Volume 20,Issue 3,2022 Table of Contents
2022, 20(3):417-428.
Abstract:
Accurately studying and judging changes in national and regional water consumption is prerequisite for rational layout of major water conservancy projects and scientific formulation of water resources management policies.The identification and quantification of the main influencing factors and their driving effects that lead to changes in water consumption is an important basis for accurately grasping the trend of changes in water consumption.At the current stage when the contradiction between water supply and demand is prominent and the economic and social development is undergoing a comprehensive transformation,in-depth research on the main factors affecting water consumption,temporal and spatial changes,and their internal mechanism is undoubtedly of important practical significance and has also received extensive attention from academic circles. The current methods for quantitatively measuring the driving effect of water consumption changes mainly include structural decomposition analysis (SDA) and index decomposition analysis (IDA).However,whether it is the structural decomposition method or the index decomposition method,the existing results are generally based on the total water consumption as a whole to conduct research or only analyze the water consumption of specific industries in specific regions.The study of total water consumption as a whole ignores the differences in the driving forces of water consumption in different industries of life,industry,and agriculture to a certain extent.Research on water consumption of specific industries in specific regions can not fully reflect the evolution of country's water use process.Considering that the logarithmic mean Divisia index (LMDI) in the index decomposition method effectively solves the problem of residual items and zero values in the index decomposition,it is not affected by the input-output table.For the impact of a long release cycle,this study uses the Kaya identity optimization to construct a multi-level LMDI method.Based on the overall analysis of the national water consumption driving effect,it further analyzes the water consumption driving effect of each industry from 2000 to 2010 and 2010 to 2020.Decomposition research is carried out,and an in-depth analysis of the spatial differentiation of driving effects and the latest changes during the 13th Five-Year Plan is carried out. From 2000 to 2020,there is an increase to decrease fluctuation in country's total water consumption.The total water consumption in 2020 is almost the same as 20 years ago,but the water use structure has undergone certain adjustments,taking 2013 as the boundary point,the change in agricultural water use before 2013 dominated the change in total water use,with an average contribution rate of 5742%.After 2013,the change in industrial water consumption has taken up a relatively dominant position,with an average contribution rate of 44.3%.Domestic water consumption before 2012 was mainly due to the increase in water quota,and after 2012,the increase in domestic water consumption was mainly due to the increase in the urbanization rate.Industrial water consumption has always been strongly affected by the two driving forces of industrial-scale expansion and decline in industrial water quotas.Before 2011,the increase in industrial output value was dominant,and after 2011,the decline in industrial water quotas was even greater.Agricultural water use has always been dominated by irrigation area and agricultural water quotas.The effect of reducing agricultural water quota is slightly greater,but the expansion of irrigation area is always an important factor that can not be ignored.During the Thirteenth Five-Year Plan,the leading factor in the provinces to promote the water consumption growth was generally the increase in industrial output value or the expansion of agricultural irrigation area,while the leading factor in restraining the water consumption growth was the decline in the industrial water quota or the decline in the agricultural water quota.
Accurately studying and judging changes in national and regional water consumption is prerequisite for rational layout of major water conservancy projects and scientific formulation of water resources management policies.The identification and quantification of the main influencing factors and their driving effects that lead to changes in water consumption is an important basis for accurately grasping the trend of changes in water consumption.At the current stage when the contradiction between water supply and demand is prominent and the economic and social development is undergoing a comprehensive transformation,in-depth research on the main factors affecting water consumption,temporal and spatial changes,and their internal mechanism is undoubtedly of important practical significance and has also received extensive attention from academic circles. The current methods for quantitatively measuring the driving effect of water consumption changes mainly include structural decomposition analysis (SDA) and index decomposition analysis (IDA).However,whether it is the structural decomposition method or the index decomposition method,the existing results are generally based on the total water consumption as a whole to conduct research or only analyze the water consumption of specific industries in specific regions.The study of total water consumption as a whole ignores the differences in the driving forces of water consumption in different industries of life,industry,and agriculture to a certain extent.Research on water consumption of specific industries in specific regions can not fully reflect the evolution of country's water use process.Considering that the logarithmic mean Divisia index (LMDI) in the index decomposition method effectively solves the problem of residual items and zero values in the index decomposition,it is not affected by the input-output table.For the impact of a long release cycle,this study uses the Kaya identity optimization to construct a multi-level LMDI method.Based on the overall analysis of the national water consumption driving effect,it further analyzes the water consumption driving effect of each industry from 2000 to 2010 and 2010 to 2020.Decomposition research is carried out,and an in-depth analysis of the spatial differentiation of driving effects and the latest changes during the 13th Five-Year Plan is carried out. From 2000 to 2020,there is an increase to decrease fluctuation in country's total water consumption.The total water consumption in 2020 is almost the same as 20 years ago,but the water use structure has undergone certain adjustments,taking 2013 as the boundary point,the change in agricultural water use before 2013 dominated the change in total water use,with an average contribution rate of 5742%.After 2013,the change in industrial water consumption has taken up a relatively dominant position,with an average contribution rate of 44.3%.Domestic water consumption before 2012 was mainly due to the increase in water quota,and after 2012,the increase in domestic water consumption was mainly due to the increase in the urbanization rate.Industrial water consumption has always been strongly affected by the two driving forces of industrial-scale expansion and decline in industrial water quotas.Before 2011,the increase in industrial output value was dominant,and after 2011,the decline in industrial water quotas was even greater.Agricultural water use has always been dominated by irrigation area and agricultural water quotas.The effect of reducing agricultural water quota is slightly greater,but the expansion of irrigation area is always an important factor that can not be ignored.During the Thirteenth Five-Year Plan,the leading factor in the provinces to promote the water consumption growth was generally the increase in industrial output value or the expansion of agricultural irrigation area,while the leading factor in restraining the water consumption growth was the decline in the industrial water quota or the decline in the agricultural water quota.
2022, 20(3):429-439.
Abstract:
Medium and long-term hydrological forecasting is an essential link in management,optimization of water resources,flood control,drought relief,and reservoir optimal operation.With the rapid development of science and technology,many modern artificial intelligence (AI) models have been applied to hydrological forecasting,such as back-propagation artificial neural network,support vector machine and long short-term memory neural network.Among the AI models,convolutional neural network (CNN) is a unique deep network,which can fully excavate the correlation between data.Gated recurrent unit neural network (GRU),a kind of the recurrent neural network,is a variant of long short-term memory neural network (LSTM).GRU is often used in time-series data prediction and can solve the problem of gradient disappearance.The combined model of convolutional neural network and gated recurrent unit neural network (CNN-GRU) was applied in various fields except runoff prediction.Additionally,for the setting of the parameters of CNN-GRU hybrid neural network,most people used the control variable method for trial calculation,which was not only low in efficiency and low in accuracy.Hence,a combined prediction model (VMD-SMA-CNN-GRU) based on convolutional neural network and gated recurrent unit neural network was proposed by introducing slime mould algorithm (SMA) and variational mode decomposition (VMD). The four main steps of the present VMD-SMA-CNN-GRU forecasting model can be summarized as follows:The original runoff series was decomposed by VMD to obtain several intrinsic mode functions and a residual.The slime mould population size n and the maximum iteration M was set.Subsequently,SMA was used to optimize key parameters such as the number of convolution layers,the number of neurons in the hidden layer of GRU,training times and learning rate.The mean square error (MAE) was chosen as the objective function of the optimization algorithm.SMA-CNN-GRU model was used to predict all the subseries.The predicted values obtained above were accumulated to deduce the ultimate prediction results. Lanxi hydrological station was selected as an example to illustrate the advantages of VMD-SMA-CNN-GRU model using annual runoff data from 1959 to 2014.The data from 1959 to 2002 was selected as a training set while from 2003 to 2014 took as a test set.The proposed hybrid model was compared with CEEMDAN (Complete ensemble empirical mode decomposition with adaptive noise)-CNN-GRU model,VMD-CNN-LSTM model,VMD-LSTM model， VMD-GRU model,VMD-PSO (Particle swarm optimization)-CNN-GRU model,SMA-CNN-GRU model,and CNN-GRU model.Additionally,three standard statistical performances measures,namely root mean squared error (RMSE),mean absolute error (MAE) and mean absolute percentage error (MAPE) were employed to evaluate the performances of the six models mentioned above.In the training phase,all models except the CEEMDAN-CNN-GRU model achieved a better fit.In the validation phase,the VMD-SMA-CNN-GRU model predicted significantly better than several other models,especially in the case of predicted peaks.Results show that the SMA optimized VMD-CNN-GRU model has the best fitting effect,and the prediction accuracy is greater than that of the above seven comparison models. According to the results,there are several conclusions as follows:Runoff series has the characteristics of nonlinearity and non-stationarity.Therefore,VMD can decompose the original sequence into several relatively stable sub-sequences,which can be better fitted while increasing data.Low efficiency of manual trial calculations is avoided by SMA to determine the parameters of CNN-GRU model.The CNN-GRU model has the advantage of utilizing two neural networks simultaneously.The VMD-SMA-CNN-GRU model established effectively improves the accuracy of runoff prediction and provides a new method for annual runoff prediction.
Medium and long-term hydrological forecasting is an essential link in management,optimization of water resources,flood control,drought relief,and reservoir optimal operation.With the rapid development of science and technology,many modern artificial intelligence (AI) models have been applied to hydrological forecasting,such as back-propagation artificial neural network,support vector machine and long short-term memory neural network.Among the AI models,convolutional neural network (CNN) is a unique deep network,which can fully excavate the correlation between data.Gated recurrent unit neural network (GRU),a kind of the recurrent neural network,is a variant of long short-term memory neural network (LSTM).GRU is often used in time-series data prediction and can solve the problem of gradient disappearance.The combined model of convolutional neural network and gated recurrent unit neural network (CNN-GRU) was applied in various fields except runoff prediction.Additionally,for the setting of the parameters of CNN-GRU hybrid neural network,most people used the control variable method for trial calculation,which was not only low in efficiency and low in accuracy.Hence,a combined prediction model (VMD-SMA-CNN-GRU) based on convolutional neural network and gated recurrent unit neural network was proposed by introducing slime mould algorithm (SMA) and variational mode decomposition (VMD). The four main steps of the present VMD-SMA-CNN-GRU forecasting model can be summarized as follows:The original runoff series was decomposed by VMD to obtain several intrinsic mode functions and a residual.The slime mould population size n and the maximum iteration M was set.Subsequently,SMA was used to optimize key parameters such as the number of convolution layers,the number of neurons in the hidden layer of GRU,training times and learning rate.The mean square error (MAE) was chosen as the objective function of the optimization algorithm.SMA-CNN-GRU model was used to predict all the subseries.The predicted values obtained above were accumulated to deduce the ultimate prediction results. Lanxi hydrological station was selected as an example to illustrate the advantages of VMD-SMA-CNN-GRU model using annual runoff data from 1959 to 2014.The data from 1959 to 2002 was selected as a training set while from 2003 to 2014 took as a test set.The proposed hybrid model was compared with CEEMDAN (Complete ensemble empirical mode decomposition with adaptive noise)-CNN-GRU model,VMD-CNN-LSTM model,VMD-LSTM model， VMD-GRU model,VMD-PSO (Particle swarm optimization)-CNN-GRU model,SMA-CNN-GRU model,and CNN-GRU model.Additionally,three standard statistical performances measures,namely root mean squared error (RMSE),mean absolute error (MAE) and mean absolute percentage error (MAPE) were employed to evaluate the performances of the six models mentioned above.In the training phase,all models except the CEEMDAN-CNN-GRU model achieved a better fit.In the validation phase,the VMD-SMA-CNN-GRU model predicted significantly better than several other models,especially in the case of predicted peaks.Results show that the SMA optimized VMD-CNN-GRU model has the best fitting effect,and the prediction accuracy is greater than that of the above seven comparison models. According to the results,there are several conclusions as follows:Runoff series has the characteristics of nonlinearity and non-stationarity.Therefore,VMD can decompose the original sequence into several relatively stable sub-sequences,which can be better fitted while increasing data.Low efficiency of manual trial calculations is avoided by SMA to determine the parameters of CNN-GRU model.The CNN-GRU model has the advantage of utilizing two neural networks simultaneously.The VMD-SMA-CNN-GRU model established effectively improves the accuracy of runoff prediction and provides a new method for annual runoff prediction.
2022, 20(3):440-450.
Abstract:
Beijing-Tianjin-Hebei region is a political and economic center of North China,but its water resources per capita are less than one-tenth of the national average.Water resources competition caused by the contradiction between supply and demand has become a normal situation in this region.The phenomenon of water competition referred to the contradictions and conflicts in the use of water resources in terms of purpose,time and location.Due to water resources scarcity and uneven distribution,the disputes between the Guanting Reservoir and the Miyun Reservoir are the same.Given the limited water supply in this area,it is far from being able to meet the needs of regional development.Through the implementation of the South-to-North Water Transfer Project,China has transferred a part of the water resources from the abundant southern areas to the waterdeficient areas in the north.The goal is to alleviate the current outstanding water competition pressure.The transfer of a large number of externally transferred water sources has contributed to ensuring the sustainable development of the social economy and water resources of the Beijing-Tianjin-Hebei.But at the same time,it has also changed regional water supply and demand pattern,directly affecting water competition situation.Therefore,a quantitative analysis of the impact of the South-to-North Water Transfer Project on the competition of water resources in the Beijing-Tianjin-Hebei region is of great significance to ensure the rational use of regional water resources. The proposed water competitiveness mainly includes four parts;the main body of the competition,the demand for interests,the nature of the competition,and the objectives of the competition.If the existing water resources can not meet the water needs of all the main water users,the main water users had to obtain more and better water resources through competition to ensure basic production and domestic water use.This kind of water main body′s attraction and competition for water resources was defined as regional water competitiveness.The competitiveness of water use was inseparable from factors such as water driving factors,rigid demand,and water efficiency.Therefore,this study used driving growth rate,rigid water demand,water efficiency,and water scarcity as the four evaluation indicators of water competitiveness.The four evaluation indicators of each industry need to be calculated according to formulas to obtain different types of water competitiveness.Then the four evaluation indicators are standardized and substituted into corresponding formulas to calculate the water competitiveness index of each industry.Finally,the water competition index of each industry in the region was added to obtain the regional water competitiveness,to quantitatively analyze the size of the water competitiveness of each industry and region. Results showed that according to the set of multiple water scenarios (S1,S2,S3),the supply amount of a baseline scenario (S0) rose more than 20%,respectively,and BeijingTianjinHebei is tapping to Handan,Xingtai,phase ii of the eastern front in the (S3),there is still a large gap of water supply,after the completion of other local rigid demand in south-to-north water transfer supply.In addition,compared to S0 scenario,agricultural,industrial and domestic water competitiveness indices of Beijing-Tianjin-Hebei water-affected cities decreased by 10.6%,15.1%,and 26.1% on average under S1,S2,and S3 scenarios,and regional water competitiveness indices decreased by 11.5%,16.9%,and 19.8%,respectively.Among them,Tianjin and Beijing displayed the biggest decline in their comprehensive,with an average of 26.6%. Under the combined supply of water from the South-to-North Water Transfer project and the local water resources,the water shortage in the three industries of living,industry,and agriculture has been alleviated to varying degrees.The rigid water demand of all industries can be satisfied,and the domestic water shortage decreases the fastest,followed by industry and agriculture.Compared with the baseline scenario (S0),the industrial water competitiveness of each water supply area in Beijing-Tianjin-Hebei decreased by 17.3% and the regional water competitiveness decreased by 16.1% on average.In terms of space,the distribution characteristics have changed from a double center in the Bohai Bay Rim and southern Hebei to a single center in southern Hebei.In general,although the water transfer from the south-to-north does not eliminate the water resource competition problem in Beijing-Tianjin-Hebei region,it still greatly alleviates the water pressure,which is of great significance to the sustainable development of water resources and the optimal allocation of water resources in the region.
Beijing-Tianjin-Hebei region is a political and economic center of North China,but its water resources per capita are less than one-tenth of the national average.Water resources competition caused by the contradiction between supply and demand has become a normal situation in this region.The phenomenon of water competition referred to the contradictions and conflicts in the use of water resources in terms of purpose,time and location.Due to water resources scarcity and uneven distribution,the disputes between the Guanting Reservoir and the Miyun Reservoir are the same.Given the limited water supply in this area,it is far from being able to meet the needs of regional development.Through the implementation of the South-to-North Water Transfer Project,China has transferred a part of the water resources from the abundant southern areas to the waterdeficient areas in the north.The goal is to alleviate the current outstanding water competition pressure.The transfer of a large number of externally transferred water sources has contributed to ensuring the sustainable development of the social economy and water resources of the Beijing-Tianjin-Hebei.But at the same time,it has also changed regional water supply and demand pattern,directly affecting water competition situation.Therefore,a quantitative analysis of the impact of the South-to-North Water Transfer Project on the competition of water resources in the Beijing-Tianjin-Hebei region is of great significance to ensure the rational use of regional water resources. The proposed water competitiveness mainly includes four parts;the main body of the competition,the demand for interests,the nature of the competition,and the objectives of the competition.If the existing water resources can not meet the water needs of all the main water users,the main water users had to obtain more and better water resources through competition to ensure basic production and domestic water use.This kind of water main body′s attraction and competition for water resources was defined as regional water competitiveness.The competitiveness of water use was inseparable from factors such as water driving factors,rigid demand,and water efficiency.Therefore,this study used driving growth rate,rigid water demand,water efficiency,and water scarcity as the four evaluation indicators of water competitiveness.The four evaluation indicators of each industry need to be calculated according to formulas to obtain different types of water competitiveness.Then the four evaluation indicators are standardized and substituted into corresponding formulas to calculate the water competitiveness index of each industry.Finally,the water competition index of each industry in the region was added to obtain the regional water competitiveness,to quantitatively analyze the size of the water competitiveness of each industry and region. Results showed that according to the set of multiple water scenarios (S1,S2,S3),the supply amount of a baseline scenario (S0) rose more than 20%,respectively,and BeijingTianjinHebei is tapping to Handan,Xingtai,phase ii of the eastern front in the (S3),there is still a large gap of water supply,after the completion of other local rigid demand in south-to-north water transfer supply.In addition,compared to S0 scenario,agricultural,industrial and domestic water competitiveness indices of Beijing-Tianjin-Hebei water-affected cities decreased by 10.6%,15.1%,and 26.1% on average under S1,S2,and S3 scenarios,and regional water competitiveness indices decreased by 11.5%,16.9%,and 19.8%,respectively.Among them,Tianjin and Beijing displayed the biggest decline in their comprehensive,with an average of 26.6%. Under the combined supply of water from the South-to-North Water Transfer project and the local water resources,the water shortage in the three industries of living,industry,and agriculture has been alleviated to varying degrees.The rigid water demand of all industries can be satisfied,and the domestic water shortage decreases the fastest,followed by industry and agriculture.Compared with the baseline scenario (S0),the industrial water competitiveness of each water supply area in Beijing-Tianjin-Hebei decreased by 17.3% and the regional water competitiveness decreased by 16.1% on average.In terms of space,the distribution characteristics have changed from a double center in the Bohai Bay Rim and southern Hebei to a single center in southern Hebei.In general,although the water transfer from the south-to-north does not eliminate the water resource competition problem in Beijing-Tianjin-Hebei region,it still greatly alleviates the water pressure,which is of great significance to the sustainable development of water resources and the optimal allocation of water resources in the region.
2022, 20(3):451-458.
Abstract:
Reservoir operation is an important cause of runoff process alteration.Quantifying the influence of reservoir on runoff [JP2]process is the basis of identifying the ecological impact of reservoir and improving the ecological protection function of a reservoir.In previous studies,the main method to evaluate the influence of reservoir on runoff process is to compare the key characteristics of the runoff process in the past and post operation period of a reservoir.However,the river runoff process is influenced by many factors,such as climate [JP]change,engineering regulation,water intake,water withdrawal,and so on.Thus,the difference in the runoff process before and after reservoir operation reflects the joint influence of multiple factors rather than only the reservoir. Longyangxia reservoir,located in the upper reaches of the Yellow River,is the only multi-year regulation reservoir on the mainstream of the Yellow River,having a strong regulation capacity for the runoff.Taking the Longyangxia Reservoir as an example,the difference indicators of hydrologic alteration and flow deviation indicator between the inflow runoff and the outflow runoff of Longyangxia Reservoir from 1986 to 2016 are compared.The influence of reservoir on runoff process was quantified based on the indicator value differences and the Mann-Kendall test.Then a significance test is used to reveal the relationship between reservoir water replenishment,the natural runoff,and the proportion of surface water consumption in natural runoff in the Yellow River Basin. Results showed that the outflow runoff of Longyangxia Reservoir changed significantly compared with the inflow runoff from 1986 to 2016.For mean annual flow,the extreme value ratio decreased by 24.84% and the coefficient of variation decreased by 26.92%.For mean monthly flow,it decreased from June to October while increased from November to May.For mean daily flow,the runoff process became smoother but small-scale fluctuation increased.The annual maxima 1,3,7,30,and 90 day mean decreased 34.74%~47.30%;the annual minima 1,3,7,30,and 90 day means increased 38.99%~144.43%;the means of all positive differences between consecutive daily values,the mean of all negative differences between consecutive daily values and the number of flow reversals increased significantly.Among the 33 indicators of hydrologic alteration,27 indicators were highly altered.The overall degree of hydrologic alteration was 95.04%,meaning the outflow runoff of Longyangxia Reservoir was highly altered compared with the inflow runoff.The operation of Longyangxia Reservoir led to a serious deviation of the runoff process from the natural situation.The result of the Mann-Kendall test showed that the value of the flow deviation indicator of reservoir outflow runoff mutated in 1986 when Longyangxia Reservoir firstly impounded water.The mean value of the flow deviation indicator after impoundment was 43 times that before impoundment.From 1980 to 1985,the mean value of flow deviation indicator was 0.05,while from 1986 to 2016,the mean value of flow deviation indicator increased to 2.15. Longyangxia Reservoir changed the runoff process of the Yellow River by impounding and replenishing water.It was revealed that there was a significant negative correlation between the annual replenishment of Longyangxia Reservoir and the natural runoff of the Yellow River,while there was a significant positive correlation between the annual replenishment of Longyangxia[JP] Reservoir and the proportion of surface water consumption in the natural runoff in the Yellow River basin.From 1986 to 2016,when the proportion of surface water consumption in natural runoff in the Yellow River basin exceeded 64%,the year that Longyangxia Reservoir replenished water took up 8462%.When the proportion of surface water consumption in natural runoff in the Yellow [JP2]River basin was below 64%,the year that Longyangxia Reservoir impounded water took up 75.00%.The Longyangxia [JP]Reservoir played an important role in ensuring the social water supply and river ecological water supply in dry years.
Reservoir operation is an important cause of runoff process alteration.Quantifying the influence of reservoir on runoff [JP2]process is the basis of identifying the ecological impact of reservoir and improving the ecological protection function of a reservoir.In previous studies,the main method to evaluate the influence of reservoir on runoff process is to compare the key characteristics of the runoff process in the past and post operation period of a reservoir.However,the river runoff process is influenced by many factors,such as climate [JP]change,engineering regulation,water intake,water withdrawal,and so on.Thus,the difference in the runoff process before and after reservoir operation reflects the joint influence of multiple factors rather than only the reservoir. Longyangxia reservoir,located in the upper reaches of the Yellow River,is the only multi-year regulation reservoir on the mainstream of the Yellow River,having a strong regulation capacity for the runoff.Taking the Longyangxia Reservoir as an example,the difference indicators of hydrologic alteration and flow deviation indicator between the inflow runoff and the outflow runoff of Longyangxia Reservoir from 1986 to 2016 are compared.The influence of reservoir on runoff process was quantified based on the indicator value differences and the Mann-Kendall test.Then a significance test is used to reveal the relationship between reservoir water replenishment,the natural runoff,and the proportion of surface water consumption in natural runoff in the Yellow River Basin. Results showed that the outflow runoff of Longyangxia Reservoir changed significantly compared with the inflow runoff from 1986 to 2016.For mean annual flow,the extreme value ratio decreased by 24.84% and the coefficient of variation decreased by 26.92%.For mean monthly flow,it decreased from June to October while increased from November to May.For mean daily flow,the runoff process became smoother but small-scale fluctuation increased.The annual maxima 1,3,7,30,and 90 day mean decreased 34.74%~47.30%;the annual minima 1,3,7,30,and 90 day means increased 38.99%~144.43%;the means of all positive differences between consecutive daily values,the mean of all negative differences between consecutive daily values and the number of flow reversals increased significantly.Among the 33 indicators of hydrologic alteration,27 indicators were highly altered.The overall degree of hydrologic alteration was 95.04%,meaning the outflow runoff of Longyangxia Reservoir was highly altered compared with the inflow runoff.The operation of Longyangxia Reservoir led to a serious deviation of the runoff process from the natural situation.The result of the Mann-Kendall test showed that the value of the flow deviation indicator of reservoir outflow runoff mutated in 1986 when Longyangxia Reservoir firstly impounded water.The mean value of the flow deviation indicator after impoundment was 43 times that before impoundment.From 1980 to 1985,the mean value of flow deviation indicator was 0.05,while from 1986 to 2016,the mean value of flow deviation indicator increased to 2.15. Longyangxia Reservoir changed the runoff process of the Yellow River by impounding and replenishing water.It was revealed that there was a significant negative correlation between the annual replenishment of Longyangxia Reservoir and the natural runoff of the Yellow River,while there was a significant positive correlation between the annual replenishment of Longyangxia[JP] Reservoir and the proportion of surface water consumption in the natural runoff in the Yellow River basin.From 1986 to 2016,when the proportion of surface water consumption in natural runoff in the Yellow River basin exceeded 64%,the year that Longyangxia Reservoir replenished water took up 8462%.When the proportion of surface water consumption in natural runoff in the Yellow [JP2]River basin was below 64%,the year that Longyangxia Reservoir impounded water took up 75.00%.The Longyangxia [JP]Reservoir played an important role in ensuring the social water supply and river ecological water supply in dry years.
2022, 20(3):459-467.
Abstract:
Drought is considered to be the most costly natural disaster,and it is repetitive.This disaster has a serious impact on agricultural production and life.Compared with other types of disasters,it has a wide range,long impacted,large losses,and spreading trends.Since 1990s,drought in China has become more serious and frequent.According to the differences of water-affected objects in different links of the water cycle,drought is generally divided into meteorological drought,hydrological drought,agricultural drought,and socio-economic drought.The occurrence of different types of drought has a progressive relationship in time.Meteorological drought is the root of other drought types and plays a key role in the transmission chain of drought disasters.The occurrence of hydrological drought is slower than that of meteorological drought,and its duration is longer than meteorological drought.The occurrence of meteorological drought is generally difficult to control,but the impact of hydrological drought can be avoided or reduced through certain measures.In the research on the transmission of different types of drought,the analysis of the characteristics and spatial distribution of specific types of drought in the basin are focused on.In the analysis process,a single drought index is selected to discuss the drought situation. Losses are caused by the evolution of different types of drought. In order to reduce the occurrence of such phenomena,meteorological drought and hydrological drought will be analyzed by calculating the standardized precipitation index (SPI) and standardized runoff index (SRI) for the monthly precipitation and monthly runoff of Delingha station from 1961 to 2019.The Mann-Kendall test will be used to used to evaluate drought trends.The propagation time between meteorological drought and hydrological drought and the seasonal response of hydrological drought to meteorological drought will be studied in this paper to explore the possible influence and driving factors of meteorological drought on the spread of hydrological drought. The results show that there are obvious differences in the standardized precipitation index (SPI) values at different time scales,but the drought trend is roughly the same.The fluctuation of the monthly scale (SPI1) is the strongest,and the fluctuation slows down with the increase of the time scale.The results of SRI have similar characteristics to meteorological drought.The fluctuation range of SRI value under different time scales is different,but the drought trend is roughly the same.The fluctuation of SRI1 is the strongest,which shows that the smaller the time scale,the stronger the SRI response to hydrological drought.From 1961 to 2019,the meteorological drought and hydrological drought in Bayin River basin showed a slowing trend,the precipitation in the basin increased and tended to basin become wet.The meteorological drought situation in the basin was the most severe in the 1960s,showing moderate to severe drought on the whole.There was a sudden change in meteorological drought in 1985,and then the wet years in the basin increased significantly.The hydrological drought in the basin was more serious in the 1990s,showing a moderate to severe drought state.Hydrological drought has rarely occurred in the basin since the 21st century.Mann Kendall trend test results show that the abrupt change point of hydrological drought in the basin is 2002,and the number of years showing a hydrological humid state has increased since 2002.The correlation between hydrological drought and meteorological drought in the Bayin River basin is the strongest on the 12-month scale.The time lag cross-correlation analysis of meteorological drought index and hydrological drought index on the 12-month scale shows that the response of [JP2]hydrological drought to meteorological drought in Bayin River basin shows time lag,and the hydrological drought lags behind the meteorological drought for 1-2 months.The seasonal response of hydrological drought to meteorological drought shows that the correlation intensity of the rainy season is higher than that of the dry season.Hydrological drought responds most rapidly to meteorological drought in spring.The response of hydrological drought to meteorological drought in spring and summer is faster than that in autumn and winter.The seasonal response of hydrological drought to meteorological drought lags 5,6,9,and 8 months in spring,summer,autumn and winter.On the whole,The lag time in spring and summer is shorter than that in autumn and winter. This shows that timely detection and corresponding measures in the meteorological drought stage can effectively prevent the further development of meteorological drought into hydrological drought.Because the hydrological drought in Bayin River basin responds quickly to meteorological drought in spring and summer,more attention should be paid to the drought state of the basin in the rainy season.Although the Bayin River basin shows a wetting trend during the study period,the prevention and control of drought in the Bayin River basin are still worthy of attention in the northwest inland area with a lack of water resources.In the context of global warming,considering the continuous rise of temperature,evapotranspiration will become an important part of the future.In addition,with the gradual improvement and operation of water conservancy projects,the impact of future human activities will also aggravate the impact of the water cycle in the convective domain.Therefore,it will become one of the important directions of watershed hydrological research to select the comprehensive drought index from the perspective of ecology and social economy,carry out multi-factor comprehensive analysis,and reasonably simulate the increasingly complex hydrological process to provide a more perfect drought risk assessment.
Drought is considered to be the most costly natural disaster,and it is repetitive.This disaster has a serious impact on agricultural production and life.Compared with other types of disasters,it has a wide range,long impacted,large losses,and spreading trends.Since 1990s,drought in China has become more serious and frequent.According to the differences of water-affected objects in different links of the water cycle,drought is generally divided into meteorological drought,hydrological drought,agricultural drought,and socio-economic drought.The occurrence of different types of drought has a progressive relationship in time.Meteorological drought is the root of other drought types and plays a key role in the transmission chain of drought disasters.The occurrence of hydrological drought is slower than that of meteorological drought,and its duration is longer than meteorological drought.The occurrence of meteorological drought is generally difficult to control,but the impact of hydrological drought can be avoided or reduced through certain measures.In the research on the transmission of different types of drought,the analysis of the characteristics and spatial distribution of specific types of drought in the basin are focused on.In the analysis process,a single drought index is selected to discuss the drought situation. Losses are caused by the evolution of different types of drought. In order to reduce the occurrence of such phenomena,meteorological drought and hydrological drought will be analyzed by calculating the standardized precipitation index (SPI) and standardized runoff index (SRI) for the monthly precipitation and monthly runoff of Delingha station from 1961 to 2019.The Mann-Kendall test will be used to used to evaluate drought trends.The propagation time between meteorological drought and hydrological drought and the seasonal response of hydrological drought to meteorological drought will be studied in this paper to explore the possible influence and driving factors of meteorological drought on the spread of hydrological drought. The results show that there are obvious differences in the standardized precipitation index (SPI) values at different time scales,but the drought trend is roughly the same.The fluctuation of the monthly scale (SPI1) is the strongest,and the fluctuation slows down with the increase of the time scale.The results of SRI have similar characteristics to meteorological drought.The fluctuation range of SRI value under different time scales is different,but the drought trend is roughly the same.The fluctuation of SRI1 is the strongest,which shows that the smaller the time scale,the stronger the SRI response to hydrological drought.From 1961 to 2019,the meteorological drought and hydrological drought in Bayin River basin showed a slowing trend,the precipitation in the basin increased and tended to basin become wet.The meteorological drought situation in the basin was the most severe in the 1960s,showing moderate to severe drought on the whole.There was a sudden change in meteorological drought in 1985,and then the wet years in the basin increased significantly.The hydrological drought in the basin was more serious in the 1990s,showing a moderate to severe drought state.Hydrological drought has rarely occurred in the basin since the 21st century.Mann Kendall trend test results show that the abrupt change point of hydrological drought in the basin is 2002,and the number of years showing a hydrological humid state has increased since 2002.The correlation between hydrological drought and meteorological drought in the Bayin River basin is the strongest on the 12-month scale.The time lag cross-correlation analysis of meteorological drought index and hydrological drought index on the 12-month scale shows that the response of [JP2]hydrological drought to meteorological drought in Bayin River basin shows time lag,and the hydrological drought lags behind the meteorological drought for 1-2 months.The seasonal response of hydrological drought to meteorological drought shows that the correlation intensity of the rainy season is higher than that of the dry season.Hydrological drought responds most rapidly to meteorological drought in spring.The response of hydrological drought to meteorological drought in spring and summer is faster than that in autumn and winter.The seasonal response of hydrological drought to meteorological drought lags 5,6,9,and 8 months in spring,summer,autumn and winter.On the whole,The lag time in spring and summer is shorter than that in autumn and winter. This shows that timely detection and corresponding measures in the meteorological drought stage can effectively prevent the further development of meteorological drought into hydrological drought.Because the hydrological drought in Bayin River basin responds quickly to meteorological drought in spring and summer,more attention should be paid to the drought state of the basin in the rainy season.Although the Bayin River basin shows a wetting trend during the study period,the prevention and control of drought in the Bayin River basin are still worthy of attention in the northwest inland area with a lack of water resources.In the context of global warming,considering the continuous rise of temperature,evapotranspiration will become an important part of the future.In addition,with the gradual improvement and operation of water conservancy projects,the impact of future human activities will also aggravate the impact of the water cycle in the convective domain.Therefore,it will become one of the important directions of watershed hydrological research to select the comprehensive drought index from the perspective of ecology and social economy,carry out multi-factor comprehensive analysis,and reasonably simulate the increasingly complex hydrological process to provide a more perfect drought risk assessment.
2022, 20(3):468-477.
Abstract:
Hydrologic stochastic model can provide a scientific and decision-making basis for alleviating water resources problems by simulating a large number of random sequences for hydrologic system.However,the simulation series generated by the same stochastic model was quite different in time and process changes and the traditional statistical parameter test method ignored the variation characteristics of runoff as a time series,which can not fully reflect the complex variation characteristics of flow in time series distribution,and failed to select the most suitable runoff simulation series for engineering planning and design and risk analysis.Therefore,a set of evaluation index system of monthly runoff random generation series is proposed,which incoporates statistical characteristics of runoff simulation series at different time intersections and the complex variation characteristics of runoff series.Three hydrological stations in the main and tributary streams of the Huaihe River basin are taken as the research object to establish a seasonal autoregressive model,three evaluation methods are selected based on constructed index system and multiple sets of randomly generated monthly runoff simulation sequences.The sequence comparison aimed to provide a more accurate and reliable new way to identify the random simulation sequence of monthly runoff. Starting from the nonlinear and complex characteristics of runoff series,indicators such as concentration,uneven coefficient and sample entropy based on traditional test indicators,and a set of index systems is proposed that characterize the statistical parameter characteristics and complex changes of the runoff series.The accuracy of the simulation sequence was analyzed,and the simulation sequence was optimized by the gray correlation analysis method.The fitting results of the three evaluation methods (traditional index,minimum entropy index of sample and index) were compared and analyzed to illustrate the rationality of the index.Moreover,the advantages of the proposed evaluation index system were further verified from the two aspects of the abnormal situation of the year allocation and the difference of annual time history distribution (process) of runoff. Comparison results of the optimized sequences of the three evaluation methods showed that:(1) In the evaluation of statistical characteristics of runoff simulation series at different time intersections,the difference of the average absolute percentage error of the simulation sequence optimized by the three indexes was small,and the maximum error was 2%.(2) In the evaluation of complex change characteristics,the difference of average absolute percentage error was large.The maximum error difference between the optimization sequence based on the index and the traditional index was 8%,and the maximum error difference between the optimization sequence based on the index and the sample entropy index was 4%.The selected sequence performed well in the evaluation of statistical parameter characteristics and complex change characteristics,and the most significant difference was in complex change characteristics compared with the other two evaluation methods.(3) The results showed that the performance of the series selected was good in the annual distribution characteristics of each level,and the relative error was generally smaller than that of the series selected by traditional index and sample entropy index,and the difference between the relative error in normal and dry years was the most obvious. In conclusion,the three evaluation methods were effective in maintaining the characteristics of the runoff series,but the previous index system can not comprehensively evaluate the simulation series,which may omit the important details of the runoff series,thus affecting the accuracy of the simulation series.In this index system,the indexes which represented the complex change characteristics can simply and effectively distinguish the ability of simulation series in maintaining the complex change characteristics of measured series.The selected series can better reflect the change process and complex characteristics of the measured series,and the overall fitting effect of annual distribution was also the best.The order of merit and demerit of the three methods was the proposed index of this paper>the index of sample entropy>the traditional index.The results showed that the proposed index system comprehensively considered the statistical parameters of the section and the characteristics of complex changes was feasible.The abnormal situation of the year allocation and the difference of annual time history distribution (process) of runoff were analyzed,the results showed that the advantage of proposed index,which is beneficial to a comprehensive evaluation of runoff simulation series and realizes the random simulation comparison and optimization among different series,thereby provided more accurate hydrological simulation sequences.
Hydrologic stochastic model can provide a scientific and decision-making basis for alleviating water resources problems by simulating a large number of random sequences for hydrologic system.However,the simulation series generated by the same stochastic model was quite different in time and process changes and the traditional statistical parameter test method ignored the variation characteristics of runoff as a time series,which can not fully reflect the complex variation characteristics of flow in time series distribution,and failed to select the most suitable runoff simulation series for engineering planning and design and risk analysis.Therefore,a set of evaluation index system of monthly runoff random generation series is proposed,which incoporates statistical characteristics of runoff simulation series at different time intersections and the complex variation characteristics of runoff series.Three hydrological stations in the main and tributary streams of the Huaihe River basin are taken as the research object to establish a seasonal autoregressive model,three evaluation methods are selected based on constructed index system and multiple sets of randomly generated monthly runoff simulation sequences.The sequence comparison aimed to provide a more accurate and reliable new way to identify the random simulation sequence of monthly runoff. Starting from the nonlinear and complex characteristics of runoff series,indicators such as concentration,uneven coefficient and sample entropy based on traditional test indicators,and a set of index systems is proposed that characterize the statistical parameter characteristics and complex changes of the runoff series.The accuracy of the simulation sequence was analyzed,and the simulation sequence was optimized by the gray correlation analysis method.The fitting results of the three evaluation methods (traditional index,minimum entropy index of sample and index) were compared and analyzed to illustrate the rationality of the index.Moreover,the advantages of the proposed evaluation index system were further verified from the two aspects of the abnormal situation of the year allocation and the difference of annual time history distribution (process) of runoff. Comparison results of the optimized sequences of the three evaluation methods showed that:(1) In the evaluation of statistical characteristics of runoff simulation series at different time intersections,the difference of the average absolute percentage error of the simulation sequence optimized by the three indexes was small,and the maximum error was 2%.(2) In the evaluation of complex change characteristics,the difference of average absolute percentage error was large.The maximum error difference between the optimization sequence based on the index and the traditional index was 8%,and the maximum error difference between the optimization sequence based on the index and the sample entropy index was 4%.The selected sequence performed well in the evaluation of statistical parameter characteristics and complex change characteristics,and the most significant difference was in complex change characteristics compared with the other two evaluation methods.(3) The results showed that the performance of the series selected was good in the annual distribution characteristics of each level,and the relative error was generally smaller than that of the series selected by traditional index and sample entropy index,and the difference between the relative error in normal and dry years was the most obvious. In conclusion,the three evaluation methods were effective in maintaining the characteristics of the runoff series,but the previous index system can not comprehensively evaluate the simulation series,which may omit the important details of the runoff series,thus affecting the accuracy of the simulation series.In this index system,the indexes which represented the complex change characteristics can simply and effectively distinguish the ability of simulation series in maintaining the complex change characteristics of measured series.The selected series can better reflect the change process and complex characteristics of the measured series,and the overall fitting effect of annual distribution was also the best.The order of merit and demerit of the three methods was the proposed index of this paper>the index of sample entropy>the traditional index.The results showed that the proposed index system comprehensively considered the statistical parameters of the section and the characteristics of complex changes was feasible.The abnormal situation of the year allocation and the difference of annual time history distribution (process) of runoff were analyzed,the results showed that the advantage of proposed index,which is beneficial to a comprehensive evaluation of runoff simulation series and realizes the random simulation comparison and optimization among different series,thereby provided more accurate hydrological simulation sequences.
2022, 20(3):478-486.
Abstract:
Predicting the migration and transformation process of contaminants by utilizing numerical models is a commonly used method.The accuracy of model parameters could seriously affect the simulation results.While in practical site investigation,model parameters are often unavailable to obtain directly,thus it is needed to be estimated by solving the inverse problem of groundwater.In recent years,data assimilation has become a prevalent method for parametric uncertainty quantification.It can provide an estimate of the unknown model parameters by combining the observation data with the underlying dynamical principles governing the system.When solving high dimensional inversion problems,conventional observation methods can only provide sparse information (such as mass concentration and hydraulic head),so it can hinder the accuracy of the results.To deal with this issue,geophysical methods (such as electrical resistance tomography) are introduced to combine with the data assimilation because they can provide a large amount of continuous observation data. The groundwater flow and solute transport model was constructed with the MODFLOW and MT3DMS programs and KL expansion was introduced to implement the dimensionality reduction of the hydraulic conductivity field.An inversion method for groundwater model parameters based on the ensemble smoother with multiple data assimilation (ES-MDA) was proposed.The joint inversion of contaminant source strength and hydraulic conductivity field was realized by integrating conventional observation data (mass concentration and hydraulic head) and geophysical data (ERT data) collected through the electrical resistance tomography (ERT).Three numerical cases were designed based on the former ideas to compare the inversion accuracy with different types of observation data.All three cases were the ES-MDA algorithm as the data assimilation method,while Case 1 was integrated the mass concentration and hydraulic head as the observation data;Case 2 was integrated the ERT data as the observation data and Case 3 was integrated the three types of data simultaneously.The root-mean-square error (ERMS) was used to quantify the accuracy of the inversion results of the three cases. The results showed that the ERMS value for estimating the contaminant source strength got smaller (closer to zero) from Case 1 to Case 3,which exhibited that Case 3 obtained more accurate results by integrating multi-source observation data.As for the characterization of the hydraulic conductivity field,the posterior mean estimate of the log-conductivity field of Case 3 depicted the spatial distribution of the lnK field more accurately and its goodness of fit with the reference field was better than that of Case 1 and Case 2,which also demonstrated the advantage of using multi-source data as the observation. ES-MDA algorithm could be utilized to realize the joint inversion of contaminant source strength and hydraulic conductivity field by assimilating both conventional observation data (mass concentration and hydraulic head) and ERT data.The inversion results by assimilating ERT data showed better accuracy than the case with conventional observation data,which demonstrated that a large amount of continuous geophysical data could provide more effective information for the inversion.The inversion results could be further optimized by combing the ERT data with the conventional observation data of mass concentration and head.It also showed the importance of using multi-source observation data when dealing with inversion problems.
Predicting the migration and transformation process of contaminants by utilizing numerical models is a commonly used method.The accuracy of model parameters could seriously affect the simulation results.While in practical site investigation,model parameters are often unavailable to obtain directly,thus it is needed to be estimated by solving the inverse problem of groundwater.In recent years,data assimilation has become a prevalent method for parametric uncertainty quantification.It can provide an estimate of the unknown model parameters by combining the observation data with the underlying dynamical principles governing the system.When solving high dimensional inversion problems,conventional observation methods can only provide sparse information (such as mass concentration and hydraulic head),so it can hinder the accuracy of the results.To deal with this issue,geophysical methods (such as electrical resistance tomography) are introduced to combine with the data assimilation because they can provide a large amount of continuous observation data. The groundwater flow and solute transport model was constructed with the MODFLOW and MT3DMS programs and KL expansion was introduced to implement the dimensionality reduction of the hydraulic conductivity field.An inversion method for groundwater model parameters based on the ensemble smoother with multiple data assimilation (ES-MDA) was proposed.The joint inversion of contaminant source strength and hydraulic conductivity field was realized by integrating conventional observation data (mass concentration and hydraulic head) and geophysical data (ERT data) collected through the electrical resistance tomography (ERT).Three numerical cases were designed based on the former ideas to compare the inversion accuracy with different types of observation data.All three cases were the ES-MDA algorithm as the data assimilation method,while Case 1 was integrated the mass concentration and hydraulic head as the observation data;Case 2 was integrated the ERT data as the observation data and Case 3 was integrated the three types of data simultaneously.The root-mean-square error (ERMS) was used to quantify the accuracy of the inversion results of the three cases. The results showed that the ERMS value for estimating the contaminant source strength got smaller (closer to zero) from Case 1 to Case 3,which exhibited that Case 3 obtained more accurate results by integrating multi-source observation data.As for the characterization of the hydraulic conductivity field,the posterior mean estimate of the log-conductivity field of Case 3 depicted the spatial distribution of the lnK field more accurately and its goodness of fit with the reference field was better than that of Case 1 and Case 2,which also demonstrated the advantage of using multi-source data as the observation. ES-MDA algorithm could be utilized to realize the joint inversion of contaminant source strength and hydraulic conductivity field by assimilating both conventional observation data (mass concentration and hydraulic head) and ERT data.The inversion results by assimilating ERT data showed better accuracy than the case with conventional observation data,which demonstrated that a large amount of continuous geophysical data could provide more effective information for the inversion.The inversion results could be further optimized by combing the ERT data with the conventional observation data of mass concentration and head.It also showed the importance of using multi-source observation data when dealing with inversion problems.
2022, 20(3):487-497,551.
Abstract:
Metal-based compounds are promising adsorbents for phosphate.A novel dual metal-organic framework as an effective adsorbent for phosphate was synthesized by a solvothermal method.The structure analysis revealed that the as-prepared adsorbent (denoted as MIL-101(Fe/Zr)) possessed a porous polyhedral structure with a large specific surface area of 479.1 m2/g and a pore width of 3.4 nm.The X-ray diffraction pattern and Fourier transform infrared spectra suggested that the MIL-101(Fe/Zr) shared a similar structure with MIL-101(Fe),implying successful incorporation of Zr atoms as a second metal into the MIL-101(Fe) structure.Kinetic adsorption of PO43—by MIL-101(Fe/Zr) conformed to the pseudo-second-order model and intraparticle diffusion model,while adsorption isotherm fitted the Freundlich model well (R2=0.978 5).It is suggested that such an adsorption belonged to multiply-layer adsorption.The adsorption capacity of MIL-101(Fe/Zr) was to be 66.00 mg/g.MIL-101(Fe/Zr) performed well at a wide range of pH 2.0~10.0 and high ionic strength (0~40 mg/L NaCl).A structural analysis indicated that the complexation interaction was mainly responsible for PO43—adsorption.These findings can inspire preparation of other dual metal MOFs adsorbent for phosphate removal and recovery from water.
Metal-based compounds are promising adsorbents for phosphate.A novel dual metal-organic framework as an effective adsorbent for phosphate was synthesized by a solvothermal method.The structure analysis revealed that the as-prepared adsorbent (denoted as MIL-101(Fe/Zr)) possessed a porous polyhedral structure with a large specific surface area of 479.1 m2/g and a pore width of 3.4 nm.The X-ray diffraction pattern and Fourier transform infrared spectra suggested that the MIL-101(Fe/Zr) shared a similar structure with MIL-101(Fe),implying successful incorporation of Zr atoms as a second metal into the MIL-101(Fe) structure.Kinetic adsorption of PO43—by MIL-101(Fe/Zr) conformed to the pseudo-second-order model and intraparticle diffusion model,while adsorption isotherm fitted the Freundlich model well (R2=0.978 5).It is suggested that such an adsorption belonged to multiply-layer adsorption.The adsorption capacity of MIL-101(Fe/Zr) was to be 66.00 mg/g.MIL-101(Fe/Zr) performed well at a wide range of pH 2.0~10.0 and high ionic strength (0~40 mg/L NaCl).A structural analysis indicated that the complexation interaction was mainly responsible for PO43—adsorption.These findings can inspire preparation of other dual metal MOFs adsorbent for phosphate removal and recovery from water.
2022, 20(3):498-505.
Abstract:
Under climate warming and anthropogenic activities,the hydrological cycle and river flow regime have been significantly altered,challenging the traditional strategies of water resources management.Recently,water ecological environment protection on basin-scale has been paid great attention in China.Most of administrative regions are the key water ecological civilization construction regions,thus,it is urgent to evaluate the water ecological civilization construction at a river basin scale.Han River basin is the first pilot of the most stringent water resource management basin,and water source area of the Middle Route South-to-North Water Transfer Project in China.The basin governed by 14 administrative regions (or cities) is selected as evaluation units,and a multi-system,multi-landform and multi-scale indicator characterization method based on the characteristics of the water ecological civilization of the basin is developed. The evaluation indexes for water ecological civilization basin is based on the evaluation guide of water ecological civilization construction.The selection guideline is based on upper,middle and lower reaches of the basin and single landform to multiple landforms,that can not only reflect the characteristics of regional features but also grasp the overall situation.After comprehensive consideration,the evaluation index system of water ecological civilization construction was established at an administrative region scale.This system is characterized by natural and social sub-systems,three basin geomorphologic units (mountains,plains,and water area),and six human-water interaction units (water security,water ecology,water environment,water saving,water supervision,and water culture) and 25 indicators. To avoid the one-sidedness of the single weighting method,the merging weights were estimated by employing the Analytic Hierarchy Process (AHP) and entropy method.The main steps are as follows:calculate the subjective weights of indexes based on the AHP;calculate the objective weights of indexes based on the entropy method;calculate the merging weights of the indexes.The subjective weight of indexes based on the AHP was determined by the personal experience of experts,and the objective weight indexes by entropy method were determined by evaluating the relative importance with consideration of experts′ experiences,and the merging weights were the combination of the above two weights.The synthesized method was proposed according to the advantage and disadvantages of subjective and objective ways of giving weight. The degree of water ecological civilization construction in 2017 was evaluated by the fuzzy comprehensive evaluation and gray relational analysis methods.The research data were mainly collected from official government documents such as the water resources bulletin,environmental quality bulletin,statistical bulletin of national economic and social development,land and resources bulletin,statistical yearbook,and departmental reports of the three provinces (Shanxi,Henan,Hubei) and the administrative regions.Jenks natural fault classification method was adopted to divide the indexes into five levels that are excellent,good,medium,poor and worse to compare the degree of water ecological civilization construction in each unit.The results show that the water ecological civilization construction in Han River basin highly depends on social properties with a correlation coefficient of 0.844,thus exhibiting a spatial pattern that their developments in the middle and lower reaches are far superior to those in the upper reaches.Among the social elements,water security,water environment and water-saving are the key factors affecting water ecological civilization construction.These results are expected to provide rich information as references for the construction and planning of Han River ecological economic belt.
Under climate warming and anthropogenic activities,the hydrological cycle and river flow regime have been significantly altered,challenging the traditional strategies of water resources management.Recently,water ecological environment protection on basin-scale has been paid great attention in China.Most of administrative regions are the key water ecological civilization construction regions,thus,it is urgent to evaluate the water ecological civilization construction at a river basin scale.Han River basin is the first pilot of the most stringent water resource management basin,and water source area of the Middle Route South-to-North Water Transfer Project in China.The basin governed by 14 administrative regions (or cities) is selected as evaluation units,and a multi-system,multi-landform and multi-scale indicator characterization method based on the characteristics of the water ecological civilization of the basin is developed. The evaluation indexes for water ecological civilization basin is based on the evaluation guide of water ecological civilization construction.The selection guideline is based on upper,middle and lower reaches of the basin and single landform to multiple landforms,that can not only reflect the characteristics of regional features but also grasp the overall situation.After comprehensive consideration,the evaluation index system of water ecological civilization construction was established at an administrative region scale.This system is characterized by natural and social sub-systems,three basin geomorphologic units (mountains,plains,and water area),and six human-water interaction units (water security,water ecology,water environment,water saving,water supervision,and water culture) and 25 indicators. To avoid the one-sidedness of the single weighting method,the merging weights were estimated by employing the Analytic Hierarchy Process (AHP) and entropy method.The main steps are as follows:calculate the subjective weights of indexes based on the AHP;calculate the objective weights of indexes based on the entropy method;calculate the merging weights of the indexes.The subjective weight of indexes based on the AHP was determined by the personal experience of experts,and the objective weight indexes by entropy method were determined by evaluating the relative importance with consideration of experts′ experiences,and the merging weights were the combination of the above two weights.The synthesized method was proposed according to the advantage and disadvantages of subjective and objective ways of giving weight. The degree of water ecological civilization construction in 2017 was evaluated by the fuzzy comprehensive evaluation and gray relational analysis methods.The research data were mainly collected from official government documents such as the water resources bulletin,environmental quality bulletin,statistical bulletin of national economic and social development,land and resources bulletin,statistical yearbook,and departmental reports of the three provinces (Shanxi,Henan,Hubei) and the administrative regions.Jenks natural fault classification method was adopted to divide the indexes into five levels that are excellent,good,medium,poor and worse to compare the degree of water ecological civilization construction in each unit.The results show that the water ecological civilization construction in Han River basin highly depends on social properties with a correlation coefficient of 0.844,thus exhibiting a spatial pattern that their developments in the middle and lower reaches are far superior to those in the upper reaches.Among the social elements,water security,water environment and water-saving are the key factors affecting water ecological civilization construction.These results are expected to provide rich information as references for the construction and planning of Han River ecological economic belt.
2022, 20(3):506-515.
Abstract:
hyporheic zone is a saturated sediment layer with the interaction between surface and groundwater in rivers.The riverbed medium is highly inhomogeneous and the flow direction is complex.Solute diffusion is prone to exhibit abnormal diffusion characteristics of trailing and non-Gaussian distribution.It is difficult to describe such diffusion characteristics by traditional convection dispersion equation.Therefore,a space-time fractional derivative term is introduced in the hyporheic zone solute transport model,and the applicability of the fractional derivative method in the hyporheic zone solute transport simulation is discussed from one-dimensional and two-dimensional perspectives,respectively. The influence of fractional order on the physical meaning of solute transport and the sensitivity of fractional order to physical parameters of solute transport were discussed.A two-dimensional fractional-order derivative model was also established to compare the simulation results of different dimensions to the fractional-order derivative method with field tracing experiments. The physical significance of fractional order is analyzed and it is found that timefractional orderαreflects the lagging effect of the solute transport process and makes the breakthrough curve have obvious trailing characteristics.Space fractional-order β characterize the phenomenon of solute hyper-diffusion caused by inhomogeneity of media.The results of parameter sensitivity -analysis show that the fractional-order method is more sensitive to velocity and dispersion coefficient than the traditional convection-dispersion equation.It overcomes the defect that the traditional integer-order method can not accurately describe the strong inhomogeneity in the hyporheic zone.Field tracing test shows that the traditional two-dimensional integer-order convection-diffusion equation has shortcomings in characterizing the solute transport process due to strong inhomogeneity and multi-dimensional flow in the hyporheic zone.The one-dimensional fractional derivative model can more accurately calculate the peak time of solute concentration and describe the tailing phenomenon of the penetration curve when simulating the solute transport in the hyporheic zone.Affected by parameter settings in different directions,the simulation results of the two-dimensional fractional-order model are inferior to the one-dimensional fractional-order model.However,more point-level solute data can be observed on the isometric plane by the two-dimensional fractional-order model and it would be more applicable without the difference of flow and medium parameters caused by medium differences in the depth direction. Although the applicability of one-dimensional and two-dimensional fractional derivative models differs in different scenarios,the introduction of fractional derivative improves the simulation effect of traditional convection-dispersion equations and is suitable for special media with strong inhomogeneity and complex flow conditions,such as hyporheic zone.
hyporheic zone is a saturated sediment layer with the interaction between surface and groundwater in rivers.The riverbed medium is highly inhomogeneous and the flow direction is complex.Solute diffusion is prone to exhibit abnormal diffusion characteristics of trailing and non-Gaussian distribution.It is difficult to describe such diffusion characteristics by traditional convection dispersion equation.Therefore,a space-time fractional derivative term is introduced in the hyporheic zone solute transport model,and the applicability of the fractional derivative method in the hyporheic zone solute transport simulation is discussed from one-dimensional and two-dimensional perspectives,respectively. The influence of fractional order on the physical meaning of solute transport and the sensitivity of fractional order to physical parameters of solute transport were discussed.A two-dimensional fractional-order derivative model was also established to compare the simulation results of different dimensions to the fractional-order derivative method with field tracing experiments. The physical significance of fractional order is analyzed and it is found that timefractional orderαreflects the lagging effect of the solute transport process and makes the breakthrough curve have obvious trailing characteristics.Space fractional-order β characterize the phenomenon of solute hyper-diffusion caused by inhomogeneity of media.The results of parameter sensitivity -analysis show that the fractional-order method is more sensitive to velocity and dispersion coefficient than the traditional convection-dispersion equation.It overcomes the defect that the traditional integer-order method can not accurately describe the strong inhomogeneity in the hyporheic zone.Field tracing test shows that the traditional two-dimensional integer-order convection-diffusion equation has shortcomings in characterizing the solute transport process due to strong inhomogeneity and multi-dimensional flow in the hyporheic zone.The one-dimensional fractional derivative model can more accurately calculate the peak time of solute concentration and describe the tailing phenomenon of the penetration curve when simulating the solute transport in the hyporheic zone.Affected by parameter settings in different directions,the simulation results of the two-dimensional fractional-order model are inferior to the one-dimensional fractional-order model.However,more point-level solute data can be observed on the isometric plane by the two-dimensional fractional-order model and it would be more applicable without the difference of flow and medium parameters caused by medium differences in the depth direction. Although the applicability of one-dimensional and two-dimensional fractional derivative models differs in different scenarios,the introduction of fractional derivative improves the simulation effect of traditional convection-dispersion equations and is suitable for special media with strong inhomogeneity and complex flow conditions,such as hyporheic zone.
2022, 20(3):516-524.
Abstract:
The restoration and polluted water resource utilization in arid regions is an important way to solve the shortage of regional water resources.The Xinjiang Uygur Autonomous Region is an inland arid zone and lacks water resources with a fragile ecological environment,and shows a prominent contradiction between water supply and demand.Over-exploitation of water resources and water pollution have exacerbated the contradiction between water supply and demand,resulting in the continuous deterioration of the water environment.Water pollution control is an emerging problem that needs to be solved urgently to favor Xinjiang′s economy and social development.This study took the project of Xinjiang′s Alaer sewage pit pond ecological restoration and landscape improvement as an example to explore key technologies for the process of ecological restoration of high-salt water bodies. A comprehensive treatment plan was formulated according to the regional environment and pollution characteristics of the oxidation pond.For this purpose,water safety,water environment,water resources,and water ecology was adopted.Innovations were made basis on the existing integrated technology of water quality enhanced purification and water ecological restoration.In addition to traditional sewage interception and water diversion projects,the application of modified mineral materials,targeted microbial agents and salt-tolerant plants simultaneously achieved water quality improvement and endogenous control.Specifically,it included 4 measures.(1) Source control and pollution interception:Prevented pollution sources from entering the oxidation pond;(2) Water quality improvement:Eliminated pollutants in water,achieved water quality standards,and restored water body functions;(3) Living water circulation:Improved the self-purification capacity of the oxidation pond and reduced water pollution,and improved the regional water circulation system;(4) Ecological restoration:Repaired and improved the regional water ecological environment and realized the comprehensive utilization of wastewater resources.From source blocking in the early stage,polluted water treatment in the middle-term to the long-term maintenance of the later restoration,and finally realized water quality purification and ecological system reconstruction in the Alaer oxidation pond. Before treatment,the total salt,chloride,chroma,and COD of the oxidation pond exceeded the national standards,which was inferior to category V waters.As the construction progressed,the chroma,COD,and ammonia nitrogen in the water bodies of the oxidation ponds showed a gradual decline and became stable day by day.After project implementation,the black and odor of the water body disappeared,the transparency increased from less than 30 cm to more than 80 cm,the chroma decreased from 20 times to 4~8 times,and the COD decreased from 96~148 mg/L to 37~50 mg/L,respectively.The growth rate of aquatic plants was accelerated,a large number of submerged plants could be observed in the pond,the singleness of the ecosystem was changed,and the selfpurification ability of water was enhanced.Within one month after the completion of construction,the water quality did not change much.Eight months later,COD and chroma had increased significantly,and the results of the changes were consistent.It was speculated that the corresponding pollutants were refractory organic dyes,and the modified zeolite was the main reason for their removal,a small amount of modified zeolite was needed to be sprayed for maintenance.Ammonia nitrogen and total nitrogen slightly increased,but the total phosphorus mass concentration continued to decrease after construction,indicating that the technical scheme proposed could effectively remove phosphorus from water and the results could be maintained for a long time. After the undergoing harmless treatment and ecological restoration,the water quality in the oxidation pond had been significantly improved.All indicators meet the requirements of the remediation goals,and all pollutants had a downward trend.The results showed that the application of modified mineral materials targeted microbial agents,and saline-tolerant aquatic plants synergistic technology treat Xinjiang cotton pulp and viscose fiber industry production wastewater,and could effectively reduce water pollutants,and improve the water quality.This research can provide reference for ecological restoration of high-salt wastewater in arid regions.
The restoration and polluted water resource utilization in arid regions is an important way to solve the shortage of regional water resources.The Xinjiang Uygur Autonomous Region is an inland arid zone and lacks water resources with a fragile ecological environment,and shows a prominent contradiction between water supply and demand.Over-exploitation of water resources and water pollution have exacerbated the contradiction between water supply and demand,resulting in the continuous deterioration of the water environment.Water pollution control is an emerging problem that needs to be solved urgently to favor Xinjiang′s economy and social development.This study took the project of Xinjiang′s Alaer sewage pit pond ecological restoration and landscape improvement as an example to explore key technologies for the process of ecological restoration of high-salt water bodies. A comprehensive treatment plan was formulated according to the regional environment and pollution characteristics of the oxidation pond.For this purpose,water safety,water environment,water resources,and water ecology was adopted.Innovations were made basis on the existing integrated technology of water quality enhanced purification and water ecological restoration.In addition to traditional sewage interception and water diversion projects,the application of modified mineral materials,targeted microbial agents and salt-tolerant plants simultaneously achieved water quality improvement and endogenous control.Specifically,it included 4 measures.(1) Source control and pollution interception:Prevented pollution sources from entering the oxidation pond;(2) Water quality improvement:Eliminated pollutants in water,achieved water quality standards,and restored water body functions;(3) Living water circulation:Improved the self-purification capacity of the oxidation pond and reduced water pollution,and improved the regional water circulation system;(4) Ecological restoration:Repaired and improved the regional water ecological environment and realized the comprehensive utilization of wastewater resources.From source blocking in the early stage,polluted water treatment in the middle-term to the long-term maintenance of the later restoration,and finally realized water quality purification and ecological system reconstruction in the Alaer oxidation pond. Before treatment,the total salt,chloride,chroma,and COD of the oxidation pond exceeded the national standards,which was inferior to category V waters.As the construction progressed,the chroma,COD,and ammonia nitrogen in the water bodies of the oxidation ponds showed a gradual decline and became stable day by day.After project implementation,the black and odor of the water body disappeared,the transparency increased from less than 30 cm to more than 80 cm,the chroma decreased from 20 times to 4~8 times,and the COD decreased from 96~148 mg/L to 37~50 mg/L,respectively.The growth rate of aquatic plants was accelerated,a large number of submerged plants could be observed in the pond,the singleness of the ecosystem was changed,and the selfpurification ability of water was enhanced.Within one month after the completion of construction,the water quality did not change much.Eight months later,COD and chroma had increased significantly,and the results of the changes were consistent.It was speculated that the corresponding pollutants were refractory organic dyes,and the modified zeolite was the main reason for their removal,a small amount of modified zeolite was needed to be sprayed for maintenance.Ammonia nitrogen and total nitrogen slightly increased,but the total phosphorus mass concentration continued to decrease after construction,indicating that the technical scheme proposed could effectively remove phosphorus from water and the results could be maintained for a long time. After the undergoing harmless treatment and ecological restoration,the water quality in the oxidation pond had been significantly improved.All indicators meet the requirements of the remediation goals,and all pollutants had a downward trend.The results showed that the application of modified mineral materials targeted microbial agents,and saline-tolerant aquatic plants synergistic technology treat Xinjiang cotton pulp and viscose fiber industry production wastewater,and could effectively reduce water pollutants,and improve the water quality.This research can provide reference for ecological restoration of high-salt wastewater in arid regions.
2022, 20(3):525-535.
Abstract:
The sustainable use of groundwater in arid and semi-arid regions is related to regional ecological security and food security.However,with the rapid development of social and economic construction,the exploitation of groundwater resources is significantly increased,which made severe water supply shortage.Likewise,the water resource problem caused by the water quality crisis are more serious than the reduction of water quantity.Carrying out research on groundwater chemistry in arid and semi-arid areas not only had important academic significance for clarifying the origin and formation of groundwater but also had important value for scientific and reasonable regional groundwater development and protection of groundwater resources. This research took Wulagai area of Inner Mongolia as the research area,and comprehensively utilized water stoichiometric analysis,multivariate statistical analysis,spatial statistical analysis,and redox analysis to carry out regional groundwater hydrochemical characteristics and causes. The results showed that the groundwater hydrochemical characteristics had significant spatial zoning characteristics.There were certain differences in the water chemistry of deep and shallow groundwater in different regions.The shallow groundwater in Zone 1 was Ca-HCO3 pattern (40%),the deep groundwater was Ca-HCO3 (38%) and Na-HCO3 patterns (38%);shallow groundwater in Zone 2 was also Ca-HCO3 pattern (57%),and deep water chemistry patterns had Ca-HCO3 (54%) and Na-HCO3 patterns (45%) .The types of water chemistry in Zone 3 were relatively diverse.The shallow groundwater was mainly a Ca-Mg-Na-HCO3 pattern (37%),other types were also distributed,and the deep groundwater was Ca-Na-HCO3 pattern (29%),respectively. Waterrock interaction was the main factor controlling the evolution of water chemistry in the study area,and there were still certain differences in different regions and stratifications.Among them,zone 3 was also affected by evaporation,concentration and ion exchange.The weathering of silicate rock was the main controlling effect in the water-rock interaction,followed by the dissolution of carbonate rock,and the influence of evaporite was relatively weak,which matched the regional geological background.Furthermore,factor analysis showed that human activities were also an important factor affecting the hydrochemical characteristics of groundwater.There was a certain amount of nitrate pollution in groundwater.Spatial analysis showed that nitrate in the whole area was a typical random distribution pattern,and there was no discrete and aggregation effect at the pollution point,which indicated that the regional dispersion of agriculture,animal husbandry and human activities become an important point source of groundwater nitrate pollution.Redox analysis showed that there was a potential denitrification trend in the area.The results provided a scientific basis and technical support for the sustainable development and utilization of groundwater resources in arid and semi-arid areas.
The sustainable use of groundwater in arid and semi-arid regions is related to regional ecological security and food security.However,with the rapid development of social and economic construction,the exploitation of groundwater resources is significantly increased,which made severe water supply shortage.Likewise,the water resource problem caused by the water quality crisis are more serious than the reduction of water quantity.Carrying out research on groundwater chemistry in arid and semi-arid areas not only had important academic significance for clarifying the origin and formation of groundwater but also had important value for scientific and reasonable regional groundwater development and protection of groundwater resources. This research took Wulagai area of Inner Mongolia as the research area,and comprehensively utilized water stoichiometric analysis,multivariate statistical analysis,spatial statistical analysis,and redox analysis to carry out regional groundwater hydrochemical characteristics and causes. The results showed that the groundwater hydrochemical characteristics had significant spatial zoning characteristics.There were certain differences in the water chemistry of deep and shallow groundwater in different regions.The shallow groundwater in Zone 1 was Ca-HCO3 pattern (40%),the deep groundwater was Ca-HCO3 (38%) and Na-HCO3 patterns (38%);shallow groundwater in Zone 2 was also Ca-HCO3 pattern (57%),and deep water chemistry patterns had Ca-HCO3 (54%) and Na-HCO3 patterns (45%) .The types of water chemistry in Zone 3 were relatively diverse.The shallow groundwater was mainly a Ca-Mg-Na-HCO3 pattern (37%),other types were also distributed,and the deep groundwater was Ca-Na-HCO3 pattern (29%),respectively. Waterrock interaction was the main factor controlling the evolution of water chemistry in the study area,and there were still certain differences in different regions and stratifications.Among them,zone 3 was also affected by evaporation,concentration and ion exchange.The weathering of silicate rock was the main controlling effect in the water-rock interaction,followed by the dissolution of carbonate rock,and the influence of evaporite was relatively weak,which matched the regional geological background.Furthermore,factor analysis showed that human activities were also an important factor affecting the hydrochemical characteristics of groundwater.There was a certain amount of nitrate pollution in groundwater.Spatial analysis showed that nitrate in the whole area was a typical random distribution pattern,and there was no discrete and aggregation effect at the pollution point,which indicated that the regional dispersion of agriculture,animal husbandry and human activities become an important point source of groundwater nitrate pollution.Redox analysis showed that there was a potential denitrification trend in the area.The results provided a scientific basis and technical support for the sustainable development and utilization of groundwater resources in arid and semi-arid areas.
2022, 20(3):536-543.
Abstract:
The hydropower resources of small and medium-sized rivers account for a large proportion of domestic hydropower distribution .There is a large space for development and utilization.The development and operation of hydropower inevitably bring adverse effects to the ecological environment,such as the reduction of river runoff,dewatering of local river reach,and the damage to the local ecological environment.To reduce the negative impact of the construction and development of small hydropower on the ecological environment of the downstream river,it is a key method to ensure the minimum ecological discharge of small hydropower.At present,the researches referring to the domestic and overseas ecological discharge mainly concentrate on big rivers.However,the research related to the ecological discharge of small and medium-sized rivers,especially small hydropower stations are few.The available methods for calculating the ecological discharge also lack scientific analysis.A considerable number of small hydropower stations have not yet determined the minimum ecological discharge.Based on this situation,the related research was carried out on the minimum ecological discharge of small hydropower stations. At present,domestic and overseas calculation methods of ecological flow can be roughly divided into the hydrological method,hydraulic method,habitat norm method,and integral method.The hydrological research method is the most commonly used,convenient,lowest cost of ecological flow calculation method and is one of the classic calculation method.This study uses the improved Tennant method,the annual distribution method,the Q90 method,the improved frequency method,and the NGPRP method to calculate the minimum ecological flow of the leading reservoir.Taking 95% guarantee rate of the runoff data from the recent 30 years as a protection target,this study analyzes the satisfaction degree of the five methods and evaluates the rationality of the calculation results.This shows the evaluating results of calculation in the process of natural runoff of the section with satisfying the degree of 95 percent guarantee rate.If the degree of satisfaction exceeds or is lower than the requirement of the due guarantee rate,this method is considered not suitable for Dayang reservoirs.Finally,by comparing various methods,the calculation method of the minimum ecological discharge of the Dayang reservoir is selected,and the inner envelope of the calculated minimum ecological discharge is taken as the minimum ecological discharge of the reach.Finally,the minimum ecological flow process of Panxi cascade Ⅰ~Ⅳ power stations is obtained. According to the calculation,the lower limit of the minimum ecological discharge of the Dayang reservoir is 0.152 m3/s,and the minimum ecological discharge of 0.182 m3/s guaranteed between the second and third stage hydropower stations,and 0.102 m3/s guaranteed between the third and fourth stage hydropower stations.The discharge also guaranteed in the dry months.The minimum ecological discharge of each hydropower station can be satisfied with the water inflow from each hydropower station.This results have a reference value for the study of the minimum ecological flow of small hydropower stations in China.
The hydropower resources of small and medium-sized rivers account for a large proportion of domestic hydropower distribution .There is a large space for development and utilization.The development and operation of hydropower inevitably bring adverse effects to the ecological environment,such as the reduction of river runoff,dewatering of local river reach,and the damage to the local ecological environment.To reduce the negative impact of the construction and development of small hydropower on the ecological environment of the downstream river,it is a key method to ensure the minimum ecological discharge of small hydropower.At present,the researches referring to the domestic and overseas ecological discharge mainly concentrate on big rivers.However,the research related to the ecological discharge of small and medium-sized rivers,especially small hydropower stations are few.The available methods for calculating the ecological discharge also lack scientific analysis.A considerable number of small hydropower stations have not yet determined the minimum ecological discharge.Based on this situation,the related research was carried out on the minimum ecological discharge of small hydropower stations. At present,domestic and overseas calculation methods of ecological flow can be roughly divided into the hydrological method,hydraulic method,habitat norm method,and integral method.The hydrological research method is the most commonly used,convenient,lowest cost of ecological flow calculation method and is one of the classic calculation method.This study uses the improved Tennant method,the annual distribution method,the Q90 method,the improved frequency method,and the NGPRP method to calculate the minimum ecological flow of the leading reservoir.Taking 95% guarantee rate of the runoff data from the recent 30 years as a protection target,this study analyzes the satisfaction degree of the five methods and evaluates the rationality of the calculation results.This shows the evaluating results of calculation in the process of natural runoff of the section with satisfying the degree of 95 percent guarantee rate.If the degree of satisfaction exceeds or is lower than the requirement of the due guarantee rate,this method is considered not suitable for Dayang reservoirs.Finally,by comparing various methods,the calculation method of the minimum ecological discharge of the Dayang reservoir is selected,and the inner envelope of the calculated minimum ecological discharge is taken as the minimum ecological discharge of the reach.Finally,the minimum ecological flow process of Panxi cascade Ⅰ~Ⅳ power stations is obtained. According to the calculation,the lower limit of the minimum ecological discharge of the Dayang reservoir is 0.152 m3/s,and the minimum ecological discharge of 0.182 m3/s guaranteed between the second and third stage hydropower stations,and 0.102 m3/s guaranteed between the third and fourth stage hydropower stations.The discharge also guaranteed in the dry months.The minimum ecological discharge of each hydropower station can be satisfied with the water inflow from each hydropower station.This results have a reference value for the study of the minimum ecological flow of small hydropower stations in China.
2022, 20(3):544-551.
Abstract:
With the development of industrialization and urbanization,the water environment problems in Haihe River basin are becoming increasingly prominent,and the ecological security of reservoirs is facing threats in Haihe River basin.Sediment is an important index to distinguish [HJ2.2mm]water pollution status.The reservoir ecological risk level can be effectively understood through sediment ecological risk assessment.Shahe Reservoir,Miyun Reservoir,Guanting Reservoir and Yuqiao Reservoir are selected as the main research objects because of heavy metal pollution and ecological effects in reservoirs.The data on the mass fraction and toxicology of heavy metals in reservoir sediments were obtained from published articles and journals.Through the analysis of distribution characteristics and correlation analysis,the distribution characteristics and pollution sources of heavy metal sediments were judged.The geological accumulation index and potential ecological risk index were used to evaluate the ecological risk level of heavy metal sediments.Finally,the species sensitivity index was used to evaluate the proportion of potentially harmful species in heavy metal sediments.The distribution characteristics and correlation analysis results show that the distribution of heavy metals in the sediments of the four typical reservoirs are similar to some extent,and the mass fraction of heavy metals are comparable.The distribution of heavy metal deposits in reservoirs of Haihe River basin is similar to some extent,and the mass fraction of heavy metal in sediments may be affected by industrialization.The results of ecological risk analysis showed that As was the most polluted heavy metal in the sediments of the four reservoirs.The ecological risk grade of Shahe Reservoir,Miyun Reservoir and Yuqiao Reservoir is low,but for Guanting Reservoir is medium.Species sensitivity distribution showed that different heavy metals had different mass fraction of harmful mass (HC5) to 5% of benthic species.The average harmful species proportion (PAF) of heavy metals in the sediments of four typical reservoirs from high to low is Zn(97.5%)>Cu(97.1%)>Cr(96.6%)>Zn(92.2%)>Pb (91.8%)>Ni(90.8%).These results indicate that the six heavy metals in sediment may have certain effects on the survival of more than 90% of the benthic organisms in the reservoir.The overall results show that the mass fraction of heavy metals in the sediment a reservoir is relatively low,and the ecological risk level is good,but the impact of heavy metals in the sediment on the benthos of the reservoir cannot be ignored.The research results are helpful to understand the ecological risk of heavy metals in reservoir sediments and provide the basis for reservoir ecological management.
With the development of industrialization and urbanization,the water environment problems in Haihe River basin are becoming increasingly prominent,and the ecological security of reservoirs is facing threats in Haihe River basin.Sediment is an important index to distinguish [HJ2.2mm]water pollution status.The reservoir ecological risk level can be effectively understood through sediment ecological risk assessment.Shahe Reservoir,Miyun Reservoir,Guanting Reservoir and Yuqiao Reservoir are selected as the main research objects because of heavy metal pollution and ecological effects in reservoirs.The data on the mass fraction and toxicology of heavy metals in reservoir sediments were obtained from published articles and journals.Through the analysis of distribution characteristics and correlation analysis,the distribution characteristics and pollution sources of heavy metal sediments were judged.The geological accumulation index and potential ecological risk index were used to evaluate the ecological risk level of heavy metal sediments.Finally,the species sensitivity index was used to evaluate the proportion of potentially harmful species in heavy metal sediments.The distribution characteristics and correlation analysis results show that the distribution of heavy metals in the sediments of the four typical reservoirs are similar to some extent,and the mass fraction of heavy metals are comparable.The distribution of heavy metal deposits in reservoirs of Haihe River basin is similar to some extent,and the mass fraction of heavy metal in sediments may be affected by industrialization.The results of ecological risk analysis showed that As was the most polluted heavy metal in the sediments of the four reservoirs.The ecological risk grade of Shahe Reservoir,Miyun Reservoir and Yuqiao Reservoir is low,but for Guanting Reservoir is medium.Species sensitivity distribution showed that different heavy metals had different mass fraction of harmful mass (HC5) to 5% of benthic species.The average harmful species proportion (PAF) of heavy metals in the sediments of four typical reservoirs from high to low is Zn(97.5%)>Cu(97.1%)>Cr(96.6%)>Zn(92.2%)>Pb (91.8%)>Ni(90.8%).These results indicate that the six heavy metals in sediment may have certain effects on the survival of more than 90% of the benthic organisms in the reservoir.The overall results show that the mass fraction of heavy metals in the sediment a reservoir is relatively low,and the ecological risk level is good,but the impact of heavy metals in the sediment on the benthos of the reservoir cannot be ignored.The research results are helpful to understand the ecological risk of heavy metals in reservoir sediments and provide the basis for reservoir ecological management.
2022, 20(3):552-562.
Abstract:
With the development of global urbanization,cities have been severely threatened by the negative hydrological effects of urbanization,and the healthy and sustainable development of cities is threatened in past decades.The concept of sponge city was proposed under this background.The core of sponge city construction is Low Impact Development (LID).The research on the optimal layout of LID measures has received more attention.Domestic scholars began to pay attention to the research and practice of LID at the beginning of this century.Currently,in the exploratory stage,there is still a lack of a complete theoretical system for urban runoff control and LID optimization.Therefore,it is imperative to apply LID measures and optimization techniques to the construction of sponge cities in large-scale urban watersheds. The connotation of sponge city was explained in both broad and narrow perspectives.The functional characteristics of common LID facilities were sorted out.The model tools,optimization algorithms and optimization target used in the field of optimization of LID facilities were summarized systematically.Typically,the models employed by researchers include SWMM,SUSTAIN,HEC-HMS and MUSIC,etc.The heuristic algorithms used in research are GA,NSGA-Ⅱ and PSO.Meanwhile,it was illustrated that both the pattern of LID layout and the location of LID facilities had an impact on the urban hydrological process. The present research on LID optimal layout should meet the requirements of the regional sponge plan.For this purpose,the Huangtaiqiao catchment in Jinan City was selected as the study area.Using NSGA-Ⅱ algorithm and SWMM model,the multi-objective optimization of the LID layout was carried out considering the cost of LID facilities and the control rate of flood factors.The optimization was carried out according to the division of functional areas and the proportion of LID facilities in each functional area. The result shows that:(1) When selecting different objective functions,the NSGA-Ⅱ algorithm can more accurately give a certain cost-effective LID layout scheme,to further determine the most economical scheme and maximum reduction scheme under the corresponding scenario,and can give the corresponding LID.The layout ratio shows good applicability,indicating that the NSGA-Ⅱ algorithm is suitable for LID optimization layout in urban areas at the watershed scale.(2) The most significant reduction effect on the total runoff is the permeable pavement in the residential area and the public facility area.The combination of the permeable pavement in the residential area,the public facility area and the garden area and the green roof in the public facility area have the most significant effect on the delay time of the flood peak.The most significant reduction effect on flood peak flow is the combination of permeable pavement and green roof in the public facility area. This study is a preliminary discussion on sponge planning in large-scale urban watersheds to provide some reference for research and engineering construction in this area.
With the development of global urbanization,cities have been severely threatened by the negative hydrological effects of urbanization,and the healthy and sustainable development of cities is threatened in past decades.The concept of sponge city was proposed under this background.The core of sponge city construction is Low Impact Development (LID).The research on the optimal layout of LID measures has received more attention.Domestic scholars began to pay attention to the research and practice of LID at the beginning of this century.Currently,in the exploratory stage,there is still a lack of a complete theoretical system for urban runoff control and LID optimization.Therefore,it is imperative to apply LID measures and optimization techniques to the construction of sponge cities in large-scale urban watersheds. The connotation of sponge city was explained in both broad and narrow perspectives.The functional characteristics of common LID facilities were sorted out.The model tools,optimization algorithms and optimization target used in the field of optimization of LID facilities were summarized systematically.Typically,the models employed by researchers include SWMM,SUSTAIN,HEC-HMS and MUSIC,etc.The heuristic algorithms used in research are GA,NSGA-Ⅱ and PSO.Meanwhile,it was illustrated that both the pattern of LID layout and the location of LID facilities had an impact on the urban hydrological process. The present research on LID optimal layout should meet the requirements of the regional sponge plan.For this purpose,the Huangtaiqiao catchment in Jinan City was selected as the study area.Using NSGA-Ⅱ algorithm and SWMM model,the multi-objective optimization of the LID layout was carried out considering the cost of LID facilities and the control rate of flood factors.The optimization was carried out according to the division of functional areas and the proportion of LID facilities in each functional area. The result shows that:(1) When selecting different objective functions,the NSGA-Ⅱ algorithm can more accurately give a certain cost-effective LID layout scheme,to further determine the most economical scheme and maximum reduction scheme under the corresponding scenario,and can give the corresponding LID.The layout ratio shows good applicability,indicating that the NSGA-Ⅱ algorithm is suitable for LID optimization layout in urban areas at the watershed scale.(2) The most significant reduction effect on the total runoff is the permeable pavement in the residential area and the public facility area.The combination of the permeable pavement in the residential area,the public facility area and the garden area and the green roof in the public facility area have the most significant effect on the delay time of the flood peak.The most significant reduction effect on flood peak flow is the combination of permeable pavement and green roof in the public facility area. This study is a preliminary discussion on sponge planning in large-scale urban watersheds to provide some reference for research and engineering construction in this area.
2022, 20(3):563-572.
Abstract:
River cross-section data is necessary for one-dimensional and one-two-dimensional coupled hydrodynamic flood routing numerical simulations.However,river cross-section field measurement is time-consuming,labor-intensive,and expensive.Under a sudden flood,it is impossible to carry out on-site measurements when modeling the emergency flood evolution.Rapid acquisition of river section data is the key to hydrodynamic flood evolution model modeling. To solve the above-mentioned problems,two methods for river cross-section are proposed.One is to directly extract river cross-sections (called DEM cross-sections) based on the digital elevation model(DEM),and the other is the improved cross-section construction method using parabola.The elevation at the thalweg is corrected by the lowest point elevation correction coefficient k (called constructed cross-sections).Two sets of river section data is obtained by the above two methods as the main input of the hydrodynamic simulation software HECRAS to carry out one-dimensional and one-two-dimensional coupled hydrodynamic numerical simulations,and then simulation results are compared with the flood routing results modeled by the measured river section data to evaluate the effect of rapid acquisition of the two river sections. The research method is applied in the lower reaches of the Miami River in Florida,USA.Two typical floods in 2004,2017 and 2014 are selected to analyze the differences in the simulation results of flood evolution under two different crosssections.The results show that the simulated water level of the measured cross-sections and constructed cross-sections are consistent with the observed water level process,and the simulated maximum inundation range is very close to the results of the model based on the measured cross-sections.In the simulation scheme using the DEM cross-sections,the average error of the simulated water level is up to 3.57 m.The maximum submergence range is calculated using the model based on the DEM cross-sections which is larger than measured cross-sections. DEM data has limitations in accurate hydraulic modeling.The description of the riverbed by DEM data is insufficient due to the ignorance of the terrain below the water surface as LiDAR scanned the terrain.The overflow capability provide by the DEM cross-sections is insufficient.The water level calculated by the DEM cross-sections is not consistent with the actual observed water level process,and the simulated submergence depth and submerged range deviate from the simulation results using the measured cross-sections.In the flood routing simulation,using the improved cross-section construction method proposed to correct the DEM data below the water surface can achieve similar to field measured river cross-section data,which is better than the method of directly extracting the river cross-section only from DEM data.By improving the river cross-section data in the digital elevation model data,the time and effort required for field survey.The methods of obtaining river cross-section data apply to plain river network areas,and the DEM data has a high resolution.In the future study of mountainous rivers or areas with only coarse DEM that can be obtained,the accuracy and applicability of different acquisition methods of river cross-section data to the calculation results of the hydrodynamic model still need to be further studied.
River cross-section data is necessary for one-dimensional and one-two-dimensional coupled hydrodynamic flood routing numerical simulations.However,river cross-section field measurement is time-consuming,labor-intensive,and expensive.Under a sudden flood,it is impossible to carry out on-site measurements when modeling the emergency flood evolution.Rapid acquisition of river section data is the key to hydrodynamic flood evolution model modeling. To solve the above-mentioned problems,two methods for river cross-section are proposed.One is to directly extract river cross-sections (called DEM cross-sections) based on the digital elevation model(DEM),and the other is the improved cross-section construction method using parabola.The elevation at the thalweg is corrected by the lowest point elevation correction coefficient k (called constructed cross-sections).Two sets of river section data is obtained by the above two methods as the main input of the hydrodynamic simulation software HECRAS to carry out one-dimensional and one-two-dimensional coupled hydrodynamic numerical simulations,and then simulation results are compared with the flood routing results modeled by the measured river section data to evaluate the effect of rapid acquisition of the two river sections. The research method is applied in the lower reaches of the Miami River in Florida,USA.Two typical floods in 2004,2017 and 2014 are selected to analyze the differences in the simulation results of flood evolution under two different crosssections.The results show that the simulated water level of the measured cross-sections and constructed cross-sections are consistent with the observed water level process,and the simulated maximum inundation range is very close to the results of the model based on the measured cross-sections.In the simulation scheme using the DEM cross-sections,the average error of the simulated water level is up to 3.57 m.The maximum submergence range is calculated using the model based on the DEM cross-sections which is larger than measured cross-sections. DEM data has limitations in accurate hydraulic modeling.The description of the riverbed by DEM data is insufficient due to the ignorance of the terrain below the water surface as LiDAR scanned the terrain.The overflow capability provide by the DEM cross-sections is insufficient.The water level calculated by the DEM cross-sections is not consistent with the actual observed water level process,and the simulated submergence depth and submerged range deviate from the simulation results using the measured cross-sections.In the flood routing simulation,using the improved cross-section construction method proposed to correct the DEM data below the water surface can achieve similar to field measured river cross-section data,which is better than the method of directly extracting the river cross-section only from DEM data.By improving the river cross-section data in the digital elevation model data,the time and effort required for field survey.The methods of obtaining river cross-section data apply to plain river network areas,and the DEM data has a high resolution.In the future study of mountainous rivers or areas with only coarse DEM that can be obtained,the accuracy and applicability of different acquisition methods of river cross-section data to the calculation results of the hydrodynamic model still need to be further studied.
2022, 20(3):573-580,599.
Abstract:
At present,urban storms and floods have already been one of the major disasters that threaten the sustainable development of cities.With the rapid development of Beijing′s sub-center,storms,and floods vulnerability has continued to increase.Historical or real-time observed data,interpreted data from weather radar or satellite remote sensing,and simulated data from numerical atmospheric models are currently used to study precipitation characteristics.The regional atmospheric model,which could realize the quantitative precipitation simulation and forecasting and provide data support for related research in ungauged areas,was of great significance for urban flood forecast and control.The new generation of mesoscale weather research and forecast model named Weather Research and Forecasting (WRF)model can provide more complete,efficient,and accurate weather simulation and forecast.The improvement of regional-scale precipitation simulation and forecasting capabilities has made the model gradually applied to smaller-scale storm simulations and forecasts in various countries and regions.In recent years,Beijing′s sub-center has realized the stable and healthy economic and social development of the whole region with the rapid increase of building area and population density,increasing the vulnerability to the effects of storms and floods. Based on WRF,the numerical weather simulation model was built by considering a more comprehensive optimization of the physical parameterization schemes and applied to Beijing′s sub-center.According to the divisions of the Tongzhou District Government concerning water environment management work,the study area included the Chengbei area,Hexi area,Lianghe area,and North canal ecological belt.Three-level two-way nested domains were set according to Lambert Conformal coordinates.Considering cloud microphysical schemes,cumulus convection schemes,planetary boundary layer schemes,and land surface schemes,16 different parameterization scheme combinations were set.To select the optimal combinations,relative error (ER),rootmeansquare error (ERMS),mean deviation error (EMB) and standard deviation (DS) were used to evaluate the simulation effects on temporal and spatial scales. The results showed that different schemes and their combinations had different results,and the simulation results for ′7·20′ were better than those for other rainfalls.The cumulus convective parameterization scheme had the most significant impact on the simulation of heavy rainfall in the study area,and generally,model performance was better when the cumulus parameterization scheme was Grell-Freitas.The combination of the WRF Single-Moment 5-class scheme,the Grell-Freitas scheme,the Yonsei University scheme,the newer version of the Rapid Radiative Transfer Model scheme,the Revised MM5 Monin-Obukhov scheme,the Noah land surface model and the urban canopy model had the best result. In summary,it is feasible to simulate heavy rainfall by the WRF model.The method could extend the forecast period and provide data support for related research in areas lacking precipitation data.Under the current background of increasing short-duration heavy rainfall,the application of above method to urban flood control had important practical significance.Although the simulation accuracy of the WRF model could meet the requirements of actual operations,there were still some shortcomings that required further excavation and analysis.With the solving of the limitations of observed data,the model performance could be improved further in the future.
At present,urban storms and floods have already been one of the major disasters that threaten the sustainable development of cities.With the rapid development of Beijing′s sub-center,storms,and floods vulnerability has continued to increase.Historical or real-time observed data,interpreted data from weather radar or satellite remote sensing,and simulated data from numerical atmospheric models are currently used to study precipitation characteristics.The regional atmospheric model,which could realize the quantitative precipitation simulation and forecasting and provide data support for related research in ungauged areas,was of great significance for urban flood forecast and control.The new generation of mesoscale weather research and forecast model named Weather Research and Forecasting (WRF)model can provide more complete,efficient,and accurate weather simulation and forecast.The improvement of regional-scale precipitation simulation and forecasting capabilities has made the model gradually applied to smaller-scale storm simulations and forecasts in various countries and regions.In recent years,Beijing′s sub-center has realized the stable and healthy economic and social development of the whole region with the rapid increase of building area and population density,increasing the vulnerability to the effects of storms and floods. Based on WRF,the numerical weather simulation model was built by considering a more comprehensive optimization of the physical parameterization schemes and applied to Beijing′s sub-center.According to the divisions of the Tongzhou District Government concerning water environment management work,the study area included the Chengbei area,Hexi area,Lianghe area,and North canal ecological belt.Three-level two-way nested domains were set according to Lambert Conformal coordinates.Considering cloud microphysical schemes,cumulus convection schemes,planetary boundary layer schemes,and land surface schemes,16 different parameterization scheme combinations were set.To select the optimal combinations,relative error (ER),rootmeansquare error (ERMS),mean deviation error (EMB) and standard deviation (DS) were used to evaluate the simulation effects on temporal and spatial scales. The results showed that different schemes and their combinations had different results,and the simulation results for ′7·20′ were better than those for other rainfalls.The cumulus convective parameterization scheme had the most significant impact on the simulation of heavy rainfall in the study area,and generally,model performance was better when the cumulus parameterization scheme was Grell-Freitas.The combination of the WRF Single-Moment 5-class scheme,the Grell-Freitas scheme,the Yonsei University scheme,the newer version of the Rapid Radiative Transfer Model scheme,the Revised MM5 Monin-Obukhov scheme,the Noah land surface model and the urban canopy model had the best result. In summary,it is feasible to simulate heavy rainfall by the WRF model.The method could extend the forecast period and provide data support for related research in areas lacking precipitation data.Under the current background of increasing short-duration heavy rainfall,the application of above method to urban flood control had important practical significance.Although the simulation accuracy of the WRF model could meet the requirements of actual operations,there were still some shortcomings that required further excavation and analysis.With the solving of the limitations of observed data,the model performance could be improved further in the future.
2022, 20(3):581-589.
Abstract:
Soilbags can enhance the strength and restrict the swelling deformation of the expansive soil,and the assembly of soilbags on the expansive soil slope acts as an overburden can avoid the collapse of expansive soil slope during operation period .It has been proved that the soilbag layer arranged on the slope can effectively retard the moisture movement into the underlying expansive soil/rock slope and can be regarded as a reinforcement layer to take effect of restraining the expansion and contraction of expansive soils.It is a promising method to repair the failed expansive soil slopes by the use of soilbags.Unlike other methods such as chemical and mechanical stabilization,when dealing with shallow slope failure,the collapsed expansive soils can be directly filled into bags,and large construction machines are not required for the repairing work.It is particularly suitable for repairing the expansive soil channel slope on a small scale during the operation of the project as it is very flexible and convenient.A method to analyze the sliding stability of the soilbags-repaired expansive soil slope was proposed by introducing a single safety factor.And,a series of laboratory tests were conducted to study the frictional characteristics of stacked soilbags with different filling materials under different inter-layered arrangements of soilbags and the applied vertical stresses.Different filled materials refer to 10%,20%,and 30% of the gravel content and different gravel particle size in the expansive soil.The inter-layered arrangements of soilbags mainly include four kinds.The influence of the water on the interlayer friction of soilbags was also investigated.The results show that the interlayer frictional coefficient between the vertically stacked soilbags is around 0.714,and it can increase up to 0.920 for the staggered soilbags owing to the interlocking effect.When soilbags are soaked in water,the interlayer friction coefficient between the staggered soilbags will decrease to 0.901 owing to the lubrication of water.The case study on a failed expansive channel slope in the South-to-North Water Transfer Project showed that the proposed stability analysis method based on the limit equilibrium of the soilbags-repaired assembly is appropriate for the design of a soilbags-repaired expansive soil channel slope.
Soilbags can enhance the strength and restrict the swelling deformation of the expansive soil,and the assembly of soilbags on the expansive soil slope acts as an overburden can avoid the collapse of expansive soil slope during operation period .It has been proved that the soilbag layer arranged on the slope can effectively retard the moisture movement into the underlying expansive soil/rock slope and can be regarded as a reinforcement layer to take effect of restraining the expansion and contraction of expansive soils.It is a promising method to repair the failed expansive soil slopes by the use of soilbags.Unlike other methods such as chemical and mechanical stabilization,when dealing with shallow slope failure,the collapsed expansive soils can be directly filled into bags,and large construction machines are not required for the repairing work.It is particularly suitable for repairing the expansive soil channel slope on a small scale during the operation of the project as it is very flexible and convenient.A method to analyze the sliding stability of the soilbags-repaired expansive soil slope was proposed by introducing a single safety factor.And,a series of laboratory tests were conducted to study the frictional characteristics of stacked soilbags with different filling materials under different inter-layered arrangements of soilbags and the applied vertical stresses.Different filled materials refer to 10%,20%,and 30% of the gravel content and different gravel particle size in the expansive soil.The inter-layered arrangements of soilbags mainly include four kinds.The influence of the water on the interlayer friction of soilbags was also investigated.The results show that the interlayer frictional coefficient between the vertically stacked soilbags is around 0.714,and it can increase up to 0.920 for the staggered soilbags owing to the interlocking effect.When soilbags are soaked in water,the interlayer friction coefficient between the staggered soilbags will decrease to 0.901 owing to the lubrication of water.The case study on a failed expansive channel slope in the South-to-North Water Transfer Project showed that the proposed stability analysis method based on the limit equilibrium of the soilbags-repaired assembly is appropriate for the design of a soilbags-repaired expansive soil channel slope.
2022, 20(3):590-599.
Abstract:
The control gate is an important control hydraulic structure in open channel water transfer project,which controls the water level and discharge of the channel by adjusting the opening of the gate.Currently,the safety performance and service performance of the arc gate have been paid much attention.The arc gate has been widely used in various open channel water transfer projects because of its advantages such as light weight,small lifting force,stable water flow pattern,simple operation and maintenance.Therefore,the accurate calculation of the discharge of arc gate is of great significance to ensure the reasonable design of the engineering building,the scientific control of the water transmission channel and the safe operation of the water transfer system. In previous studies,the discharge of arc gate was mainly calculated by empirical formula.Due to the complex structure of the arc gate,it was difficult to calibrate the discharge coefficient,submergence coefficient and other parameters in the empirical formula.Besides,the coefficient changed with the change of flow state,so its applicable conditions had certain limitations.In addition,the discharge coefficient of arc gate of the empirical formula was a function of the gate opening degree and the upstream and downstream head difference,and the relationship was mostly nonlinear,which made parameter calibration process complicated and more erroneous.Based on this,the improved arc gate discharge calculation methods are put forward from two different levels of mechanism and data:dimensional analysis method and Long-Short Term Memory neural network. Since the beginning of water transmission of Middle Route of South-to-North Water Transfer Project,a long series of historical water situation data have been accumulated,and the amount of data fully meets the needs of model construction.Consequently,taking 59 control gates in the Middle Route of South-to-North Water Transfer Project as the research object,two different discharge calculation method of arc gates based on dimensional analysis method and Long-Short Term Memory neural network (LSTM) were established.Selecting the original observation data of 2-hour time scale from 2018 to 2019,the average absolute error, average relative error,root mean square error and Nash efficiency coefficient of two models were compared and analyzed,which showed that the error results of the Long-Short Term Memory neural network method was a little better than the dimensional analysis method for the project as a whole,with the average relative errors between the two methods were 2%~2.5% and 3%~4%,respectively. In conclusion, as for parameter calibration,compared with the conventional formula of arc gate discharge,the dimensional analysis method only contained two parameters so that it was simple,economical and easy to linearize.The method of LSTM neural network did not need parameter calibration,which further reduced the workload of calculation.As for method applicability,the dimensional analysis method was greatly affected by the water level fluctuations,and it was more suitable for the overflow calculation of arc gates in the middle and downstream (medium and small discharge) of the Middle Route of South-to-North Water Transfer Project.Contrarily, the LSTM neural network method was relatively slightly affected by water level fluctuation,which was more suitable for discharge calculation of arc gates in the middle and upstream (large and medium discharge).This study provided a scientific basis for the hydraulic calculation and scheduling operation of the gates of the Middle Route of South-to-North Water Transfer Project.However,the methods used were only verified in the arc gates in the Middle Route of South-to-North Water Transfer Project.Whether there are other methods with higher calculation accuracy is worthy of further study.
The control gate is an important control hydraulic structure in open channel water transfer project,which controls the water level and discharge of the channel by adjusting the opening of the gate.Currently,the safety performance and service performance of the arc gate have been paid much attention.The arc gate has been widely used in various open channel water transfer projects because of its advantages such as light weight,small lifting force,stable water flow pattern,simple operation and maintenance.Therefore,the accurate calculation of the discharge of arc gate is of great significance to ensure the reasonable design of the engineering building,the scientific control of the water transmission channel and the safe operation of the water transfer system. In previous studies,the discharge of arc gate was mainly calculated by empirical formula.Due to the complex structure of the arc gate,it was difficult to calibrate the discharge coefficient,submergence coefficient and other parameters in the empirical formula.Besides,the coefficient changed with the change of flow state,so its applicable conditions had certain limitations.In addition,the discharge coefficient of arc gate of the empirical formula was a function of the gate opening degree and the upstream and downstream head difference,and the relationship was mostly nonlinear,which made parameter calibration process complicated and more erroneous.Based on this,the improved arc gate discharge calculation methods are put forward from two different levels of mechanism and data:dimensional analysis method and Long-Short Term Memory neural network. Since the beginning of water transmission of Middle Route of South-to-North Water Transfer Project,a long series of historical water situation data have been accumulated,and the amount of data fully meets the needs of model construction.Consequently,taking 59 control gates in the Middle Route of South-to-North Water Transfer Project as the research object,two different discharge calculation method of arc gates based on dimensional analysis method and Long-Short Term Memory neural network (LSTM) were established.Selecting the original observation data of 2-hour time scale from 2018 to 2019,the average absolute error, average relative error,root mean square error and Nash efficiency coefficient of two models were compared and analyzed,which showed that the error results of the Long-Short Term Memory neural network method was a little better than the dimensional analysis method for the project as a whole,with the average relative errors between the two methods were 2%~2.5% and 3%~4%,respectively. In conclusion, as for parameter calibration,compared with the conventional formula of arc gate discharge,the dimensional analysis method only contained two parameters so that it was simple,economical and easy to linearize.The method of LSTM neural network did not need parameter calibration,which further reduced the workload of calculation.As for method applicability,the dimensional analysis method was greatly affected by the water level fluctuations,and it was more suitable for the overflow calculation of arc gates in the middle and downstream (medium and small discharge) of the Middle Route of South-to-North Water Transfer Project.Contrarily, the LSTM neural network method was relatively slightly affected by water level fluctuation,which was more suitable for discharge calculation of arc gates in the middle and upstream (large and medium discharge).This study provided a scientific basis for the hydraulic calculation and scheduling operation of the gates of the Middle Route of South-to-North Water Transfer Project.However,the methods used were only verified in the arc gates in the Middle Route of South-to-North Water Transfer Project.Whether there are other methods with higher calculation accuracy is worthy of further study.
2022, 20(3):600-609.
Abstract:
The main task of water dispatching of long-distance water transfer projects is to properly determine the amount,process,and scope of water transfer based on overall considering the water input and storage situation of headwater area and the water demand in the water receiving area,of which the water loss is the key parameter in organizing the water dispatching plan,and directly affects the dispatching accuracy.Therefore,there is a great significance to achieve accurate dispatching,ensure water supply safety,and improve dispatching management level.However,previous studies mainly focus on the calculation methods of canal seepage,little was known about the variation of water loss during the operation period of long-distance water transfer projects. By integrating the synchronized flow and water level measurements data,the variation process of water loss in the six typical canal sections of the Middle Route of South-to-North Water Transfer First Stage Project over the annually-averaged,monthly-averaged,and daily-averaged timescales from 2018 to 2021 was calculated based on the principle of water balance,and the calculated water loss was also compared to the results of four empirical canal water loss methods including Davison-Wilson,Mauriz,Molesworth,and Kostiakov methods to evaluate the performance and applicability of empirical methods in estimating water loss in long-distance water transfer projects. The results showed that the water loss of the Middle Route of South-to-North Water Transfer First Stage Project exhibited pronounced spatiotemporal variations.The magnitude and change amplitude of loss discharge in the southern canals of the Yellow River were larger than that of the northern canals,but there was a minor difference in loss rate between them,indicating that the amount of inflow canal discharge is the main factor affecting the canal water loss discharge.The calculated water loss by empirical methods varied greatly.Specifically,the averaged water loss calculated by the methods of DavisonWilson and Kostiakov was in good agreement with the average results by the principle of water balance in part of typical canals,but the change magnitude of their results within canal was much smaller.The calculated canal water loss by the method of Molesworth is significantly greater than the results of other methods as this method underestimated the effect of anti-seepage measures on canal water loss.Overall,the calculated water loss by the empirical method deviated from calculated results by the principle of water balance,suggesting that the change process of water loss of the Middle Route of South-to-North Water Transfer First Stage Project can not be effectively reflected by only considering canal seepage.The impacts of external factors including natural condition changes,operating condition changes,and measurement error on canal water loss were analyzed preliminarily,and the results indicated that evaporation variation,precipitation,and freezing and thawing during the ice period were crucial factors triggering spatial and temporal variations of water loss of the Middle Route of South-to-North Water Transfer First Stage Project.The adjustment of the water dispatching plan affects canal water loss by changing the water contact area in the canal section.Besides,the measurement errors may greatly affect the calculated results of canal water loss when applying the principle of water balance. The calculated water loss of the current study illustrated that it is necessary to consider the dynamic process of water loss,especially in the long-distance water transfer projects where meteorological and engineering operating conditions exhibited significant variation along the canal.
The main task of water dispatching of long-distance water transfer projects is to properly determine the amount,process,and scope of water transfer based on overall considering the water input and storage situation of headwater area and the water demand in the water receiving area,of which the water loss is the key parameter in organizing the water dispatching plan,and directly affects the dispatching accuracy.Therefore,there is a great significance to achieve accurate dispatching,ensure water supply safety,and improve dispatching management level.However,previous studies mainly focus on the calculation methods of canal seepage,little was known about the variation of water loss during the operation period of long-distance water transfer projects. By integrating the synchronized flow and water level measurements data,the variation process of water loss in the six typical canal sections of the Middle Route of South-to-North Water Transfer First Stage Project over the annually-averaged,monthly-averaged,and daily-averaged timescales from 2018 to 2021 was calculated based on the principle of water balance,and the calculated water loss was also compared to the results of four empirical canal water loss methods including Davison-Wilson,Mauriz,Molesworth,and Kostiakov methods to evaluate the performance and applicability of empirical methods in estimating water loss in long-distance water transfer projects. The results showed that the water loss of the Middle Route of South-to-North Water Transfer First Stage Project exhibited pronounced spatiotemporal variations.The magnitude and change amplitude of loss discharge in the southern canals of the Yellow River were larger than that of the northern canals,but there was a minor difference in loss rate between them,indicating that the amount of inflow canal discharge is the main factor affecting the canal water loss discharge.The calculated water loss by empirical methods varied greatly.Specifically,the averaged water loss calculated by the methods of DavisonWilson and Kostiakov was in good agreement with the average results by the principle of water balance in part of typical canals,but the change magnitude of their results within canal was much smaller.The calculated canal water loss by the method of Molesworth is significantly greater than the results of other methods as this method underestimated the effect of anti-seepage measures on canal water loss.Overall,the calculated water loss by the empirical method deviated from calculated results by the principle of water balance,suggesting that the change process of water loss of the Middle Route of South-to-North Water Transfer First Stage Project can not be effectively reflected by only considering canal seepage.The impacts of external factors including natural condition changes,operating condition changes,and measurement error on canal water loss were analyzed preliminarily,and the results indicated that evaporation variation,precipitation,and freezing and thawing during the ice period were crucial factors triggering spatial and temporal variations of water loss of the Middle Route of South-to-North Water Transfer First Stage Project.The adjustment of the water dispatching plan affects canal water loss by changing the water contact area in the canal section.Besides,the measurement errors may greatly affect the calculated results of canal water loss when applying the principle of water balance. The calculated water loss of the current study illustrated that it is necessary to consider the dynamic process of water loss,especially in the long-distance water transfer projects where meteorological and engineering operating conditions exhibited significant variation along the canal.
2022, 20(3):610-618.
Abstract:
Bulb tubular pump is widely used in South-to-North Water Transfer Project because of high efficiency,large flow rate,and excellent hydraulic performance.Abnormal hydraulic resonance could cause when large pumping stations operate under off-design conditions,and the operation of pumping stations could disturbed by abnormal hydraulic resonance.Therefore,it is urgent to study and prevent abnormal hydraulic resonance due pressure fluctuation of impeller and guide vane of postpositional bulb tubular pump in South-to-North Water Transfer pumping station under different working conditions. The pressure fluctuation in the vane area of the impeller under the condition of partial flow and water level was calculated and analyzed by CFD method.To analyze the pressure fluctuation law of impeller and guide vane area in bulb tubular pump,18 pressure fluctuation monitoring points were arranged.The frequency-domain diagram of pressure fluctuation was obtained by fast Fourier transform of time-domain data of pressure fluctuation.The variation characteristics of amplitude and frequency of pressure fluctuation were analyzed by frequency domain diagram of pressure fluctuation. The results showed that the time-domain diagram of pressure fluctuation in the impeller and guide vane was periodical.The primary and secondary frequency of pressure fluctuation was influenced by the number of impeller blades.The primary and secondary frequencies of the impeller and guide vane area were all integral multiples,and the pressure fluctuation amplitude of the impeller and guide vane area was decreased from the rim to the hub.The pressure fluctuation amplitude in the impeller area was significantly greater than that in the guide vane area.Under the partial water level condition,the amplitude of pressure fluctuation in the impeller and guide vane area was slightly larger than that under the design condition,and the primary and secondary frequencies were not changed.The pressure fluctuation amplitude of small and large flow conditions under partial flow conditions was greater than the design condition.The pressure fluctuation amplitude of the small flow condition at each monitoring point was about 23 times of the design condition.The low-frequency fluctuation was obvious under the small flow condition.The pressure fluctuation amplitude of the pumping units was greatly influenced by the operation under the partial working condition.Pumping unit operation efficiency was seriously affected by the long-term off-design operation. Under the design condition,the time-domain diagram of pressure fluctuation of each section was obvious periodicity.The law of fluctuating pressure in a cycle was affected by the number of impeller guide vanes,and the pressure fluctuation amplitude in the guide vane area was less than that in the impeller area as a whole.The primary and secondary frequency of pressure fluctuation at the inlet and outlet of the impeller and the outlet of the guide vane were affected by the impeller,guide vane and front and rear support plates,which was an integral multiple of the conversion frequency.The distribution law of pressure fluctuation was affected by the dynamic and static interference between the impeller and the guide vane or support plate.The pressure fluctuation amplitude at the impeller inlet changed little from the rim to the hub,the pressure fluctuation amplitude at the hub was slightly larger than the rim,and the pressure fluctuation amplitude at the impeller outlet and guide vane outlet was decreased gradually from the rim to the hub.The pressure fluctuation amplitude under partial water level conditions was large than that under design conditions,and the pressure fluctuation was affected by the amplitude of the water level difference between upstream and downstream.Under the off-design conditions,the pressure fluctuation amplitude of each section monitoring point was large than that of the design condition both under small flow rate and large flow rate,and frequent low-frequency fluctuation occurred under small flow rate.Abnormal hydraulic resonance was easy to occur under off-design conditions,which aggravated the cavitation of the pump impeller and generated adverse flow patterns.During the operation of the pumping station,off-design conditions,especially small flow conditions,should be avoided as far as possible.
Bulb tubular pump is widely used in South-to-North Water Transfer Project because of high efficiency,large flow rate,and excellent hydraulic performance.Abnormal hydraulic resonance could cause when large pumping stations operate under off-design conditions,and the operation of pumping stations could disturbed by abnormal hydraulic resonance.Therefore,it is urgent to study and prevent abnormal hydraulic resonance due pressure fluctuation of impeller and guide vane of postpositional bulb tubular pump in South-to-North Water Transfer pumping station under different working conditions. The pressure fluctuation in the vane area of the impeller under the condition of partial flow and water level was calculated and analyzed by CFD method.To analyze the pressure fluctuation law of impeller and guide vane area in bulb tubular pump,18 pressure fluctuation monitoring points were arranged.The frequency-domain diagram of pressure fluctuation was obtained by fast Fourier transform of time-domain data of pressure fluctuation.The variation characteristics of amplitude and frequency of pressure fluctuation were analyzed by frequency domain diagram of pressure fluctuation. The results showed that the time-domain diagram of pressure fluctuation in the impeller and guide vane was periodical.The primary and secondary frequency of pressure fluctuation was influenced by the number of impeller blades.The primary and secondary frequencies of the impeller and guide vane area were all integral multiples,and the pressure fluctuation amplitude of the impeller and guide vane area was decreased from the rim to the hub.The pressure fluctuation amplitude in the impeller area was significantly greater than that in the guide vane area.Under the partial water level condition,the amplitude of pressure fluctuation in the impeller and guide vane area was slightly larger than that under the design condition,and the primary and secondary frequencies were not changed.The pressure fluctuation amplitude of small and large flow conditions under partial flow conditions was greater than the design condition.The pressure fluctuation amplitude of the small flow condition at each monitoring point was about 23 times of the design condition.The low-frequency fluctuation was obvious under the small flow condition.The pressure fluctuation amplitude of the pumping units was greatly influenced by the operation under the partial working condition.Pumping unit operation efficiency was seriously affected by the long-term off-design operation. Under the design condition,the time-domain diagram of pressure fluctuation of each section was obvious periodicity.The law of fluctuating pressure in a cycle was affected by the number of impeller guide vanes,and the pressure fluctuation amplitude in the guide vane area was less than that in the impeller area as a whole.The primary and secondary frequency of pressure fluctuation at the inlet and outlet of the impeller and the outlet of the guide vane were affected by the impeller,guide vane and front and rear support plates,which was an integral multiple of the conversion frequency.The distribution law of pressure fluctuation was affected by the dynamic and static interference between the impeller and the guide vane or support plate.The pressure fluctuation amplitude at the impeller inlet changed little from the rim to the hub,the pressure fluctuation amplitude at the hub was slightly larger than the rim,and the pressure fluctuation amplitude at the impeller outlet and guide vane outlet was decreased gradually from the rim to the hub.The pressure fluctuation amplitude under partial water level conditions was large than that under design conditions,and the pressure fluctuation was affected by the amplitude of the water level difference between upstream and downstream.Under the off-design conditions,the pressure fluctuation amplitude of each section monitoring point was large than that of the design condition both under small flow rate and large flow rate,and frequent low-frequency fluctuation occurred under small flow rate.Abnormal hydraulic resonance was easy to occur under off-design conditions,which aggravated the cavitation of the pump impeller and generated adverse flow patterns.During the operation of the pumping station,off-design conditions,especially small flow conditions,should be avoided as far as possible.
2022, 20(3):619-624.
Abstract:
The water supply network is the lifeline project of the city.Under the background of the implementation of the rural revitalization strategy,the security of rural drinking water and the accelerated construction of the urban-rural water supply integration project,the water supply network has also become the lifeline project of the vast rural areas.In order to ensure the quality and quantity of water supply and complete the water supply task economically and reasonably,it is necessary to carry out scientific planning and design and precise optimization and scheduling of the water supply network.The hydraulic simulation calculation of the water supply network is the basis for the planning,design,operation scheduling and fault diagnosis of the pipeline network.Among the factors affecting the accuracy of the hydraulic calculation model of the pipeline network,the influence of the friction coefficient is particularly prominent.In order to narrow the gap between friction factor theory and practice,a calculation method based on hybrid particle swarm optimization algorithm and nodal water pressure method is proposed. Hybrid particle swarm optimization model is obtained by combining the selection mechanism of basic particle swarm optimization and genetic algorithm.The difference between hybrid particle swarm optimization and particle swarm optimization lies in that the particle swarm has to cross operate after updating the velocity and position,and replace the parent particle with the offspring particle.The crossover operation makes the offspring inherit the advantages of the parent particles and theoretically strengthens the ability to search the region between the particles.In the algorithm,the initial friction resistance factor is randomly selected and put into the Hazen-William formula.The square root of the square error of the square error between the water pressures is calculated based on the actual water pressure value of the nodes monitored by the pipeline network model as the fitness value,and the fitness is evaluated.When the accuracy is met or the maximum number of iterations is reached,the frictional resistance factor is output. In order to verify the feasibility of the method,a 2.5 m×2.5 m square flat pipeline network model was established in the laboratory experiment,which contained 9 basic rings.Four water pressure monitoring points are set in the model pipeline network node.Based on the friction resistance factor inversion under normal working conditions,the hydraulic simulation model of the pipeline network is established on this basis.In the case of pipe bursting,virtual nodes are introduced into the pipeline network model to simulate the pipe bursting point,and the simulation results are compared with the measured values to verify the accuracy of the model. The results show that:(1) HPSO has a strong global optimization ability.The maximum relative error of the Hazen-Williams factor of each pipe section obtained by inversion under normal and special conditions (pipe burst) is 7%,with high accuracy and better adaptability.(2) Calculate the outlet water pressure of the monitoring point under the normal condition and the pipe burst condition with the inversion value of the Hazen-Williams factor under the normal condition.The maximum relative error between the result and the actual water pressure monitoring value is only 2.87%.The inverse problem solved by the method in this paper is well-posed.
The water supply network is the lifeline project of the city.Under the background of the implementation of the rural revitalization strategy,the security of rural drinking water and the accelerated construction of the urban-rural water supply integration project,the water supply network has also become the lifeline project of the vast rural areas.In order to ensure the quality and quantity of water supply and complete the water supply task economically and reasonably,it is necessary to carry out scientific planning and design and precise optimization and scheduling of the water supply network.The hydraulic simulation calculation of the water supply network is the basis for the planning,design,operation scheduling and fault diagnosis of the pipeline network.Among the factors affecting the accuracy of the hydraulic calculation model of the pipeline network,the influence of the friction coefficient is particularly prominent.In order to narrow the gap between friction factor theory and practice,a calculation method based on hybrid particle swarm optimization algorithm and nodal water pressure method is proposed. Hybrid particle swarm optimization model is obtained by combining the selection mechanism of basic particle swarm optimization and genetic algorithm.The difference between hybrid particle swarm optimization and particle swarm optimization lies in that the particle swarm has to cross operate after updating the velocity and position,and replace the parent particle with the offspring particle.The crossover operation makes the offspring inherit the advantages of the parent particles and theoretically strengthens the ability to search the region between the particles.In the algorithm,the initial friction resistance factor is randomly selected and put into the Hazen-William formula.The square root of the square error of the square error between the water pressures is calculated based on the actual water pressure value of the nodes monitored by the pipeline network model as the fitness value,and the fitness is evaluated.When the accuracy is met or the maximum number of iterations is reached,the frictional resistance factor is output. In order to verify the feasibility of the method,a 2.5 m×2.5 m square flat pipeline network model was established in the laboratory experiment,which contained 9 basic rings.Four water pressure monitoring points are set in the model pipeline network node.Based on the friction resistance factor inversion under normal working conditions,the hydraulic simulation model of the pipeline network is established on this basis.In the case of pipe bursting,virtual nodes are introduced into the pipeline network model to simulate the pipe bursting point,and the simulation results are compared with the measured values to verify the accuracy of the model. The results show that:(1) HPSO has a strong global optimization ability.The maximum relative error of the Hazen-Williams factor of each pipe section obtained by inversion under normal and special conditions (pipe burst) is 7%,with high accuracy and better adaptability.(2) Calculate the outlet water pressure of the monitoring point under the normal condition and the pipe burst condition with the inversion value of the Hazen-Williams factor under the normal condition.The maximum relative error between the result and the actual water pressure monitoring value is only 2.87%.The inverse problem solved by the method in this paper is well-posed.
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