Volume 0,Issue 2,2023 Table of Contents
2023(2):209-217.
Abstract:
With rapid population growth, industrial expansion, improved urbanization level and living standards, the water resources has been excessively utilized, which leads to a series of ecological problems such as rivers and lakes atrophy, land subsidence, and so on. It has directly threatens the high-quality development of China's economy and society and the virtuous cycle of the ecological environment. Water resources carrying capacity is not only an important condition to support regional sustainable development, but also the key to solve water resources problems. At present, the research on water resources carrying capacity has not formed a unified theoretical and technical system, and it still needs further research. At the same time, for China, water resources carrying capacity varies greatly in different regions, affected by water resources endowment conditions, industrial structure, economic and social development level and layout, and other factors. Zoning management is the foundation to strengthen the maximum rigid constraint of water resources, and is also the fundamental need to implement "spatial balance" and "four water and four determination" from the perspective of water resources. Therefore, it is of great significance to implement accurate zoning management of water resources based on the evaluation results of water resources carrying capacity.Based on the existing research, the carrying capacity of water resources in China was analyzed from three aspects of groundwater, surface water and total water consumption. The carrying capacity of surface water was evaluated. The carrying capacity of groundwater was evaluated. The carrying capacity of total water consumption was evaluated. The worst evaluation result of surface water, groundwater and total water consumption was taken as the comprehensive evaluation result of water resources carrying capacity. The zoning management countermeasures for different areas were also put forward.The results are as follows :(1) water resource overload zone and critical overload zone involve 53% of the national land area, nearly 60% of the population and GDP, and only 28% of the national water resource. (2) For surface water, there are 77 overloading units, which are mainly distributed in Haihe River, Liaohe River, middle and lower reaches of the Yellow River, middle reaches of the Huaihe River system and partial reaches of the northwest inland river. For groundwater, there are 100 overloading units, and the overexploited groundwater is mainly used for agricultural irrigation and urban development. (3) Important urban agglomerations, economic zones and energy bases are almost all distributed in areas with water resource overload or critical overload; 14 of the 17 grain production bases are in areas of water overload and critical overload. (4) Based on the evaluation results of water resources carrying capacity, the watershed regions in China were divided into three types: overloading area, critical area and non-overloading area. And the zoning management measures of "water replenishment" in the overloading area, "water control" in the critical overloading area and "water conservation" in the non-overloading area were proposed.The comprehensive evaluation results showed that among the 410 evaluation units of cities in China, there are 129 overloading units, 81 critical overloading units and 200 units not overloading. By 2035, the scope of water overloading and critical overloading zones will be further expanded under the condition that adequate water saving is considered but no new water supply is added. The reasons for overloading was the lack of water resources endowment, and the relatively heavy burden of economic and social development. In China, the distribution of water resources did match the development of economic and social, especially in population, economy, energy, food. The research results can not only reveal the spatial distribution characteristics of water resources carrying status in China, but also provide some reference value for strengthening the precise control of water resources zoning.
With rapid population growth, industrial expansion, improved urbanization level and living standards, the water resources has been excessively utilized, which leads to a series of ecological problems such as rivers and lakes atrophy, land subsidence, and so on. It has directly threatens the high-quality development of China's economy and society and the virtuous cycle of the ecological environment. Water resources carrying capacity is not only an important condition to support regional sustainable development, but also the key to solve water resources problems. At present, the research on water resources carrying capacity has not formed a unified theoretical and technical system, and it still needs further research. At the same time, for China, water resources carrying capacity varies greatly in different regions, affected by water resources endowment conditions, industrial structure, economic and social development level and layout, and other factors. Zoning management is the foundation to strengthen the maximum rigid constraint of water resources, and is also the fundamental need to implement "spatial balance" and "four water and four determination" from the perspective of water resources. Therefore, it is of great significance to implement accurate zoning management of water resources based on the evaluation results of water resources carrying capacity.Based on the existing research, the carrying capacity of water resources in China was analyzed from three aspects of groundwater, surface water and total water consumption. The carrying capacity of surface water was evaluated. The carrying capacity of groundwater was evaluated. The carrying capacity of total water consumption was evaluated. The worst evaluation result of surface water, groundwater and total water consumption was taken as the comprehensive evaluation result of water resources carrying capacity. The zoning management countermeasures for different areas were also put forward.The results are as follows :(1) water resource overload zone and critical overload zone involve 53% of the national land area, nearly 60% of the population and GDP, and only 28% of the national water resource. (2) For surface water, there are 77 overloading units, which are mainly distributed in Haihe River, Liaohe River, middle and lower reaches of the Yellow River, middle reaches of the Huaihe River system and partial reaches of the northwest inland river. For groundwater, there are 100 overloading units, and the overexploited groundwater is mainly used for agricultural irrigation and urban development. (3) Important urban agglomerations, economic zones and energy bases are almost all distributed in areas with water resource overload or critical overload; 14 of the 17 grain production bases are in areas of water overload and critical overload. (4) Based on the evaluation results of water resources carrying capacity, the watershed regions in China were divided into three types: overloading area, critical area and non-overloading area. And the zoning management measures of "water replenishment" in the overloading area, "water control" in the critical overloading area and "water conservation" in the non-overloading area were proposed.The comprehensive evaluation results showed that among the 410 evaluation units of cities in China, there are 129 overloading units, 81 critical overloading units and 200 units not overloading. By 2035, the scope of water overloading and critical overloading zones will be further expanded under the condition that adequate water saving is considered but no new water supply is added. The reasons for overloading was the lack of water resources endowment, and the relatively heavy burden of economic and social development. In China, the distribution of water resources did match the development of economic and social, especially in population, economy, energy, food. The research results can not only reveal the spatial distribution characteristics of water resources carrying status in China, but also provide some reference value for strengthening the precise control of water resources zoning.
2023(2):218-232.
Abstract:
As an organic whole, the system of "water-economy-ecology" complements each other, and the coupled and coordinated development is the premise of realizing high quality regional development. However, as the problem of resource supply and economic development derailment gradually emerged, the phenomenon of multi-system imbalance and regional development imbalance became more serious, which restricted the high-quality development of the region.In view of the imbalance and instability of water resources, economic society and ecological environment system in the Beijing-Tianjin-Hebei region in the future, a dynamic simulation model of "water-economy-ecological" system was constructed, and five scenarios were set up, including open source and reduce expenditure, economic development and environmental protection, to predict the development trend of water resources, economic society and ecological environment system indicators in the Beijing-Tianjin-Hebei region. The coupling coordination degree model was used to simulate the development trend of coupling coordination under different scenarios in the Beijing-Tianjin-Hebei region from 2020 to 2035.The results show that under five scenarios from 2020 to 2035, the coupling coordination degree of water-economy-ecological system in Beijing, Tianjin and Hebei will all show an increasing trend, among which the coupling coordination degree of the continuation of the status quo will be the lowest, followed by the coupling coordination degree of the open source and expenditure reduction, economic development and environmental protection, and the comprehensive coordination degree will be the highest. It indicates that under the condition of maintaining the current development, the degree of coordinated development of water-economy-ecological system coupling in Beijing-Tianjin-Hebei region increases slightly but changes little. Only when water conservation and economic development are fully considered while environmental protection can regional coordinated development be promoted. Continuation of the status quo in 2035 Beijing, Tianjin and Hebei scenario coupled coordination development level all belong to the intermediate type coupling coordination, comprehensive coordination situation of Beijing and Tianjin coupling coordination development belongs to the good coupling coordination model, coupling due to economic development is relatively lagging in Hebei Province coordinated development is slow, still belong to the intermediate type coupling coordination, should pay attention to the integration of the Beijing-Tianjin-Hebei region development in the future.In conclusion, the research results can provide a reference for the sustainable economic and social development of the Beijing-Tianjin-Hebei region.
As an organic whole, the system of "water-economy-ecology" complements each other, and the coupled and coordinated development is the premise of realizing high quality regional development. However, as the problem of resource supply and economic development derailment gradually emerged, the phenomenon of multi-system imbalance and regional development imbalance became more serious, which restricted the high-quality development of the region.In view of the imbalance and instability of water resources, economic society and ecological environment system in the Beijing-Tianjin-Hebei region in the future, a dynamic simulation model of "water-economy-ecological" system was constructed, and five scenarios were set up, including open source and reduce expenditure, economic development and environmental protection, to predict the development trend of water resources, economic society and ecological environment system indicators in the Beijing-Tianjin-Hebei region. The coupling coordination degree model was used to simulate the development trend of coupling coordination under different scenarios in the Beijing-Tianjin-Hebei region from 2020 to 2035.The results show that under five scenarios from 2020 to 2035, the coupling coordination degree of water-economy-ecological system in Beijing, Tianjin and Hebei will all show an increasing trend, among which the coupling coordination degree of the continuation of the status quo will be the lowest, followed by the coupling coordination degree of the open source and expenditure reduction, economic development and environmental protection, and the comprehensive coordination degree will be the highest. It indicates that under the condition of maintaining the current development, the degree of coordinated development of water-economy-ecological system coupling in Beijing-Tianjin-Hebei region increases slightly but changes little. Only when water conservation and economic development are fully considered while environmental protection can regional coordinated development be promoted. Continuation of the status quo in 2035 Beijing, Tianjin and Hebei scenario coupled coordination development level all belong to the intermediate type coupling coordination, comprehensive coordination situation of Beijing and Tianjin coupling coordination development belongs to the good coupling coordination model, coupling due to economic development is relatively lagging in Hebei Province coordinated development is slow, still belong to the intermediate type coupling coordination, should pay attention to the integration of the Beijing-Tianjin-Hebei region development in the future.In conclusion, the research results can provide a reference for the sustainable economic and social development of the Beijing-Tianjin-Hebei region.
2023(2):233-247.
Abstract:
The SWAT model is a widely used hydrological model that offers a range of simulation capabilities. However, it is well-established that the accuracy of model simulations is heavily dependent on the proper specification of SWAT model parameters. While the official SWAT-CUP software is widely used for parameter uncertainty quantification of SWAT model, it has several limitations. For example, it relies on simple sensitivity analysis methods, lacks flexibility in terms of additional options, and its parameter optimization methods are computationally inefficient. Furthermore, as a closed-source software, SWAT-CUP can only be used on the Windows platform, which hampers the applicability of the SWAT model and may compromise simulation results. To overcome these issues, the Uncertainty Quantification Python Laboratory (UQ-PyL) platform, which offers a comprehensive toolset for parameter uncertainty analysis. In addition, a new module has been developed to couple UQ-PyL with the SWAT model, providing a user-friendly and efficient way to perform parameter uncertainty analysis using various algorithms offered by UQ-PyL.To assess the efficacy of UQ-PyL in analyzing parameter uncertainty of SWAT models, four distinct SWAT models across different watersheds in China were constructed, each subjected to varying climatic conditions. The results of parameter uncertainty analysis were comprehensively evaluated by comparing UQ-PyL with SWAT-CUP. In terms of sensitivity analysis, four different methods (Morris, MARS, DT, and Sobol') in UQ-PyL, and qualitative sensitivity analysis in SWAT-CUP were employed to analyze model parameters. The selection of sensitive parameters between UQ-PyL and SWAT-CUP was compared in terms of rationality, by the Sobol' method as a reference to test the validity of the results from the four qualitative methods of sensitivity analysis. Additionally, the SCE-UA algorithm was used to optimize the sensitive parameter groups selected by UQ-PyL and SWAT-CUP separately, and the final converged objective function values was compared, thereby indirectly validating the appropriateness of the selected sensitive parameters by both software tools. Regarding optimization effectiveness, the sensitive parameters using ASMO, SCE-UA of UQ-PyL, and SUFI-2, which is the most widely used algorithm in SWAT-CUP. The computational efficiency and accuracy of different optimization algorithms were compared by evaluating the number of runs required for the final objective function to converge, and the value of the objective function when it converged. Moreover, the applicability of UQ-PyL in watersheds with different climate zones was further validated .The findings reveal that, among the four sensitivity analysis techniques, MARS exhibits the strongest performance, followed by Morris, DT and the SWAT-CUP sensitivity analysis method. Moreover, when utilizing the SCE-UA optimization algorithm to optimize the sensitive parameters identified by UQ-PyL and SWAT-CUP, the optimization outcomes of the UQ-PyL parameter group are relatively superior to those of the SWAT-CUP parameter group across the four watersheds. In terms of parameter optimization, the ASMO optimization algorithm in UQ-PyL demonstrates a higher level of computing efficiency, while the SCE-UA optimization algorithm yields greater accuracy compared to the SUFI-2 algorithm. Additionally, when optimizing independent processes, UQ-PyL solutions offer higher efficiency and accuracy compared to SWAT-CUP solutions. Moreover, UQ-PyL outperformed SWAT-CUP in terms of overall performance across the four watersheds, indicating its robustness .In summary, compared to the single sensitivity analysis method in SWAT-CUP, UQ-PyL offers both quantitative sensitivity analysis using the Sobol' algorithm, as well as qualitative sensitivity analysis using the MARS, Morris, and DT algorithms. This enables a more comprehensive and reasonable screening of sensitive parameters. In terms of parameter optimization, UQ-PyL outperforms the SUFI-2 algorithm in SWAT-CUP by providing two optimization algorithms with better computational efficiency (ASMO) and higher accuracy (SCE-UA). In the four watersheds, UQ-PyL demonstrated superior performance to SWAT-CUP, with the best results observed in humid watersheds and slightly lower performance in drier watersheds.
The SWAT model is a widely used hydrological model that offers a range of simulation capabilities. However, it is well-established that the accuracy of model simulations is heavily dependent on the proper specification of SWAT model parameters. While the official SWAT-CUP software is widely used for parameter uncertainty quantification of SWAT model, it has several limitations. For example, it relies on simple sensitivity analysis methods, lacks flexibility in terms of additional options, and its parameter optimization methods are computationally inefficient. Furthermore, as a closed-source software, SWAT-CUP can only be used on the Windows platform, which hampers the applicability of the SWAT model and may compromise simulation results. To overcome these issues, the Uncertainty Quantification Python Laboratory (UQ-PyL) platform, which offers a comprehensive toolset for parameter uncertainty analysis. In addition, a new module has been developed to couple UQ-PyL with the SWAT model, providing a user-friendly and efficient way to perform parameter uncertainty analysis using various algorithms offered by UQ-PyL.To assess the efficacy of UQ-PyL in analyzing parameter uncertainty of SWAT models, four distinct SWAT models across different watersheds in China were constructed, each subjected to varying climatic conditions. The results of parameter uncertainty analysis were comprehensively evaluated by comparing UQ-PyL with SWAT-CUP. In terms of sensitivity analysis, four different methods (Morris, MARS, DT, and Sobol') in UQ-PyL, and qualitative sensitivity analysis in SWAT-CUP were employed to analyze model parameters. The selection of sensitive parameters between UQ-PyL and SWAT-CUP was compared in terms of rationality, by the Sobol' method as a reference to test the validity of the results from the four qualitative methods of sensitivity analysis. Additionally, the SCE-UA algorithm was used to optimize the sensitive parameter groups selected by UQ-PyL and SWAT-CUP separately, and the final converged objective function values was compared, thereby indirectly validating the appropriateness of the selected sensitive parameters by both software tools. Regarding optimization effectiveness, the sensitive parameters using ASMO, SCE-UA of UQ-PyL, and SUFI-2, which is the most widely used algorithm in SWAT-CUP. The computational efficiency and accuracy of different optimization algorithms were compared by evaluating the number of runs required for the final objective function to converge, and the value of the objective function when it converged. Moreover, the applicability of UQ-PyL in watersheds with different climate zones was further validated .The findings reveal that, among the four sensitivity analysis techniques, MARS exhibits the strongest performance, followed by Morris, DT and the SWAT-CUP sensitivity analysis method. Moreover, when utilizing the SCE-UA optimization algorithm to optimize the sensitive parameters identified by UQ-PyL and SWAT-CUP, the optimization outcomes of the UQ-PyL parameter group are relatively superior to those of the SWAT-CUP parameter group across the four watersheds. In terms of parameter optimization, the ASMO optimization algorithm in UQ-PyL demonstrates a higher level of computing efficiency, while the SCE-UA optimization algorithm yields greater accuracy compared to the SUFI-2 algorithm. Additionally, when optimizing independent processes, UQ-PyL solutions offer higher efficiency and accuracy compared to SWAT-CUP solutions. Moreover, UQ-PyL outperformed SWAT-CUP in terms of overall performance across the four watersheds, indicating its robustness .In summary, compared to the single sensitivity analysis method in SWAT-CUP, UQ-PyL offers both quantitative sensitivity analysis using the Sobol' algorithm, as well as qualitative sensitivity analysis using the MARS, Morris, and DT algorithms. This enables a more comprehensive and reasonable screening of sensitive parameters. In terms of parameter optimization, UQ-PyL outperforms the SUFI-2 algorithm in SWAT-CUP by providing two optimization algorithms with better computational efficiency (ASMO) and higher accuracy (SCE-UA). In the four watersheds, UQ-PyL demonstrated superior performance to SWAT-CUP, with the best results observed in humid watersheds and slightly lower performance in drier watersheds.
2023(2):248-257.
Abstract:
Jinsha River is the mainstream of the upper reaches of the Yangtze River, which originates from the Tanggula Mountains Galadan Snow Mountain. The river has superior hydropower development conditions, but it is also accompanied by serious soil erosion problems. In recent years, large-scale water and soil control and water conservancy project construction activities have been carried out in the Jinsha River basin (JRB), which has affected the intra-annual and inter-annual variation process of runoff to some extent. In the future, with the continuous demonstration and implementation of a series of major national strategic projects, the trend of water resources demand in JRB will rise significantly and continue to increase. Therefore, it is of great significance for the sustainable utilization of water resources to carry out the analysis and research on the characteristics and causes of runoff under the changing environment in the Jinsha River basin.Based on 60 years of measured precipitation and runoff data of JRB, the impact quantity change process of long-term human activities such as reservoir projects and production and living water intake on runoff was estimated and the water balance method wsa used to calculate and restore the natural runoff. The Mann-Kendall test, wavelet analysis, and other mathematical statistics methods were used to study the variation trend, change cycle, and possible abrupt years of precipitation and natural runoff in JRB. At the same time, the concept of normalized vegetation index was introduced to analyze the variation causes of natural runoff, and the correlative relationship between natural runoff and the combined effect of precipitation and normalized difference vegetation index was constructed. The results show that: (1) The average annual precipitation is 604.6 mm, and the average annual natural runoff is 149 billion m3in JRB. Both of them show an increasing trend, but the increasing trend of precipitation is obvious, and the increasing trend of natural runoff is not significant. The corresponding ten-year average increment of precipitation and natural runoff is 7.7 mm and 860 million m3, and the ten-year relative increase percentage is 1.28% and 0.57%, respectively. The precipitation and natural runoff in JRB generally change periodically, and the main change cycle is consistent, which is 28 years. The precipitation has an abrupt point in 1990, and the natural runoff shows that there is no abrupt point. (2) The precipitation is the main impact factor causing runoff changes in JRB, but the relative increase percentage of natural runoff is smaller than that of precipitation. The reason for the difference in increased amplitude between the two research objects is mainly due to the increase of vegetation cover in the basin. There is a negative correlation between vegetation cover and runoff change. Overall, the better the vegetation cover, the more pronounced the runoff attenuation. The average normalized difference vegetation index of JRB was 0.592, and the increasing trend was obvious, with a ten-year average annual increase of 0.045. (3) Compared with the single impact factor analysis of precipitation or normalized difference vegetation index, the established response relationship correlation between natural runoff and the combined effect of the two impact factors increases, and the correlation coefficient reaches 0.940. Considering the combined effect of precipitation and vegetation can more accurately reflect the actual situation of runoff change. The relationship between natural runoff and the combined effect of precipitation and normalized difference vegetation index is R = 0.017 7 P1.691N?0.923. The research results can provide decision-making reference and scientific guidance for hydropower development and comprehensive management in JRB.
Jinsha River is the mainstream of the upper reaches of the Yangtze River, which originates from the Tanggula Mountains Galadan Snow Mountain. The river has superior hydropower development conditions, but it is also accompanied by serious soil erosion problems. In recent years, large-scale water and soil control and water conservancy project construction activities have been carried out in the Jinsha River basin (JRB), which has affected the intra-annual and inter-annual variation process of runoff to some extent. In the future, with the continuous demonstration and implementation of a series of major national strategic projects, the trend of water resources demand in JRB will rise significantly and continue to increase. Therefore, it is of great significance for the sustainable utilization of water resources to carry out the analysis and research on the characteristics and causes of runoff under the changing environment in the Jinsha River basin.Based on 60 years of measured precipitation and runoff data of JRB, the impact quantity change process of long-term human activities such as reservoir projects and production and living water intake on runoff was estimated and the water balance method wsa used to calculate and restore the natural runoff. The Mann-Kendall test, wavelet analysis, and other mathematical statistics methods were used to study the variation trend, change cycle, and possible abrupt years of precipitation and natural runoff in JRB. At the same time, the concept of normalized vegetation index was introduced to analyze the variation causes of natural runoff, and the correlative relationship between natural runoff and the combined effect of precipitation and normalized difference vegetation index was constructed. The results show that: (1) The average annual precipitation is 604.6 mm, and the average annual natural runoff is 149 billion m3in JRB. Both of them show an increasing trend, but the increasing trend of precipitation is obvious, and the increasing trend of natural runoff is not significant. The corresponding ten-year average increment of precipitation and natural runoff is 7.7 mm and 860 million m3, and the ten-year relative increase percentage is 1.28% and 0.57%, respectively. The precipitation and natural runoff in JRB generally change periodically, and the main change cycle is consistent, which is 28 years. The precipitation has an abrupt point in 1990, and the natural runoff shows that there is no abrupt point. (2) The precipitation is the main impact factor causing runoff changes in JRB, but the relative increase percentage of natural runoff is smaller than that of precipitation. The reason for the difference in increased amplitude between the two research objects is mainly due to the increase of vegetation cover in the basin. There is a negative correlation between vegetation cover and runoff change. Overall, the better the vegetation cover, the more pronounced the runoff attenuation. The average normalized difference vegetation index of JRB was 0.592, and the increasing trend was obvious, with a ten-year average annual increase of 0.045. (3) Compared with the single impact factor analysis of precipitation or normalized difference vegetation index, the established response relationship correlation between natural runoff and the combined effect of the two impact factors increases, and the correlation coefficient reaches 0.940. Considering the combined effect of precipitation and vegetation can more accurately reflect the actual situation of runoff change. The relationship between natural runoff and the combined effect of precipitation and normalized difference vegetation index is R = 0.017 7 P1.691N?0.923. The research results can provide decision-making reference and scientific guidance for hydropower development and comprehensive management in JRB.
2023(2):267-275.
Abstract:
Water ecological carrying capacity is a comprehensive concept based on the theory of carrying capacity, considering water resources, water environment, and other factors to study the water ecosystem. It is based on the principle of sustainable development, covering water resources and the water environment, emphasizing the sustainable carrying capacity of water ecosystem to human society and economy. At present, the evaluation methods of water ecological carrying capacity mostly referred to the research of water resources carrying capacity and water environment carrying capacity, including SD, fuzzy evaluation method, TOPSIS model, and so on. The Bonferroni mean operator proposed by Bonferroni can effectively capture the correlation between input variables and can aggregate multiple input variables into one input variable. It is an aggregation operator between the maximum and the minimum. This method eliminated the mutual influence and interdependence between variables through iterative operation so that the comprehensive evaluation results can be fair. In recent years, the Bonferroni mean had been well expanded and applied in practical problems such as multi-attribute comprehensive evaluation and group decision-making. Xia et. al introduced the weight vector of the variable into Bonferroni mean and proposed the weighted Bonferroni mean, which considered the relative importance of the variable itself. Try to weaken the influence of the correlation between indicators on the evaluation results of water ecological carrying capacity and enrich the research methods of water ecological carrying capacity, the weighted Bonferroni mean operator was employed in the evaluation system of water ecological carrying capacity, and a comprehensive evaluation model of water ecological carrying capacity-WBM evaluation model was established. Taiyuan City was taken as the research object to verify the reliability of WBM, to provide an alternative method for the evaluation of water ecological carrying capacity, and provide support for promoting regional ecosystem protection.Based on the framework of 'target layer-criterion layer-index layer', the index system of water ecological carrying capacity was established. The analytic hierarchy process and the improved entropy weight method were used to determine the subjective and objective weights of the indicators, and the combined weights of the indicators were obtained by the multiplication integration method. The weighted Bonferroni mean evaluation model was established to evaluate the dynamic change process of water ecological carrying capacity, and it was compared with the widely used and recognized TOPSIS model evaluation results. The key obstacle factors in the study area were identified by the obstacle degree model, and the applicability of the weighted Bonferroni mean model is analyzed.The evaluation index system and WBM model were applied to the evaluation of the water ecological carrying capacity in Taiyuan city. The results show that the water ecological carrying capacity in Taiyuan City fluctuates up and down in the critical overload state from 2009 to 2020. The overall trend of change was not obvious and had developed in a good way in recent years. For the four subsystems: The carrying capacity of water resources subsystem decreases from safe carrying capacity to severe overload, the carrying capacity of water environment subsystem increases from overload to optimal carrying capacity, the carrying capacity of water ecology subsystem fluctuates up, and down in the critical overload state, and the carrying capacity of water security subsystem decreases to critical overload. The water resources and water ecological subsystems had large fluctuations in their bearing status. The identification of the barrier factors showed that the barrier factors constraining the area were mainly concentrated in the water resources subsystem.In comparison with TOPSIS evaluation results, it can be seen that the weighted Bonferroni mean model was reasonable and reliable for water ecological carrying capacity evaluation. The above results showed that the proposed model was reasonable and reliable, and enriched the research results of quantifying the water ecological carrying capacity. This study provided an optional method to weaken the influence of correlation between indicators on the evaluation of water ecological carrying capacity and to objectively quantify the water ecological carrying capacity, but how to quantify the influence of correlation between indicators on the evaluation results needed further study.
Water ecological carrying capacity is a comprehensive concept based on the theory of carrying capacity, considering water resources, water environment, and other factors to study the water ecosystem. It is based on the principle of sustainable development, covering water resources and the water environment, emphasizing the sustainable carrying capacity of water ecosystem to human society and economy. At present, the evaluation methods of water ecological carrying capacity mostly referred to the research of water resources carrying capacity and water environment carrying capacity, including SD, fuzzy evaluation method, TOPSIS model, and so on. The Bonferroni mean operator proposed by Bonferroni can effectively capture the correlation between input variables and can aggregate multiple input variables into one input variable. It is an aggregation operator between the maximum and the minimum. This method eliminated the mutual influence and interdependence between variables through iterative operation so that the comprehensive evaluation results can be fair. In recent years, the Bonferroni mean had been well expanded and applied in practical problems such as multi-attribute comprehensive evaluation and group decision-making. Xia et. al introduced the weight vector of the variable into Bonferroni mean and proposed the weighted Bonferroni mean, which considered the relative importance of the variable itself. Try to weaken the influence of the correlation between indicators on the evaluation results of water ecological carrying capacity and enrich the research methods of water ecological carrying capacity, the weighted Bonferroni mean operator was employed in the evaluation system of water ecological carrying capacity, and a comprehensive evaluation model of water ecological carrying capacity-WBM evaluation model was established. Taiyuan City was taken as the research object to verify the reliability of WBM, to provide an alternative method for the evaluation of water ecological carrying capacity, and provide support for promoting regional ecosystem protection.Based on the framework of 'target layer-criterion layer-index layer', the index system of water ecological carrying capacity was established. The analytic hierarchy process and the improved entropy weight method were used to determine the subjective and objective weights of the indicators, and the combined weights of the indicators were obtained by the multiplication integration method. The weighted Bonferroni mean evaluation model was established to evaluate the dynamic change process of water ecological carrying capacity, and it was compared with the widely used and recognized TOPSIS model evaluation results. The key obstacle factors in the study area were identified by the obstacle degree model, and the applicability of the weighted Bonferroni mean model is analyzed.The evaluation index system and WBM model were applied to the evaluation of the water ecological carrying capacity in Taiyuan city. The results show that the water ecological carrying capacity in Taiyuan City fluctuates up and down in the critical overload state from 2009 to 2020. The overall trend of change was not obvious and had developed in a good way in recent years. For the four subsystems: The carrying capacity of water resources subsystem decreases from safe carrying capacity to severe overload, the carrying capacity of water environment subsystem increases from overload to optimal carrying capacity, the carrying capacity of water ecology subsystem fluctuates up, and down in the critical overload state, and the carrying capacity of water security subsystem decreases to critical overload. The water resources and water ecological subsystems had large fluctuations in their bearing status. The identification of the barrier factors showed that the barrier factors constraining the area were mainly concentrated in the water resources subsystem.In comparison with TOPSIS evaluation results, it can be seen that the weighted Bonferroni mean model was reasonable and reliable for water ecological carrying capacity evaluation. The above results showed that the proposed model was reasonable and reliable, and enriched the research results of quantifying the water ecological carrying capacity. This study provided an optional method to weaken the influence of correlation between indicators on the evaluation of water ecological carrying capacity and to objectively quantify the water ecological carrying capacity, but how to quantify the influence of correlation between indicators on the evaluation results needed further study.
2023(2):276-288.
Abstract:
The Beijing-Tianjin-Hebei region is one of the core areas of industrial development in China, and the layout of its industrial and economic development does not match the carrying capacity of water resources, and the contradiction between water demand and water endowment needs to be solved urgently. In order to identify the relationship between industrial development and water shortage, the degree of coordination between water resources and industrial development layout in Beijing-Tianjin-Hebei region was analyzed with the goal of optimizing the water-appropriate development layout of industrial economy.Based on the deepening of the connotation of industrial water-appropriate development, an industrial water-appropriate development evaluation index system in terms of water endowment and utilization, industrial structure and economic benefits. Was constructed industrial water-appropriate development evaluation model was established based on entropy weight method and coupled coordination degree model to explore the spatial and temporal change characteristics of industrial water-appropriate development in Beijing-Tianjin-Hebei region and its obstacle factors.The results showed that: (1) The comprehensive evaluation indexes of the composite system and its subsystems in the Beijing-Tianjin-Hebei region showed a spatial distribution pattern with Beijing-Tianjin as the core, among which the development level of the water resources system was higher and showed a fluctuating growth trend, but the increase was smaller than that of the industrial development system. The spatial and temporal distribution of water resources and the imbalance of regional water use efficiency greatly affected the spatial and temporal distribution of the water resources system evaluation index; the development of Hebei's industrial economy was driven by the Beijing-Tianjin-Hebei synergistic development. (2) From 2008 to 2018, the Beijing-Tianjin-Hebei region gradually evolved from near-unsuitable water to primary water-suitable development (from 0.475 to 0.690), showing the distribution characteristics of “central gradually driving balanced around” with Beijing-Tianjin as the core. The Beijing-Tianjin-Hebei region has mainly experienced the three development states of near-unsuitable water, barely suitable water and primary suitable water; while the prefecture-level cities in Hebei Province have a large gap compared with Beijing and Tianjin. (3) From the analysis of the influencing factors, the type of water-appropriate development in the Beijing-Tianjin-Hebei region is mainly the type of lagging industrial development. The water-appropriate development of industry in the Beijing-Tianjin-Hebei region was limited by water resources endowment and the level of industrial development between regions. The study results can provide reference for optimizing the industrial development layout in Beijing-Tianjin-Hebei region and promoting the coordinated and sustainable development of water resources and industry.
The Beijing-Tianjin-Hebei region is one of the core areas of industrial development in China, and the layout of its industrial and economic development does not match the carrying capacity of water resources, and the contradiction between water demand and water endowment needs to be solved urgently. In order to identify the relationship between industrial development and water shortage, the degree of coordination between water resources and industrial development layout in Beijing-Tianjin-Hebei region was analyzed with the goal of optimizing the water-appropriate development layout of industrial economy.Based on the deepening of the connotation of industrial water-appropriate development, an industrial water-appropriate development evaluation index system in terms of water endowment and utilization, industrial structure and economic benefits. Was constructed industrial water-appropriate development evaluation model was established based on entropy weight method and coupled coordination degree model to explore the spatial and temporal change characteristics of industrial water-appropriate development in Beijing-Tianjin-Hebei region and its obstacle factors.The results showed that: (1) The comprehensive evaluation indexes of the composite system and its subsystems in the Beijing-Tianjin-Hebei region showed a spatial distribution pattern with Beijing-Tianjin as the core, among which the development level of the water resources system was higher and showed a fluctuating growth trend, but the increase was smaller than that of the industrial development system. The spatial and temporal distribution of water resources and the imbalance of regional water use efficiency greatly affected the spatial and temporal distribution of the water resources system evaluation index; the development of Hebei's industrial economy was driven by the Beijing-Tianjin-Hebei synergistic development. (2) From 2008 to 2018, the Beijing-Tianjin-Hebei region gradually evolved from near-unsuitable water to primary water-suitable development (from 0.475 to 0.690), showing the distribution characteristics of “central gradually driving balanced around” with Beijing-Tianjin as the core. The Beijing-Tianjin-Hebei region has mainly experienced the three development states of near-unsuitable water, barely suitable water and primary suitable water; while the prefecture-level cities in Hebei Province have a large gap compared with Beijing and Tianjin. (3) From the analysis of the influencing factors, the type of water-appropriate development in the Beijing-Tianjin-Hebei region is mainly the type of lagging industrial development. The water-appropriate development of industry in the Beijing-Tianjin-Hebei region was limited by water resources endowment and the level of industrial development between regions. The study results can provide reference for optimizing the industrial development layout in Beijing-Tianjin-Hebei region and promoting the coordinated and sustainable development of water resources and industry.
2023(2):289-300.
Abstract:
The traditional automatic calibration of hydrological model parameters are mainly focusing on single-objective optimization, but the optimization based on a single objective can not capture and utilize all the characteristic information of hydrological observations. Several studies have shown that the single- objective calibration of hydrological models can not reproduce all the characteristics of hydrological factors (such as runoff) well, so it is necessary to constrain multiple features of hydrological factors by multiple objective functions. At present, many studies apply classical multi-objective optimization algorithms to calibrating hydrological models. Compared with the single-objective optimization methods, the classical multi-objective optimization algorithms need to run the model tens of thousands of times to find the optimal solutions. Despite the rapid development of computer technology in the past decades, the use of multi-objective optimization algorithms in hydrological models (especially complex physical distributed hydrological models) still causes a large computational burden. Therefore, the study of efficient and reliable multi-objective optimization methods has important engineering application value. In 2016, Professor Duan's group proposed MO-ASMO, a multi-objective optimization method based on a surrogate model. The core of MO-ASMO is to use cheap statistical surrogate models to replace the original computationally expensive physical models in the optimization process, aiming to significantly reduce the computational burden while maintaining the optimization effect. Clark et al pointed out that it is necessary to quantify the uncertainty of statistical performance metrics in the process of parameter calibration of hydrological models. This is because when the Nash-Sutcliffe efficiency coefficient (ENS) and Kling-Gupta efficiency coefficient (EKG) are used as objective functions for parameter calibration, the optimization results may be seriously affected by a small number of data points. It leads to great uncertainty in the statistical metrics, which will affect the simulation effect after the model parameters are calibrated. The distributed hydrological model SWAT model was constructed in the Sihu basin. The MO-ASMO method was used to calibrate the parameters of SWAT model. The results were compared with the classical multi-objective optimization method NSGA-Ⅱ and the single-objective optimization method SCE-UA. At the same time, to further evaluate the reliability and robustness of the parameter optimization results, Bootstrap and Jackknife methods were used to quantify the uncertainty of the statistical metrics. The following conclusions were obtained: (1) According to the Pareto front and evaluation metrics of the multi-objective optimization, MO-ASMO and NSGA-Ⅱ were close to convergence when the number of runs are 2 300 and 10 000, respectively. The two methods can achieve similar optimization results after convergence, but MO-ASMO can greatly reduce the running time of the model in the process of multi-objective optimization. The optimization results of the single-objective optimization method were good during the calibration period, but the simulation effect degraded significantly during the validation period, indicating that there is a situation of overfitting and the optimization results are unstable. (2) The uncertainty of statistics metrics ENS and EKG of optimization results of different algorithms was quantified by Bootstrap and Jackknife methods. The uncertainty order of the optimization results of the three optimization methods is NSGA-Ⅱ (10 000) ≈ MO-ASMO(2 300) < NSGA-Ⅱ (2 300) < SCE-UA.The optimization results of MO-ASMO (2 300) and NSGA-Ⅱ (10 000) have the best robustness and less uncertainty. The results of NSGA-Ⅱ (2 300) are the second, and the optimization results of model parameters under single-objective optimization are less robust. The results of multi-objective optimization have less uncertainty than those of single-objective optimization, which indicates that it is necessary to use multiple objective functions in the process of hydrological model parameter optimization to avoid problems of compensatory parameters caused by traditional single-objective optimization, to reduce the uncertainty of parameter optimization.
The traditional automatic calibration of hydrological model parameters are mainly focusing on single-objective optimization, but the optimization based on a single objective can not capture and utilize all the characteristic information of hydrological observations. Several studies have shown that the single- objective calibration of hydrological models can not reproduce all the characteristics of hydrological factors (such as runoff) well, so it is necessary to constrain multiple features of hydrological factors by multiple objective functions. At present, many studies apply classical multi-objective optimization algorithms to calibrating hydrological models. Compared with the single-objective optimization methods, the classical multi-objective optimization algorithms need to run the model tens of thousands of times to find the optimal solutions. Despite the rapid development of computer technology in the past decades, the use of multi-objective optimization algorithms in hydrological models (especially complex physical distributed hydrological models) still causes a large computational burden. Therefore, the study of efficient and reliable multi-objective optimization methods has important engineering application value. In 2016, Professor Duan's group proposed MO-ASMO, a multi-objective optimization method based on a surrogate model. The core of MO-ASMO is to use cheap statistical surrogate models to replace the original computationally expensive physical models in the optimization process, aiming to significantly reduce the computational burden while maintaining the optimization effect. Clark et al pointed out that it is necessary to quantify the uncertainty of statistical performance metrics in the process of parameter calibration of hydrological models. This is because when the Nash-Sutcliffe efficiency coefficient (ENS) and Kling-Gupta efficiency coefficient (EKG) are used as objective functions for parameter calibration, the optimization results may be seriously affected by a small number of data points. It leads to great uncertainty in the statistical metrics, which will affect the simulation effect after the model parameters are calibrated. The distributed hydrological model SWAT model was constructed in the Sihu basin. The MO-ASMO method was used to calibrate the parameters of SWAT model. The results were compared with the classical multi-objective optimization method NSGA-Ⅱ and the single-objective optimization method SCE-UA. At the same time, to further evaluate the reliability and robustness of the parameter optimization results, Bootstrap and Jackknife methods were used to quantify the uncertainty of the statistical metrics. The following conclusions were obtained: (1) According to the Pareto front and evaluation metrics of the multi-objective optimization, MO-ASMO and NSGA-Ⅱ were close to convergence when the number of runs are 2 300 and 10 000, respectively. The two methods can achieve similar optimization results after convergence, but MO-ASMO can greatly reduce the running time of the model in the process of multi-objective optimization. The optimization results of the single-objective optimization method were good during the calibration period, but the simulation effect degraded significantly during the validation period, indicating that there is a situation of overfitting and the optimization results are unstable. (2) The uncertainty of statistics metrics ENS and EKG of optimization results of different algorithms was quantified by Bootstrap and Jackknife methods. The uncertainty order of the optimization results of the three optimization methods is NSGA-Ⅱ (10 000) ≈ MO-ASMO(2 300) < NSGA-Ⅱ (2 300) < SCE-UA.The optimization results of MO-ASMO (2 300) and NSGA-Ⅱ (10 000) have the best robustness and less uncertainty. The results of NSGA-Ⅱ (2 300) are the second, and the optimization results of model parameters under single-objective optimization are less robust. The results of multi-objective optimization have less uncertainty than those of single-objective optimization, which indicates that it is necessary to use multiple objective functions in the process of hydrological model parameter optimization to avoid problems of compensatory parameters caused by traditional single-objective optimization, to reduce the uncertainty of parameter optimization.
2023(2):301-312.
Abstract:
Completion of the Binhai Reservoir may experience serious salinization or sudden brackishness, thus affecting the normal water supply function. The research on reservoir water salinization mainly focuses on total salinity, chloride ion, or other single indicators, but the release of sediment salt is a complex process. In fact, during the hydrogeochemical process of sediments and reservoir water, various ions may change to different degrees, and the changes of ions will affect the TDS content, which in turn affects the salinity content of the reservoir water. Therefore, the research on the regularity of salt release also needs to carry out a full analysis of ion indicators, to provide theoretical support for the hydrogeochemical interactions between sediments and reservoir water. Taking Beidagang Reservoir as the research area, through the method of combining field sampling and batch experiment, the change law of salinity and main ion indexes after the mixing of coastal reservoir water and sediment is analyzed to explore reservoir water and sediment. The hydrogeochemical interaction between the objects reveal the mechanism of reservoir salinization. Illation condition of reservoir water and sediment, the water chemical indexes can quickly reach equilibrium. The TDS mass concentration of each sampling point increased rapidly at first, and the salt release reached equilibrium after 30 s. Na+and Cl-were the main ions involved in water-rock interaction; the maximum release amounts of Na+and Cl-were 7 597.25 mg/kg, 11 097.00 mg/kg. The Na+, K+, Mg2+, Ca2+, SO42-of each sampling point increased or decreased in different degrees in the sediment-reservoir water interaction. Cl-was increased, HCO3-decreased slightly. Except for HCO3-and Ca2+, the changes of other ions showed the rule of sampling points in the downstream of the reservoir > sampling points in the upstream of the reservoir. During the hydrogeochemical process of sediment-reservoir water, the total salt in the sediment was released, and the changes of each ion in the process of salt release were related to the mass concentration difference of each ion in the sediment and the reservoir water. After mixing with the reservoir water, it will be released into the water, and the ions with very low content in the sediment will be adsorbed into the sediment after mixing with the reservoir water, resulting in the reduction of the ion content in the reservoir water. It can be seen from the experiment that the release of salt from sediments can lead to an increase in the salinity of the reservoir water, resulting in the salinization of the reservoir. In the process of salinization of the reservoir water, Na+, and Cl-are the main ions involved in water-rock interaction. The change in salinity showed the rule of sampling points downstream of the reservoir > sampling points upstream of the reservoir.
Completion of the Binhai Reservoir may experience serious salinization or sudden brackishness, thus affecting the normal water supply function. The research on reservoir water salinization mainly focuses on total salinity, chloride ion, or other single indicators, but the release of sediment salt is a complex process. In fact, during the hydrogeochemical process of sediments and reservoir water, various ions may change to different degrees, and the changes of ions will affect the TDS content, which in turn affects the salinity content of the reservoir water. Therefore, the research on the regularity of salt release also needs to carry out a full analysis of ion indicators, to provide theoretical support for the hydrogeochemical interactions between sediments and reservoir water. Taking Beidagang Reservoir as the research area, through the method of combining field sampling and batch experiment, the change law of salinity and main ion indexes after the mixing of coastal reservoir water and sediment is analyzed to explore reservoir water and sediment. The hydrogeochemical interaction between the objects reveal the mechanism of reservoir salinization. Illation condition of reservoir water and sediment, the water chemical indexes can quickly reach equilibrium. The TDS mass concentration of each sampling point increased rapidly at first, and the salt release reached equilibrium after 30 s. Na+and Cl-were the main ions involved in water-rock interaction; the maximum release amounts of Na+and Cl-were 7 597.25 mg/kg, 11 097.00 mg/kg. The Na+, K+, Mg2+, Ca2+, SO42-of each sampling point increased or decreased in different degrees in the sediment-reservoir water interaction. Cl-was increased, HCO3-decreased slightly. Except for HCO3-and Ca2+, the changes of other ions showed the rule of sampling points in the downstream of the reservoir > sampling points in the upstream of the reservoir. During the hydrogeochemical process of sediment-reservoir water, the total salt in the sediment was released, and the changes of each ion in the process of salt release were related to the mass concentration difference of each ion in the sediment and the reservoir water. After mixing with the reservoir water, it will be released into the water, and the ions with very low content in the sediment will be adsorbed into the sediment after mixing with the reservoir water, resulting in the reduction of the ion content in the reservoir water. It can be seen from the experiment that the release of salt from sediments can lead to an increase in the salinity of the reservoir water, resulting in the salinization of the reservoir. In the process of salinization of the reservoir water, Na+, and Cl-are the main ions involved in water-rock interaction. The change in salinity showed the rule of sampling points downstream of the reservoir > sampling points upstream of the reservoir.
2023(2):313-323.
Abstract:
Climate change has caused the redistribution of water resources by changing the global hydrological cycle. The main factors are changes in temperature and rainfall, and the variation of these climate factors directly led to the change in surface runoff. At present, people pay too much attention to economic development and ignore the protection of the ecological environment, which has led to the contradiction between the supply and demand of water resources in the watershed. At the same time, under the environment of global warming, the ecological water demand of the watershed has been more or less affected, and the ecological balance of the watershed has been seriously threatened. The previous research results were drawn up and Tennant, Penman-Monteith formula, and other methods were used to calculate the current annual ecological water demand of Haoxi Watershed. The results showed that the current ecological water demand of Haoxi Watershed was 157 million m3 from September to February of the next year, and 248 million m3 from March to August. Using CanESM2 meteorological prediction data under RCP2.6, RCP4.5, and RCP8.5 scenarios, the location of Haoxi Watershed was extracted and downscaled to obtain the climate prediction data. The grid data of 26 prediction factors were obtained by inverse distance weight interpolation NCEP reanalysis data. Multivariate stepwise linear regression was applied to establish the statistical relationship between the three prediction variables and the prediction factors, and finally, the prediction factors were determined. The daily precipitation, daily maximum temperature, and daily minimum temperature from 2025 to 2100 were selected as predictive variables to analyze climate change and the changing trend of ecological water demand of the watershed under each scenario in the next 75 years. The CanESM2 model data was standardized and verified in SDSM model to generate the long-term series data of the watershed in the future. The changes in precipitation, daily maximum mild temperature and daily minimum temperature in future years were also estimated. The obtained meteorological forecast data was put into the high-precision ecological water demand model established above to generate the long-term forecast value of ecological water demand to 2100. Based on the predicted value of ecological water demand, the degree of ecological water demand guarantee in the future years was calculated. Due to the lack of accuracy of land use data sources applied in the current research, the simulation accuracy of ecological water demand in Haoxi Watershed was low. Therefore, the remote sensing image data of GF1-WFV and ENVI software were used for remote sensing interpretation to obtain the surface albedo and high-precision land use data in the study area, and the interpreted data were put into the existing SWAT model to compare the improvement effect of data accuracy before and after substitution. In terms of the comparison of the simulation results of ecological water demand, the results of the original model were as follows: Periodic R2 is 0.75. The high-precision land use data and surface albedo obtained from the interpretation of multivariate remote sensing data were substituted into the simulation results obtained by the model. The periodic R2 value was 0.85 and the validation R2 is 0.8, and the verification period value was 0.78. Therefore, the simulation accuracy of the model was significantly improved. In the forecast changes of meteorological data in the next 75 years, the maximum temperature and minimum temperature under RCP2.6, RCP4.5, and RCP8.5 all had different amplitude increases. From the general trend, the temperature increase was the largest under RCP8.5 and the lowest under RCP2.6. Compared with the temperature, the rainfall showed no obvious change trend, and the overall fluctuation was large. In terms of the forecast of ecological water requirement, the ecological water requirement of the three different scenarios will increase to varying degrees, but the two scenarios of RCP2.6 and RCP4.5 will gradually stabilize after 2065, while the RCP8.5 will continue to increase. Therefore, the variation trend of ecological water demand guarantee degree can be obtained. RCP2.6 tends to be stable, RCP4.5 shows a downward trend, and RCP8.5 shows an upward trend. In terms of the comparison of the simulation results of ecological water demand, the simulation results of the original model were as follows: the rate periodic R2 is 0.8, and the verification period R2 is 0.75. The high-precision land use data and surface albedo obtained from the interpretation of multivariate remote sensing data were substituted into the simulation results obtained by the model. The periodic R2 value was 0.85 and the validation R2value was 0.78. Therefore, the simulation accuracy of the model was significantly improved. In the forecast changes of meteorological data in the next 75 years, the maximum temperature and minimum temperature under RCP2.6, RCP4.5 and RCP8.5 all had different amplitude increases. From the general trend, the temperature increase was the largest under RCP8.5 and the lowest under RCP2.6. Compared with the temperature, the rainfall showed no obvious change trend, and the overall fluctuation was large. In terms of the forecast of ecological water requirement, the ecological water requirement of the three different scenarios will increase to varying degrees, but the two scenarios of RCP2.6 and RCP4.5 will gradually stabilize after 2065, while the RCP8.5 will continue to increase. Therefore, the variation trend of ecological water demand guarantee degree can be obtained. RCP2.6 tends to be stable, RCP4.5 shows a downward trend, and RCP8.5 shows an upward trend. The results showed that the established ecological water demand model could be applied to the study of Haoxi Watershed, and the simulation accuracy improvement method based on the remote sensing simulation interpretation method could improve the accuracy of the model. In addition, the predicted ecological water demand and the degree of ecological water demand guarantee in the next 75 years and clarified the law of its change, which had important reference significance for guaranteeing the basic ecological functions of the river watershed.
Climate change has caused the redistribution of water resources by changing the global hydrological cycle. The main factors are changes in temperature and rainfall, and the variation of these climate factors directly led to the change in surface runoff. At present, people pay too much attention to economic development and ignore the protection of the ecological environment, which has led to the contradiction between the supply and demand of water resources in the watershed. At the same time, under the environment of global warming, the ecological water demand of the watershed has been more or less affected, and the ecological balance of the watershed has been seriously threatened. The previous research results were drawn up and Tennant, Penman-Monteith formula, and other methods were used to calculate the current annual ecological water demand of Haoxi Watershed. The results showed that the current ecological water demand of Haoxi Watershed was 157 million m3 from September to February of the next year, and 248 million m3 from March to August. Using CanESM2 meteorological prediction data under RCP2.6, RCP4.5, and RCP8.5 scenarios, the location of Haoxi Watershed was extracted and downscaled to obtain the climate prediction data. The grid data of 26 prediction factors were obtained by inverse distance weight interpolation NCEP reanalysis data. Multivariate stepwise linear regression was applied to establish the statistical relationship between the three prediction variables and the prediction factors, and finally, the prediction factors were determined. The daily precipitation, daily maximum temperature, and daily minimum temperature from 2025 to 2100 were selected as predictive variables to analyze climate change and the changing trend of ecological water demand of the watershed under each scenario in the next 75 years. The CanESM2 model data was standardized and verified in SDSM model to generate the long-term series data of the watershed in the future. The changes in precipitation, daily maximum mild temperature and daily minimum temperature in future years were also estimated. The obtained meteorological forecast data was put into the high-precision ecological water demand model established above to generate the long-term forecast value of ecological water demand to 2100. Based on the predicted value of ecological water demand, the degree of ecological water demand guarantee in the future years was calculated. Due to the lack of accuracy of land use data sources applied in the current research, the simulation accuracy of ecological water demand in Haoxi Watershed was low. Therefore, the remote sensing image data of GF1-WFV and ENVI software were used for remote sensing interpretation to obtain the surface albedo and high-precision land use data in the study area, and the interpreted data were put into the existing SWAT model to compare the improvement effect of data accuracy before and after substitution. In terms of the comparison of the simulation results of ecological water demand, the results of the original model were as follows: Periodic R2 is 0.75. The high-precision land use data and surface albedo obtained from the interpretation of multivariate remote sensing data were substituted into the simulation results obtained by the model. The periodic R2 value was 0.85 and the validation R2 is 0.8, and the verification period value was 0.78. Therefore, the simulation accuracy of the model was significantly improved. In the forecast changes of meteorological data in the next 75 years, the maximum temperature and minimum temperature under RCP2.6, RCP4.5, and RCP8.5 all had different amplitude increases. From the general trend, the temperature increase was the largest under RCP8.5 and the lowest under RCP2.6. Compared with the temperature, the rainfall showed no obvious change trend, and the overall fluctuation was large. In terms of the forecast of ecological water requirement, the ecological water requirement of the three different scenarios will increase to varying degrees, but the two scenarios of RCP2.6 and RCP4.5 will gradually stabilize after 2065, while the RCP8.5 will continue to increase. Therefore, the variation trend of ecological water demand guarantee degree can be obtained. RCP2.6 tends to be stable, RCP4.5 shows a downward trend, and RCP8.5 shows an upward trend. In terms of the comparison of the simulation results of ecological water demand, the simulation results of the original model were as follows: the rate periodic R2 is 0.8, and the verification period R2 is 0.75. The high-precision land use data and surface albedo obtained from the interpretation of multivariate remote sensing data were substituted into the simulation results obtained by the model. The periodic R2 value was 0.85 and the validation R2value was 0.78. Therefore, the simulation accuracy of the model was significantly improved. In the forecast changes of meteorological data in the next 75 years, the maximum temperature and minimum temperature under RCP2.6, RCP4.5 and RCP8.5 all had different amplitude increases. From the general trend, the temperature increase was the largest under RCP8.5 and the lowest under RCP2.6. Compared with the temperature, the rainfall showed no obvious change trend, and the overall fluctuation was large. In terms of the forecast of ecological water requirement, the ecological water requirement of the three different scenarios will increase to varying degrees, but the two scenarios of RCP2.6 and RCP4.5 will gradually stabilize after 2065, while the RCP8.5 will continue to increase. Therefore, the variation trend of ecological water demand guarantee degree can be obtained. RCP2.6 tends to be stable, RCP4.5 shows a downward trend, and RCP8.5 shows an upward trend. The results showed that the established ecological water demand model could be applied to the study of Haoxi Watershed, and the simulation accuracy improvement method based on the remote sensing simulation interpretation method could improve the accuracy of the model. In addition, the predicted ecological water demand and the degree of ecological water demand guarantee in the next 75 years and clarified the law of its change, which had important reference significance for guaranteeing the basic ecological functions of the river watershed.
2023(2):324-331.
Abstract:
Reservoirs improve the spatial and temporal distribution of water resources and create huge socio-economic benefits, while also providing a powerful tool for operating the downstream ecological environment. In the middle and lower reaches of the Han River, water bloom tends to occur in late winter and early spring. Operating through hydrodynamic methods can destroy the growth conditions of phytoplankton and effectively prevent and control phytoplankton growth. However, the formation mechanism of phytoplankton growth is complex and difficult to simulate accurately, which makes the reservoir operating for phytoplankton growth prevention and control inefficient. The problem of missing mechanism can be solved to some extent by machine learning method for phytoplankton simulation.A Long Short-Term Memory-based operating method is suitable for phytoplankton growth prevention and control, which can improve the accuracy of phytoplankton growth simulation and enhance the efficiency of reservoir operating. Taken the water bloom problem in the middle and lower reaches of Han River and Danjiangkou Reservoir as the research object, a phytoplankton growth prevention and control operating model including economic and ecological objective functions; the LSTM model of comprehensive nutritional index and phytoplankton density of water bodies is used to establish ecological objective functions; and the cuckoo optimization algorithm is used to solve the problem.The results show that: (1) the simulated values of comprehensive nutritional index and phytoplankton density simulation model based on LSTM model are significantly correlated with the measured values at 0.01 level, and the phytoplankton density simulation effect is good; (2) compared with the conventional operating, the proposed phytoplankton prevention and control operating scheme can increase the multi-year average water supply by 0.45%, the multi-year average power generation by 1.06%, and the average phytoplankton density is reduced by 1.57%, which further enhances the comprehensive benefits of Danjiangkou Reservoir operating while effectively controlling phytoplankton in the middle and lower reaches of Han River.The non-inferior solution is obtained from the operating chart of Danjiangkou Reservoir for phytoplankton growth prevention and control. The operating chart contains the flood limit line, normal storage level line, first reduced water supply line, second reduced water supply line, restricted water supply line and dead water level line, and the reservoir operating according to this chart can effectively prevent and control the phytoplankton growth in the middle and lower reaches of Han River. The research results can provide technical support for the prevention and control of river phytoplankton.
Reservoirs improve the spatial and temporal distribution of water resources and create huge socio-economic benefits, while also providing a powerful tool for operating the downstream ecological environment. In the middle and lower reaches of the Han River, water bloom tends to occur in late winter and early spring. Operating through hydrodynamic methods can destroy the growth conditions of phytoplankton and effectively prevent and control phytoplankton growth. However, the formation mechanism of phytoplankton growth is complex and difficult to simulate accurately, which makes the reservoir operating for phytoplankton growth prevention and control inefficient. The problem of missing mechanism can be solved to some extent by machine learning method for phytoplankton simulation.A Long Short-Term Memory-based operating method is suitable for phytoplankton growth prevention and control, which can improve the accuracy of phytoplankton growth simulation and enhance the efficiency of reservoir operating. Taken the water bloom problem in the middle and lower reaches of Han River and Danjiangkou Reservoir as the research object, a phytoplankton growth prevention and control operating model including economic and ecological objective functions; the LSTM model of comprehensive nutritional index and phytoplankton density of water bodies is used to establish ecological objective functions; and the cuckoo optimization algorithm is used to solve the problem.The results show that: (1) the simulated values of comprehensive nutritional index and phytoplankton density simulation model based on LSTM model are significantly correlated with the measured values at 0.01 level, and the phytoplankton density simulation effect is good; (2) compared with the conventional operating, the proposed phytoplankton prevention and control operating scheme can increase the multi-year average water supply by 0.45%, the multi-year average power generation by 1.06%, and the average phytoplankton density is reduced by 1.57%, which further enhances the comprehensive benefits of Danjiangkou Reservoir operating while effectively controlling phytoplankton in the middle and lower reaches of Han River.The non-inferior solution is obtained from the operating chart of Danjiangkou Reservoir for phytoplankton growth prevention and control. The operating chart contains the flood limit line, normal storage level line, first reduced water supply line, second reduced water supply line, restricted water supply line and dead water level line, and the reservoir operating according to this chart can effectively prevent and control the phytoplankton growth in the middle and lower reaches of Han River. The research results can provide technical support for the prevention and control of river phytoplankton.
2023(2):332-341.
Abstract:
With the rapid development of industrialization and urbanization, the wide spread of heavy metal pollution in river sediments is posing a threat to the ecological security. As a typical river on the Loess Plateau, the pollution of Beiluo River is becoming increasingly prominent, whereas no attempt has been made to systematically evaluate the spatial distribution of heavy metals in the watershed. Therefore, the monitoring and analysis of typical heavy metals in sediments of Beiluo River is of great significance to the ecological health of the basin.In June 2021, sediments were sampled from 17 sites in the main and tributaries of the Beiluo River. The spatial distribution of eight heavy metals (Hg, As, Cd, Cr, Cu, Pb, Ni, Zn) was determined by microwave digestion-atomic fluorescence spectrometry and Aqua regia extraction-inductively coupled plasma mass spectrometry, followed by evaluating the degree of heavy metal pollution and the ecological risk assessment using geoaccumulation index, Nemerow pollution index, and potential ecological risk index, respectively. The source apportionment was conducted using Positive Matrix Factorization (PMF) model and Pearson correlation analysis. The distribution characteristics of heavy metals showed that the content of heavy metals in each sampling site varied greatly. In particular, the content of Zn was significantly higher than that of other heavy metals. The highest content of total heavy metals appeared in the upstream B1 (448.46 mg/kg), followed by the downstream B13 (323.43 mg/kg). Some heavy metal contents were higher than the heavy metal background values of Shaanxi Province. The order of coefficient of variation was as follows: Zn (68.21%) > Hg (51.78%) > Cd (49.65%) > Pb (41.61%) > As (31.82%) > Cu (30.77%) > Ni (23.89%) > Cr (23.74%). In the matter of ecological risk assessment, the geoaccumulation index analyses showed that the accumulative conditions of Cd and Zn were moderately polluted, and most of the other heavy metals were at the pollution-free level. The Nemerow pollution index ranged from 0.74 to 3.64, with an average value of 1.37, and the values of more than half of the sites were within 1 to 2, indicating that the overall pollution in the study area was slightly polluted. The mean values of individual potential ecological risk indexes were: Cd (39.05) > Hg (30.37) > As (12.56) > Cu (4.37) > Ni (4.29) > Pb (3.19) > Zn (1.41) > Cr (0.87). The comprehensive ecological risk index ( RI ) values ranged from 51.60 to 199.75, with an average of 96.09. In addition to the intermediate ecological risk at B10 (158.63) in the middle reaches and B13 (199.75) in the lower reaches, risks in all the other sites were low. Conclusions: (1) The results of geoaccumulation index and Nemerow pollution index show that the heavy metal pollution in the upstream B1 and downstream B13 are ranged from the medium to high levels. According to the results of potential ecological risk index, Cd and Hg in the Beiluo River may pose a threat to the ecosystem. In addition to the ecological risks in the middle stream B10 and the downstream B13 that are classified as moderate, the whole basin has slight potential ecological risks. (2) Based on the PMF model and correlation analysis, the sources of heavy metals in the sediments of Beiluo River were analyzed. The results showed that the sources of eight heavy metals could be divided into three categories: traffic pollution sources, coal and oil industrial pollution sources, and mixed sources of agricultural activities and natural parent materials. (3) Based on the results of this study, it is suggested to divide the pollution levels of the Beiluo River basin into regions, focusing on the heavy metal pollution at B1 in the upper reaches and B13 in the lower reaches, especially reducing the input of metal Zn and Hg in the river basin, and taking certain measures to supervise and control related industries involved in heavy metal pollution, so as to eliminate the pollution of heavy metals in the sediments. In future studies, the enrichment characteristics of heavy metals in sediments with different grain sizes will be revealed to provide more comprehensive scientific data for the prediction of heavy metal pollution in sediments and the overall ecological protection of the basin.
With the rapid development of industrialization and urbanization, the wide spread of heavy metal pollution in river sediments is posing a threat to the ecological security. As a typical river on the Loess Plateau, the pollution of Beiluo River is becoming increasingly prominent, whereas no attempt has been made to systematically evaluate the spatial distribution of heavy metals in the watershed. Therefore, the monitoring and analysis of typical heavy metals in sediments of Beiluo River is of great significance to the ecological health of the basin.In June 2021, sediments were sampled from 17 sites in the main and tributaries of the Beiluo River. The spatial distribution of eight heavy metals (Hg, As, Cd, Cr, Cu, Pb, Ni, Zn) was determined by microwave digestion-atomic fluorescence spectrometry and Aqua regia extraction-inductively coupled plasma mass spectrometry, followed by evaluating the degree of heavy metal pollution and the ecological risk assessment using geoaccumulation index, Nemerow pollution index, and potential ecological risk index, respectively. The source apportionment was conducted using Positive Matrix Factorization (PMF) model and Pearson correlation analysis. The distribution characteristics of heavy metals showed that the content of heavy metals in each sampling site varied greatly. In particular, the content of Zn was significantly higher than that of other heavy metals. The highest content of total heavy metals appeared in the upstream B1 (448.46 mg/kg), followed by the downstream B13 (323.43 mg/kg). Some heavy metal contents were higher than the heavy metal background values of Shaanxi Province. The order of coefficient of variation was as follows: Zn (68.21%) > Hg (51.78%) > Cd (49.65%) > Pb (41.61%) > As (31.82%) > Cu (30.77%) > Ni (23.89%) > Cr (23.74%). In the matter of ecological risk assessment, the geoaccumulation index analyses showed that the accumulative conditions of Cd and Zn were moderately polluted, and most of the other heavy metals were at the pollution-free level. The Nemerow pollution index ranged from 0.74 to 3.64, with an average value of 1.37, and the values of more than half of the sites were within 1 to 2, indicating that the overall pollution in the study area was slightly polluted. The mean values of individual potential ecological risk indexes were: Cd (39.05) > Hg (30.37) > As (12.56) > Cu (4.37) > Ni (4.29) > Pb (3.19) > Zn (1.41) > Cr (0.87). The comprehensive ecological risk index ( RI ) values ranged from 51.60 to 199.75, with an average of 96.09. In addition to the intermediate ecological risk at B10 (158.63) in the middle reaches and B13 (199.75) in the lower reaches, risks in all the other sites were low. Conclusions: (1) The results of geoaccumulation index and Nemerow pollution index show that the heavy metal pollution in the upstream B1 and downstream B13 are ranged from the medium to high levels. According to the results of potential ecological risk index, Cd and Hg in the Beiluo River may pose a threat to the ecosystem. In addition to the ecological risks in the middle stream B10 and the downstream B13 that are classified as moderate, the whole basin has slight potential ecological risks. (2) Based on the PMF model and correlation analysis, the sources of heavy metals in the sediments of Beiluo River were analyzed. The results showed that the sources of eight heavy metals could be divided into three categories: traffic pollution sources, coal and oil industrial pollution sources, and mixed sources of agricultural activities and natural parent materials. (3) Based on the results of this study, it is suggested to divide the pollution levels of the Beiluo River basin into regions, focusing on the heavy metal pollution at B1 in the upper reaches and B13 in the lower reaches, especially reducing the input of metal Zn and Hg in the river basin, and taking certain measures to supervise and control related industries involved in heavy metal pollution, so as to eliminate the pollution of heavy metals in the sediments. In future studies, the enrichment characteristics of heavy metals in sediments with different grain sizes will be revealed to provide more comprehensive scientific data for the prediction of heavy metal pollution in sediments and the overall ecological protection of the basin.
2023(2):342-351.
Abstract:
The middle route of South-to-North Water Transfer Project is a large-scale water diversion project with cross-basin, large flow, and long distance. It is a major strategic infrastructure to alleviate the shortage of water resources in northern China, realize the rational allocation of water resources, and ensure sustainable economic and social development. With global warming, the frequency of extreme rainstorm and flood disasters has increased significantly. Since its operation, the middle route of South-to-North Water Transfer Project has encountered severe torrential rainstorm disasters many times, and is facing serious problems of water damage. Therefore, it is necessary to further study the degree of risk in the middle route project when encountering over-standard rainstorms floods.The channels and buildings of the middle route of South-to-North Water Transfer Project were taken as the research object, and the method of combining the overall risk assessment and the typical unit analysis was used to evaluate the overall risk of 639 units of the middle route project, and the five typical units of Guanqu River, Jia River, Jinshui River, Shimen River, and Shagou were focuses on. In engineering risk analysis, methods such as engineering risk event possibility index and engineering risk event consequence severity were adopted. In the risk analysis of over-standard rainstorms floods, the risk of typical assessment units was analyzed through the construction of rainstorms flood analysis model, extreme rainfall migration (planting) setting, scheme simulation, and statistical analysis of results.The results show that among the 639 evaluation units of the middle route of South-to-North Water Transfer Project, the units with a risk event probability index of 1 account for the largest proportion, and the risk level is mainly general risk. In the five typical units, the flood formed at the cross-section after extreme rainfall migration (planting) presents the characteristics that the smaller the watershed area, the larger the flood magnitude. In addition, the risk of overflow at the top of the irrigation canal river drainage inverted siphon is low. The Jiahe beam aqueduct, Shagou flood discharge aqueduct, and Shimen River channel inverted siphon all have high engineering risks. The erosion of Jinshui River channel inverted siphon meets the requirements under over-standard flood, and the project risk is low.The conclusion indicates that under the condition of over-standard rainstorm flood, the channels and buildings of the middle route of South-to-North Water Transfer Project are generally low-risk, but some typical units have engineering risks such as insufficient flood control capacity, overflow of trough body, and embankment top, erosion and exposure of piers and abutments, and dam failure. Therefore, to ensure the safe operation of the middle route project, it is still necessary to further strengthen the engineering and non-engineering protection measures, and scientifically and reasonably formulate the revision mechanism of the over-standard rainstorm flood prevention plan. The research results have guiding significance for the early deployment of defense against the over-standard rainstorm flood in the middle route of South-to-North Water Transfer Project.
The middle route of South-to-North Water Transfer Project is a large-scale water diversion project with cross-basin, large flow, and long distance. It is a major strategic infrastructure to alleviate the shortage of water resources in northern China, realize the rational allocation of water resources, and ensure sustainable economic and social development. With global warming, the frequency of extreme rainstorm and flood disasters has increased significantly. Since its operation, the middle route of South-to-North Water Transfer Project has encountered severe torrential rainstorm disasters many times, and is facing serious problems of water damage. Therefore, it is necessary to further study the degree of risk in the middle route project when encountering over-standard rainstorms floods.The channels and buildings of the middle route of South-to-North Water Transfer Project were taken as the research object, and the method of combining the overall risk assessment and the typical unit analysis was used to evaluate the overall risk of 639 units of the middle route project, and the five typical units of Guanqu River, Jia River, Jinshui River, Shimen River, and Shagou were focuses on. In engineering risk analysis, methods such as engineering risk event possibility index and engineering risk event consequence severity were adopted. In the risk analysis of over-standard rainstorms floods, the risk of typical assessment units was analyzed through the construction of rainstorms flood analysis model, extreme rainfall migration (planting) setting, scheme simulation, and statistical analysis of results.The results show that among the 639 evaluation units of the middle route of South-to-North Water Transfer Project, the units with a risk event probability index of 1 account for the largest proportion, and the risk level is mainly general risk. In the five typical units, the flood formed at the cross-section after extreme rainfall migration (planting) presents the characteristics that the smaller the watershed area, the larger the flood magnitude. In addition, the risk of overflow at the top of the irrigation canal river drainage inverted siphon is low. The Jiahe beam aqueduct, Shagou flood discharge aqueduct, and Shimen River channel inverted siphon all have high engineering risks. The erosion of Jinshui River channel inverted siphon meets the requirements under over-standard flood, and the project risk is low.The conclusion indicates that under the condition of over-standard rainstorm flood, the channels and buildings of the middle route of South-to-North Water Transfer Project are generally low-risk, but some typical units have engineering risks such as insufficient flood control capacity, overflow of trough body, and embankment top, erosion and exposure of piers and abutments, and dam failure. Therefore, to ensure the safe operation of the middle route project, it is still necessary to further strengthen the engineering and non-engineering protection measures, and scientifically and reasonably formulate the revision mechanism of the over-standard rainstorm flood prevention plan. The research results have guiding significance for the early deployment of defense against the over-standard rainstorm flood in the middle route of South-to-North Water Transfer Project.
2023(2):352-361.
Abstract:
As a strategic infrastructure project to solve the uneven distribution of water resources in China, the middle route of South-to-North Water Transfer Project was increasingly dependent in Beijing, Tianjin and other water receiving areas due to its good quality and stable water supply. In winter, the water temperature of the open channel gradually decreased with the air temperature, and there was ice in the canal north of Anyang. When the water temperature dropped below 0.5 ℃, a large number of ice crystals began to form. In order to prevent ice jam, the safe water delivery flow under the ice sheet was only 31.6% ~ 47.6% of the design flow. There was a huge contradiction between the increasing water demand in north China and the declining water delivery capacity of the project in ice period. Ice condition prediction was an important means to solve the safe operation of water conveyance in the ice period of the project, meet the control requirements of water level and flow under various complex operating conditions, and ensure the safe and efficient operation of the middle route of South-to-North Water Transfer Project. Water temperature prediction model was the most important sub model in ice condition prediction. The occurrence and evolution process of ice condition was closely related to water temperature factors.According to the characteristics of linear, unidirectional and sequential flow in open channel, a calculation model based on initial section water temperature along the temperature chain was established. Based on the data of meteorological and water temperature during the ice period in 2019, 2020 and 2021, five groups of 15 regression parameter models of water temperature prediction in the prediction period of 1 - 5 days in the 217.5 km canal section from Hutuo River Siphon outlet sluice (K 980 + 263) to the North Juma River culvert inlet sluice (K 1197 + 773) at the northernmost end of the main canal were established. Based on the analysis and sorting of the field measurement data of water transmission in winter since the first water supply of the whole line of the project, according to the statistical data of North Juma River canal segment from 2015 to 2022, the freezing of ice carapace only accounted for 14% of the whole ice period. The minimum value of R2 in regression models was 0.957 and the maximum value was 0.991. Using the data of 2018 for prediction test, the DC values of each group of model test could reach 0.90. Taking the North Juma River station as the prediction section, the RMSE values of 1 - 5 day forecast period were 0.05, 0.11, 0.15, 0.14 and 0.22 respectively, and the MAE values were 0.17, 0.25, 0.28, 0.28 and 0.37 respectively, which increased regularly with the growth of the forecast period. The water transmission dispatching mode in winter had a lot of room to optimize. Water temperature could be used as the judgment basis for the initiation and development of ice condition. Water temperature Twn,i and air temperature Tan,x had a good interpretation to the water temperature Tw(n+1),i+1 ,, and the predicted value and the observed value was matched well. The method to establish the model had a certain practical value.
As a strategic infrastructure project to solve the uneven distribution of water resources in China, the middle route of South-to-North Water Transfer Project was increasingly dependent in Beijing, Tianjin and other water receiving areas due to its good quality and stable water supply. In winter, the water temperature of the open channel gradually decreased with the air temperature, and there was ice in the canal north of Anyang. When the water temperature dropped below 0.5 ℃, a large number of ice crystals began to form. In order to prevent ice jam, the safe water delivery flow under the ice sheet was only 31.6% ~ 47.6% of the design flow. There was a huge contradiction between the increasing water demand in north China and the declining water delivery capacity of the project in ice period. Ice condition prediction was an important means to solve the safe operation of water conveyance in the ice period of the project, meet the control requirements of water level and flow under various complex operating conditions, and ensure the safe and efficient operation of the middle route of South-to-North Water Transfer Project. Water temperature prediction model was the most important sub model in ice condition prediction. The occurrence and evolution process of ice condition was closely related to water temperature factors.According to the characteristics of linear, unidirectional and sequential flow in open channel, a calculation model based on initial section water temperature along the temperature chain was established. Based on the data of meteorological and water temperature during the ice period in 2019, 2020 and 2021, five groups of 15 regression parameter models of water temperature prediction in the prediction period of 1 - 5 days in the 217.5 km canal section from Hutuo River Siphon outlet sluice (K 980 + 263) to the North Juma River culvert inlet sluice (K 1197 + 773) at the northernmost end of the main canal were established. Based on the analysis and sorting of the field measurement data of water transmission in winter since the first water supply of the whole line of the project, according to the statistical data of North Juma River canal segment from 2015 to 2022, the freezing of ice carapace only accounted for 14% of the whole ice period. The minimum value of R2 in regression models was 0.957 and the maximum value was 0.991. Using the data of 2018 for prediction test, the DC values of each group of model test could reach 0.90. Taking the North Juma River station as the prediction section, the RMSE values of 1 - 5 day forecast period were 0.05, 0.11, 0.15, 0.14 and 0.22 respectively, and the MAE values were 0.17, 0.25, 0.28, 0.28 and 0.37 respectively, which increased regularly with the growth of the forecast period. The water transmission dispatching mode in winter had a lot of room to optimize. Water temperature could be used as the judgment basis for the initiation and development of ice condition. Water temperature Twn,i and air temperature Tan,x had a good interpretation to the water temperature Tw(n+1),i+1 ,, and the predicted value and the observed value was matched well. The method to establish the model had a certain practical value.
2023(2):362-370.
Abstract:
A model experiment is one of the most effective and important ways to study landslide surge in a reservoir. A large-scale model can usually help obtain more reliable results. Therefore, to investigate the characteristics of a surge in front of a dam and its contributing factors, especially when the whole volume of unstable landsides is relatively large, a physical model with a scale as large as 1:100 was built up to simulate the topography of the reservoir in a narrow deep valley. Furthermore, the generation and the propagation of the landslide surge in the reservoir and near the dam were studied by utilizing the rigid sliding blocks. It is found that the shoulders of the dam have the most probable risks of overtopping. The height of the initial surge wave and that of the maximal wave were investigated. The influences of different volume of the sliding blocks, as well as the entry velocity on the heights of the surge wave were compared and analyzed. Furthermore, a formula to predict the surge wave height on the shoulders of the dam is proposed by nonlinear regression based on dimensional analysis. It is shown from the experimental results that although the trend of surge wave heights in front of different gauging points is similar, the maximal wave heights usually occurred near the right shoulder of the dam, so it possesses more risks of overtopping. In addition, the influence of the volume of the sliding blocks on the wave heights is larger than that of the entry velocity. The initial wave height is more sensitive to the volume and entry velocity of the blocks than the maximal one. The mean sensitivity to the volume of the blocks on the initial and maximal wave height at the right shoulder of the dam is 0.858 and 0.358, respectively, while the mean sensitivity to the entry velocity is 0.217 and 0.115, respectively. The difference between the predicted results from the fitting formula and the experimental data for the initial wave height is less than 3%, indicating that the fitting formulae for the initial height have great accuracy and consistency. On the other hand, the maximal surge wave height has larger randomness, with the difference between the predicted results and the experimental data being less than 15%.
A model experiment is one of the most effective and important ways to study landslide surge in a reservoir. A large-scale model can usually help obtain more reliable results. Therefore, to investigate the characteristics of a surge in front of a dam and its contributing factors, especially when the whole volume of unstable landsides is relatively large, a physical model with a scale as large as 1:100 was built up to simulate the topography of the reservoir in a narrow deep valley. Furthermore, the generation and the propagation of the landslide surge in the reservoir and near the dam were studied by utilizing the rigid sliding blocks. It is found that the shoulders of the dam have the most probable risks of overtopping. The height of the initial surge wave and that of the maximal wave were investigated. The influences of different volume of the sliding blocks, as well as the entry velocity on the heights of the surge wave were compared and analyzed. Furthermore, a formula to predict the surge wave height on the shoulders of the dam is proposed by nonlinear regression based on dimensional analysis. It is shown from the experimental results that although the trend of surge wave heights in front of different gauging points is similar, the maximal wave heights usually occurred near the right shoulder of the dam, so it possesses more risks of overtopping. In addition, the influence of the volume of the sliding blocks on the wave heights is larger than that of the entry velocity. The initial wave height is more sensitive to the volume and entry velocity of the blocks than the maximal one. The mean sensitivity to the volume of the blocks on the initial and maximal wave height at the right shoulder of the dam is 0.858 and 0.358, respectively, while the mean sensitivity to the entry velocity is 0.217 and 0.115, respectively. The difference between the predicted results from the fitting formula and the experimental data for the initial wave height is less than 3%, indicating that the fitting formulae for the initial height have great accuracy and consistency. On the other hand, the maximal surge wave height has larger randomness, with the difference between the predicted results and the experimental data being less than 15%.
2023(2):371-378.
Abstract:
The inter-basin water transfer project is an essential instrument for achieving better water resource distribution. The hydraulic parameters will fluctuate significantly while the water supply system is transitioning, endangering its stability and security. Therefore, it is necessary to investigate the transition process of the hydraulic system and the water hammer protection measures.For a typical long-distance pumping station pressurized water supply system with a gravity flow branch in a large-scale water supply project in Northeast China. A mathematical model of the hydraulic system was established based on the characteristic line method, and the hydraulic transition process simulation was carried out.The water supply system did not have negative pressure under steady-state operating conditions and met the requirements of overflow capacity. The calculated values of water level at each water diversion were in good agreement with the engineering values, which verified the credibility of the simulation results. Under unprotected accidental pump stopping conditions, the pump went into flyaway reversal and the maximum reversal speed was exceeded. The pressure drops after the pump led to vaporization in several sections of the pipeline. Gravity flow branches necessitated the regular use of flow regulating valves at the pipeline's end to adjust the flow rate, and it was quite possible to cause serious water hammer accidents if the regulating valve did not function properly. It was generally considered that the worst operating condition was when all branch regulators were closed at the same time. Therefore, this condition was usually used to verify whether the protection measures could still meet the water hammer protection requirements under the most severe conditions. The condition in which the valves closed one after the other, generated the greatest increase in water hammer pressure. And the calculation formula when each valve started to operate successively under the successive shut-off condition was given. With the combined protection of the 4.5 s one-stage linear fast closing of the pump outlet valve and the air valve layout, the maximum reversing speed of the unit and the pressure extremum in the main pipeline was effectively lowered. Under steady-state operating circumstances, the estimated values of the water level of each water diversion were in good agreement with the engineering values (the calculated error of the water level of each water diversion was less than 0.5%), confirming the trustworthiness of the simulation findings. Under an unprotected accidental pump stopping circumstance, the pump entered a flyaway reversal and exceeded the limit reversal speed. Pressure drops caused vaporization in numerous portions of the pipeline. Therefore, water hammer protection measures must be taken. The successive shutdown scheme of the regulating valve can generate the maximum water hammer pressure. By comparing the regulating valve successive shutdown operating conditions and simultaneous shutdown operating conditions, it was discovered that the successive shut-off scheme derived induced a larger water hammer pressure (92.91 m), which was 4.4% higher than that of the simultaneous shut-off scheme (88.99 m). The calculation formula when each valve started to operate successively under the successive shut-off condition could provide a theoretical basis for the calibration of water hammer protection of water supply systems with gravity flow branches. The joint water hammer protection scheme was proposed and the hydraulic instability characteristics of the pump outage process were effectively mitigated. With the combined protection of the 4.5 s one-stage linear fast closing of the pump outlet valve and the air valve layout, the maximum reversing speed of the unit was reduced by 94.95%; meanwhile, the maximum positive pressure in the main pipeline was effectively lowered by 33.82% and the maximum negative pressure was decreased by 89.24%. This water hammer protection solution can provide a reference for water hammer protection of the same type of water supply system.
The inter-basin water transfer project is an essential instrument for achieving better water resource distribution. The hydraulic parameters will fluctuate significantly while the water supply system is transitioning, endangering its stability and security. Therefore, it is necessary to investigate the transition process of the hydraulic system and the water hammer protection measures.For a typical long-distance pumping station pressurized water supply system with a gravity flow branch in a large-scale water supply project in Northeast China. A mathematical model of the hydraulic system was established based on the characteristic line method, and the hydraulic transition process simulation was carried out.The water supply system did not have negative pressure under steady-state operating conditions and met the requirements of overflow capacity. The calculated values of water level at each water diversion were in good agreement with the engineering values, which verified the credibility of the simulation results. Under unprotected accidental pump stopping conditions, the pump went into flyaway reversal and the maximum reversal speed was exceeded. The pressure drops after the pump led to vaporization in several sections of the pipeline. Gravity flow branches necessitated the regular use of flow regulating valves at the pipeline's end to adjust the flow rate, and it was quite possible to cause serious water hammer accidents if the regulating valve did not function properly. It was generally considered that the worst operating condition was when all branch regulators were closed at the same time. Therefore, this condition was usually used to verify whether the protection measures could still meet the water hammer protection requirements under the most severe conditions. The condition in which the valves closed one after the other, generated the greatest increase in water hammer pressure. And the calculation formula when each valve started to operate successively under the successive shut-off condition was given. With the combined protection of the 4.5 s one-stage linear fast closing of the pump outlet valve and the air valve layout, the maximum reversing speed of the unit and the pressure extremum in the main pipeline was effectively lowered. Under steady-state operating circumstances, the estimated values of the water level of each water diversion were in good agreement with the engineering values (the calculated error of the water level of each water diversion was less than 0.5%), confirming the trustworthiness of the simulation findings. Under an unprotected accidental pump stopping circumstance, the pump entered a flyaway reversal and exceeded the limit reversal speed. Pressure drops caused vaporization in numerous portions of the pipeline. Therefore, water hammer protection measures must be taken. The successive shutdown scheme of the regulating valve can generate the maximum water hammer pressure. By comparing the regulating valve successive shutdown operating conditions and simultaneous shutdown operating conditions, it was discovered that the successive shut-off scheme derived induced a larger water hammer pressure (92.91 m), which was 4.4% higher than that of the simultaneous shut-off scheme (88.99 m). The calculation formula when each valve started to operate successively under the successive shut-off condition could provide a theoretical basis for the calibration of water hammer protection of water supply systems with gravity flow branches. The joint water hammer protection scheme was proposed and the hydraulic instability characteristics of the pump outage process were effectively mitigated. With the combined protection of the 4.5 s one-stage linear fast closing of the pump outlet valve and the air valve layout, the maximum reversing speed of the unit was reduced by 94.95%; meanwhile, the maximum positive pressure in the main pipeline was effectively lowered by 33.82% and the maximum negative pressure was decreased by 89.24%. This water hammer protection solution can provide a reference for water hammer protection of the same type of water supply system.
2023(2):379-389.
Abstract:
Special underwater topography formed in the estuary area makes it abundant for available resources. The Shanghai section of northern Hangzhou Bay is located on the north side of the middle and rear sections from the top to the mouth of the bay. It is affected by the Yangtze River and Qiantang River runoff and ocean. Thus, it is of great guiding significance for the construction, development, and maintenance of the northern edge of Hangzhou Bay to study the evolution law and change the reason for the underwater topography erosion and deposition. Despite previous analysis, there is a lack of accurate and continuous topographic data. With the advancement of development and construction in recent years, overall analysis and detailed research in key areas are needed.The annual square grid digital elevation model in the north edge of Hangzhou Bay from 2005 to 2020 was generated based on the measured CAD topography data combined with the isobath data of some offshore isobaths according to the analysis requirements of underwater topography scouring and silting in the north edge of Hangzhou Bay. Then for further research, the focal areas were selected with local evolution and used the contour line and the morphological change of the typical section profile to describe the evolution process of terrain over time. To analyze the influence of hydrological and hydrodynamic factors and human activities on the evolution of erosion and deposition along the northern edge of Hangzhou Bay, hydrological and hydrodynamic factors such as water and sediment, tidal current data, and the reclamation were studied. The results show that the northern part of Hangzhou Bay along the Shanghai section showed a weak erosion trend, with a total erosion of 148.2 million m3 and an average annual erosion depth of 2.886 cm in recent 16 years. The Jinshan deep trough is the lowest area, and the terrain elevation dropped in front of Luchao Port. The study area suddenly deposited heavily in 2011. The highest scour happened between 2005 and 2008, and 2008 to 2011 was the highest siltation period. Although the Jinshan deep trough was affected by strong tide and encirclement projects, it contained strong erosion and strong deposition, but the overall performance was a slight erosion with a balanced erosion and deposition, and the erosion intensity was only 12.1% of that in the study area. There were many deep scour pits and steep slopes in Section # 2 and Section #3. The decrease of incoming water and sediment upstream made the north edge of Hangzhou Bay maintain the scouring situation. The supplement effect of tidal current-carrying sediment increased with the tide difference, and the scouring intensity was weakened. It is the equilibrium state formed by the synergy of various influencing factors that will last for a long time. Reclamation engineering is the main influencing factor of topography and erosion-deposition in the Jinshan deep trough. Some areas were blocked by reefs. The shoreline of the surrounding area was stable, but the nearshore scouring was strong, and the topographic change was more intense. Whether long-term scouring will bring risks such as foundation instability and bank collapse, the evolution of scouring and silting terrain characteristics, and the feedback relationship between beach and port development and construction need to be continuously observed and further studied.
Special underwater topography formed in the estuary area makes it abundant for available resources. The Shanghai section of northern Hangzhou Bay is located on the north side of the middle and rear sections from the top to the mouth of the bay. It is affected by the Yangtze River and Qiantang River runoff and ocean. Thus, it is of great guiding significance for the construction, development, and maintenance of the northern edge of Hangzhou Bay to study the evolution law and change the reason for the underwater topography erosion and deposition. Despite previous analysis, there is a lack of accurate and continuous topographic data. With the advancement of development and construction in recent years, overall analysis and detailed research in key areas are needed.The annual square grid digital elevation model in the north edge of Hangzhou Bay from 2005 to 2020 was generated based on the measured CAD topography data combined with the isobath data of some offshore isobaths according to the analysis requirements of underwater topography scouring and silting in the north edge of Hangzhou Bay. Then for further research, the focal areas were selected with local evolution and used the contour line and the morphological change of the typical section profile to describe the evolution process of terrain over time. To analyze the influence of hydrological and hydrodynamic factors and human activities on the evolution of erosion and deposition along the northern edge of Hangzhou Bay, hydrological and hydrodynamic factors such as water and sediment, tidal current data, and the reclamation were studied. The results show that the northern part of Hangzhou Bay along the Shanghai section showed a weak erosion trend, with a total erosion of 148.2 million m3 and an average annual erosion depth of 2.886 cm in recent 16 years. The Jinshan deep trough is the lowest area, and the terrain elevation dropped in front of Luchao Port. The study area suddenly deposited heavily in 2011. The highest scour happened between 2005 and 2008, and 2008 to 2011 was the highest siltation period. Although the Jinshan deep trough was affected by strong tide and encirclement projects, it contained strong erosion and strong deposition, but the overall performance was a slight erosion with a balanced erosion and deposition, and the erosion intensity was only 12.1% of that in the study area. There were many deep scour pits and steep slopes in Section # 2 and Section #3. The decrease of incoming water and sediment upstream made the north edge of Hangzhou Bay maintain the scouring situation. The supplement effect of tidal current-carrying sediment increased with the tide difference, and the scouring intensity was weakened. It is the equilibrium state formed by the synergy of various influencing factors that will last for a long time. Reclamation engineering is the main influencing factor of topography and erosion-deposition in the Jinshan deep trough. Some areas were blocked by reefs. The shoreline of the surrounding area was stable, but the nearshore scouring was strong, and the topographic change was more intense. Whether long-term scouring will bring risks such as foundation instability and bank collapse, the evolution of scouring and silting terrain characteristics, and the feedback relationship between beach and port development and construction need to be continuously observed and further studied.
17 Hydraulic loss distribution of pump-turbine operated in pump mode
based on entropy production method
2023(2):390-398.
Abstract:
Energy is irrevocably lost within the pump-turbine due to the activities of viscous forces near the wall. The conventional pressure drop method can not get exact details of the hydraulic loss within the machine's flow passageways. On the other hand, the entropy production method has obvious advantages in hydraulic loss assessment and it can accurately identify precise information on the position of irreversible losses.The composition and distribution of hydraulic loss under different flow rate operating points was explored for a prototype pump-turbine in pump mode using the entropy production theory. The entropy production method was verified to be reasonable and credible within a certain error range by comparison with the pressure drop method.The total entropy production and total hydraulic loss obtained by the method of differential pressure were consistent with the variation. With an increase in flow rate, the total entropy production decreased dramatically initially and then gradually increases. The entropy production rate caused by turbulence dissipation, direct dissipation, and wall shear stress exhibited the same variation pattern as the total entropy production. The major flow region's entropy production was predominantly induced by flow separation, backflow, and vortex creation. Entropy production was prominent in the main flow zone, with the entropy production rate caused by turbulence dissipation contributing the most to the total entropy production (50%-61%) and the entropy production rate caused by direct dissipation coming in second (37%-48%). The entropy production in the near-wall region primarily originated from the significant velocity gradient triggered by the wall shear stress, which could be roughly equivalent to friction loss and made a negligible 1%-2% contribution to total entropy production. Under various flow rate conditions, the hydraulic loss in the runner, guide vanes and stay vanes were dominant (67%-86%). Under low flow rate conditions, hydraulic loss in the draft tube was greater. However, under high flow rate conditions, hydraulic loss in spiral casing was greater. The distributions of the entropy production rate caused by turbulence dissipation and the entropy production rate caused by direct dissipation were highly consistent with the distribution of turbulent kinetic energy. But the entropy production rate caused by direct dissipation was mainly caused by strain rate, so it was closer to the main vortex regions, whereas the entropy production rate caused by turbulence dissipation was affected by turbulence intensity and had a wider distribution range in the flow field. High hydraulic loss under low flow conditions mainly came from the high-speed circulation in the vaneless region, vortices in the guide vane flow channels, and the flow separation within the elbow and the conical part of the draft tube. But the spiral casing’s hydraulic loss was much lesser. Hydraulic loss under the best efficiency operating point was small and mainly due to vortices in some stay vane flow channels and the blade wake. High hydraulic loss under high flow conditions mainly came from flow impact on the guide vanes, diffusion of unstable flow in stay vane flow channels, and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet; Whereas the draft tube’s hydraulic loss was rarely small.The total entropy production and total hydraulic loss decreased significantly and then slowly increased with an increase in flow rate. The entropy production rate caused by turbulence dissipation contributed the most to total entropy production (50%-61%), with direct dissipation coming in second (37%-48%), and wall shear stress coming in last (1%-2%). Under various flow rate conditions, the hydraulic loss in the runner, guide vanes and stay vanes were dominant (67%-86%). Hydraulic loss in the draft tube was larger at low flow rate conditions. While the hydraulic loss in spiral casing was greater under high flow rate conditions. The entropy production distributions were highly consistent with the distribution of turbulent kinetic energy. The entropy production rate caused by direct dissipation was closer to the main vortex regions, whereas turbulence dissipation had a wider distribution range in the flow field. The detailed location of hydraulic loss within the pump-turbine’s flow domain strongly depended on flow conditions. Under low flow conditions, hydraulic loss mainly came from the high-speed circulation in the vaneless region, vortices in the guide vane flow channels, and the flow separation within the elbow and the conical part of the draft tube. Under the best efficiency operating point, the hydraulic loss was small and mainly due to vortices in some stay vane flow channels and the blade wake. Under high flow conditions, hydraulic loss mainly came from flow impact on the guide vanes, diffusion of unstable flow in stay vane flow channels, and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet.
Energy is irrevocably lost within the pump-turbine due to the activities of viscous forces near the wall. The conventional pressure drop method can not get exact details of the hydraulic loss within the machine's flow passageways. On the other hand, the entropy production method has obvious advantages in hydraulic loss assessment and it can accurately identify precise information on the position of irreversible losses.The composition and distribution of hydraulic loss under different flow rate operating points was explored for a prototype pump-turbine in pump mode using the entropy production theory. The entropy production method was verified to be reasonable and credible within a certain error range by comparison with the pressure drop method.The total entropy production and total hydraulic loss obtained by the method of differential pressure were consistent with the variation. With an increase in flow rate, the total entropy production decreased dramatically initially and then gradually increases. The entropy production rate caused by turbulence dissipation, direct dissipation, and wall shear stress exhibited the same variation pattern as the total entropy production. The major flow region's entropy production was predominantly induced by flow separation, backflow, and vortex creation. Entropy production was prominent in the main flow zone, with the entropy production rate caused by turbulence dissipation contributing the most to the total entropy production (50%-61%) and the entropy production rate caused by direct dissipation coming in second (37%-48%). The entropy production in the near-wall region primarily originated from the significant velocity gradient triggered by the wall shear stress, which could be roughly equivalent to friction loss and made a negligible 1%-2% contribution to total entropy production. Under various flow rate conditions, the hydraulic loss in the runner, guide vanes and stay vanes were dominant (67%-86%). Under low flow rate conditions, hydraulic loss in the draft tube was greater. However, under high flow rate conditions, hydraulic loss in spiral casing was greater. The distributions of the entropy production rate caused by turbulence dissipation and the entropy production rate caused by direct dissipation were highly consistent with the distribution of turbulent kinetic energy. But the entropy production rate caused by direct dissipation was mainly caused by strain rate, so it was closer to the main vortex regions, whereas the entropy production rate caused by turbulence dissipation was affected by turbulence intensity and had a wider distribution range in the flow field. High hydraulic loss under low flow conditions mainly came from the high-speed circulation in the vaneless region, vortices in the guide vane flow channels, and the flow separation within the elbow and the conical part of the draft tube. But the spiral casing’s hydraulic loss was much lesser. Hydraulic loss under the best efficiency operating point was small and mainly due to vortices in some stay vane flow channels and the blade wake. High hydraulic loss under high flow conditions mainly came from flow impact on the guide vanes, diffusion of unstable flow in stay vane flow channels, and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet; Whereas the draft tube’s hydraulic loss was rarely small.The total entropy production and total hydraulic loss decreased significantly and then slowly increased with an increase in flow rate. The entropy production rate caused by turbulence dissipation contributed the most to total entropy production (50%-61%), with direct dissipation coming in second (37%-48%), and wall shear stress coming in last (1%-2%). Under various flow rate conditions, the hydraulic loss in the runner, guide vanes and stay vanes were dominant (67%-86%). Hydraulic loss in the draft tube was larger at low flow rate conditions. While the hydraulic loss in spiral casing was greater under high flow rate conditions. The entropy production distributions were highly consistent with the distribution of turbulent kinetic energy. The entropy production rate caused by direct dissipation was closer to the main vortex regions, whereas turbulence dissipation had a wider distribution range in the flow field. The detailed location of hydraulic loss within the pump-turbine’s flow domain strongly depended on flow conditions. Under low flow conditions, hydraulic loss mainly came from the high-speed circulation in the vaneless region, vortices in the guide vane flow channels, and the flow separation within the elbow and the conical part of the draft tube. Under the best efficiency operating point, the hydraulic loss was small and mainly due to vortices in some stay vane flow channels and the blade wake. Under high flow conditions, hydraulic loss mainly came from flow impact on the guide vanes, diffusion of unstable flow in stay vane flow channels, and the circumferentially spaced vortices and high-speed flows at the spiral casing inlet.
2023(2):399-406.
Abstract:
Underground film control irrigation is an irrigation technique that combines drip irrigation and film mulching technology by burying the drip irrigation pipe underground. The upper and lower layers of the control film are square impermeable polyethylene film, 25 cm x 40 cm, with a permeable substrate layer of filter cotton in the middle and the same size as the upper film. The drip head is designed for a flow rate of 2.0 L/h and a spacing of 80 cm. After the drip irrigation pipe is placed in the ground at 35 cm, the upper and lower films are placed at the top and bottom of the drip head respectively, and the symmetrical centres of the upper and lower films coincide with the drip head. The principle of underground film regulated wet irrigation is to use the water absorption force of soil water to make water and fertilizer stay and evenly distribute in the main root layer of the crop, which will help the root system to fully absorb and use water resources, thus reducing the loss of ineffective water and fertilizer, and play an important role in promoting the solution of the problem of water scarcity in agriculture in the North China Plain. This experiment was divided into a pit test and a field test. The pit test used 9 pits of 2 m×3.33 m, and the test factor was total irrigation control, with three treatments of total irrigation level: 4 500 m3 /hm2 (T1 ), 4 200 m3 /hm2 (T2) and 3 900 m3/hm2(T3 ). The plots were randomly arranged in nine test pits. The trial field was 44.2m wide from east to west and 64 m long from north to south, covering an area of about 4 acre. The three irrigation level treatments were 540 m3/hm2 (H), 450 m3/hm2 (M) and 360m3/hm2 (L), using an orthogonal test design with six treatments, each replicated three times, in a total of 18 plots, each 30 m long and 5 m wide, with a plot area of 150 m2 . The pit and field tests were conducted to investigate the water consumption, water intensity and modal coefficients of winter wheat at various stages of fertility under underground film-controlled wet irrigation, to investigate the effects of different water supply conditions on crop yield and water use efficiency, and finally to propose suitable irrigation quotas and irrigation systems for the crops studied under underground film-controlled wet irrigation technology. The results of the pit test showed that the water consumption and yield of winter wheat increased with the increase of irrigation water within a certain irrigation range, the crop yield was the highest in the high water treatment T1 , but the water use efficiency was the highest in the medium water treatment T2 . The analysis of variance showed that the treatment with the highest irrigation amount achieved the highest yield but did not reach a significant difference with the medium water treatment. In the field trials, the water use efficiency of SH , SM and SL with a lower irrigation limit of 55% field water holding capacity was generally higher than that of NH, NM and NL with a lower irrigation limit of 65% field water holding capacity. The NH treatment had the lowest water use efficiency of 2.33 kg/m3 and the SM treatment had the highest water use efficiency of 2.85 kg/m3 . This shows that the SM treatment was the better irrigation treatment under the experimental conditions. This is in line with the results of the pit test, which showed that a smaller irrigation rate can achieve higher water use efficiency. Under the SM treatment, the yield of winter wheat could reach 9 520.03 kg/hm2 and the water use efficiency could reach 2.85 kg/m3, which could provide a reasonable reference for exploring efficient and feasible irrigation methods for wheat cultivation in water-scarce areas.
Underground film control irrigation is an irrigation technique that combines drip irrigation and film mulching technology by burying the drip irrigation pipe underground. The upper and lower layers of the control film are square impermeable polyethylene film, 25 cm x 40 cm, with a permeable substrate layer of filter cotton in the middle and the same size as the upper film. The drip head is designed for a flow rate of 2.0 L/h and a spacing of 80 cm. After the drip irrigation pipe is placed in the ground at 35 cm, the upper and lower films are placed at the top and bottom of the drip head respectively, and the symmetrical centres of the upper and lower films coincide with the drip head. The principle of underground film regulated wet irrigation is to use the water absorption force of soil water to make water and fertilizer stay and evenly distribute in the main root layer of the crop, which will help the root system to fully absorb and use water resources, thus reducing the loss of ineffective water and fertilizer, and play an important role in promoting the solution of the problem of water scarcity in agriculture in the North China Plain. This experiment was divided into a pit test and a field test. The pit test used 9 pits of 2 m×3.33 m, and the test factor was total irrigation control, with three treatments of total irrigation level: 4 500 m3 /hm2 (T1 ), 4 200 m3 /hm2 (T2) and 3 900 m3/hm2(T3 ). The plots were randomly arranged in nine test pits. The trial field was 44.2m wide from east to west and 64 m long from north to south, covering an area of about 4 acre. The three irrigation level treatments were 540 m3/hm2 (H), 450 m3/hm2 (M) and 360m3/hm2 (L), using an orthogonal test design with six treatments, each replicated three times, in a total of 18 plots, each 30 m long and 5 m wide, with a plot area of 150 m2 . The pit and field tests were conducted to investigate the water consumption, water intensity and modal coefficients of winter wheat at various stages of fertility under underground film-controlled wet irrigation, to investigate the effects of different water supply conditions on crop yield and water use efficiency, and finally to propose suitable irrigation quotas and irrigation systems for the crops studied under underground film-controlled wet irrigation technology. The results of the pit test showed that the water consumption and yield of winter wheat increased with the increase of irrigation water within a certain irrigation range, the crop yield was the highest in the high water treatment T1 , but the water use efficiency was the highest in the medium water treatment T2 . The analysis of variance showed that the treatment with the highest irrigation amount achieved the highest yield but did not reach a significant difference with the medium water treatment. In the field trials, the water use efficiency of SH , SM and SL with a lower irrigation limit of 55% field water holding capacity was generally higher than that of NH, NM and NL with a lower irrigation limit of 65% field water holding capacity. The NH treatment had the lowest water use efficiency of 2.33 kg/m3 and the SM treatment had the highest water use efficiency of 2.85 kg/m3 . This shows that the SM treatment was the better irrigation treatment under the experimental conditions. This is in line with the results of the pit test, which showed that a smaller irrigation rate can achieve higher water use efficiency. Under the SM treatment, the yield of winter wheat could reach 9 520.03 kg/hm2 and the water use efficiency could reach 2.85 kg/m3, which could provide a reasonable reference for exploring efficient and feasible irrigation methods for wheat cultivation in water-scarce areas.
2023(2):407-416.
Abstract:
In the context of global change, extreme weather events are frequent and recurring, leading to a continuous increase in both affected areas and risks. Among them, droughts and floods have the most widespread impact and become one of the major meteorological disasters affecting agricultural production. According to the relevant statistical results, the area affected by agriculture in 2021 is as high as 1.17×107 hm2 in China. Hebei Province is located in the North China Plain of China which belongs to the temperate continental monsoon climate. Under the influence of global climate change, the temperature in Hebei Province has increased while precipitation has decreased, and the occurrence of droughts and floods has changed the growth and development of corn, which has had a huge impact on agricultural production and economic activities. Therefore, the spatial and temporal evolution characteristics of droughts and floods during maize reproductive period are greatly significant for the disaster for the prevention and mitigation of maize production.The research methods include SAPEI (Standardized Antecedent Precipitation Evapotranspiration Index) and ArcGIS to reflect the drought and flooding characteristics of maize in Hebei Province during the reproductive period. SAPEI can not only evaluate the single-day drought and flood conditions by precipitation time and amount, but also take into account the influence of soil moisture in the early stages, which is more comprehensive and has higher monitoring accuracy. And the map in ArcGIS will visualize the spatial evolution trend of SAPEI values. Conclusion: (1) The SAPEI in Hebei Province fluctuated from ?1.0 to 1.5 in the initial growth stage, rapid development stage, middle development stage and maturity stage of maize, and the fluctuation in the initial growth stage showed an upward trend from 1980 to 2020. (2) The overall spatial variation of SAPEI in Hebei Province was characterized by a wetting trend in the initial growth period and the rapid development period of maize. The trend of wetting was obvious during the initial growth period and rapid development period, while the eastern and southern meteorological stations showed a trend of drought during the middle and mature periods. (3) The multi-year average drought accumulation index Qdl was generally distributed in a pattern of high southeast and low northwest during the maize reproductive period in Hebei Province, that means the drought in the northwest was greater than in the southeast. The multi-year average flood accumulated index Qwl varied from 21.07 to 37.85, and the distribution pattern of annual average of accumulated index of drought and flood corresponded with the distribution pattern of precipitation in Hebei Province. The results will provide a theoretical basis for agricultural meteorological disaster risk assessment and disaster prevention and mitigation management decisions in Hebei Province.
In the context of global change, extreme weather events are frequent and recurring, leading to a continuous increase in both affected areas and risks. Among them, droughts and floods have the most widespread impact and become one of the major meteorological disasters affecting agricultural production. According to the relevant statistical results, the area affected by agriculture in 2021 is as high as 1.17×107 hm2 in China. Hebei Province is located in the North China Plain of China which belongs to the temperate continental monsoon climate. Under the influence of global climate change, the temperature in Hebei Province has increased while precipitation has decreased, and the occurrence of droughts and floods has changed the growth and development of corn, which has had a huge impact on agricultural production and economic activities. Therefore, the spatial and temporal evolution characteristics of droughts and floods during maize reproductive period are greatly significant for the disaster for the prevention and mitigation of maize production.The research methods include SAPEI (Standardized Antecedent Precipitation Evapotranspiration Index) and ArcGIS to reflect the drought and flooding characteristics of maize in Hebei Province during the reproductive period. SAPEI can not only evaluate the single-day drought and flood conditions by precipitation time and amount, but also take into account the influence of soil moisture in the early stages, which is more comprehensive and has higher monitoring accuracy. And the map in ArcGIS will visualize the spatial evolution trend of SAPEI values. Conclusion: (1) The SAPEI in Hebei Province fluctuated from ?1.0 to 1.5 in the initial growth stage, rapid development stage, middle development stage and maturity stage of maize, and the fluctuation in the initial growth stage showed an upward trend from 1980 to 2020. (2) The overall spatial variation of SAPEI in Hebei Province was characterized by a wetting trend in the initial growth period and the rapid development period of maize. The trend of wetting was obvious during the initial growth period and rapid development period, while the eastern and southern meteorological stations showed a trend of drought during the middle and mature periods. (3) The multi-year average drought accumulation index Qdl was generally distributed in a pattern of high southeast and low northwest during the maize reproductive period in Hebei Province, that means the drought in the northwest was greater than in the southeast. The multi-year average flood accumulated index Qwl varied from 21.07 to 37.85, and the distribution pattern of annual average of accumulated index of drought and flood corresponded with the distribution pattern of precipitation in Hebei Province. The results will provide a theoretical basis for agricultural meteorological disaster risk assessment and disaster prevention and mitigation management decisions in Hebei Province.
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