In terms of spatial variation,R10mm and R25mm showed a download trend for all the stations,and reaches a 005 significant level in Dazhong and Zimei Stations.R25mm showed a downward trend for the stations in the exception of the Dongguan and Shanmei Stations while the trend was not significant.The R50mm and extreme precipitation intensity indices showed an upward trend in the southeastern part of the basin (Yongchun Station,Huyang Station,Dongguan Station,and Shanmei Station),and the trend was significant.The PRCPTOT had decreased significantly in the northwest of the basin.The GAMLSS model was fitted well to each precipitation station,and the Filliben coefficient passed the 0.05 significance level.R10mm and R25mm showed stationary characteristics.The R50mm showed non-stationary characteristics at 50% of the stations in the basin,and that was dominated by mean non-stationary.Except for PRCPTOT,the other intensity indices mainly showed non-stationary characteristics which mainly manifested as the mean non-stationary.Under the non-stationary conditions,the mean and variance of the extreme precipitation indices was mainly characterized by an increasing trend in the southeastern basin,and mainly showed a decreasing trend in the northwest. In light of climate variability and anthropogenic activities,the stable environment of extreme precipitation events in the Shanmei reservoir basin had been disturbed.The intensity of extreme precipitation and R50mm increased significantly in the Shanmei reservoir basin,especially in the southeastern part of the basin.This showed non-stationary characteristics in the study area.The intensity of extreme precipitations as well as uncertainty would increase,which may lead to more related disasters in the future.
The probability distribution of extreme precipitation in the Shanmei reservoir basin is expected to change due to the dual influence of global climate change and human activities,showing non-stationary characteristics.Therefore,investigating the temporal and spatial trend characteristics and the non-stationarity of the extreme precipitation are valuable for policy decisions. Based on the daily precipitation data of 8 meteorological stations in the Shanmei reservoir basin from 1972 to 2010,9 extreme precipitation indices including 6 intensity indices and 3 frequency indices were used to describe the extreme precipitation characteristics.The Pre-Whitening Mann-Kendall (P -WM-K) method was adopted to analyze the temporal and spatial trend changes of extreme precipitation,and the generalized additive models for location,scale,and shape (GAMLSS) was employed to characterize the non-stationarities in the 9 indices in the Shanmei reservoir basin. The number of moderate precipitation days (R10 mm) and the number of heavy rain days (R25mm) showed a downward trend while the number of very heavy rain days (R50mm) showed an upward trend with a 0.05 significant level.Except for the total precipitation (PRCPTOT),the other intensity indices (daily intensity (SDII),very wet day precipitation (R95P),extremely wet day precipitation (R99P),max 1-day precipitation (RX1day) and the max 5-day precipitation (RX5day) increased significantly.The linear trend rate of R95 reached 30.5 mm/（10 a）.The extreme precipitation indices had abrupt changes in the whole basin,and the mutation years mainly occurred in the late 1980s and early 1990s.In terms of spatial variation,R10mm and R25mm showed a download trend for all the stations,and reaches a 005 significant level in Dazhong and Zimei Stations.R25mm showed a downward trend for the stations in the exception of the Dongguan and Shanmei Stations while the trend was not significant.The R50mm and extreme precipitation intensity indices showed an upward trend in the southeastern part of the basin (Yongchun Station,Huyang Station,Dongguan Station,and Shanmei Station),and the trend was significant.The PRCPTOT had decreased significantly in the northwest of the basin.The GAMLSS model was fitted well to each precipitation station,and the Filliben coefficient passed the 0.05 significance level.R10mm and R25mm showed stationary characteristics.The R50mm showed non-stationary characteristics at 50% of the stations in the basin,and that was dominated by mean non-stationary.Except for PRCPTOT,the other intensity indices mainly showed non-stationary characteristics which mainly manifested as the mean non-stationary.Under the non-stationary conditions,the mean and variance of the extreme precipitation indices was mainly characterized by an increasing trend in the southeastern basin,and mainly showed a decreasing trend in the northwest. In light of climate variability and anthropogenic activities,the stable environment of extreme precipitation events in the Shanmei reservoir basin had been disturbed.The intensity of extreme precipitation and R50mm increased significantly in the Shanmei reservoir basin,especially in the southeastern part of the basin.This showed non-stationary characteristics in the study area.The intensity of extreme precipitations as well as uncertainty would increase,which may lead to more related disasters in the future.
2022, 20(2):338-351.
Abstract:
In recent years,it is common for cities to accumulate rain and flood during rainstorm.On the one hand,due to the negative impact of human activities on the environment,extreme rainstorm events occur frequently.On the other hand,with the acceleration of urbanization,urban hardening road surface increases,green space decreases,urban rainwater infiltration capacity is insufficient,easy to form waterlogging water.To solve urban waterlogging problem,urban waterlogging model needs to be built.An important part of urban waterlogging model is urban stormwater pipe network model.The key step of urban rainwater pipe network model construction is the division of subcatchment area,and the division result has great influence on the simulation accuracy of urban rainwater pipe network. Based on the theory of surface hydrological analysis of urban DEM,a basin analysis based Thiessen polygon subcatchment division method was proposed to solve the problem of inaccurate division of urban subcatchment area.This method took into account the effect of topography on the simulation accuracy of stormwater pipe network model.Basin analysis was carried out based on the raster data of the high resolution urban digital elevation model,and the runoff unit with concentrated catchment area was divided.The elevation variation in the runoff unit was small,and the runoff unit was defined as the primary sub-catchment area.The primary catchment area was revised to ensure that there are pipe network nodes in each primary catchment area.The primary catchment area was subdivided by Thiessen polygon method and the corresponding sub-catchment area was obtained. Taking a certain area in Beijing as an example,the basin analysis based Thiessen polygon subcatchment division method was compared with the two most commonly used subcatchment partitioning methods:manual drawing method and traditional Thiessen polygon method.The manual drawing method is a method for professionals to manually delineate the sub-catchment area corresponding to each pipe network node according to DEM elevation raster data,satellite image and data of different land use types in the study area,and then refine ground object elevation data.The classification process of this method is tedious and the workload is heavy,but it can accurately match the catchment area served by the actual pipe network nodes.Thiessen polygon method uses geographic information system software to delimit molecular catchment area based on inspection well,which is quick,simple and easy to operate.Based on the simulation results of downhole liquid level peak,peak emergence time,flow peak,peak emergence time and total runoff,the simulation accuracy of different catchment division methods was analyzed and the advantages of basin analysis based Thiessen polygon subcatchment division method were evaluated.The case study showed that the error between basin analysis based Thiessen polygon subcatchment division method and measured data was the smallest,and the deviation of the peak value of underground liquid level,peak flow value and total water amount were 1.115%,1.301% and 6.796%,respectively. The indexes of the model obtained by the Thiessen polygon method to divide the molecular catchment area had great deviations from the measured values,among which the total water amount deviation is 40.343%,showing a poor fitting degree.Moreover,the model flow peak value of Thiessen polygon method was significantly smaller than that of manual drawing method,resulting in low accuracy of simulation results.The deviation between the manual drawing method results and the measured data was small,which met the requirements of the specification and had high precision.The basin analysis based Thiessen polygon subcatchment division method had a small deviation between the simulated results of molecular catchment and the measured values,which met the specification requirements.Compared with the manual drawing method,the index error was smaller and the model accuracy was higher.Therefore,the urban stormwater network model constructed by the method proposed to divide the molecular catchment area had high precision,and the method proposed was simpler to operate than manual drawing method,which can reduce the workload and improve the drawing efficiency.
In recent years,it is common for cities to accumulate rain and flood during rainstorm.On the one hand,due to the negative impact of human activities on the environment,extreme rainstorm events occur frequently.On the other hand,with the acceleration of urbanization,urban hardening road surface increases,green space decreases,urban rainwater infiltration capacity is insufficient,easy to form waterlogging water.To solve urban waterlogging problem,urban waterlogging model needs to be built.An important part of urban waterlogging model is urban stormwater pipe network model.The key step of urban rainwater pipe network model construction is the division of subcatchment area,and the division result has great influence on the simulation accuracy of urban rainwater pipe network. Based on the theory of surface hydrological analysis of urban DEM,a basin analysis based Thiessen polygon subcatchment division method was proposed to solve the problem of inaccurate division of urban subcatchment area.This method took into account the effect of topography on the simulation accuracy of stormwater pipe network model.Basin analysis was carried out based on the raster data of the high resolution urban digital elevation model,and the runoff unit with concentrated catchment area was divided.The elevation variation in the runoff unit was small,and the runoff unit was defined as the primary sub-catchment area.The primary catchment area was revised to ensure that there are pipe network nodes in each primary catchment area.The primary catchment area was subdivided by Thiessen polygon method and the corresponding sub-catchment area was obtained. Taking a certain area in Beijing as an example,the basin analysis based Thiessen polygon subcatchment division method was compared with the two most commonly used subcatchment partitioning methods:manual drawing method and traditional Thiessen polygon method.The manual drawing method is a method for professionals to manually delineate the sub-catchment area corresponding to each pipe network node according to DEM elevation raster data,satellite image and data of different land use types in the study area,and then refine ground object elevation data.The classification process of this method is tedious and the workload is heavy,but it can accurately match the catchment area served by the actual pipe network nodes.Thiessen polygon method uses geographic information system software to delimit molecular catchment area based on inspection well,which is quick,simple and easy to operate.Based on the simulation results of downhole liquid level peak,peak emergence time,flow peak,peak emergence time and total runoff,the simulation accuracy of different catchment division methods was analyzed and the advantages of basin analysis based Thiessen polygon subcatchment division method were evaluated.The case study showed that the error between basin analysis based Thiessen polygon subcatchment division method and measured data was the smallest,and the deviation of the peak value of underground liquid level,peak flow value and total water amount were 1.115%,1.301% and 6.796%,respectively. The indexes of the model obtained by the Thiessen polygon method to divide the molecular catchment area had great deviations from the measured values,among which the total water amount deviation is 40.343%,showing a poor fitting degree.Moreover,the model flow peak value of Thiessen polygon method was significantly smaller than that of manual drawing method,resulting in low accuracy of simulation results.The deviation between the manual drawing method results and the measured data was small,which met the requirements of the specification and had high precision.The basin analysis based Thiessen polygon subcatchment division method had a small deviation between the simulated results of molecular catchment and the measured values,which met the specification requirements.Compared with the manual drawing method,the index error was smaller and the model accuracy was higher.Therefore,the urban stormwater network model constructed by the method proposed to divide the molecular catchment area had high precision,and the method proposed was simpler to operate than manual drawing method,which can reduce the workload and improve the drawing efficiency.
2022, 20(2):352-364.
Abstract:
Under water conservancy projects control such as gates and pumps,the complex river network in plain cities has a complicated water flow and a blocked water system,which affects its self-purification capacity.Instead,there are diverse factors that affect water system connectivity,makes more uncertain due to the regulation of dam gates.Therefore,the system pattern,structural connectivity,and hydraulic connectivity should be integrally considered to evaluate the connectivity of river networks in plain cities. Taking the optimal solution of water system connectivity as the target layer and water system pattern,structural connectivity,and hydraulic connectivity as the criterion layer,considering both static and dynamic factors,four indicators of water surface rate,river network density,river frequency,and river channel storage were selected to evaluate the morphological characteristics of urban water system more comprehensively.Water system ring degree,node connection rate,and water system connectivity were selected to evaluate structural connectivity.Based on structural connectivity,the influence of water flow capacity on the connectivity of the water system was fully considered,and three indicators of flow velocity,water flow potential,and water level are used for hydraulic connectivity evaluation.The above 10 evaluation indicators are used as the index layer to build the water system connectivity evaluation system.To comprehensively evaluate the water system connectivity of different schemes,a comprehensive evaluation method is used to assign weights to the 10 indicators,and then to comprehensively evaluate different water system connectivity schemes. Taking Langfang urban water system as an example,the water system connectivity evaluation system of the plain city river network was constructed to quantitatively evaluate the water system connectivity status of eight water system connectivity schemes.The results showed that there were differences in the three criterion levels of water system pattern,structural connectivity,and hydraulic connectivity for different working conditions.Combining the comprehensive evaluation scores and the grade cut-off values,the optimal water system connectivity solution can be obtained to improve the water system connectivity of the whole river network for Langfang city and could suggest that the river network should open the Shengli branch canal,Shengfeng branch canal,and Xiaoliuzhuang branch canal in the water transmission process,and dredge and desilt of the three branch canals with serious pollution according to the local actual situation. The system can evaluate the water system connectivity of the plain city river network in a more comprehensive way,and reflect the water system connectivity status of different water system connectivity schemes.The hydraulic connectivity index can reflect the mobility of water bodies in water systems.The calculation method of the hydraulic connectivity index in the hydraulic connectivity criterion layer was improved,so that it can be applied to the whole river network,making up for the limitation that the index was only applicable to the calculation of a single river in the past.To address the limitations,the evaluation of water system connectivity by index values can not take into account the influence of multiple factors,based on the water system connectivity evaluation system.The AHP-entropy integrated evaluation method was used to evaluate different water system connectivity schemes in terms of water system pattern,structural connectivity,and hydraulic connectivity to obtain the final evaluation scores of different water system connectivity schemes,to determine the optimal solution for water system connectivity and to make reasonable planning suggestions for the whole river network.The overall connectivity of the river network is optimal after connecting the three heavily polluted rivers with other rivers.
Under water conservancy projects control such as gates and pumps,the complex river network in plain cities has a complicated water flow and a blocked water system,which affects its self-purification capacity.Instead,there are diverse factors that affect water system connectivity,makes more uncertain due to the regulation of dam gates.Therefore,the system pattern,structural connectivity,and hydraulic connectivity should be integrally considered to evaluate the connectivity of river networks in plain cities. Taking the optimal solution of water system connectivity as the target layer and water system pattern,structural connectivity,and hydraulic connectivity as the criterion layer,considering both static and dynamic factors,four indicators of water surface rate,river network density,river frequency,and river channel storage were selected to evaluate the morphological characteristics of urban water system more comprehensively.Water system ring degree,node connection rate,and water system connectivity were selected to evaluate structural connectivity.Based on structural connectivity,the influence of water flow capacity on the connectivity of the water system was fully considered,and three indicators of flow velocity,water flow potential,and water level are used for hydraulic connectivity evaluation.The above 10 evaluation indicators are used as the index layer to build the water system connectivity evaluation system.To comprehensively evaluate the water system connectivity of different schemes,a comprehensive evaluation method is used to assign weights to the 10 indicators,and then to comprehensively evaluate different water system connectivity schemes. Taking Langfang urban water system as an example,the water system connectivity evaluation system of the plain city river network was constructed to quantitatively evaluate the water system connectivity status of eight water system connectivity schemes.The results showed that there were differences in the three criterion levels of water system pattern,structural connectivity,and hydraulic connectivity for different working conditions.Combining the comprehensive evaluation scores and the grade cut-off values,the optimal water system connectivity solution can be obtained to improve the water system connectivity of the whole river network for Langfang city and could suggest that the river network should open the Shengli branch canal,Shengfeng branch canal,and Xiaoliuzhuang branch canal in the water transmission process,and dredge and desilt of the three branch canals with serious pollution according to the local actual situation. The system can evaluate the water system connectivity of the plain city river network in a more comprehensive way,and reflect the water system connectivity status of different water system connectivity schemes.The hydraulic connectivity index can reflect the mobility of water bodies in water systems.The calculation method of the hydraulic connectivity index in the hydraulic connectivity criterion layer was improved,so that it can be applied to the whole river network,making up for the limitation that the index was only applicable to the calculation of a single river in the past.To address the limitations,the evaluation of water system connectivity by index values can not take into account the influence of multiple factors,based on the water system connectivity evaluation system.The AHP-entropy integrated evaluation method was used to evaluate different water system connectivity schemes in terms of water system pattern,structural connectivity,and hydraulic connectivity to obtain the final evaluation scores of different water system connectivity schemes,to determine the optimal solution for water system connectivity and to make reasonable planning suggestions for the whole river network.The overall connectivity of the river network is optimal after connecting the three heavily polluted rivers with other rivers.
2022, 20(2):365-374.
Abstract:
Since the 1960s,the problem of ecological water demand has gradually attracted attention at home and abroad.The determination of the ecological water demand of lakes is of great significance to lake health and ecological civilization because of an important part of water ecosystem.Since the 21st century,many experts and scholars have also carried out relevant research on the ecological water demand of lakes.Most of the current studies focused on the comprehensive consideration of different hydrological conditions and ecological information,but there are still some problems,such as unclear classification of calculation methods.Therefore,it is necessary to study these methods. Statistical analysis and generalization were used to summarize the concepts,classification,and composition related to the ecological water demand of lakes,and the key words of relevant domestic and foreign literature from 2001 to 2020 were visualized and analyzed by CiteSpace software.The methods of calculating ecological water demand of lakes based on both hydrological principle and ecological principle are summarized,and the applicability of different methods is compared.Finally,taking Taihu Lake as an example,three methods were selected to analyze the minimum ecological water demand,including the minimum water level method,the water exchange cycle method,and the ecological evolution analysis method. It was summarized that lake ecological water demand is "the amount of water of lake ecosystem when it reaches a certain level in a specific area,time and condition".General lakes are mostly the lakes with water input and water output,whose ecological water demand mainly consists of ecological water demand in the lake and inlet and outlet ecological water demand.The keyword cooccurrence network diagrams were obtained,and the analysis shows that current studies of lake ecological water demand at home and abroad mainly focused on two aspects of hydrological principles and ecological principles.The calculation methods based on hydrological principles include minimum water level method,water quantity balance method,and water exchange cycle method,and the calculation methods based on ecological principles include curve correlation method,ecological evolution analysis method and functional method.The annual ecological water demand of Taihu Lake is 3.601 billion m3,2.714 billion m3 and 3.881 billion m3 calculated by the lowest water level method,the water exchange cycle method and the ecological evolution analysis method,respectively.The results of the three methods have some deviations due to different calculation principles and focus.The water exchange period method are greatly affected by the water exchange period of the lake.The lowest water level method are limited by the lack of consistency and representativeness of the water level data of Taihu Lake.The ecological evolution analysis method considers both the hydrological and biological conditions,and its results are the most reasonable. Different methods for lake ecological water demand have a different scope of application.The lowest water level method is suitable for lakes with long series of water level data.The water quantity balance method is mostly used in natural lakes with less human interference.The water change cycle method is not suitable for dry areas or small water storage conditions.The curve correlation method and the functional method both require enough ecological and hydrological data,and the functional method has a wider application.The ecological evolution analysis method focuses on the requirements of biological living space,which is suitable for some lakes lacking ecological data.Taking Taihu Lake as an example,through different calculation methods and comparison with other research results,it is believed that the result of the ecological evolution analysis method is the most reasonable,and the annual ecological water demand of Taihu Lake is finally determined to be 3.881 billion m3.This study provides support for the reasonable calculation of lake ecological water demand and the study of ecological protection,restoration,and high-quality development.
Since the 1960s,the problem of ecological water demand has gradually attracted attention at home and abroad.The determination of the ecological water demand of lakes is of great significance to lake health and ecological civilization because of an important part of water ecosystem.Since the 21st century,many experts and scholars have also carried out relevant research on the ecological water demand of lakes.Most of the current studies focused on the comprehensive consideration of different hydrological conditions and ecological information,but there are still some problems,such as unclear classification of calculation methods.Therefore,it is necessary to study these methods. Statistical analysis and generalization were used to summarize the concepts,classification,and composition related to the ecological water demand of lakes,and the key words of relevant domestic and foreign literature from 2001 to 2020 were visualized and analyzed by CiteSpace software.The methods of calculating ecological water demand of lakes based on both hydrological principle and ecological principle are summarized,and the applicability of different methods is compared.Finally,taking Taihu Lake as an example,three methods were selected to analyze the minimum ecological water demand,including the minimum water level method,the water exchange cycle method,and the ecological evolution analysis method. It was summarized that lake ecological water demand is "the amount of water of lake ecosystem when it reaches a certain level in a specific area,time and condition".General lakes are mostly the lakes with water input and water output,whose ecological water demand mainly consists of ecological water demand in the lake and inlet and outlet ecological water demand.The keyword cooccurrence network diagrams were obtained,and the analysis shows that current studies of lake ecological water demand at home and abroad mainly focused on two aspects of hydrological principles and ecological principles.The calculation methods based on hydrological principles include minimum water level method,water quantity balance method,and water exchange cycle method,and the calculation methods based on ecological principles include curve correlation method,ecological evolution analysis method and functional method.The annual ecological water demand of Taihu Lake is 3.601 billion m3,2.714 billion m3 and 3.881 billion m3 calculated by the lowest water level method,the water exchange cycle method and the ecological evolution analysis method,respectively.The results of the three methods have some deviations due to different calculation principles and focus.The water exchange period method are greatly affected by the water exchange period of the lake.The lowest water level method are limited by the lack of consistency and representativeness of the water level data of Taihu Lake.The ecological evolution analysis method considers both the hydrological and biological conditions,and its results are the most reasonable. Different methods for lake ecological water demand have a different scope of application.The lowest water level method is suitable for lakes with long series of water level data.The water quantity balance method is mostly used in natural lakes with less human interference.The water change cycle method is not suitable for dry areas or small water storage conditions.The curve correlation method and the functional method both require enough ecological and hydrological data,and the functional method has a wider application.The ecological evolution analysis method focuses on the requirements of biological living space,which is suitable for some lakes lacking ecological data.Taking Taihu Lake as an example,through different calculation methods and comparison with other research results,it is believed that the result of the ecological evolution analysis method is the most reasonable,and the annual ecological water demand of Taihu Lake is finally determined to be 3.881 billion m3.This study provides support for the reasonable calculation of lake ecological water demand and the study of ecological protection,restoration,and high-quality development.
LI Zhiqiang
,
WANG Yajuan
,
WEN Zixi
,
ZHANG Qiulan
,
CUI Yali
,
ZHANG Linlin
,
YANG Guojun
,
ZHANG Lina
,
LIU Cuizhu
,
DONG He
2022, 20(2):375-384.
Abstract:
The middle and upper reaches of the Chaobai River alluvial fan is the area with the most abundant groundwater resources in Beijing,and it occupies an important role in the urban water supply.Due to over exploitation for many years,the groundwater level has decreased continuously and formed a large groundwater level drop funnel.At the same time,it has caused a series of environmental problems such as ground subsidence and groundwater pollution.At the end of 2014,after the middle route of the South-to-North Water Transfer Project was opened officially,it not only eased the shortage of water supply in Beijing,but also provided an opportunity for groundwater conservation.Since April 30,2021,the Chaobai River basin implemented the first large-scale experimental water replenishment in 22 years.The replenishment of water was an exploratory practice to promote the comprehensive management and ecological restoration of the river basin.It is also an important part of improving the ecological environment of the river basin and promoting the comprehensive management of the overexploitation of groundwater in the river basin. The research scope was determined by analyzing the hydrogeological conditions in the Chaobai River area borehole data,replenishment items,drainage items and long-term observation hole data.By the Unstructured Grid (USG) module embedded in GMS 10.0 to refine the replenished water channels and water sources,a long-term groundwater flow model from January 2000 to December 2020 was established.To evaluate model accuracy,the determination coefficient (R2) and root mean square error (RMSE) of evaluation factors was taken as the evaluation criteria for parameter optimization of the evaluation model.After identification and verification of the model by the observation data,the identified model was applied to the spring ecological water replenishment of Chaobai River to evaluate the effect of ecological water replenishment and groundwater response. The results show that the water level around the replenishment path has risen at the end of the replenishment period.The water level in the case of replenishment minus the water level in the case of no replenishment.The maximum increase is close to 18 m.The area that the water level has a rising value greater than 0 is the impact area in this replenishment.It is calculated that the affected area is about 842.8 km 2,accounting for 58.6% of the total area of the study area.The groundwater level near the mainstream of Chaobai River rises more than 10 m,and the affected area is about 44.2 km2,accounting for about 3%.During the water replenishment period (April 30-May 27,2021),the total water replenishment volume is 206 million m3,and the groundwater replenishment by water leakage is 157 million m3 (approximately 76% of the total water volume).The storage capacity of the system has increased by 149 million m3 in the first aquifer of the study area.Obvious delay in the groundwater levels in observing wells with responses after water replenishment,and the lag response time of observation wells at different locations of the river channel is different.The water level of observation wells that are 3 km away from the river channel rises obviously,and the lag response time is short (3-6 d and the lag response time of observation wells that are 6 km away from the river channel is longer (18-30 d). The implementation of ecological water replenishment projects in the Chaobai River basin was conducive to the recovery of water levels on both sides of the river and the restoration of groundwater resources in the region.After replenishing water,the water level rose significantly and the groundwater storage was increased within the water replenishment period.Overall,the replenishment effect was good.There was a time lag in the response of groundwater to replenishment,and the lag response time varies with distance.
The middle and upper reaches of the Chaobai River alluvial fan is the area with the most abundant groundwater resources in Beijing,and it occupies an important role in the urban water supply.Due to over exploitation for many years,the groundwater level has decreased continuously and formed a large groundwater level drop funnel.At the same time,it has caused a series of environmental problems such as ground subsidence and groundwater pollution.At the end of 2014,after the middle route of the South-to-North Water Transfer Project was opened officially,it not only eased the shortage of water supply in Beijing,but also provided an opportunity for groundwater conservation.Since April 30,2021,the Chaobai River basin implemented the first large-scale experimental water replenishment in 22 years.The replenishment of water was an exploratory practice to promote the comprehensive management and ecological restoration of the river basin.It is also an important part of improving the ecological environment of the river basin and promoting the comprehensive management of the overexploitation of groundwater in the river basin. The research scope was determined by analyzing the hydrogeological conditions in the Chaobai River area borehole data,replenishment items,drainage items and long-term observation hole data.By the Unstructured Grid (USG) module embedded in GMS 10.0 to refine the replenished water channels and water sources,a long-term groundwater flow model from January 2000 to December 2020 was established.To evaluate model accuracy,the determination coefficient (R2) and root mean square error (RMSE) of evaluation factors was taken as the evaluation criteria for parameter optimization of the evaluation model.After identification and verification of the model by the observation data,the identified model was applied to the spring ecological water replenishment of Chaobai River to evaluate the effect of ecological water replenishment and groundwater response. The results show that the water level around the replenishment path has risen at the end of the replenishment period.The water level in the case of replenishment minus the water level in the case of no replenishment.The maximum increase is close to 18 m.The area that the water level has a rising value greater than 0 is the impact area in this replenishment.It is calculated that the affected area is about 842.8 km 2,accounting for 58.6% of the total area of the study area.The groundwater level near the mainstream of Chaobai River rises more than 10 m,and the affected area is about 44.2 km2,accounting for about 3%.During the water replenishment period (April 30-May 27,2021),the total water replenishment volume is 206 million m3,and the groundwater replenishment by water leakage is 157 million m3 (approximately 76% of the total water volume).The storage capacity of the system has increased by 149 million m3 in the first aquifer of the study area.Obvious delay in the groundwater levels in observing wells with responses after water replenishment,and the lag response time of observation wells at different locations of the river channel is different.The water level of observation wells that are 3 km away from the river channel rises obviously,and the lag response time is short (3-6 d and the lag response time of observation wells that are 6 km away from the river channel is longer (18-30 d). The implementation of ecological water replenishment projects in the Chaobai River basin was conducive to the recovery of water levels on both sides of the river and the restoration of groundwater resources in the region.After replenishing water,the water level rose significantly and the groundwater storage was increased within the water replenishment period.Overall,the replenishment effect was good.There was a time lag in the response of groundwater to replenishment,and the lag response time varies with distance.
2022, 20(2):385-392.
Abstract:
The north China plain is one of the hotspots of groundwater depletion in China.The long-term groundwater over-exploitation has caused numerous geological and environmental issues such as large-scale groundwater depression cones,downward leakage from upper saline water,seawater intrusion,deterioration of water quality,etc.Since 2014,the Chinese government has initiated the groundwater exploitation reduction program to restore the groundwater resources and alleviate associated environmental problems in the north China plain.Due to the implementation of this program,the hydrological processes are expected to significantly change,and the groundwater level in some areas has shown an upward trend.The Heilonggang plain in Handan City,where the groundwater pumping reduction program yields significant effects,was selected as the study area to identify the processes of the water cycle and determine the groundwater recharge sources.The results of this study will have important implications for groundwater sustainable management in the north China plain. Hydrogen and oxygen isotopes were used as tracers for the water cycle with groundwater-pumping reduction.Multivariate statistical methods and GIS techniques were used to interpret these isotopic data.Rayleigh fractionation equation was used to calculate the evaporation loss.The twocomponent method was used to reveal the interchange volume between surface water and groundwater. Results exhibited that the stable isotope values in the surface water ranged from -6.4‰ to -4.9‰ inδ(18O) with an average of -5.9‰,and from -47.5‰ to -40.2‰ inδ(D) with an average of -44.9‰ in the wet season,while these values changed from -9.1‰ to -3.6‰ in δ(18O） with an average of -7.2‰,and from -65.3‰ to -49.8‰ inδ(D) with an average of -58.4‰ in the dry season.The isotopic compositions in surface water varied greatly from enriched isotopes in the wet season to depleted isotopes in the dry season.The slope (3.8) and the intercept (-29.2) of the surface water evaporation line were much smaller than those of the Local Meteoric Water Line,indicating that the surface water was largely affected by evaporation.The average evaporation loss of surface water was about 40%.Hydrogen and oxygen isotopic compositions in groundwater had insignificant seasonal variations.The slope of the groundwater evaporation line was 6.5,similar to that of the Local Meteoric Water Line.This phenomenon showed that the groundwater was less affected by evaporation,with an average evaporation loss of about 24%.Groundwater interacts with the local surface water frequently.The recharge ratio of groundwater to Lao Zhanghe River was about 30%.The recharge ratio of the Laosha River to the groundwater in the lower reaches was about 20%. The groundwater and the surface water were mainly recharged by atmospheric precipitation while affected by evaporation.There was a close hydraulic relationship between surface water and groundwater.The isotopic composition of surface water was influenced by evaporation and the difference in water supply.The isotopic composition of surface water varied greatly with the input of different water sources.Phreatic water was closely related to the hydraulic relationship of confined groundwater.The -isotopic- enrichment in the confined groundwater indicated that the confined groundwater may be mixed with the downward flow from isotope-enriched unconfined groundwater.Additionally,the isotopic depletion of confined water in some areas may be associated with the lateral flow from old groundwater with depleted isotopes.
The north China plain is one of the hotspots of groundwater depletion in China.The long-term groundwater over-exploitation has caused numerous geological and environmental issues such as large-scale groundwater depression cones,downward leakage from upper saline water,seawater intrusion,deterioration of water quality,etc.Since 2014,the Chinese government has initiated the groundwater exploitation reduction program to restore the groundwater resources and alleviate associated environmental problems in the north China plain.Due to the implementation of this program,the hydrological processes are expected to significantly change,and the groundwater level in some areas has shown an upward trend.The Heilonggang plain in Handan City,where the groundwater pumping reduction program yields significant effects,was selected as the study area to identify the processes of the water cycle and determine the groundwater recharge sources.The results of this study will have important implications for groundwater sustainable management in the north China plain. Hydrogen and oxygen isotopes were used as tracers for the water cycle with groundwater-pumping reduction.Multivariate statistical methods and GIS techniques were used to interpret these isotopic data.Rayleigh fractionation equation was used to calculate the evaporation loss.The twocomponent method was used to reveal the interchange volume between surface water and groundwater. Results exhibited that the stable isotope values in the surface water ranged from -6.4‰ to -4.9‰ inδ(18O) with an average of -5.9‰,and from -47.5‰ to -40.2‰ inδ(D) with an average of -44.9‰ in the wet season,while these values changed from -9.1‰ to -3.6‰ in δ(18O） with an average of -7.2‰,and from -65.3‰ to -49.8‰ inδ(D) with an average of -58.4‰ in the dry season.The isotopic compositions in surface water varied greatly from enriched isotopes in the wet season to depleted isotopes in the dry season.The slope (3.8) and the intercept (-29.2) of the surface water evaporation line were much smaller than those of the Local Meteoric Water Line,indicating that the surface water was largely affected by evaporation.The average evaporation loss of surface water was about 40%.Hydrogen and oxygen isotopic compositions in groundwater had insignificant seasonal variations.The slope of the groundwater evaporation line was 6.5,similar to that of the Local Meteoric Water Line.This phenomenon showed that the groundwater was less affected by evaporation,with an average evaporation loss of about 24%.Groundwater interacts with the local surface water frequently.The recharge ratio of groundwater to Lao Zhanghe River was about 30%.The recharge ratio of the Laosha River to the groundwater in the lower reaches was about 20%. The groundwater and the surface water were mainly recharged by atmospheric precipitation while affected by evaporation.There was a close hydraulic relationship between surface water and groundwater.The isotopic composition of surface water was influenced by evaporation and the difference in water supply.The isotopic composition of surface water varied greatly with the input of different water sources.Phreatic water was closely related to the hydraulic relationship of confined groundwater.The -isotopic- enrichment in the confined groundwater indicated that the confined groundwater may be mixed with the downward flow from isotope-enriched unconfined groundwater.Additionally,the isotopic depletion of confined water in some areas may be associated with the lateral flow from old groundwater with depleted isotopes.
2022, 20(2):393-407.
Abstract:
Considering the difficulty in water level prediction under building control,a water level prediction model for the forebay of a pumping station was built on the basis of back-propagation (BP) neural networks,and the influence of time series and impact factors on the accuracy of water level prediction was analyzed under different time scales.The constructed model was applied to the Dongsong Pumping Station of the Jiaodong Water Transfer Project.The research results revealed that:when the total amount of data was fixed,and the ratio of the training period to the prediction period was 7∶3,the prediction result was good;a larger amount of data was accompanied by a greater number of positively correlated impact factors required for certain prediction accuracy;in a short period of time,when the prediction time interval was the same as the time interval of the data itself,the prediction effect was better.The constructed model can meet the demand for dynamic prediction of the water level in the forebay of the open channel water transfer project and can achieve the 2 h accurate prediction of the forebay water level of the pumping station and the 4 h general accurate prediction.Additionally,it can be popularized and applied in other similar open channel water transfer projects.
Considering the difficulty in water level prediction under building control,a water level prediction model for the forebay of a pumping station was built on the basis of back-propagation (BP) neural networks,and the influence of time series and impact factors on the accuracy of water level prediction was analyzed under different time scales.The constructed model was applied to the Dongsong Pumping Station of the Jiaodong Water Transfer Project.The research results revealed that:when the total amount of data was fixed,and the ratio of the training period to the prediction period was 7∶3,the prediction result was good;a larger amount of data was accompanied by a greater number of positively correlated impact factors required for certain prediction accuracy;in a short period of time,when the prediction time interval was the same as the time interval of the data itself,the prediction effect was better.The constructed model can meet the demand for dynamic prediction of the water level in the forebay of the open channel water transfer project and can achieve the 2 h accurate prediction of the forebay water level of the pumping station and the 4 h general accurate prediction.Additionally,it can be popularized and applied in other similar open channel water transfer projects.
2022, 20(2):408-416.
Abstract:
The research on the risk of hydropower station mainly focuses on the construction of hydropower station,while there are few studies on the risk assessment of the hydropower plant operation.The accidents in the operation of hydropower station show a trend of diversification and complexity.It is particularly difficult to evaluate hydropower station risk level from the perspective of single risk mechanism.Therefore,based on the accident data during the operation period of the hydropower station,the risk level of the hydropower station can be analyzed effectively by the comprehensive evaluation based on the index system of risk factors. The single weighting method in traditional risk assessment has certain limitations and the risk level of hydropower station is difficult to be objectively determined.A fuzzy comprehensive evaluation model for hydropower station risk has been established based on the FAHP-CRITIC-game theory method.The risk factors are determined by accident causation theory and the index system of risk factors has been established.The membership degree function is used to calculate the membership degree of each risk index based on the accident loss amount and the fuzzy relation matrix has been obtained.The subjective weight and objective weight of the factors are calculated by the fuzzy analytic hierarchy process and the CRITIC method respectively,and the combinatorial optimization is carried out by the game theory method to make the weighting more reasonable.The fuzzy relation matrix and combination weight are used to have the multi-level fuzzy evaluation.The risk assessment of a cascade hydropower station is carried out and the risk grade of hydropower station is determined according to the principle of maximum membership degree. Among the natural environmental risks,the weights of torrential rains and flood and debris flow are relatively high.In the risk of power operation,the weights of current shock and overvoltage are higher.In the risk of construction and equipment,equipment failure is the main index of risk,and its importance is relatively higher than engineering quality problems.Natural environment risk and power operation risk have higher subordination degree to the low risk level,while construction and equipment risk has a high degree of subordination to the general risk level because of the relatively high probability of occurrence and loss.The results show that the risk level of the hydropower station is low risk,and the main risk indicators are torrential rains and floods and equipment failures. According to the risk factors that affect the safety of hydropower station,the index system of risk factors is established from three aspects:natural environment,electric operation,construction and equipment,which includes 13 corresponding evaluation factors.FAHP and CRITIC methods are used to calculate the subjective and objective weight respectively and the combined weight is given by game theory,which improves the rationality of weight calculation.The membership function has been established based on the amount of accident compensation and the multi-level fuzzy comprehensive evaluation is conducted.The risk assessment of hydropower station is carried out.The risk assessment result of hydropower station is low risk and the main risk indicators are storm flood and equipment failure.The result is consistent with the practical situation of the cascade hydropower plant,which verifies the reliability and practicability of the evaluation model.
The research on the risk of hydropower station mainly focuses on the construction of hydropower station,while there are few studies on the risk assessment of the hydropower plant operation.The accidents in the operation of hydropower station show a trend of diversification and complexity.It is particularly difficult to evaluate hydropower station risk level from the perspective of single risk mechanism.Therefore,based on the accident data during the operation period of the hydropower station,the risk level of the hydropower station can be analyzed effectively by the comprehensive evaluation based on the index system of risk factors. The single weighting method in traditional risk assessment has certain limitations and the risk level of hydropower station is difficult to be objectively determined.A fuzzy comprehensive evaluation model for hydropower station risk has been established based on the FAHP-CRITIC-game theory method.The risk factors are determined by accident causation theory and the index system of risk factors has been established.The membership degree function is used to calculate the membership degree of each risk index based on the accident loss amount and the fuzzy relation matrix has been obtained.The subjective weight and objective weight of the factors are calculated by the fuzzy analytic hierarchy process and the CRITIC method respectively,and the combinatorial optimization is carried out by the game theory method to make the weighting more reasonable.The fuzzy relation matrix and combination weight are used to have the multi-level fuzzy evaluation.The risk assessment of a cascade hydropower station is carried out and the risk grade of hydropower station is determined according to the principle of maximum membership degree. Among the natural environmental risks,the weights of torrential rains and flood and debris flow are relatively high.In the risk of power operation,the weights of current shock and overvoltage are higher.In the risk of construction and equipment,equipment failure is the main index of risk,and its importance is relatively higher than engineering quality problems.Natural environment risk and power operation risk have higher subordination degree to the low risk level,while construction and equipment risk has a high degree of subordination to the general risk level because of the relatively high probability of occurrence and loss.The results show that the risk level of the hydropower station is low risk,and the main risk indicators are torrential rains and floods and equipment failures. According to the risk factors that affect the safety of hydropower station,the index system of risk factors is established from three aspects:natural environment,electric operation,construction and equipment,which includes 13 corresponding evaluation factors.FAHP and CRITIC methods are used to calculate the subjective and objective weight respectively and the combined weight is given by game theory,which improves the rationality of weight calculation.The membership function has been established based on the amount of accident compensation and the multi-level fuzzy comprehensive evaluation is conducted.The risk assessment of hydropower station is carried out.The risk assessment result of hydropower station is low risk and the main risk indicators are storm flood and equipment failure.The result is consistent with the practical situation of the cascade hydropower plant,which verifies the reliability and practicability of the evaluation model.
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