Volume 0,Issue 5,2023 Table of Contents
2023(5):833-842.
Abstract:
Agricultural water consumption accounts for over 70% of the world's water consumption. For a long time, promoting water-saving irrigation technology and improving agricultural water efficiency have been regarded as effective methods to reduce agricultural water consumption and alleviate regional water scarcity. However, an increasing number of studies have shown that with the application of water-saving technology and the improvement of water-saving levels, the shortage of water resources worldwide has become even more severe, resulting in the paradox of irrigation efficiency. The emergence of the paradox of irrigation efficiency results from various factors such as hydrology, economy, society, institutions, and management, and the expansion of irrigation area is an important reason for the paradox. Revealing the mechanism of the paradox of irrigation efficiency is the basis for improving water and land resources management in the river basins. Tarim River basin is located in an inland arid area with scarce water resources, and the natural ecology is very fragile. In the recent comprehensive management of the Tarim River basin, nearly half of the investment was spent on water-saving renovation in irrigation areas. However, the expected results were not achieved. The expansion of irrigation area resulted in the widespread phenomenon of "reclaiming land while controlling" and "saving water while consuming water". Under the condition of a certain amount of total water resources, there is a game competition relationship between natural and artificial systems regarding water consumption. Therefore, it is urgent to explore the evolution of water consumption with water use efficiency in water-saving development between natural oasis ecosystems and artificial oasis socio-economic systems.The Tarim River basin, the most apparent contradiction in water and land resources, was taken as an example. The rapid development of water-saving technology from 1990 to 2020 was selected as the study time. Under the conditions of consistent water resources, social economy, and water-saving levels in the basin, two cases was set up, i.e., the actual case with irrigation area expansion and the ideal case with irrigated area maintenance. The basin’s water consumption and water use efficiency varying with the development of water-saving irrigation were analyzed and compared with the two cases. The results show that in the past 30 years, the irrigation water use efficiency of the basin has increased from 0.28 to 0.55, the gross irrigation quota has been reduced by twice, and the water-saving level has been significantly improved. In the actual case, 3.6 billion m3of net water savings have been used to expand irrigation area, resulting in more than doubling of irrigation area and water consumption. The area ratio of artificial and natural oases has changed from 40∶60 to 55∶45, and the water consumption ratio has changed from 4∶6 to 6∶4. The proportion of oasis water consumption to water resources has increased from 72% to 91%, resulting in a severe paradox of irrigation efficiency. In the ideal case, the irrigation water consumption is reduced, the area and water consumption ratio of artificial and natural oases are maintained at around 4∶6, and the proportion of oasis water consumption to water resources is 70%, resulting in an actual water saving of 2.4 billion m3, avoiding the occurrence of the paradox of irrigation efficiency.The emergence of the paradox of irrigation efficiency is the complete result of factors such as great water conditions, water-saving development, planting structure adjustment, and irrigation area expansion. In the past 30 years, the expansion of the irrigation area has played a leading role in the emergence of the paradox of irrigation efficiency in the Tarim River basin. In order to avoid the occurrence of the paradox of irrigation efficiency, it is necessary to manage water resources strictly, adhere to the principle of "water settling land", and promote the balanced development of soil and water resources in arid inland river basins.
Agricultural water consumption accounts for over 70% of the world's water consumption. For a long time, promoting water-saving irrigation technology and improving agricultural water efficiency have been regarded as effective methods to reduce agricultural water consumption and alleviate regional water scarcity. However, an increasing number of studies have shown that with the application of water-saving technology and the improvement of water-saving levels, the shortage of water resources worldwide has become even more severe, resulting in the paradox of irrigation efficiency. The emergence of the paradox of irrigation efficiency results from various factors such as hydrology, economy, society, institutions, and management, and the expansion of irrigation area is an important reason for the paradox. Revealing the mechanism of the paradox of irrigation efficiency is the basis for improving water and land resources management in the river basins. Tarim River basin is located in an inland arid area with scarce water resources, and the natural ecology is very fragile. In the recent comprehensive management of the Tarim River basin, nearly half of the investment was spent on water-saving renovation in irrigation areas. However, the expected results were not achieved. The expansion of irrigation area resulted in the widespread phenomenon of "reclaiming land while controlling" and "saving water while consuming water". Under the condition of a certain amount of total water resources, there is a game competition relationship between natural and artificial systems regarding water consumption. Therefore, it is urgent to explore the evolution of water consumption with water use efficiency in water-saving development between natural oasis ecosystems and artificial oasis socio-economic systems.The Tarim River basin, the most apparent contradiction in water and land resources, was taken as an example. The rapid development of water-saving technology from 1990 to 2020 was selected as the study time. Under the conditions of consistent water resources, social economy, and water-saving levels in the basin, two cases was set up, i.e., the actual case with irrigation area expansion and the ideal case with irrigated area maintenance. The basin’s water consumption and water use efficiency varying with the development of water-saving irrigation were analyzed and compared with the two cases. The results show that in the past 30 years, the irrigation water use efficiency of the basin has increased from 0.28 to 0.55, the gross irrigation quota has been reduced by twice, and the water-saving level has been significantly improved. In the actual case, 3.6 billion m3of net water savings have been used to expand irrigation area, resulting in more than doubling of irrigation area and water consumption. The area ratio of artificial and natural oases has changed from 40∶60 to 55∶45, and the water consumption ratio has changed from 4∶6 to 6∶4. The proportion of oasis water consumption to water resources has increased from 72% to 91%, resulting in a severe paradox of irrigation efficiency. In the ideal case, the irrigation water consumption is reduced, the area and water consumption ratio of artificial and natural oases are maintained at around 4∶6, and the proportion of oasis water consumption to water resources is 70%, resulting in an actual water saving of 2.4 billion m3, avoiding the occurrence of the paradox of irrigation efficiency.The emergence of the paradox of irrigation efficiency is the complete result of factors such as great water conditions, water-saving development, planting structure adjustment, and irrigation area expansion. In the past 30 years, the expansion of the irrigation area has played a leading role in the emergence of the paradox of irrigation efficiency in the Tarim River basin. In order to avoid the occurrence of the paradox of irrigation efficiency, it is necessary to manage water resources strictly, adhere to the principle of "water settling land", and promote the balanced development of soil and water resources in arid inland river basins.
2023(5):843-861,950.
Abstract:
Rainfall is a direct factor in the formation of flood, and the combination of accurate rainfall forecast data in the long forecast period and hydrological model is the key to improve the accuracy of flood forecast and increase the forecast period, which can strive for a longer emergency response time for flood control and disaster reduction. Rainfall forecast data mainly come from meteorological radar, satellite cloud image and numerical weather forecast products. Although the meteorological observation technology and equipment have made great progress in the past few decades, due to the chaos of atmospheric system, the error of atmospheric initial data and the error of model, the rainfall forecast products inevitably have large errors and limitations, and need to be effectively corrected to improve its accuracy and reliability. The research took 12 stations in Chaobai River basin as the research object, the forecast precipitation data of 12 stations in different forecast periods in the next 12 hours were selected. Rainfall error correction models based on support vector machine, random forest and multilayer perceptron in different forecast periods were constructed. The model input is the rainfall forecast data of the corresponding grid of the station and its surrounding 8 grids, and the model parameters are estimated by Bayesian optimization technology. The root mean square error and deterministic coefficient indexes were used to evaluate the correction effect of each model on precipitation forecast in different forecast periods. The results showed that the prediction accuracy of uncorrected original forecast was poor in different forecast periods. Each error correction model has a good correction effect on rainfall in different forecast periods. After correction by support vector machine model, random forest model and multilayer perceptron model, the average root mean square error decreases by 54.2%, 50.0% and 20.8%, respectively. During the validation period, the reduction was 42.9%, 33.3% and 14.3%, respectively. The average certainty coefficient also increased significantly in both the rate period and the validation period. Among the three error correction models, support vector machine model is the best, followed by random forest model. Based on support vector machine, random forest and multi-layer perceptron model, combined with Bayesian optimization technology, the error correction models of forecast rainfall data in different forecast periods were constructed to correct and analyze the forecast rainfall data of 12 stations in the Chaobai River basin in 12 different forecast periods. The root mean square error and deterministic coefficient were used. The correction effect is good and the accuracy of rainfall forecast is improved, and it can be used as a reference for the numerical rainfall correction of other watershed stations.
Rainfall is a direct factor in the formation of flood, and the combination of accurate rainfall forecast data in the long forecast period and hydrological model is the key to improve the accuracy of flood forecast and increase the forecast period, which can strive for a longer emergency response time for flood control and disaster reduction. Rainfall forecast data mainly come from meteorological radar, satellite cloud image and numerical weather forecast products. Although the meteorological observation technology and equipment have made great progress in the past few decades, due to the chaos of atmospheric system, the error of atmospheric initial data and the error of model, the rainfall forecast products inevitably have large errors and limitations, and need to be effectively corrected to improve its accuracy and reliability. The research took 12 stations in Chaobai River basin as the research object, the forecast precipitation data of 12 stations in different forecast periods in the next 12 hours were selected. Rainfall error correction models based on support vector machine, random forest and multilayer perceptron in different forecast periods were constructed. The model input is the rainfall forecast data of the corresponding grid of the station and its surrounding 8 grids, and the model parameters are estimated by Bayesian optimization technology. The root mean square error and deterministic coefficient indexes were used to evaluate the correction effect of each model on precipitation forecast in different forecast periods. The results showed that the prediction accuracy of uncorrected original forecast was poor in different forecast periods. Each error correction model has a good correction effect on rainfall in different forecast periods. After correction by support vector machine model, random forest model and multilayer perceptron model, the average root mean square error decreases by 54.2%, 50.0% and 20.8%, respectively. During the validation period, the reduction was 42.9%, 33.3% and 14.3%, respectively. The average certainty coefficient also increased significantly in both the rate period and the validation period. Among the three error correction models, support vector machine model is the best, followed by random forest model. Based on support vector machine, random forest and multi-layer perceptron model, combined with Bayesian optimization technology, the error correction models of forecast rainfall data in different forecast periods were constructed to correct and analyze the forecast rainfall data of 12 stations in the Chaobai River basin in 12 different forecast periods. The root mean square error and deterministic coefficient were used. The correction effect is good and the accuracy of rainfall forecast is improved, and it can be used as a reference for the numerical rainfall correction of other watershed stations.
2023(5):862-872.
Abstract:
In the context of global climate change, excessive deforestation, urban construction and irrational use of water resources have been carried out by human beings for a long time, and the phenomena of water resource shortage, water environment pollution, water ecology deterioration and river closure have become increasingly prominent. The original ecosystems in many river basins were destroyed and the ecosystem service functions were reduced. Water conservation capacity has important service functions such as regulating runoff, purifying water quality, and regulating and storing flood water. As a first-level tributary of the Yellow River, the Qinhe River is an important part of the ecosystem along the river. However, due to the influence of climate change and human activities in recent years, the land use change of the Qinhe River basin is significant, and the inter-annual variation characteristics of water conservation function are gradually complicated. Therefore, exploring the water conservation capacity of Qinhe River basin in the changing environment can provide scientific reference value for ecological protection and high-quality development strategy of the Yellow River basin.SWAT model was constructed, and the land use data set of the Qinhe River basin in 2030 was predicted based on the CA-Markov model to analyze and predict the temporal and spatial changes of water conservation capacity in the Qinhe River basin. Combined with CMIP6 meteorological data, the hydrological factors of the river basin simulated by the SWAT model were obtained according to the principle of water balance. The temporal and spatial changes in water conservation in the past and future years were calculated. In addition, by calculating the ratio of water conservation and precipitation, the index of water conservation rate was introduced to further quantify the water conservation capacity of the basin for storing precipitation and supplying water.The results show that the average annual water conservation is 49 mm and the average annual water conservation rate is 8% in the Qinhe River basin. From 2010 to 2016, water conservation showed a trend of fluctuation and increase, and the water conservation is consistent with the inter-annual variation trend of precipitation. The spatial distribution characteristics of water conservation and water conservation rate in 2010, 2015, and 2025 are similar, showing a trend of increasing from upstream to downstream and decreasing from west to east. However, the spatial distribution characteristics of water conservation and water conservation rate in 2030 are different from other years, and the overall trend is decreasing from the upstream to the downstream, and the water conservation and water conservation rate are negative in the downstream multi-section basins.The analysis showed that the spatial distribution of water conservation rate and water conservation in the basin has a good consistency, and there are negative values in the sub-basins, indicating that the water conservation capacity of the basin is low, the ecological environment is damaged to a high degree, and the ecological water consumption in the river is insufficient, which is in line with the actual situation that the relevant river reaches were cut off.
In the context of global climate change, excessive deforestation, urban construction and irrational use of water resources have been carried out by human beings for a long time, and the phenomena of water resource shortage, water environment pollution, water ecology deterioration and river closure have become increasingly prominent. The original ecosystems in many river basins were destroyed and the ecosystem service functions were reduced. Water conservation capacity has important service functions such as regulating runoff, purifying water quality, and regulating and storing flood water. As a first-level tributary of the Yellow River, the Qinhe River is an important part of the ecosystem along the river. However, due to the influence of climate change and human activities in recent years, the land use change of the Qinhe River basin is significant, and the inter-annual variation characteristics of water conservation function are gradually complicated. Therefore, exploring the water conservation capacity of Qinhe River basin in the changing environment can provide scientific reference value for ecological protection and high-quality development strategy of the Yellow River basin.SWAT model was constructed, and the land use data set of the Qinhe River basin in 2030 was predicted based on the CA-Markov model to analyze and predict the temporal and spatial changes of water conservation capacity in the Qinhe River basin. Combined with CMIP6 meteorological data, the hydrological factors of the river basin simulated by the SWAT model were obtained according to the principle of water balance. The temporal and spatial changes in water conservation in the past and future years were calculated. In addition, by calculating the ratio of water conservation and precipitation, the index of water conservation rate was introduced to further quantify the water conservation capacity of the basin for storing precipitation and supplying water.The results show that the average annual water conservation is 49 mm and the average annual water conservation rate is 8% in the Qinhe River basin. From 2010 to 2016, water conservation showed a trend of fluctuation and increase, and the water conservation is consistent with the inter-annual variation trend of precipitation. The spatial distribution characteristics of water conservation and water conservation rate in 2010, 2015, and 2025 are similar, showing a trend of increasing from upstream to downstream and decreasing from west to east. However, the spatial distribution characteristics of water conservation and water conservation rate in 2030 are different from other years, and the overall trend is decreasing from the upstream to the downstream, and the water conservation and water conservation rate are negative in the downstream multi-section basins.The analysis showed that the spatial distribution of water conservation rate and water conservation in the basin has a good consistency, and there are negative values in the sub-basins, indicating that the water conservation capacity of the basin is low, the ecological environment is damaged to a high degree, and the ecological water consumption in the river is insufficient, which is in line with the actual situation that the relevant river reaches were cut off.
2023(5):873-885.
Abstract:
Hebei Province is an important ecological barrier in northern China and an important support for the coordinated development of Beijing, Tianjin and Hebei. However, its water resources problem was prominent, the per capita possession was low, the spatial and temporal distribution was uneven, and the contradiction between supply and demand of water resources was increasing. With the continuous development of social economy, the intensity and pressure of water resources development and utilization were increasing year by year, and the problem of water ecological environment was becoming more and more serious. In order to objectively and effectively evaluate the water resources security degree of Hebei Province, ensure that the natural circulation system of water resources can meet the natural guarantee function of national or regional development needs without being destroyed or threatened by people.
Hebei Province is an important ecological barrier in northern China and an important support for the coordinated development of Beijing, Tianjin and Hebei. However, its water resources problem was prominent, the per capita possession was low, the spatial and temporal distribution was uneven, and the contradiction between supply and demand of water resources was increasing. With the continuous development of social economy, the intensity and pressure of water resources development and utilization were increasing year by year, and the problem of water ecological environment was becoming more and more serious. In order to objectively and effectively evaluate the water resources security degree of Hebei Province, ensure that the natural circulation system of water resources can meet the natural guarantee function of national or regional development needs without being destroyed or threatened by people.
Based on the DPSIR model, the evaluation system of water resources security degree was preliminarily constructed. By collecting relevant data of Hebei Province, the correlation analysis and screening of the primary evaluation indexes were carried out to determine the evaluation system of water resources security degree. The TOPSIS model combined with the variation coefficient method and the rank sum ratio method was introduced to comprehensively evaluate the water resources security degree of Hebei Province from 2001 to 2020, and the evaluation results were diagnosed with obstacle factors.The results showed that the relative closeness of water resources security degree in Hebei Province increased from 0.217 to 0.745 from 2001 to 2020, from extremely low to high, and reached a medium level as a whole. From 2001 to 2007, the level of water resources security degree was grade V. From 2008 to 2010, the level of water resources security degree reached grade IV.From 2011 to 2012, the level of water resources security reached grade III.From the end of 2014, the progress has been increasing year by year, which was closely related to the increase of the proportion of cross-basin water supply in the response subsystem. From the weight calculation results, it was concluded that the response subsystem was the main subsystem affecting the water resources security degree of Hebei Province, and the obstacle degree of the proportion index of inter-basin water supply was the highest, indicating that the proportion of inter-basin water supply was the primary obstacle factor affecting the water resources security degree.In order to further improve the situation of water resources security degree in Hebei Province, it was necessary to optimize the allocation of water resources and alleviate the pressure of water resources. The biological treatment and physical and chemical treatment technology, are adopted, the process flow, is optimize the economic structure and industrial structure, are adjusted, and improve labor productivity is improved ; it was necessary to advocate residents to improve their lifestyles and reduce the use of cleaners and detergents containing chemical substances. At the same time, it was necessary to improve the efficiency of water resources utilization and promote the circular economy model. The DPSIR-game theory combined weighting TOPSIS model had good objectivity and applicability for the evaluation of water resources security evolution, and was of great significance to the development of economy, society and ecological environment in the region. The research results provided a reference for the rational development, utilization and management of water resources in Hebei Province in the future.
2023(5):886-894.
Abstract:
Flood forecasting and prediction are integral components of non-structural flood management measures. Methods for flood forecasting and prediction can generally be classified into two categories: process-driven approaches (hydrological models) and data-driven approaches. Traditionally, the focus has been on process-driven approaches, but with the accumulation of hydrological data and advancements in big data analytics, data-driven approaches have gained increasing attention. In particular, the application of artificial intelligence technology in the water industry has led to the emergence of hydrological data mining-based forecasting and prediction methods as a research hotspot. Conducting hydrological knowledge mining and prediction based on the principle of similarity has become an important research direction, offering a new technical means to uncover hidden patterns within rainfall, floods, and watershed surface information. This approach also promotes the automation and intelligence of water resources data processing, assisting in improving the accuracy of flood forecasting and prediction, thereby facilitating the modernization and precision of the water industry.In theory, the longer the series of hydrological data, the more torrential rain-induced flood knowledge can be extracted. However, hydrological data series in a changing environment often exhibit inconsistencies, which affect the accuracy of flood forecasting and prediction based on torrential rain-induced flood knowledge. Currently, research on historical similar torrential rain-induced flood knowledge considering inconsistencies in guiding real-time flood forecasting is relatively limited. In this context, a methodology based on the knowledge of torrential rain-induced floods for real-time flood forecasting and prediction is proposed. The proposed method focuses on historical records of typical torrential rain-induced floods and extracts rainfall feature indicators, such as the position of the rainstorm center, antecedent precipitation, total average rainfall, and rainfall processes. Multiple feature indicators are simultaneously assessed for their similarity using criteria such as Euclidean distance. By inferring historical typical floods based on similarity knowledge and incorporating the "rainfall-peak flow" or "rainfall-runoff" relationship before and after the change, a combined "peak-flow" correction approach is applied to ensure consistency. Real-time rolling extrapolation is then performed to estimate future flood processes, forming a comprehensive "multi-feature indicator extraction-historical torrential rain-induced flood similarity determination-real-time flood correction and extrapolation" technique.The application results at the Mengyin Station on the Yi River demonstrate the effectiveness of the proposed methodology. For any given torrential rain-induced flood event, the most similar historical flood event can be accurately identified through multiple feature indicators, ensuring the theoretical correctness of the technique. By considering the most identified similar flood event and applying suitable corrections to ensure consistency, the extrapolation and prediction of future flood processes significantly improve the accuracy of real-time flood forecasting compared to the direct application of similar flood processes.In summary, the suggested methodology, grounded in torrential rain-induced flood knowledge, introduces an effective avenue for real-time flood forecasting and prediction. By extracting multiple feature indicators, evaluating their similarity, and incorporating correction and extrapolation steps, it enables accurate identification of similar historical flood events and enhances the precision of real-time flood forecasting. This study contributes to the progression of flood management and establishes the groundwork for further research aimed at enhancing flood forecasting accuracy and propelling the modernization of the water industry.
Flood forecasting and prediction are integral components of non-structural flood management measures. Methods for flood forecasting and prediction can generally be classified into two categories: process-driven approaches (hydrological models) and data-driven approaches. Traditionally, the focus has been on process-driven approaches, but with the accumulation of hydrological data and advancements in big data analytics, data-driven approaches have gained increasing attention. In particular, the application of artificial intelligence technology in the water industry has led to the emergence of hydrological data mining-based forecasting and prediction methods as a research hotspot. Conducting hydrological knowledge mining and prediction based on the principle of similarity has become an important research direction, offering a new technical means to uncover hidden patterns within rainfall, floods, and watershed surface information. This approach also promotes the automation and intelligence of water resources data processing, assisting in improving the accuracy of flood forecasting and prediction, thereby facilitating the modernization and precision of the water industry.In theory, the longer the series of hydrological data, the more torrential rain-induced flood knowledge can be extracted. However, hydrological data series in a changing environment often exhibit inconsistencies, which affect the accuracy of flood forecasting and prediction based on torrential rain-induced flood knowledge. Currently, research on historical similar torrential rain-induced flood knowledge considering inconsistencies in guiding real-time flood forecasting is relatively limited. In this context, a methodology based on the knowledge of torrential rain-induced floods for real-time flood forecasting and prediction is proposed. The proposed method focuses on historical records of typical torrential rain-induced floods and extracts rainfall feature indicators, such as the position of the rainstorm center, antecedent precipitation, total average rainfall, and rainfall processes. Multiple feature indicators are simultaneously assessed for their similarity using criteria such as Euclidean distance. By inferring historical typical floods based on similarity knowledge and incorporating the "rainfall-peak flow" or "rainfall-runoff" relationship before and after the change, a combined "peak-flow" correction approach is applied to ensure consistency. Real-time rolling extrapolation is then performed to estimate future flood processes, forming a comprehensive "multi-feature indicator extraction-historical torrential rain-induced flood similarity determination-real-time flood correction and extrapolation" technique.The application results at the Mengyin Station on the Yi River demonstrate the effectiveness of the proposed methodology. For any given torrential rain-induced flood event, the most similar historical flood event can be accurately identified through multiple feature indicators, ensuring the theoretical correctness of the technique. By considering the most identified similar flood event and applying suitable corrections to ensure consistency, the extrapolation and prediction of future flood processes significantly improve the accuracy of real-time flood forecasting compared to the direct application of similar flood processes.In summary, the suggested methodology, grounded in torrential rain-induced flood knowledge, introduces an effective avenue for real-time flood forecasting and prediction. By extracting multiple feature indicators, evaluating their similarity, and incorporating correction and extrapolation steps, it enables accurate identification of similar historical flood events and enhances the precision of real-time flood forecasting. This study contributes to the progression of flood management and establishes the groundwork for further research aimed at enhancing flood forecasting accuracy and propelling the modernization of the water industry.
2023(5):895-906.
Abstract:
In the context of global climate change, greenhouse gas emissions from water projects are received increasing attention. The impoundment of water projects submerges soil and vegetation, causing the degradation of the inner organic matter to produce greenhouse gases (CO2,CH4,N2O) and discharge them into the atmosphere. The drawdown area which is repeatedly flooded and exposed affected by the regulation of water projects is also a "hot spot" for producing greenhouse gases, while the organic carbon buried in the sediment of water bodies can store atmospheric CO2 thus forming carbon sinks in the short or long term. The assessment of greenhouse gas flux of water projects is a research hotspot, and the existing monitored data can be used for research.The middle and lower reaches of the Hanjiang River are important ecological and economic zones, and the development of society has damaged the health of the rivers in this area, for example more than ten algal bloom outbreaks have occurred so far, which is not conducive to the high-quality development of the basin. A rational operation of water projects is beneficial for alleviating algal bloom outbreaks and reducing greenhouse gas emissions. In order to effectively improve the ecological environment and ensure high-quality development of the watershed, multi-objective optimization operation research is always carried out to explore the optimal operation mode of water projects. However, most of the existing researches focused on ecological indicators such as ecological water demand, ecological flow change degree, fish habitat, and algal bloom prevention and control, lacking the consideration of greenhouse gas emissions. In this case a multi-objective optimization model that comprehensively considered power generation, algal bloom prevention and control, and greenhouse gas emission control was established to explore the optimal operation mode of water projects.To solve the multi-objective problems, more and more researchers are using evolutionary optimization algorithms, among which the non-dominated sorting genetic algorithm (NSGA-II) with elite strategy is the most representative, which can reduce the computational complexity of non-dominated sorting methods, has advantages such as fast running speed and good convergence of solution sets, and has been widely used in the field of multi-objective optimization of reservoir operation. Therefore, the NSGA-II algorithm was used to solve the proposed model.The results show that the objective of greenhouse gas emission control was in a competitive relationship with both the objective of power generation and algal bloom prevention and control. Compared with the conventional operation scheme, the optimal operation schemes can achieve improvement in some indicators. Among the three optimal operation schemes, the compromised scheme can achieve improvement of all the indicators, indicating the effectiveness of the proposed model. The analysis of the operation process during typical events reveals a close relationship between greenhouse gas emissions and water level fluctuations.Using the established model, the net greenhouse gas emissions of water projects during the operation period were estimated, and an optimal operation scheme which can achieve better benefits compared to the conventional operation scheme was found. The results can provide technical support for achieving the optimal operation of water projects, reducing greenhouse gas emissions, and repairing the ecological environment of rivers.
In the context of global climate change, greenhouse gas emissions from water projects are received increasing attention. The impoundment of water projects submerges soil and vegetation, causing the degradation of the inner organic matter to produce greenhouse gases (CO2,CH4,N2O) and discharge them into the atmosphere. The drawdown area which is repeatedly flooded and exposed affected by the regulation of water projects is also a "hot spot" for producing greenhouse gases, while the organic carbon buried in the sediment of water bodies can store atmospheric CO2 thus forming carbon sinks in the short or long term. The assessment of greenhouse gas flux of water projects is a research hotspot, and the existing monitored data can be used for research.The middle and lower reaches of the Hanjiang River are important ecological and economic zones, and the development of society has damaged the health of the rivers in this area, for example more than ten algal bloom outbreaks have occurred so far, which is not conducive to the high-quality development of the basin. A rational operation of water projects is beneficial for alleviating algal bloom outbreaks and reducing greenhouse gas emissions. In order to effectively improve the ecological environment and ensure high-quality development of the watershed, multi-objective optimization operation research is always carried out to explore the optimal operation mode of water projects. However, most of the existing researches focused on ecological indicators such as ecological water demand, ecological flow change degree, fish habitat, and algal bloom prevention and control, lacking the consideration of greenhouse gas emissions. In this case a multi-objective optimization model that comprehensively considered power generation, algal bloom prevention and control, and greenhouse gas emission control was established to explore the optimal operation mode of water projects.To solve the multi-objective problems, more and more researchers are using evolutionary optimization algorithms, among which the non-dominated sorting genetic algorithm (NSGA-II) with elite strategy is the most representative, which can reduce the computational complexity of non-dominated sorting methods, has advantages such as fast running speed and good convergence of solution sets, and has been widely used in the field of multi-objective optimization of reservoir operation. Therefore, the NSGA-II algorithm was used to solve the proposed model.The results show that the objective of greenhouse gas emission control was in a competitive relationship with both the objective of power generation and algal bloom prevention and control. Compared with the conventional operation scheme, the optimal operation schemes can achieve improvement in some indicators. Among the three optimal operation schemes, the compromised scheme can achieve improvement of all the indicators, indicating the effectiveness of the proposed model. The analysis of the operation process during typical events reveals a close relationship between greenhouse gas emissions and water level fluctuations.Using the established model, the net greenhouse gas emissions of water projects during the operation period were estimated, and an optimal operation scheme which can achieve better benefits compared to the conventional operation scheme was found. The results can provide technical support for achieving the optimal operation of water projects, reducing greenhouse gas emissions, and repairing the ecological environment of rivers.
2023(5):907-916.
Abstract:
As an integral part of the terrestrial hydrosphere, lakes play an indispensable role in regional water cycle, water balance and water resources regulation. Due to the different climatic conditions and human activities, the causes of lake shrinkage in different time and space are significantly different. The Hunshandake Sandy Land is located in the eastern part of Inner Mongolia. Due to its unique geographical pattern and climatic characteristics, the predecessors have carried out a lot of research on this area. However, most of the previous studies focused on climate change and ecological stability, and only a small amount of research focused on lake area and water volume. And the studies are mainly concentrated before 2015, and there is a lack of research on the recent Hunshandake in the current new state. In particular, there is a lack of research on the changes of water balance factors based on the water balance model and the quantitative analysis of human activities and climate change on lake evolution. Therefore, it is of great significance to reveal the mechanism of shrinkage and degradation of lakes in Hunshandake Sandy Land of Inner Mongolia Plateau for the protection and restoration of lakes in Hunshandake Sandy Land.Based on Landsat TM / ETM +, the lake area of Junma Lake from 1991 to 2021 was extracted. Combined with DEM data and field elevation point test, the water depth-area-volume curve of Junma Lake was established to calculate the lake water volume. Based on the meteorological data, the water balance model of Junma Lake from 1991 to 2021 was established. The variation characteristics of water balance factors such as precipitation, evaporation and runoff are quantitatively analyzed, the interaction between income items and expenditure items and their impact on lake water volume changes is analyzed, the impact of climate change and human activities on lake water volume changes at different stages is analyzed, and the main control factors of lake water volume changes at different stages are determined. The research results can provide basis and support for regional lake evolution and ecological protection. The results show that the lake water volume decreases from 1450×104m3 in 1991 to 380×104m3 in 2021, with an average annual change rate of ?34×104m3/a. The regional precipitation, evaporation and groundwater recharge all show a decreasing trend, with an average annual change rate of ?10×104m3/a,?7×104m3/a and ?5×104m3/a, respectively. Before 2006, the lake recharge and discharge showed a weak negative equilibrium; after 2006, due to the significant reduction of groundwater recharge, the negative balance of lake water increased and the shrinkage rate accelerated.The results show that: before 2006, climate warming and drying was the main factor leading to lake shrinkage; after 2006, the large-scale exploitation of groundwater resources affected the lake recharge, and human activities became the main controlling factor of lake shrinkage. Rational development and utilization of groundwater resources and improvement of water resources utilization efficiency can alleviate the shrinkage and degradation of lake wetlands in Hunshandake Sandy Land to a certain extent.
As an integral part of the terrestrial hydrosphere, lakes play an indispensable role in regional water cycle, water balance and water resources regulation. Due to the different climatic conditions and human activities, the causes of lake shrinkage in different time and space are significantly different. The Hunshandake Sandy Land is located in the eastern part of Inner Mongolia. Due to its unique geographical pattern and climatic characteristics, the predecessors have carried out a lot of research on this area. However, most of the previous studies focused on climate change and ecological stability, and only a small amount of research focused on lake area and water volume. And the studies are mainly concentrated before 2015, and there is a lack of research on the recent Hunshandake in the current new state. In particular, there is a lack of research on the changes of water balance factors based on the water balance model and the quantitative analysis of human activities and climate change on lake evolution. Therefore, it is of great significance to reveal the mechanism of shrinkage and degradation of lakes in Hunshandake Sandy Land of Inner Mongolia Plateau for the protection and restoration of lakes in Hunshandake Sandy Land.Based on Landsat TM / ETM +, the lake area of Junma Lake from 1991 to 2021 was extracted. Combined with DEM data and field elevation point test, the water depth-area-volume curve of Junma Lake was established to calculate the lake water volume. Based on the meteorological data, the water balance model of Junma Lake from 1991 to 2021 was established. The variation characteristics of water balance factors such as precipitation, evaporation and runoff are quantitatively analyzed, the interaction between income items and expenditure items and their impact on lake water volume changes is analyzed, the impact of climate change and human activities on lake water volume changes at different stages is analyzed, and the main control factors of lake water volume changes at different stages are determined. The research results can provide basis and support for regional lake evolution and ecological protection. The results show that the lake water volume decreases from 1450×104m3 in 1991 to 380×104m3 in 2021, with an average annual change rate of ?34×104m3/a. The regional precipitation, evaporation and groundwater recharge all show a decreasing trend, with an average annual change rate of ?10×104m3/a,?7×104m3/a and ?5×104m3/a, respectively. Before 2006, the lake recharge and discharge showed a weak negative equilibrium; after 2006, due to the significant reduction of groundwater recharge, the negative balance of lake water increased and the shrinkage rate accelerated.The results show that: before 2006, climate warming and drying was the main factor leading to lake shrinkage; after 2006, the large-scale exploitation of groundwater resources affected the lake recharge, and human activities became the main controlling factor of lake shrinkage. Rational development and utilization of groundwater resources and improvement of water resources utilization efficiency can alleviate the shrinkage and degradation of lake wetlands in Hunshandake Sandy Land to a certain extent.
2023(5):917-929.
Abstract:
The construction of a regional water network is a crucial measure to address complex water problems such as the uneven spatial and temporal distribution of water resources, while to achieve the goal of ecological protection and high-quality development. The water network, mainly consisting of water transfer and storage projects, has changed the pattern of water resources and the eco-hydrological processes of rivers, and has adverse impacts on the ecological environment. The Datong River basin is abundant in water resources and has great potential for hydropower. The three major water transfer projects (from Datong River to Qinwangchuan basin, from Datong River to Jinchang City, and from Datong River to Huangshui River basin) in this region have made great contributions to the economic and social development of the Xining-Lanzhou City cluster. Given that the Datong River basin includes environmentally sensitive areas such as the upper reaches of the Yellow River Reserve and the Qilian Mountain National Park, ensuring ecological safety is important. Unfortunately, some early projects failed to adequately consider environmental protection requirements at the planning stage, resulting in significant changes in river hydrology, including reduced river flows, deteriorating water quality, and declining biodiversity.On the basis of comprehensive understanding of the eco-hydrological conditions, the characteristics of water transfer and hydropower projects, and the current situation of water resources utilization in the Datong River basin, three key control sections (Qingshizui, Tiantang, and Xiangtang) were determined. Nine widely used hydrologically-based methods were employed to calculate 12 ecological flow processes at the three sections, which were considered in the water resource allocation of the Datong River basin. Furthermore, the Water-Energy-Ecosystem (WEE) Nexus model, which was developed based on multi-objective and nonlinear programming, was used to optimize and compare the operations of different water diversion and storage projects as well as the corresponding ecological flow guarantee rate under 12 different ecological flow processes, with the past 60-year hydrological series as the model input. The following conclusions can be drawn. (1)The ecological flows were increased from upstream to downstream along the Datong River (Qingshizui
The construction of a regional water network is a crucial measure to address complex water problems such as the uneven spatial and temporal distribution of water resources, while to achieve the goal of ecological protection and high-quality development. The water network, mainly consisting of water transfer and storage projects, has changed the pattern of water resources and the eco-hydrological processes of rivers, and has adverse impacts on the ecological environment. The Datong River basin is abundant in water resources and has great potential for hydropower. The three major water transfer projects (from Datong River to Qinwangchuan basin, from Datong River to Jinchang City, and from Datong River to Huangshui River basin) in this region have made great contributions to the economic and social development of the Xining-Lanzhou City cluster. Given that the Datong River basin includes environmentally sensitive areas such as the upper reaches of the Yellow River Reserve and the Qilian Mountain National Park, ensuring ecological safety is important. Unfortunately, some early projects failed to adequately consider environmental protection requirements at the planning stage, resulting in significant changes in river hydrology, including reduced river flows, deteriorating water quality, and declining biodiversity.On the basis of comprehensive understanding of the eco-hydrological conditions, the characteristics of water transfer and hydropower projects, and the current situation of water resources utilization in the Datong River basin, three key control sections (Qingshizui, Tiantang, and Xiangtang) were determined. Nine widely used hydrologically-based methods were employed to calculate 12 ecological flow processes at the three sections, which were considered in the water resource allocation of the Datong River basin. Furthermore, the Water-Energy-Ecosystem (WEE) Nexus model, which was developed based on multi-objective and nonlinear programming, was used to optimize and compare the operations of different water diversion and storage projects as well as the corresponding ecological flow guarantee rate under 12 different ecological flow processes, with the past 60-year hydrological series as the model input. The following conclusions can be drawn. (1)The ecological flows were increased from upstream to downstream along the Datong River (Qingshizui
2023(5):930-939.
Abstract:
To investigate the effect of low impact development (LID) facilities on alleviating urban flood disaster and reducing pollution load, four kinds of LID facilities were selected, including green roof, rainwater garden, permeable pavement and rainwater tank. By constructing the SWMM model, the catchment surface was divided into different partitions according to the actual terrain and pipe network direction. The influence of LID facility combination on runoff control and rainwater pollution load under the seven layout schemes was analyzed, the results showed that the LID facility combination could effectively reduce the runoff and rainwater pollution load for the seven layout schemes, and the LID facility combination has a better control effect on the runoff in the upstream and midstream areas. Under the same design rainfall return period, the reduction effect of each layout scheme was as follows: the whole area > upstream and midstream areas > midstream and downstream areas > upstream and downstream areas > downstream area > midstream area > upstream area. The runoff reduction rate in the downstream area was 5.19% - 6.82% higher than the upstream area, the upstream and midstream areas were 1.87%- 3.62% higher than the upstream and downstream areas, and 16.48%-18.97% higher than the downstream area. When the whole area was deployed, it was 29.60%-31.17% higher than the downstream area and 12.20% -13.12% higher than the upstream and midstream areas.Therefore, before the planning and construction of sponge city, it was suggested that: the LID facilities should be set up on demand in the whole area; in the transformation of old residential areas, the LID facilities could be emphatically considered in the upstream and midstream areas.
To investigate the effect of low impact development (LID) facilities on alleviating urban flood disaster and reducing pollution load, four kinds of LID facilities were selected, including green roof, rainwater garden, permeable pavement and rainwater tank. By constructing the SWMM model, the catchment surface was divided into different partitions according to the actual terrain and pipe network direction. The influence of LID facility combination on runoff control and rainwater pollution load under the seven layout schemes was analyzed, the results showed that the LID facility combination could effectively reduce the runoff and rainwater pollution load for the seven layout schemes, and the LID facility combination has a better control effect on the runoff in the upstream and midstream areas. Under the same design rainfall return period, the reduction effect of each layout scheme was as follows: the whole area > upstream and midstream areas > midstream and downstream areas > upstream and downstream areas > downstream area > midstream area > upstream area. The runoff reduction rate in the downstream area was 5.19% - 6.82% higher than the upstream area, the upstream and midstream areas were 1.87%- 3.62% higher than the upstream and downstream areas, and 16.48%-18.97% higher than the downstream area. When the whole area was deployed, it was 29.60%-31.17% higher than the downstream area and 12.20% -13.12% higher than the upstream and midstream areas.Therefore, before the planning and construction of sponge city, it was suggested that: the LID facilities should be set up on demand in the whole area; in the transformation of old residential areas, the LID facilities could be emphatically considered in the upstream and midstream areas.
2023(5):940-950.
Abstract:
The prediction of reservoir water level is of great significance in the daily operation and management of reservoir, the reinforcement of dam, the mitigation of flood disaster, and the protection of people's life and property safety. However, with the change of global temperature, the frequency of extreme weather increases and the uncertainty of abnormal rainfall increases, which lead to the lagging of reservoir level prediction methods relying on traditional engineering hydrology. Due to the high practicability of deep learning algorithms used in various fields, there are a few examples of domestic and foreign scholars using artificial intelligence to predict water levels. In order to make up for the shortcomings of single artificial intelligence model, some scholars also used the neural network model coupling method to study water level prediction, and a small number of scholars input a single variable to predict water level. The above research shows that it is feasible to use the coupled model for water level prediction, and the advantages of multiple models complement each other, and the prediction accuracy is improved to different degrees compared with the previous single model. Considering various practical factors, the monitoring data of water level of Siling Reservoir was taken as an example and the coupling prediction model of water level of reservoir was put forward based on Embedding GRU on the condition that there was only a single characteristic rainfall, in order to provide a reference for realizing the high-precision prediction of water level with single characteristics. According to the rainfall scale of the data set and the largest rainfall in the history of Zhejiang Province, the training parameter rainfall scale sets of the Embedding stage is defined as {500,550,600,650,700,750} with the accuracy of mm×10?1. In order to study the optimal parameter setting, the range of feature dimension setting was extended to {2,3,4,5,6} on the premise of adopting the control variates. The ERMS indicator was selected for this experiment. To further validate the predictive performance and generalization ability of the Embedding GRU model, an experiment was conducted based on the total daily rainfall to predict the next day's reservoir water level. The comparison algorithm is still LSTM, GRU, and BiGRU, with a total of 1826 sets of data with a data volume of 5 years.Compared with other existing artificial intelligence models of reservoir water level, the prediction accuracy is higher and the scope of reservoir is wider. In the comparative experiment of predicting the next hour's water level, the prediction ability of the four models was excellent, and they could fit the real water level data relatively accurately, which shows that the method of predicting the reservoir water level by deep learning algorithm is effective and feasible. By comparing of prediction accuracy of four models, the experiment proved that GRU algorithm is better than LSTM in prediction effect, and the embedding method can further effectively reduce the prediction error and improve the prediction accuracy of the model.It is the Embedding method that enlarges the features between rainfall and climate, coupled with lightweight deep learning algorithm GRU to predict reservoir water level. Conclusions are as follows:(1)The prediction accuracy of the Embedding GRU model is obviously better than that of LSTM, GRU, BiGRU and other single deep learning models.(2)Embedding parameters in the Embedding GRU model shall be determined by comparative test according to the actual data set.(3)The Embedding-GRU model has excellent performance in predicting different period of multiple times within 7 days, and has good prediction effect and generalization ability, which fully proves the effectiveness of the model.
The prediction of reservoir water level is of great significance in the daily operation and management of reservoir, the reinforcement of dam, the mitigation of flood disaster, and the protection of people's life and property safety. However, with the change of global temperature, the frequency of extreme weather increases and the uncertainty of abnormal rainfall increases, which lead to the lagging of reservoir level prediction methods relying on traditional engineering hydrology. Due to the high practicability of deep learning algorithms used in various fields, there are a few examples of domestic and foreign scholars using artificial intelligence to predict water levels. In order to make up for the shortcomings of single artificial intelligence model, some scholars also used the neural network model coupling method to study water level prediction, and a small number of scholars input a single variable to predict water level. The above research shows that it is feasible to use the coupled model for water level prediction, and the advantages of multiple models complement each other, and the prediction accuracy is improved to different degrees compared with the previous single model. Considering various practical factors, the monitoring data of water level of Siling Reservoir was taken as an example and the coupling prediction model of water level of reservoir was put forward based on Embedding GRU on the condition that there was only a single characteristic rainfall, in order to provide a reference for realizing the high-precision prediction of water level with single characteristics. According to the rainfall scale of the data set and the largest rainfall in the history of Zhejiang Province, the training parameter rainfall scale sets of the Embedding stage is defined as {500,550,600,650,700,750} with the accuracy of mm×10?1. In order to study the optimal parameter setting, the range of feature dimension setting was extended to {2,3,4,5,6} on the premise of adopting the control variates. The ERMS indicator was selected for this experiment. To further validate the predictive performance and generalization ability of the Embedding GRU model, an experiment was conducted based on the total daily rainfall to predict the next day's reservoir water level. The comparison algorithm is still LSTM, GRU, and BiGRU, with a total of 1826 sets of data with a data volume of 5 years.Compared with other existing artificial intelligence models of reservoir water level, the prediction accuracy is higher and the scope of reservoir is wider. In the comparative experiment of predicting the next hour's water level, the prediction ability of the four models was excellent, and they could fit the real water level data relatively accurately, which shows that the method of predicting the reservoir water level by deep learning algorithm is effective and feasible. By comparing of prediction accuracy of four models, the experiment proved that GRU algorithm is better than LSTM in prediction effect, and the embedding method can further effectively reduce the prediction error and improve the prediction accuracy of the model.It is the Embedding method that enlarges the features between rainfall and climate, coupled with lightweight deep learning algorithm GRU to predict reservoir water level. Conclusions are as follows:(1)The prediction accuracy of the Embedding GRU model is obviously better than that of LSTM, GRU, BiGRU and other single deep learning models.(2)Embedding parameters in the Embedding GRU model shall be determined by comparative test according to the actual data set.(3)The Embedding-GRU model has excellent performance in predicting different period of multiple times within 7 days, and has good prediction effect and generalization ability, which fully proves the effectiveness of the model.
2023(5):951-961.
Abstract:
Landscape pattern and its changes are of great importance to ecological processes and security in basin or region. Liangzi Lake is a typical well protected grassy shallow lake in China. It plays important roles of flood storage, water supply, gene pool, freshwater products supply and so on. However, due to continuous reclamations for farmlands and urbanization, problems related to water area shrinkage, ecological functional degeneration and landscape fragmentation are raising continuously. Exploring the dynamic changes of water landscape and its driving factors from the perspective of landscape pattern in whole basin would obtain in-deep understanding of landscape characteristics and provide scientific references of Liangzi Lake protection from basin-wide perspective.The methods of spatial analysis, landscape metrics analysis and biostatistical analysis are applied in this paper. Taking water landscape as the research object, transition matrix analysis is used to describe transitions between water area and other types of land use during study phase. Aggregation feature and outlier distribution of water area are studied through spatial autocorrelation analysis. Landscape metrics analysis is used to express the features of area, shape, aggregation and connectivity quantitively, while redundancy analysis is employed to seek for the driving forces of dynamics changes.From 2000 to 2020, farmland area remained unchanged basically, while water area showed 21% decrease because of water coverage being reclaimed for use as farmlands. Urban area increased by more than 4 times by means of farmlands transferred into. Water area clustered spatially with a weakening trend. The distribution of High value aggregation and Low value aggregation in water area got more fragmented, and the area of Not Significant type increased by 40% in last decade. PLAND and LPI of water area had trend of increasing followed by trend of decreasing. PD dropped gradually with an obvious decline of LSI. There were significant differences between upper and lower basin - PLAND and LPI of water area in upper area were about 16% and 14% respectively, while PLAND and LPI in lower area decreased by more than 40% and 60% respectively. Shape of water area in lower area was more complicated than in upper area, and LSI of upper and lower area declined by 32% and 51% respectively. Aggregation and connectivity in upper area were better than those in lower area. Variation partitioning of redundancy analysis shows the 54.7% changes of water landscape are a result of natural and artificial factors, of these influences, 24.2% of the changes coming from precipitation and temperature, while 51.6% coming from contribution of human activities, the overlapping part is 21.0%.From 2000 to 2020, surface area of water in Liangzi Lake has decreased by 21% because of agricultural reclamation directly, which then being reclaimed for urbanized purposes, leading to 4-time area increases of artificial surfaces. Farmland area remains unchanged, water area decreased attributed to urbanized purposes indirectly. There is a steady water area aggregation in whole basin, while the relevance of water area in local region are becoming decreased or disappeared. Micro-water body are disappearing with the tendency of decreasing of complexity and irregularity. Water area distribution tends to be fragmented, however significant differences present between upper and lower basin areas. There are not much changes of spatial distribution of water landscape in upper basin area, but in lower basin area, water area reduced by nearly half. Shoreline tends to be normalized and unified with an obvious obstruction and cut of water body. 54.7% of the changes of water landscape are the result of precipitation, temperature, population, GDP and area ratio of farmland and artificial surface. Human activities are the main factors, whose explanatory power are twice of natural factors. Population and farmland area rate make more contributions to the water landscape area, meanwhile GDP and urbanization process have more effects on shape complexity and connectivity.
Landscape pattern and its changes are of great importance to ecological processes and security in basin or region. Liangzi Lake is a typical well protected grassy shallow lake in China. It plays important roles of flood storage, water supply, gene pool, freshwater products supply and so on. However, due to continuous reclamations for farmlands and urbanization, problems related to water area shrinkage, ecological functional degeneration and landscape fragmentation are raising continuously. Exploring the dynamic changes of water landscape and its driving factors from the perspective of landscape pattern in whole basin would obtain in-deep understanding of landscape characteristics and provide scientific references of Liangzi Lake protection from basin-wide perspective.The methods of spatial analysis, landscape metrics analysis and biostatistical analysis are applied in this paper. Taking water landscape as the research object, transition matrix analysis is used to describe transitions between water area and other types of land use during study phase. Aggregation feature and outlier distribution of water area are studied through spatial autocorrelation analysis. Landscape metrics analysis is used to express the features of area, shape, aggregation and connectivity quantitively, while redundancy analysis is employed to seek for the driving forces of dynamics changes.From 2000 to 2020, farmland area remained unchanged basically, while water area showed 21% decrease because of water coverage being reclaimed for use as farmlands. Urban area increased by more than 4 times by means of farmlands transferred into. Water area clustered spatially with a weakening trend. The distribution of High value aggregation and Low value aggregation in water area got more fragmented, and the area of Not Significant type increased by 40% in last decade. PLAND and LPI of water area had trend of increasing followed by trend of decreasing. PD dropped gradually with an obvious decline of LSI. There were significant differences between upper and lower basin - PLAND and LPI of water area in upper area were about 16% and 14% respectively, while PLAND and LPI in lower area decreased by more than 40% and 60% respectively. Shape of water area in lower area was more complicated than in upper area, and LSI of upper and lower area declined by 32% and 51% respectively. Aggregation and connectivity in upper area were better than those in lower area. Variation partitioning of redundancy analysis shows the 54.7% changes of water landscape are a result of natural and artificial factors, of these influences, 24.2% of the changes coming from precipitation and temperature, while 51.6% coming from contribution of human activities, the overlapping part is 21.0%.From 2000 to 2020, surface area of water in Liangzi Lake has decreased by 21% because of agricultural reclamation directly, which then being reclaimed for urbanized purposes, leading to 4-time area increases of artificial surfaces. Farmland area remains unchanged, water area decreased attributed to urbanized purposes indirectly. There is a steady water area aggregation in whole basin, while the relevance of water area in local region are becoming decreased or disappeared. Micro-water body are disappearing with the tendency of decreasing of complexity and irregularity. Water area distribution tends to be fragmented, however significant differences present between upper and lower basin areas. There are not much changes of spatial distribution of water landscape in upper basin area, but in lower basin area, water area reduced by nearly half. Shoreline tends to be normalized and unified with an obvious obstruction and cut of water body. 54.7% of the changes of water landscape are the result of precipitation, temperature, population, GDP and area ratio of farmland and artificial surface. Human activities are the main factors, whose explanatory power are twice of natural factors. Population and farmland area rate make more contributions to the water landscape area, meanwhile GDP and urbanization process have more effects on shape complexity and connectivity.
2023(5):962-971.
Abstract:
Since 2000, large-scale comprehensive control of soil and water loss has been carried out in the mountainous areas of Hebei Province. Through measures such as enclosure protection, afforestation and grass planting, and return of farmland to forest, the ecological environment in the mountainous areas has been significantly improved, especially the vegetation coverage in the mountainous areas has been significantly increased. However, the current research has not systematically analyzed the vegetation evolution law and causes in the mountainous areas of Hebei Province. It was difficult to scientifically evaluate the comprehensive control of soil and water loss in mountainous areas of Hebei Province. When analyzing the causes of vegetation evolution, the traditional multiple linear regression method usually adopts the climate variables and vegetation variables corresponding to each month, and fails to consider the "time-lag effect" of climate factors, which may lead to underestimating the contribution of climate factors. The evolution of NDVI in mountainous areas of Hebei Province was systematically studied from the aspects of vegetation types, vegetation phenology and time delay effect of climate factors. On this basis, a multiple linear regression model was established considering the time delay effect of climate, which is expected to answer the cause of NDVI evolution more accurately. With precipitation P, temperature T and potential evapotranspiration PET as independent variables and vegetation NDVI as dependent variables, a multiple linear regression model was constructed to improve the traditional residual analysis method, and the effects of climate change and human activities on vegetation NDVI changes were stripped away. The results showed that NDVI in mountainous areas of Hebei showed a continuous growth trend from 2001 to 2022, with an average growth rate of 0.0037/a. The growth rates of woodland, shrub and grassland were 0.0035/a, 0.0040/a and 0.0038/a, respectively. Using the Mann-Kendall trend test method to analyze the significance of NDVI change, it was found that 78% of the regions showed a very significant increase trend, 11% showed a significant increase trend, and only less than 2% showed a significant decrease or an extremely significant decrease trend, indicating that the vegetation recovery effect of the whole Hebei mountain region after 2001 was remarkable. Due to the influence of climate change, the growth period of vegetation in mountainous areas of Hebei Province became longer, and the start time of the growing season was advanced by 9 days on average, while the end time of the growing season was advanced by only 1 day. SOS in Bashang Plateau, Yanshan District and Taihang Mountain area advanced by 6 d, 11 d and 8 d, and EOS advanced by 2 d, 1 d and 1 d, respectively, meaning that the whole growing season increased by 4 d, 10 d and 7 d, respectively. The influence of precipitation on vegetation NDVI mainly occurs in the same month, while the influence of air temperature and potential evapotranspiration on vegetation NDVI has a one-month lag. After considering the time-lag effect of climate, the contribution of climate change and human activities to the evolution of NDVI in mountainous areas of Hebei is 39% and 61%, respectively. After considering the delay effect of climate factors, the coefficient of determination R2 of multiple linear regression increases from 0.80 to 0.87, the root mean square error decreases from 0.086 to 0.071, and the average absolute error decreases from 0.108 to 0.090. The performance of the improved regression model is better than that of the original model.Since 2000, the main contribution of NDVI growth in mountainous areas of Hebei Province has been artificial vegetation restoration, but at the same time, the lengthening of growing season caused by climate change is also an important reason. Studying and identifying the impact of climate change and human activities has important guiding significance for further rational and efficient soil and water conservation in mountainous areas.
Since 2000, large-scale comprehensive control of soil and water loss has been carried out in the mountainous areas of Hebei Province. Through measures such as enclosure protection, afforestation and grass planting, and return of farmland to forest, the ecological environment in the mountainous areas has been significantly improved, especially the vegetation coverage in the mountainous areas has been significantly increased. However, the current research has not systematically analyzed the vegetation evolution law and causes in the mountainous areas of Hebei Province. It was difficult to scientifically evaluate the comprehensive control of soil and water loss in mountainous areas of Hebei Province. When analyzing the causes of vegetation evolution, the traditional multiple linear regression method usually adopts the climate variables and vegetation variables corresponding to each month, and fails to consider the "time-lag effect" of climate factors, which may lead to underestimating the contribution of climate factors. The evolution of NDVI in mountainous areas of Hebei Province was systematically studied from the aspects of vegetation types, vegetation phenology and time delay effect of climate factors. On this basis, a multiple linear regression model was established considering the time delay effect of climate, which is expected to answer the cause of NDVI evolution more accurately. With precipitation P, temperature T and potential evapotranspiration PET as independent variables and vegetation NDVI as dependent variables, a multiple linear regression model was constructed to improve the traditional residual analysis method, and the effects of climate change and human activities on vegetation NDVI changes were stripped away. The results showed that NDVI in mountainous areas of Hebei showed a continuous growth trend from 2001 to 2022, with an average growth rate of 0.0037/a. The growth rates of woodland, shrub and grassland were 0.0035/a, 0.0040/a and 0.0038/a, respectively. Using the Mann-Kendall trend test method to analyze the significance of NDVI change, it was found that 78% of the regions showed a very significant increase trend, 11% showed a significant increase trend, and only less than 2% showed a significant decrease or an extremely significant decrease trend, indicating that the vegetation recovery effect of the whole Hebei mountain region after 2001 was remarkable. Due to the influence of climate change, the growth period of vegetation in mountainous areas of Hebei Province became longer, and the start time of the growing season was advanced by 9 days on average, while the end time of the growing season was advanced by only 1 day. SOS in Bashang Plateau, Yanshan District and Taihang Mountain area advanced by 6 d, 11 d and 8 d, and EOS advanced by 2 d, 1 d and 1 d, respectively, meaning that the whole growing season increased by 4 d, 10 d and 7 d, respectively. The influence of precipitation on vegetation NDVI mainly occurs in the same month, while the influence of air temperature and potential evapotranspiration on vegetation NDVI has a one-month lag. After considering the time-lag effect of climate, the contribution of climate change and human activities to the evolution of NDVI in mountainous areas of Hebei is 39% and 61%, respectively. After considering the delay effect of climate factors, the coefficient of determination R2 of multiple linear regression increases from 0.80 to 0.87, the root mean square error decreases from 0.086 to 0.071, and the average absolute error decreases from 0.108 to 0.090. The performance of the improved regression model is better than that of the original model.Since 2000, the main contribution of NDVI growth in mountainous areas of Hebei Province has been artificial vegetation restoration, but at the same time, the lengthening of growing season caused by climate change is also an important reason. Studying and identifying the impact of climate change and human activities has important guiding significance for further rational and efficient soil and water conservation in mountainous areas.
2023(5):972-984.
Abstract:
Beidagang Reservoir has the function of water supply in the utilization of water resources. The reservoir can provide local residents with drinking water and irrigation water. There is a problem of salting in the water quality in the Beidagang Reservoir. The salting law and mechanism of Beidagang Reservoir were mainly studied, and the microbial community structure was less studied. Salinization of water quality may lead to significant changes in microbial community composition and diversity. The reservoir mainly focuses on the exploration of the diversity of microbial communities. There is a lack of comparative studies of reservoirs between different microorganisms at different water depths. The microbial communities of coastal reservoirs have been poorly studied. Microorganisms are sensitive indicators of salinity. The spatial distribution characteristics of microbial community composition under salinization of water quality in reservoirs are still unclear. It is of great significance to study the community distribution of microorganisms in salty reservoirs. It can not only understand the structural composition of microbial communities and the relationship between salinity, but also provide a theoretical basis for bioremediation of high salt water treatment. It provides basic data and scientific basis for Beidagang Reservoir to play the function of water supply and water resource utilization.In order to explore the salinization and the spatial distribution characteristics of microbial communities, Beidagang Reservoir was chosen as our research area. The water samples from the surface, middle and bottom layers of Beidagang Reservoir were collected in December 2021. The composition and diversity of microbial communities at different depths and upstream and downstream of Beidagang Reservoir were analyzed by high-throughput sequencing technology to understand the spatial distribution characteristics of the microbial community composition structure of Beidagang Reservoir. The relationship between dissolved total solids and microbial communities was explored. The influence of reservoir salty water on microbial community structure was explored. The results show that there are differences in the surface, middle and bottom layers of dissolved total solids (TDS) mass concentration in Beidagang Reservoir, and the downstream is higher than that in the upstream. The main dominant phylums of microorganisms are Proteobacteria,Bacteroidetes and Actinobacteria, and the abundance of Proteobacteria is more than 50%. The dominant genera are Clade_III undetermined genus (1.10%-72.72%) and Flavobacterium(0.32%-20.09%), the abundance of upstream Clade_III undetermined genera is higher than that of the downstream, and the abundance of surface Flavobacterium is higher than that of the middle and bottom layers. There were significant differences between the microbial community composition of the upper surface layer and the middle and bottom microbial community composition, while the downstream microbial community composition at different depths was not significant, and the composition of the middle and bottom microbial communities was similar. The Chao1 and Shannon indices showed that the surface < middle layer < the bottom layer, and the downstream was slightly higher than the upstream, and the microbial Alpha diversity index decreased with the increase of TDS mass concentration. At the class level, the abundance of Alphaproteobacteria and Verrucomicrobiae was positively correlated with TDS mass concentration. At the family level, Clade_III abundance was positively correlated with TDS mass concentration. Comamonadaceae abundance was negatively correlated with TDS mass concentration. The abundance of Clade_III and Comamonadaceae decreased at high mass concentrations of TDS (>3 000 mg/L), which may inhibit their growth.
Beidagang Reservoir has the function of water supply in the utilization of water resources. The reservoir can provide local residents with drinking water and irrigation water. There is a problem of salting in the water quality in the Beidagang Reservoir. The salting law and mechanism of Beidagang Reservoir were mainly studied, and the microbial community structure was less studied. Salinization of water quality may lead to significant changes in microbial community composition and diversity. The reservoir mainly focuses on the exploration of the diversity of microbial communities. There is a lack of comparative studies of reservoirs between different microorganisms at different water depths. The microbial communities of coastal reservoirs have been poorly studied. Microorganisms are sensitive indicators of salinity. The spatial distribution characteristics of microbial community composition under salinization of water quality in reservoirs are still unclear. It is of great significance to study the community distribution of microorganisms in salty reservoirs. It can not only understand the structural composition of microbial communities and the relationship between salinity, but also provide a theoretical basis for bioremediation of high salt water treatment. It provides basic data and scientific basis for Beidagang Reservoir to play the function of water supply and water resource utilization.In order to explore the salinization and the spatial distribution characteristics of microbial communities, Beidagang Reservoir was chosen as our research area. The water samples from the surface, middle and bottom layers of Beidagang Reservoir were collected in December 2021. The composition and diversity of microbial communities at different depths and upstream and downstream of Beidagang Reservoir were analyzed by high-throughput sequencing technology to understand the spatial distribution characteristics of the microbial community composition structure of Beidagang Reservoir. The relationship between dissolved total solids and microbial communities was explored. The influence of reservoir salty water on microbial community structure was explored. The results show that there are differences in the surface, middle and bottom layers of dissolved total solids (TDS) mass concentration in Beidagang Reservoir, and the downstream is higher than that in the upstream. The main dominant phylums of microorganisms are Proteobacteria,Bacteroidetes and Actinobacteria, and the abundance of Proteobacteria is more than 50%. The dominant genera are Clade_III undetermined genus (1.10%-72.72%) and Flavobacterium(0.32%-20.09%), the abundance of upstream Clade_III undetermined genera is higher than that of the downstream, and the abundance of surface Flavobacterium is higher than that of the middle and bottom layers. There were significant differences between the microbial community composition of the upper surface layer and the middle and bottom microbial community composition, while the downstream microbial community composition at different depths was not significant, and the composition of the middle and bottom microbial communities was similar. The Chao1 and Shannon indices showed that the surface < middle layer < the bottom layer, and the downstream was slightly higher than the upstream, and the microbial Alpha diversity index decreased with the increase of TDS mass concentration. At the class level, the abundance of Alphaproteobacteria and Verrucomicrobiae was positively correlated with TDS mass concentration. At the family level, Clade_III abundance was positively correlated with TDS mass concentration. Comamonadaceae abundance was negatively correlated with TDS mass concentration. The abundance of Clade_III and Comamonadaceae decreased at high mass concentrations of TDS (>3 000 mg/L), which may inhibit their growth.
2023(5):985-995.
Abstract:
The change of regional land use affects carbon emission and carbon sequestration processes, which in turn causes changes in the carbon cycle and carbon storage in terrestrial ecosystems. Based on the China land cover dataset, the carbon storage and sequestration module of the integrated valuation of ecosystem services and trade-offs model was used to estimate the carbon storage and changes in terrestrial ecosystems from 1990 to 2020 in the Haihe River basin. The patch-generating land use simulation model was combined to predict future land use and carbon storage. The integrated valuation of ecosystem services and trade-offs model could quantify regional carbon storage based on regional carbon density. The carbon storage and sequestration module mainly depended on land cover types and a basic carbon pool model. The basic carbon pool model divided carbon storage into four types: aboveground biomass carbon, belowground biomass carbon, soil carbon, and dead organic matter carbon. The patch-generating land use simulation model is a cellular automata model based on raster data that could simulate land use changes at the patch scale. It integrated the land expansion analysis strategy and a cellular automata model based on multiple random patch seeds, which could be used to explore the driving factors of land expansion and predict the patch-level evolution of land use landscapes. Additionally, geodetector was utilized to quantitatively explain the driving mechanisms of carbon storage in the Haihe River basin. Geodetector is a method for detecting spatial variations of geographic features and revealing their driving factors. This method allows for direct correlation analysis between the dependent variable and the independent variables without considering collinearity among factors.The results showed that:(1)the carbon storage decreased by a total of 4.98% from 1990 to 2020, with the year 2003 as the turning point. Carbon storage exhibited a fluctuating declining trend, followed by a decrease in the magnitude of fluctuations, fluctuating around 2.05 billion tons.(2)The spatial distribution of carbon density in the basin exhibited significant heterogeneity. High carbon density values were mainly concentrated in the eastern and northern forested areas of the basin, while low values were primarily distributed in cities and the Bohai Bay region.(3)In 2030, apart from the scenario of rapid urban development, other scenarios show varying degrees of carbon stock increase. The scenario with the highest increase is the ecological conservation scenario, which has a carbon stock of 0.77 million tons higher than the scenario of rapid urban development. This indicates that ecological improvement is beneficial for carbon sequestration in regional terrestrial ecosystems. In the scenario of rapid urban development, the expansion of impervious surfaces encroached upon cropland, leading to a significant reduction in carbon storage in the eastern plain area of the Haihe River basin.(4)Natural factors had a higher explanatory power than socio-economic factors, and the interaction between population density, DEM, and other climatic factors has the strongest explanatory power for changes in carbon stock. The results will provide certain theoretical support for land regulation and future low-carbon development in the Haihe River basin and also serve as a reference for better implementation of the carbon peaking and carbon neutrality goals.
The change of regional land use affects carbon emission and carbon sequestration processes, which in turn causes changes in the carbon cycle and carbon storage in terrestrial ecosystems. Based on the China land cover dataset, the carbon storage and sequestration module of the integrated valuation of ecosystem services and trade-offs model was used to estimate the carbon storage and changes in terrestrial ecosystems from 1990 to 2020 in the Haihe River basin. The patch-generating land use simulation model was combined to predict future land use and carbon storage. The integrated valuation of ecosystem services and trade-offs model could quantify regional carbon storage based on regional carbon density. The carbon storage and sequestration module mainly depended on land cover types and a basic carbon pool model. The basic carbon pool model divided carbon storage into four types: aboveground biomass carbon, belowground biomass carbon, soil carbon, and dead organic matter carbon. The patch-generating land use simulation model is a cellular automata model based on raster data that could simulate land use changes at the patch scale. It integrated the land expansion analysis strategy and a cellular automata model based on multiple random patch seeds, which could be used to explore the driving factors of land expansion and predict the patch-level evolution of land use landscapes. Additionally, geodetector was utilized to quantitatively explain the driving mechanisms of carbon storage in the Haihe River basin. Geodetector is a method for detecting spatial variations of geographic features and revealing their driving factors. This method allows for direct correlation analysis between the dependent variable and the independent variables without considering collinearity among factors.The results showed that:(1)the carbon storage decreased by a total of 4.98% from 1990 to 2020, with the year 2003 as the turning point. Carbon storage exhibited a fluctuating declining trend, followed by a decrease in the magnitude of fluctuations, fluctuating around 2.05 billion tons.(2)The spatial distribution of carbon density in the basin exhibited significant heterogeneity. High carbon density values were mainly concentrated in the eastern and northern forested areas of the basin, while low values were primarily distributed in cities and the Bohai Bay region.(3)In 2030, apart from the scenario of rapid urban development, other scenarios show varying degrees of carbon stock increase. The scenario with the highest increase is the ecological conservation scenario, which has a carbon stock of 0.77 million tons higher than the scenario of rapid urban development. This indicates that ecological improvement is beneficial for carbon sequestration in regional terrestrial ecosystems. In the scenario of rapid urban development, the expansion of impervious surfaces encroached upon cropland, leading to a significant reduction in carbon storage in the eastern plain area of the Haihe River basin.(4)Natural factors had a higher explanatory power than socio-economic factors, and the interaction between population density, DEM, and other climatic factors has the strongest explanatory power for changes in carbon stock. The results will provide certain theoretical support for land regulation and future low-carbon development in the Haihe River basin and also serve as a reference for better implementation of the carbon peaking and carbon neutrality goals.
2023(5):996-1005.
Abstract:
The inter-basin water diversion projects transfer the water resources from basins with abundant water to that with scarce water, which aims to address the problem of uneven spatial and temporal distribution of water resources. The Yangtze-to-Huaihe River Water Diversion Project is a major strategic water resource allocation project across Yangtze River and Huaihe River basins. The middle and lower reaches of the Yangtze River and the Huaihe River basin are located in the eastern monsoon region of China. The drought disasters occur frequently in these regions with the influence of monsoon climate. Due to the temporal fluctuation and spatial variability of regional water supply, the water source and the water destination regions of the project are prone to the risk of concurrent droughts. The simultaneous occurrence of drought events across the water source and the water destination regions or other conditions that are not conducive to water transfer would have a significant impact on the normal scheduling operation and efficiency of the project. In addition, with the effects of climate change and human activities, the global water cycle will be further intensified. Compound extreme events such as drought, high temperature and heat waves on a global scale will be increasing, which have a serious impact on regional water resources management, ecosystem and sustainable socio-economic development. Therefore, it is of great significance to explore the risk of concurrent drought in the water source and the water destination regions of the Yangtze-to-Huaihe River Water Diversion Project under climate change to provide scientific support for the operation of project scheduling and sustainable utilization of water resources.The risk of concurrent drought probability between the water source and destination regions of Yangtze-to-Huaihe River Water Diversion Project was investigated. The meteorological observation and the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model dataset of precipitation were integrated for both historical and future assessment. Precipitation from nine CMIP6 dataset with three scenarios was first bias-corrected using a quantile mapping approach. The Standardized Precipitation Evapotranspiration Index (SPEI) with a time scale of 6 and 12 months was calculated by monthly precipitation and temperature to describe drought condition. The appropriate marginal distribution was selected to fit the SPEI sequence. The Copula theory was then applied to construct the joint distribution of drought index in the water source and destination regions. The drought evolution patterns and drought encounter risks from 1960 to 2020 were evaluated. And further analysis of the future changes in drought encounter risks under different scenarios based on CMIP6 data was carried out.The results showed that the frequency of drought occurrence in the water source and destination regions from 1960 to 2020 was 27.32% and 29.78% respectively. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions, especially in the high emission scenario where the frequency of severe drought occurrence increases by more than 10%. The probability of simultaneous drought occurrence in the non-flood season of the water source and destination regions was 5.49% higher compared to the flood season. The frequency of drought encounters during the flood season and throughout the year was expected to significantly increase, while the frequency of non-flood season drought encounters was slightly reduced. In the medium to high emission scenarios (SSP2-4.5 and SSP5-8.5), the frequency of long-term drought encounters was relatively higher.The SPEI could well capture the regional drought conditions in both the water source and destination regions. The joint distribution of SPEI by the Clayton Copula function was capable to characterize the concurrent drought between the water source and destination regions. The probability of concurrent drought in the two regions during the non-flood season was relatively higher than that in the flood season. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions. And the frequency of drought encounters was also projected to increase in the future. Therefore, it is urgent to formulate adaptive strategies to ensure the normal operation management of water transfer projects and the sustainable utilization of water resources.
The inter-basin water diversion projects transfer the water resources from basins with abundant water to that with scarce water, which aims to address the problem of uneven spatial and temporal distribution of water resources. The Yangtze-to-Huaihe River Water Diversion Project is a major strategic water resource allocation project across Yangtze River and Huaihe River basins. The middle and lower reaches of the Yangtze River and the Huaihe River basin are located in the eastern monsoon region of China. The drought disasters occur frequently in these regions with the influence of monsoon climate. Due to the temporal fluctuation and spatial variability of regional water supply, the water source and the water destination regions of the project are prone to the risk of concurrent droughts. The simultaneous occurrence of drought events across the water source and the water destination regions or other conditions that are not conducive to water transfer would have a significant impact on the normal scheduling operation and efficiency of the project. In addition, with the effects of climate change and human activities, the global water cycle will be further intensified. Compound extreme events such as drought, high temperature and heat waves on a global scale will be increasing, which have a serious impact on regional water resources management, ecosystem and sustainable socio-economic development. Therefore, it is of great significance to explore the risk of concurrent drought in the water source and the water destination regions of the Yangtze-to-Huaihe River Water Diversion Project under climate change to provide scientific support for the operation of project scheduling and sustainable utilization of water resources.The risk of concurrent drought probability between the water source and destination regions of Yangtze-to-Huaihe River Water Diversion Project was investigated. The meteorological observation and the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model dataset of precipitation were integrated for both historical and future assessment. Precipitation from nine CMIP6 dataset with three scenarios was first bias-corrected using a quantile mapping approach. The Standardized Precipitation Evapotranspiration Index (SPEI) with a time scale of 6 and 12 months was calculated by monthly precipitation and temperature to describe drought condition. The appropriate marginal distribution was selected to fit the SPEI sequence. The Copula theory was then applied to construct the joint distribution of drought index in the water source and destination regions. The drought evolution patterns and drought encounter risks from 1960 to 2020 were evaluated. And further analysis of the future changes in drought encounter risks under different scenarios based on CMIP6 data was carried out.The results showed that the frequency of drought occurrence in the water source and destination regions from 1960 to 2020 was 27.32% and 29.78% respectively. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions, especially in the high emission scenario where the frequency of severe drought occurrence increases by more than 10%. The probability of simultaneous drought occurrence in the non-flood season of the water source and destination regions was 5.49% higher compared to the flood season. The frequency of drought encounters during the flood season and throughout the year was expected to significantly increase, while the frequency of non-flood season drought encounters was slightly reduced. In the medium to high emission scenarios (SSP2-4.5 and SSP5-8.5), the frequency of long-term drought encounters was relatively higher.The SPEI could well capture the regional drought conditions in both the water source and destination regions. The joint distribution of SPEI by the Clayton Copula function was capable to characterize the concurrent drought between the water source and destination regions. The probability of concurrent drought in the two regions during the non-flood season was relatively higher than that in the flood season. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions. And the frequency of drought encounters was also projected to increase in the future. Therefore, it is urgent to formulate adaptive strategies to ensure the normal operation management of water transfer projects and the sustainable utilization of water resources.
2023(5):1006-1012.
Abstract:
Total length of the Yangtze-to-Huaihe Water Transfer Project is 723 km, more than 100 km of the river section is distributed with weak and medium expansive soil, and the maximum excavation depth of the canal is 46 m. The stability of the expansive soil section is one of the key technical problems of the project. In the preliminary design stage, the treatment measures of over digging, replacing and filling cement-modified soil were proposed for the expanded land section, but some ecological and environmental problems were generated, such as the cement modified soil is easy to be alkali, and makes it difficult for plants to grow. Moreover, slope overcutting would produce a large amount of waste soil which is adverse to the ecological environment. Whether simplified treatment measures can be applied to some weak expansion channels with slope heights less than 10 m is a question that needs to be addressed.Under the principle of ecological priority and technological innovation, the researchers carried out systematic research work using field experiments, indoor unit tests, and numerical analysis. The ecological restoration scheme using surface cultivated soil and grass was put forward through field sampling tests and numerical analysis for the low river embankment in the weak expansive soil around Chaohu Lake. An ecological substrate was developed to solve the problems such as soil alkali plate and plant growth difficulty in the medium expansive cement-modified soil replacement layer. The field pilot test proved that the ecological substrate is a new kind of ecological slope planting material. An ecologically friendly expansive soil slope protection structure is proposed using unsaturated soil theory based on the characteristics of a large difference in permeability coefficient between sand and clay. This structure can better solve the dual protection requirements of expansive soil slopes to prevent rainfall infiltration and water evaporation. At the same time, it can also use the compression effect of the sand layer to restrain the expansion and deformation of soil layer.The field pilot test and application results show that the ecological substrate developed can adapt to the planting needs of cement-modified soil so that the slope can achieve a good greening effect. The double-layer slope protection structure can better solve the dual protection requirements of the expansive soil slope to prevent rainfall infiltration and water evaporation. The expansion and deformation of the soil layer can also be controlled by the compression effect of the sand layer. The research results provide technical support for the engineering design and late operation management of the project, effectively solving the technical problems related to the expansion land section of the project, and provide a basis for the design and optimization of related river slope. Together, breakthroughs have been made in the engineering application of unsaturated soil theory and the ecological treatment of expansive soil slopes.
Total length of the Yangtze-to-Huaihe Water Transfer Project is 723 km, more than 100 km of the river section is distributed with weak and medium expansive soil, and the maximum excavation depth of the canal is 46 m. The stability of the expansive soil section is one of the key technical problems of the project. In the preliminary design stage, the treatment measures of over digging, replacing and filling cement-modified soil were proposed for the expanded land section, but some ecological and environmental problems were generated, such as the cement modified soil is easy to be alkali, and makes it difficult for plants to grow. Moreover, slope overcutting would produce a large amount of waste soil which is adverse to the ecological environment. Whether simplified treatment measures can be applied to some weak expansion channels with slope heights less than 10 m is a question that needs to be addressed.Under the principle of ecological priority and technological innovation, the researchers carried out systematic research work using field experiments, indoor unit tests, and numerical analysis. The ecological restoration scheme using surface cultivated soil and grass was put forward through field sampling tests and numerical analysis for the low river embankment in the weak expansive soil around Chaohu Lake. An ecological substrate was developed to solve the problems such as soil alkali plate and plant growth difficulty in the medium expansive cement-modified soil replacement layer. The field pilot test proved that the ecological substrate is a new kind of ecological slope planting material. An ecologically friendly expansive soil slope protection structure is proposed using unsaturated soil theory based on the characteristics of a large difference in permeability coefficient between sand and clay. This structure can better solve the dual protection requirements of expansive soil slopes to prevent rainfall infiltration and water evaporation. At the same time, it can also use the compression effect of the sand layer to restrain the expansion and deformation of soil layer.The field pilot test and application results show that the ecological substrate developed can adapt to the planting needs of cement-modified soil so that the slope can achieve a good greening effect. The double-layer slope protection structure can better solve the dual protection requirements of the expansive soil slope to prevent rainfall infiltration and water evaporation. The expansion and deformation of the soil layer can also be controlled by the compression effect of the sand layer. The research results provide technical support for the engineering design and late operation management of the project, effectively solving the technical problems related to the expansion land section of the project, and provide a basis for the design and optimization of related river slope. Together, breakthroughs have been made in the engineering application of unsaturated soil theory and the ecological treatment of expansive soil slopes.
2023(5):1013-1020.
Abstract:
The main canal of the Middle Route of the South-to-North Water Transfers Project is separated by gates into series channel pools. In case of emergencies and other situations, the synchronous operation technology of gates is often adopted to rapidly reduce the water flow in a large range. Rapid closing of the gates at both ends of the canal pool will cause continuous oscillation of the water level and flow in the canal pool, and affect the efficiency and effect of the gate feedback control. If the gate is not properly controlled, the water is easy to overflow. It is of great significance to deeply understand the hydraulic response characteristics of synchronous closing of gate and the influence law of related factors for guiding the control of gate scientifically and ensuring the operation safety of the project. Based on Saint-Venant equation group, a one-dimensional unsteady gradually varied flow model for the main canal of the Middle Route of the South-to-North Water Transfers Project was constructed. Taking the canal pool between Diaohe aqueduct gate and Tuanhe aqueduct gate as the research object, the hydraulic response of synchronous closing of the gate was simulated, and the hydraulic response characteristics such as peak water level, time spent to reach the peak water level, frequency and amplitude of hydraulic oscillation before the gate were analyzed. By changing the control mode of gate and the operating conditions of canal, the influences of gate closing duration, gate closing amplitude, operating water level, water delivery flow and canal roughness on hydraulic response characteristics were analyzed and summarized.Simulation results showed that the rise process of hydraulic oscillation was fast, but the fall process was slow. The amplitude of the wave was approximately logarithmic function attenuation with time, and the time interval of the adjacent wave peaks and valleys gradually tended to be consistent. The peak height of backwater and amplitude of hydraulic oscillation in front of the gate can be reduced approximately linearly by slowly closing and decreasing closing amplitude. The decreasing amplitude was a zonal distribution function with gate closing time. With the increase of operating water level, the peak value of rising water in front of the gate decreased linearly. The time taken to reach the peak and the amplitude of hydraulic oscillation had no obvious change, but the oscillation frequency increased slightly. With the increase of the water flow, the peak value of backwater in front of the gate increased linearly. The time taken to reach the peak had no obvious change in the frequency of hydraulic oscillation, but the amplitude decreased obviously and the attenuation became faster. With the increase of roughness, the peak of backwater before the gate increased linearly, the time taken to reach the peak, and the frequency and amplitude of hydraulic oscillation had no obvious change. The hydraulic response is determined by the difference of the movement characteristics between the increasing wave and the decreasing wave, as well as the difference while traveling downstream and upstream, and the energy dissipation along the travel. The amplitude of hydraulic oscillation is sensitive to the closing speed and closing amplitude of the gate. The value deviation of roughness can be ignored when estimating peak backwater before the gate.
The main canal of the Middle Route of the South-to-North Water Transfers Project is separated by gates into series channel pools. In case of emergencies and other situations, the synchronous operation technology of gates is often adopted to rapidly reduce the water flow in a large range. Rapid closing of the gates at both ends of the canal pool will cause continuous oscillation of the water level and flow in the canal pool, and affect the efficiency and effect of the gate feedback control. If the gate is not properly controlled, the water is easy to overflow. It is of great significance to deeply understand the hydraulic response characteristics of synchronous closing of gate and the influence law of related factors for guiding the control of gate scientifically and ensuring the operation safety of the project. Based on Saint-Venant equation group, a one-dimensional unsteady gradually varied flow model for the main canal of the Middle Route of the South-to-North Water Transfers Project was constructed. Taking the canal pool between Diaohe aqueduct gate and Tuanhe aqueduct gate as the research object, the hydraulic response of synchronous closing of the gate was simulated, and the hydraulic response characteristics such as peak water level, time spent to reach the peak water level, frequency and amplitude of hydraulic oscillation before the gate were analyzed. By changing the control mode of gate and the operating conditions of canal, the influences of gate closing duration, gate closing amplitude, operating water level, water delivery flow and canal roughness on hydraulic response characteristics were analyzed and summarized.Simulation results showed that the rise process of hydraulic oscillation was fast, but the fall process was slow. The amplitude of the wave was approximately logarithmic function attenuation with time, and the time interval of the adjacent wave peaks and valleys gradually tended to be consistent. The peak height of backwater and amplitude of hydraulic oscillation in front of the gate can be reduced approximately linearly by slowly closing and decreasing closing amplitude. The decreasing amplitude was a zonal distribution function with gate closing time. With the increase of operating water level, the peak value of rising water in front of the gate decreased linearly. The time taken to reach the peak and the amplitude of hydraulic oscillation had no obvious change, but the oscillation frequency increased slightly. With the increase of the water flow, the peak value of backwater in front of the gate increased linearly. The time taken to reach the peak had no obvious change in the frequency of hydraulic oscillation, but the amplitude decreased obviously and the attenuation became faster. With the increase of roughness, the peak of backwater before the gate increased linearly, the time taken to reach the peak, and the frequency and amplitude of hydraulic oscillation had no obvious change. The hydraulic response is determined by the difference of the movement characteristics between the increasing wave and the decreasing wave, as well as the difference while traveling downstream and upstream, and the energy dissipation along the travel. The amplitude of hydraulic oscillation is sensitive to the closing speed and closing amplitude of the gate. The value deviation of roughness can be ignored when estimating peak backwater before the gate.
2023(5):1021-1029.
Abstract:
Water keeping weir is a new type of overflow weir, characterized by small pressure in two sections of the transmission line, and simple hydraulic control. In order to enhance the water conveyance capacity of water keeping weir in large water diversion projects. First of all, based on the actual operation of the project, the RNGk-ε turbulent flow model is used to close the control equations and establish a three-dimensional isometric numerical simulation model of the water keeping weir, and the simulated head and flow velocity of the pressure measuring tube are in good agreement with the measured data, and on the premise of ensuring the accuracy of the flow pattern in the simulated water keeping weir, the influence of the water keeping weir body parameters on the over-flow capacity of the box culvert - water keeping weir water conveyance system is investigated. It revealed the mechanism of the generation and development of annular vortex zones in the weir section, and determined that the dispersion of high velocity water flow zone caused by the height of the water keeping weir and the presence of annular vortex zones are the main bottlenecks affecting the improvement of flow capacity. Thus, the proposed solution of reducing the height of the water keeping weir concentrate the high velocity water flow zone and reduce the scope of the annular vortex zone to reduce the energy dissipation in the weir section, so as to achieve the purpose of improving the overflow capacity of the water conveyance system. Numerical calculations were carried out for 11 options of reducing the weir height of water keeping weirs, and the flow velocity vector distribution and the extent of the annular vortex zone in the weir section as well as the variation of turbulent kinetic energy dissipation and overflow flow were analyzed. The results show that the overflow of the water conveyance system can be enhanced by the weir reduction scheme, and by compared between different weir height schemes, the optimal weir height interval that increases its overflow capacity is finally found to be [1.0 P1≥P≥0.7P1] (where P is water keeping weir height). When the weir height is within this range, the compression effect on the high velocity flow area is weakened by lowering P, resulting in smaller flow vector elevation angle in front of the weir and the annular vortex zone behind the weir, and significantly lower energy dissipation, lowering 0.1P1 flow rate increases by 2.1% on average, where the weir height P is lowered to 0.7P1 when the flow rate is increased up to 6.3%, which can basically meet the water demand requirements of the project; Outside this interval, although lowering P reduces the annular vortex zone after the weir and the flow velocity vector angle becomes smaller, the energy dissipation is reduced, but the rapid expansion of the annular vortex zone before the weir consumes part of the water flow energy, resulting in the flow lift decay, at this time, lowering 0.1P1 flow rate only increases by 0.5% on average. In consideration of the project modification cost and the effect of overflow capacity enhancement, the structure of the water keeping weir is modified in the optimal weir height interval proposed to provide reference for the overflow capacity enhancement of the water transmission system.
Water keeping weir is a new type of overflow weir, characterized by small pressure in two sections of the transmission line, and simple hydraulic control. In order to enhance the water conveyance capacity of water keeping weir in large water diversion projects. First of all, based on the actual operation of the project, the RNGk-ε turbulent flow model is used to close the control equations and establish a three-dimensional isometric numerical simulation model of the water keeping weir, and the simulated head and flow velocity of the pressure measuring tube are in good agreement with the measured data, and on the premise of ensuring the accuracy of the flow pattern in the simulated water keeping weir, the influence of the water keeping weir body parameters on the over-flow capacity of the box culvert - water keeping weir water conveyance system is investigated. It revealed the mechanism of the generation and development of annular vortex zones in the weir section, and determined that the dispersion of high velocity water flow zone caused by the height of the water keeping weir and the presence of annular vortex zones are the main bottlenecks affecting the improvement of flow capacity. Thus, the proposed solution of reducing the height of the water keeping weir concentrate the high velocity water flow zone and reduce the scope of the annular vortex zone to reduce the energy dissipation in the weir section, so as to achieve the purpose of improving the overflow capacity of the water conveyance system. Numerical calculations were carried out for 11 options of reducing the weir height of water keeping weirs, and the flow velocity vector distribution and the extent of the annular vortex zone in the weir section as well as the variation of turbulent kinetic energy dissipation and overflow flow were analyzed. The results show that the overflow of the water conveyance system can be enhanced by the weir reduction scheme, and by compared between different weir height schemes, the optimal weir height interval that increases its overflow capacity is finally found to be [1.0 P1≥P≥0.7P1] (where P is water keeping weir height). When the weir height is within this range, the compression effect on the high velocity flow area is weakened by lowering P, resulting in smaller flow vector elevation angle in front of the weir and the annular vortex zone behind the weir, and significantly lower energy dissipation, lowering 0.1P1 flow rate increases by 2.1% on average, where the weir height P is lowered to 0.7P1 when the flow rate is increased up to 6.3%, which can basically meet the water demand requirements of the project; Outside this interval, although lowering P reduces the annular vortex zone after the weir and the flow velocity vector angle becomes smaller, the energy dissipation is reduced, but the rapid expansion of the annular vortex zone before the weir consumes part of the water flow energy, resulting in the flow lift decay, at this time, lowering 0.1P1 flow rate only increases by 0.5% on average. In consideration of the project modification cost and the effect of overflow capacity enhancement, the structure of the water keeping weir is modified in the optimal weir height interval proposed to provide reference for the overflow capacity enhancement of the water transmission system.
2023(5):1030-1039.
Abstract:
The western region of China is rich in hydropower resources, but strong earthquakes occur frequently. Hydraulic structures may withstand strong earthquakes during their life cycle. The damage caused by earthquakes will affect the normal operation of water conservancy projects, which seriously threatens people's lives and social stability. The seismic vulnerability analysis provides the seismic basis for seismic design of hydraulic structure and earthquake prevention and disaster reduction, which is very important to ensure the expected performance of concrete gravity dam and safe operation under earthquake.The seismic vulnerability assessment of dams often requires the use of nonlinear numerical simulation methods and a huge amount of calculation work. Considering the efficiency and accuracy of seismic vulnerability assessment of dams, a way based on incremental dynamic analysis and multilayer perceptron for seismic vulnerability assessment of concrete dams is proposed. Taking a concrete gravity dam in northwest China as an example, a three-dimensional finite element model of dam body-reservoir water-foundation is established and multiple seismic response calculations are carried out. The selected ground motion records are processed by equal step amplitude modulation, and the amplitude input is carried out by three-way seismic. The peak ground acceleration is selected as the index of ground motion intensity, and the displacement of dam top along river is selected as the index of dam damage. The multilayer perceptron model was trained and tested by extracting the vibration characteristic parameters as input and the displacement of dam top along river as output. The ground motion is extended to obtain the vibration characteristic parameters. The MLP model is used to quickly predict the displacement of the dam top along the river, and the finite element results are extended. The vulnerability analysis of the concrete dam is carried out, and the vulnerability curve is drawn.The results are as follows:(1)The seismic vulnerability of concrete gravity dam is analyzed based on incremental dynamic analysis method. Incremental dynamic analysis's curve clusters of river-side displacement, transverse river flow displacement and vertical displacement of the dam crest are plotted, and seismic vulnerability curves are plotted. In summary, the earthquake damage grade of the selected gravity dam under the designed ground motion is low, and about 80% probability belongs to the basically intact state.(2)The multi-layer perceptron model is introduced into the incremental dynamic analysis method, and the seismic vulnerability analysis method of concrete gravity dam based on incremental dynamic analysis-multi-layer perceptron is proposed. After the training of the multi-layer perceptron model, the accuracy of the damage prediction index is higher. The coefficient of determination is 0.960 2, the mean square error is 0.005 6, and the mean absolute error is 0.056 1. Based on this method, more analytical data can be constructed to expand the finite element dynamic calculation results. It saves the calculation work up to 75% and reduces the nonlinear dynamic calculation time. The seismic vulnerability of dams can be predicted quickly and accurately as close as possible to the reality, and the vulnerability curve can be drawn to improve the efficiency of seismic vulnerability analysis of dams.
The western region of China is rich in hydropower resources, but strong earthquakes occur frequently. Hydraulic structures may withstand strong earthquakes during their life cycle. The damage caused by earthquakes will affect the normal operation of water conservancy projects, which seriously threatens people's lives and social stability. The seismic vulnerability analysis provides the seismic basis for seismic design of hydraulic structure and earthquake prevention and disaster reduction, which is very important to ensure the expected performance of concrete gravity dam and safe operation under earthquake.The seismic vulnerability assessment of dams often requires the use of nonlinear numerical simulation methods and a huge amount of calculation work. Considering the efficiency and accuracy of seismic vulnerability assessment of dams, a way based on incremental dynamic analysis and multilayer perceptron for seismic vulnerability assessment of concrete dams is proposed. Taking a concrete gravity dam in northwest China as an example, a three-dimensional finite element model of dam body-reservoir water-foundation is established and multiple seismic response calculations are carried out. The selected ground motion records are processed by equal step amplitude modulation, and the amplitude input is carried out by three-way seismic. The peak ground acceleration is selected as the index of ground motion intensity, and the displacement of dam top along river is selected as the index of dam damage. The multilayer perceptron model was trained and tested by extracting the vibration characteristic parameters as input and the displacement of dam top along river as output. The ground motion is extended to obtain the vibration characteristic parameters. The MLP model is used to quickly predict the displacement of the dam top along the river, and the finite element results are extended. The vulnerability analysis of the concrete dam is carried out, and the vulnerability curve is drawn.The results are as follows:(1)The seismic vulnerability of concrete gravity dam is analyzed based on incremental dynamic analysis method. Incremental dynamic analysis's curve clusters of river-side displacement, transverse river flow displacement and vertical displacement of the dam crest are plotted, and seismic vulnerability curves are plotted. In summary, the earthquake damage grade of the selected gravity dam under the designed ground motion is low, and about 80% probability belongs to the basically intact state.(2)The multi-layer perceptron model is introduced into the incremental dynamic analysis method, and the seismic vulnerability analysis method of concrete gravity dam based on incremental dynamic analysis-multi-layer perceptron is proposed. After the training of the multi-layer perceptron model, the accuracy of the damage prediction index is higher. The coefficient of determination is 0.960 2, the mean square error is 0.005 6, and the mean absolute error is 0.056 1. Based on this method, more analytical data can be constructed to expand the finite element dynamic calculation results. It saves the calculation work up to 75% and reduces the nonlinear dynamic calculation time. The seismic vulnerability of dams can be predicted quickly and accurately as close as possible to the reality, and the vulnerability curve can be drawn to improve the efficiency of seismic vulnerability analysis of dams.
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