Volume 22,Issue 6,2024 Table of Contents
2024, 22(6):1041-1050.
Abstract:
Control gates play a crucial role in managing water levels and flow rates in water transfer canal systems. Arc gates are particularly favored due to their hydraulic efficiency and lightweight construction. Accurate flow rate calculation through these gates is essential for hydraulic simulation models and water management decisions. However, traditional empirical formulas face challenges due to the complex nature of arc gates, leading to the proposal of dimensionless analysis-based approaches. Combined with emerging technologies like artificial intelligence, these approaches improve adaptability and flow calculation accuracy. Yet, challenges persist, such as the need for representative data for parameter calibration and the impact of factors like equipment failures and dispatch instruction operations on monitoring data accuracy. In digital twin basin construction, accurately characterizing gate flow characteristics is crucial for effective water management. Therefore, identifying stable water delivery states and obtaining representative hydrological data are essential steps for analyzing gate flow coefficients and ensuring accurate flow rate calculations, ultimately supporting real-time monitoring and decision-making in water transfer projects. A stable water conveyance state identification method was introduced to accurately characterize stable water delivery states and select representative data for gate parameter calibration in digital twin basin construction. Leveraging dimensionless analysis, it contrasts flow rate calculation accuracy between monitoring and stable state data, validating the method's effectiveness. The aim is to provide scientific basis and technical support for precise gate flow capacity depiction and real-time gate state synchronization in water transfer projects. The methodology involves deriving discharge formulas, stable state identification, and dimensionless analysis. Threshold values for discharge coefficient change and cumulative change are determined by selecting stable state data from historical monitoring data. The dimensionless analysis method establishes a mathematical model for gate flow calculation. Additionally, the dimensionless analysis method establishes a mathematical model for gate flow calculation. Evaluation criteria, including R2,ERMS,EMA,EMAP, and ENS, assess method accuracy and performance. This comprehensive approach ensures reliable gate parameter calibration and enhances the robustness of water management decisions in open channel water transfer systems. The study examines three control gates from different South-to-North Water Transfers Project segments: Jinshui River Control Gate, Qi River Control Gate, and Qili River Control Gate. Using one year data from July 2022 to July 2023, at 2-hour intervals, stable state identification involved normality testing of comprehensive flow coefficient changes, revealing a bell-shaped distribution for three gates. Thresholds, based on a 95% confidence interval and a 4-hour cumulative change duration, identified stable water conveyance states. Specific thresholds were set for change values and cumulative changes at each gate, ensuring reliable data for water transfer management decisions. Stable state data showed greater representatives, utilizing stable state data identified through dimensionless analysis, the determination coefficients of the comprehensive flow coefficients for the Jinshui River Control Gate, Qi River Control Gate, and Qili Control River Control Gate were all improved compared to original monitoring data. Additionally, the root mean square error (ERMS) significantly decreased, with reductions of 43%, 47%, and 29%, respectively. Moreover, the accuracy of flow rate calculations using stable state data surpassed that of original monitoring data, reducing the average relative errors for the Jinshui River Control Gate, Qi River Control Gate, and Qili River Control Gate from 7.26%, 3.35%, and 3.80% to 6.55%, 3.22%, and 2.19%, respectively. Significant insights emerge when comparing results derived from original monitoring data and stable state-identified data. First, parameter calibration utilizing stable state-identified data enhances the determination coefficient of the comprehensive flow coefficient for all three gates, leading to notable reductions in root mean square error (ERMS). Second, the precision of flow calculations improves when using stable state data, resulting in decreased average relative errors in flow for each gate. Third, the proposed stable water conveyance state identification method enables the extraction of representative datasets for different scheduling conditions, and offering robust support for high-precision water transfer scheduling simulations and canal hydraulic capacity analyses. In conclusion, this method demonstrates promising applicability and potential for widespread adoption in practice.
Control gates play a crucial role in managing water levels and flow rates in water transfer canal systems. Arc gates are particularly favored due to their hydraulic efficiency and lightweight construction. Accurate flow rate calculation through these gates is essential for hydraulic simulation models and water management decisions. However, traditional empirical formulas face challenges due to the complex nature of arc gates, leading to the proposal of dimensionless analysis-based approaches. Combined with emerging technologies like artificial intelligence, these approaches improve adaptability and flow calculation accuracy. Yet, challenges persist, such as the need for representative data for parameter calibration and the impact of factors like equipment failures and dispatch instruction operations on monitoring data accuracy. In digital twin basin construction, accurately characterizing gate flow characteristics is crucial for effective water management. Therefore, identifying stable water delivery states and obtaining representative hydrological data are essential steps for analyzing gate flow coefficients and ensuring accurate flow rate calculations, ultimately supporting real-time monitoring and decision-making in water transfer projects. A stable water conveyance state identification method was introduced to accurately characterize stable water delivery states and select representative data for gate parameter calibration in digital twin basin construction. Leveraging dimensionless analysis, it contrasts flow rate calculation accuracy between monitoring and stable state data, validating the method's effectiveness. The aim is to provide scientific basis and technical support for precise gate flow capacity depiction and real-time gate state synchronization in water transfer projects. The methodology involves deriving discharge formulas, stable state identification, and dimensionless analysis. Threshold values for discharge coefficient change and cumulative change are determined by selecting stable state data from historical monitoring data. The dimensionless analysis method establishes a mathematical model for gate flow calculation. Additionally, the dimensionless analysis method establishes a mathematical model for gate flow calculation. Evaluation criteria, including R2,ERMS,EMA,EMAP, and ENS, assess method accuracy and performance. This comprehensive approach ensures reliable gate parameter calibration and enhances the robustness of water management decisions in open channel water transfer systems. The study examines three control gates from different South-to-North Water Transfers Project segments: Jinshui River Control Gate, Qi River Control Gate, and Qili River Control Gate. Using one year data from July 2022 to July 2023, at 2-hour intervals, stable state identification involved normality testing of comprehensive flow coefficient changes, revealing a bell-shaped distribution for three gates. Thresholds, based on a 95% confidence interval and a 4-hour cumulative change duration, identified stable water conveyance states. Specific thresholds were set for change values and cumulative changes at each gate, ensuring reliable data for water transfer management decisions. Stable state data showed greater representatives, utilizing stable state data identified through dimensionless analysis, the determination coefficients of the comprehensive flow coefficients for the Jinshui River Control Gate, Qi River Control Gate, and Qili Control River Control Gate were all improved compared to original monitoring data. Additionally, the root mean square error (ERMS) significantly decreased, with reductions of 43%, 47%, and 29%, respectively. Moreover, the accuracy of flow rate calculations using stable state data surpassed that of original monitoring data, reducing the average relative errors for the Jinshui River Control Gate, Qi River Control Gate, and Qili River Control Gate from 7.26%, 3.35%, and 3.80% to 6.55%, 3.22%, and 2.19%, respectively. Significant insights emerge when comparing results derived from original monitoring data and stable state-identified data. First, parameter calibration utilizing stable state-identified data enhances the determination coefficient of the comprehensive flow coefficient for all three gates, leading to notable reductions in root mean square error (ERMS). Second, the precision of flow calculations improves when using stable state data, resulting in decreased average relative errors in flow for each gate. Third, the proposed stable water conveyance state identification method enables the extraction of representative datasets for different scheduling conditions, and offering robust support for high-precision water transfer scheduling simulations and canal hydraulic capacity analyses. In conclusion, this method demonstrates promising applicability and potential for widespread adoption in practice.
2024, 22(6):1051-1062.
Abstract:
The local water price of the South-to-North Water Transfers Project was comparatively higher in some receiving areas. Driven by economic interests, the water users tended to illegally over-exploit the scarce local water resources, leading to a series of ecological and environmental problems in these regions. It is necessary to study the regulatory mechanisms of water use behavior under the dual constraints of government regulation and public supervision in order to reduce the illegal water use behavior in receiving areas. The research took local governments, water users, and the public as three main participants. An evolutionary game model was established to explore the strategic choices of the participants under different scenarios. A system dynamics model was constructed for simulating the evolution of strategies in the three-party game system and the impact of key parameters on the behavior strategies of the participants. The results showed that: (1) government regulation is affected by the cost of regulation, but only when the cost of strict regulation is controlled within a specific acceptable range could the government be more active in adopting the strategy of strict regulation. (2) Increasing government water fee subsidies and penalties could encourage users to choose external water. Water users were more sensitive to government subsidies than to penalties. (3) Supervision cost was a crucial factor influencing public participation in supervision and reporting. High supervision costs would lead the public to abandon participation in supervision and reporting. It is concluded that the government played a guiding and constraining role in the water use behavior. It was necessary to establish reasonable and effective regulatory and punitive mechanisms to reduce illegal water use while providing appropriate water use subsidies to increase the willingness of water users to use external water. Additionally, as an essential supplement to the government's regulatory power, the public requires an incentive mechanism to enhance their participation in supervision and reporting. Relevant policy recommendations were proposed for reducing illegal water use behavior by improving government regulatory mechanisms and methods, perfecting effective punitive systems, and promoting public supervision.
The local water price of the South-to-North Water Transfers Project was comparatively higher in some receiving areas. Driven by economic interests, the water users tended to illegally over-exploit the scarce local water resources, leading to a series of ecological and environmental problems in these regions. It is necessary to study the regulatory mechanisms of water use behavior under the dual constraints of government regulation and public supervision in order to reduce the illegal water use behavior in receiving areas. The research took local governments, water users, and the public as three main participants. An evolutionary game model was established to explore the strategic choices of the participants under different scenarios. A system dynamics model was constructed for simulating the evolution of strategies in the three-party game system and the impact of key parameters on the behavior strategies of the participants. The results showed that: (1) government regulation is affected by the cost of regulation, but only when the cost of strict regulation is controlled within a specific acceptable range could the government be more active in adopting the strategy of strict regulation. (2) Increasing government water fee subsidies and penalties could encourage users to choose external water. Water users were more sensitive to government subsidies than to penalties. (3) Supervision cost was a crucial factor influencing public participation in supervision and reporting. High supervision costs would lead the public to abandon participation in supervision and reporting. It is concluded that the government played a guiding and constraining role in the water use behavior. It was necessary to establish reasonable and effective regulatory and punitive mechanisms to reduce illegal water use while providing appropriate water use subsidies to increase the willingness of water users to use external water. Additionally, as an essential supplement to the government's regulatory power, the public requires an incentive mechanism to enhance their participation in supervision and reporting. Relevant policy recommendations were proposed for reducing illegal water use behavior by improving government regulatory mechanisms and methods, perfecting effective punitive systems, and promoting public supervision.
2024, 22(6):1063-1070.
Abstract:
The research focused on six counties and districts in Nanyang City, which is a vital part of the water source area for the Middle Route of the South-to-North Water Transfers Project. The study aimed to explore the adaptability between water ecology and economic development. The study aimed to assess the progress made in the region regarding the protection of water ecology and economic advancement. An evaluation index system for system adaptability was constructed based on the Pressure-State-Response (PSR) model using economic scale, economic structure, economic vitality, economic potential, economic response, water ecological status, water ecological pressure, and water ecological response. The Kaley weighting method was applied to distribute weights to various indicators. The system adaptability of the six counties and districts in Nanyang City from 2012 to 2022 was calculated, and an in-depth analysis of their spatiotemporal differences and changing trends was conducted. The study's findings were as follows: (1) The overall system adaptability of the six counties and districts in Nanyang City showed an upward trend during the research period, indicating positive progress in the region's water ecological conservation and economic development. (2) The changes in system adaptability among the counties exhibited strong convergence, closely related to agriculture being the primary pillar industry in these areas. (3) With the launch of the Middle Route Project for water transfer, the adaptability of the six counties and districts in Nanyang City has considerably improved. This advancement has not only enhanced water resource conditions but has also positively influenced the local ecological environment, agricultural and industrial development, and the optimization of the economic structure. The study revealed the interactive relationship between water ecological protection and sustainable economic development in the study area. It provided a scientific basis for formulating regional development strategies and water resource management policies. The research emphasized that regional development under the influence of large-scale hydraulic projects should consider the coordination between ecological conservation and economic growth to achieve proper sustainable development.
The research focused on six counties and districts in Nanyang City, which is a vital part of the water source area for the Middle Route of the South-to-North Water Transfers Project. The study aimed to explore the adaptability between water ecology and economic development. The study aimed to assess the progress made in the region regarding the protection of water ecology and economic advancement. An evaluation index system for system adaptability was constructed based on the Pressure-State-Response (PSR) model using economic scale, economic structure, economic vitality, economic potential, economic response, water ecological status, water ecological pressure, and water ecological response. The Kaley weighting method was applied to distribute weights to various indicators. The system adaptability of the six counties and districts in Nanyang City from 2012 to 2022 was calculated, and an in-depth analysis of their spatiotemporal differences and changing trends was conducted. The study's findings were as follows: (1) The overall system adaptability of the six counties and districts in Nanyang City showed an upward trend during the research period, indicating positive progress in the region's water ecological conservation and economic development. (2) The changes in system adaptability among the counties exhibited strong convergence, closely related to agriculture being the primary pillar industry in these areas. (3) With the launch of the Middle Route Project for water transfer, the adaptability of the six counties and districts in Nanyang City has considerably improved. This advancement has not only enhanced water resource conditions but has also positively influenced the local ecological environment, agricultural and industrial development, and the optimization of the economic structure. The study revealed the interactive relationship between water ecological protection and sustainable economic development in the study area. It provided a scientific basis for formulating regional development strategies and water resource management policies. The research emphasized that regional development under the influence of large-scale hydraulic projects should consider the coordination between ecological conservation and economic growth to achieve proper sustainable development.
2024, 22(6):1071-1079.
Abstract:
The shortage of water resources is an important constraint on regional development. The Yellow River basin belongs to the resource water shortage area. To solve the contradiction between the supply and demand of water resources in the water shortage cities in the lower reaches of the Yellow River and its economic and social development mismatch, a number of cross-basin water transfer project constructions have been proposed in China. Water resources regulation brings certain changes and challenges to the water resources management and allocation work of the recipient cities. In this context, it is important to achieve spatial balance and efficient use of water resources in the receiving zones. Liaocheng was chosen as the study area to quantitatively study the spatial equilibrium regulation of water resources carrying capacity by external water transfer from receiving cities. Firstly, the regulatory role of external water on the receiving area was fully considered. External water was introduced into the water resources sub-system as a single indicator to construct a regional water resources carrying capacity evaluation index system consisting of four sub-systems: water resources, economy, society, and ecology. The comprehensive weighting method was used to determine the weights of the indicators, and the fuzzy comprehensive evaluation method was used to calculate the status quo evaluation of the water resources carrying capacity of Liaocheng City from 2016 to 2022. Then, the barrier degree model was used to analyze the reasons for the formation of spatial differences in the water resources carrying capacity of Liaocheng City. The optimization strategy for the spatial balance of water resources in the districts and counties of Liaocheng City, which prioritized water conservation and efficiently utilized the external water and reclaimed water, was proposed in response to the results of the analysis of the influential factors. Finally, through the prediction of future water demand and available water supply, the supply and demand of water resources in Liaocheng City in 2035 under different water supply frequencies and the level of carrying capacity were evaluated. The results of the study showed that the water resources carrying capacity of Liaocheng City showed a spatial pattern of high in the east and low in the west. The spatial differences always existed and had an increasing trend. The difference between the ratings of the best and worst evaluated areas rose from 0.177 in 2016 to 0.323 in 2022. The water resources sub-systems were considered to be the main cause of these spatial differences. In addition, a number of factors in the other sub-systems were also important in influencing spatial balance. These factors included GDP per capita in the economic sub-system, urbanization rate in the social sub-system, ecosystem water use rate, and groundwater extraction coefficient in the ecological sub-system. Under the spatial regulation of water conservation control and external water transfer, the future water resources carrying capacity of all districts and counties increased to different degrees. The optimization effect was more obvious in districts and counties with lagging carrying capacity, with an average optimization rate of 25 percent in the year of levelling off, and an average optimization rate of 11 percent in districts with higher original assessment values. The spatial difference in the value of the carrying capacity was reduced from 0.314 to 0.151, and the spatial equilibrium effect of the water resources carrying capacity was remarkable. This paper combined the study of water resources carrying capacity and spatial equilibrium, evaluated the level of water resources carrying capacity of different incoming water frequencies under the balanced regulation of supply and demand, and demonstrated the optimization effect of spatial equilibrium of water resources based on the regulation of external water transfer. The results of the study can provide a reference basis for water resources management and control in similar cities with multiple water sources in the Yellow River basin.
The shortage of water resources is an important constraint on regional development. The Yellow River basin belongs to the resource water shortage area. To solve the contradiction between the supply and demand of water resources in the water shortage cities in the lower reaches of the Yellow River and its economic and social development mismatch, a number of cross-basin water transfer project constructions have been proposed in China. Water resources regulation brings certain changes and challenges to the water resources management and allocation work of the recipient cities. In this context, it is important to achieve spatial balance and efficient use of water resources in the receiving zones. Liaocheng was chosen as the study area to quantitatively study the spatial equilibrium regulation of water resources carrying capacity by external water transfer from receiving cities. Firstly, the regulatory role of external water on the receiving area was fully considered. External water was introduced into the water resources sub-system as a single indicator to construct a regional water resources carrying capacity evaluation index system consisting of four sub-systems: water resources, economy, society, and ecology. The comprehensive weighting method was used to determine the weights of the indicators, and the fuzzy comprehensive evaluation method was used to calculate the status quo evaluation of the water resources carrying capacity of Liaocheng City from 2016 to 2022. Then, the barrier degree model was used to analyze the reasons for the formation of spatial differences in the water resources carrying capacity of Liaocheng City. The optimization strategy for the spatial balance of water resources in the districts and counties of Liaocheng City, which prioritized water conservation and efficiently utilized the external water and reclaimed water, was proposed in response to the results of the analysis of the influential factors. Finally, through the prediction of future water demand and available water supply, the supply and demand of water resources in Liaocheng City in 2035 under different water supply frequencies and the level of carrying capacity were evaluated. The results of the study showed that the water resources carrying capacity of Liaocheng City showed a spatial pattern of high in the east and low in the west. The spatial differences always existed and had an increasing trend. The difference between the ratings of the best and worst evaluated areas rose from 0.177 in 2016 to 0.323 in 2022. The water resources sub-systems were considered to be the main cause of these spatial differences. In addition, a number of factors in the other sub-systems were also important in influencing spatial balance. These factors included GDP per capita in the economic sub-system, urbanization rate in the social sub-system, ecosystem water use rate, and groundwater extraction coefficient in the ecological sub-system. Under the spatial regulation of water conservation control and external water transfer, the future water resources carrying capacity of all districts and counties increased to different degrees. The optimization effect was more obvious in districts and counties with lagging carrying capacity, with an average optimization rate of 25 percent in the year of levelling off, and an average optimization rate of 11 percent in districts with higher original assessment values. The spatial difference in the value of the carrying capacity was reduced from 0.314 to 0.151, and the spatial equilibrium effect of the water resources carrying capacity was remarkable. This paper combined the study of water resources carrying capacity and spatial equilibrium, evaluated the level of water resources carrying capacity of different incoming water frequencies under the balanced regulation of supply and demand, and demonstrated the optimization effect of spatial equilibrium of water resources based on the regulation of external water transfer. The results of the study can provide a reference basis for water resources management and control in similar cities with multiple water sources in the Yellow River basin.
2024, 22(6):1091-1099.
Abstract:
The Western Route of South-to-North Water Transfers Project is a major strategic infrastructure in the national "four horizontal and three vertical" water resources allocation pattern, diverting water from the upper reaches of the Yangtze River into the Yellow River. In 2020, the Comparison and Demonstration of Planning Schemes for the Western Route of South-to-North Water Transfers Project was examined and approved by the General Institute of Water Planning of the Ministry of Water Resources, and following schemes were formulated: the upper route (UR), the upper and lower combination routes (ULR), and the lower route scheme (LR). The water diversion for the first phase of the Western Route Project is 8 billion m3. Two water transfer processes were set up in each scheme to study the influence on power generation of the cascade hydropower stations in Taohe River based on the ULR and the LR schemes. At the same time a maximum power generation scheduling model and a guaranteed output calculation model of cascade hydropower stations were constructed. The two-layer improved invasive weeds optimization (TIIWO) algorithm was used to solve the above models. Meanwhile, a method for assessing the expansion potential of the cascade hydropower stations was proposed. The results showed that the expansion potential of cascade hydropower stations in the Taohe River was greatly enhanced by the first phase of the Western Route Project. The installed scale of the cascade hydropower stations in the Taohe River was increased to 1,128.62 MW and 1,642.1 2 MW, respectively, by the ULR and the LR schemes in the uniform water diversion mode, and to 1,109.12 MW and 1,603.62 MW respectively, by the rich and poor water diversion mode without altering the installed utilization hours of the hydropower stations. Considering the expansion potential of the cascade hydropower stations in the first phase of the West Route Project, the power generation of the cascade hydropower stations in the Taohe River was increased by 105.13% and 194.87% by the ULR and the LR schemes, and by 101.89% and 192.90% respectively by the water diversion scheme of the rich and poor water diversion mode. Considering the expansion of the cascade hydropower stations in the first phase of the West Route Project, the guaranteed output of the cascade hydropower stations in the Tao River was increased by 171.30% and 319.96% through the ULR and the LR schemes, and by 113.69% and 225.39% through the rich and poor water diversion mode. The power generation efficiency of the cascade hydropower stations in the Taohe River is greatly increased by the water diversion of the Western Route Project, and the added value based on the LR scheme is approximately double that of the ULR scheme. Under the same water diversion scheme (the ULR scheme or the LR scheme) of the first phase of the Western Route Project, the uniform water diversion mode has comparatively more advantages than the rich and poor water diversion mode for improving the power generation efficiency of the cascade hydropower stations in the Taohe River.
The Western Route of South-to-North Water Transfers Project is a major strategic infrastructure in the national "four horizontal and three vertical" water resources allocation pattern, diverting water from the upper reaches of the Yangtze River into the Yellow River. In 2020, the Comparison and Demonstration of Planning Schemes for the Western Route of South-to-North Water Transfers Project was examined and approved by the General Institute of Water Planning of the Ministry of Water Resources, and following schemes were formulated: the upper route (UR), the upper and lower combination routes (ULR), and the lower route scheme (LR). The water diversion for the first phase of the Western Route Project is 8 billion m3. Two water transfer processes were set up in each scheme to study the influence on power generation of the cascade hydropower stations in Taohe River based on the ULR and the LR schemes. At the same time a maximum power generation scheduling model and a guaranteed output calculation model of cascade hydropower stations were constructed. The two-layer improved invasive weeds optimization (TIIWO) algorithm was used to solve the above models. Meanwhile, a method for assessing the expansion potential of the cascade hydropower stations was proposed. The results showed that the expansion potential of cascade hydropower stations in the Taohe River was greatly enhanced by the first phase of the Western Route Project. The installed scale of the cascade hydropower stations in the Taohe River was increased to 1,128.62 MW and 1,642.1 2 MW, respectively, by the ULR and the LR schemes in the uniform water diversion mode, and to 1,109.12 MW and 1,603.62 MW respectively, by the rich and poor water diversion mode without altering the installed utilization hours of the hydropower stations. Considering the expansion potential of the cascade hydropower stations in the first phase of the West Route Project, the power generation of the cascade hydropower stations in the Taohe River was increased by 105.13% and 194.87% by the ULR and the LR schemes, and by 101.89% and 192.90% respectively by the water diversion scheme of the rich and poor water diversion mode. Considering the expansion of the cascade hydropower stations in the first phase of the West Route Project, the guaranteed output of the cascade hydropower stations in the Tao River was increased by 171.30% and 319.96% through the ULR and the LR schemes, and by 113.69% and 225.39% through the rich and poor water diversion mode. The power generation efficiency of the cascade hydropower stations in the Taohe River is greatly increased by the water diversion of the Western Route Project, and the added value based on the LR scheme is approximately double that of the ULR scheme. Under the same water diversion scheme (the ULR scheme or the LR scheme) of the first phase of the Western Route Project, the uniform water diversion mode has comparatively more advantages than the rich and poor water diversion mode for improving the power generation efficiency of the cascade hydropower stations in the Taohe River.
2024, 22(6):1100-1109.
Abstract:
Precipitation in Qinling-Huaihe region not only varied greatly at both the inter- and intra-annual time scales, but also exhibited strong spatial variability due to complex and diverse landforms, along with unstable monsoon climate. The amount of precipitation amount as well as its variation showed strong regional characteristics over multi-year time scale, especially in case of multi-year annual precipitation. However, the current research adopted study area for the spatial-temporal characteristics analysis of precipitation in Qinling-Huaihe region which is identical to the administrative regions, or was directly bounded by Qinling Mountains or Huaihe River. Therefore, spatial variability of precipitation in Qinling-Huaihe region has not been fully reflected. Three types of precipitation indexes were used to divide the subregions of Qinling-Huaihe with step-wise clustering method. They were the multi-year average precipitation amount at different time scales, including multi-year average (daily, monthly, yearly and five years and 10 years) precipitation amount, the connection numbers of every two stations in terms of the abundant, normal, or dry states of annual precipitation at each site, and the connection number of every two stations based on the trends of annual precipitation change in adjacent years. Average and standard deviation analysis method was used to identify the abundant, normal, or dry states of annual precipitation at each site, assuming that each state had equal probability, and this method was also suitable to identify the trends of increase, decrease, and unchangeability, of annual precipitation change in adjacent years. The Qinling-Huaihe region can be divided into four subregions based on the pentad precipitation according to the indexes of multi-year average precipitation amount at different time scales, namely the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, the subregion north of Qinling Mountains, and the subregion south of the Qinling Mountains. Furthermore, with the connection number of stations based on the annual precipitation amount of abundant, normal, or dry states, the Qinling-Huaihe region could be divided into four subregions, namely the subregion between Yangtze and Huaihe with multi-year annual precipitation greater than 900 mm, the subregion between Huanghe and Huaihe with multi-year annual precipitation less than 900 mm, the subregion of surrounding area near the junction of Qinling Mountains and Huaihe River, and the subregion containing Loess Plateau Region at the north of Qinling Mountains and west section at the south of the Qinling Mountains. At the same time, with the connection number of stations based on the increase, decrease or unchangeability state of annual precipitation change in adjacent years, the Qinling-Huaihe region could be divided into three regions, namely the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, and the subregion containing the south and north regions of the Qinling Mountains. After combining the results of subregion with the three precipitation indexes, the Qinling-Huaihe region could be spatially divided into six regions, i.e., five major subregions and one transitional subregion, namely, the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, the subregion at the south of Qinling Mountains, the subregion of west section at the north of the Qinling Mountains and the loess Plateau Region at the north of Qinling Mountains, the subregion of Guanzhong Plain and its nearby regions, and the transitional region between Qinling and Huaihe River in north-south orientation. The discordancy measure test was carried out using the L-moment ratios approach, and the results showed that six subregions divided in this study could be considered as homogeneous regions.
Precipitation in Qinling-Huaihe region not only varied greatly at both the inter- and intra-annual time scales, but also exhibited strong spatial variability due to complex and diverse landforms, along with unstable monsoon climate. The amount of precipitation amount as well as its variation showed strong regional characteristics over multi-year time scale, especially in case of multi-year annual precipitation. However, the current research adopted study area for the spatial-temporal characteristics analysis of precipitation in Qinling-Huaihe region which is identical to the administrative regions, or was directly bounded by Qinling Mountains or Huaihe River. Therefore, spatial variability of precipitation in Qinling-Huaihe region has not been fully reflected. Three types of precipitation indexes were used to divide the subregions of Qinling-Huaihe with step-wise clustering method. They were the multi-year average precipitation amount at different time scales, including multi-year average (daily, monthly, yearly and five years and 10 years) precipitation amount, the connection numbers of every two stations in terms of the abundant, normal, or dry states of annual precipitation at each site, and the connection number of every two stations based on the trends of annual precipitation change in adjacent years. Average and standard deviation analysis method was used to identify the abundant, normal, or dry states of annual precipitation at each site, assuming that each state had equal probability, and this method was also suitable to identify the trends of increase, decrease, and unchangeability, of annual precipitation change in adjacent years. The Qinling-Huaihe region can be divided into four subregions based on the pentad precipitation according to the indexes of multi-year average precipitation amount at different time scales, namely the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, the subregion north of Qinling Mountains, and the subregion south of the Qinling Mountains. Furthermore, with the connection number of stations based on the annual precipitation amount of abundant, normal, or dry states, the Qinling-Huaihe region could be divided into four subregions, namely the subregion between Yangtze and Huaihe with multi-year annual precipitation greater than 900 mm, the subregion between Huanghe and Huaihe with multi-year annual precipitation less than 900 mm, the subregion of surrounding area near the junction of Qinling Mountains and Huaihe River, and the subregion containing Loess Plateau Region at the north of Qinling Mountains and west section at the south of the Qinling Mountains. At the same time, with the connection number of stations based on the increase, decrease or unchangeability state of annual precipitation change in adjacent years, the Qinling-Huaihe region could be divided into three regions, namely the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, and the subregion containing the south and north regions of the Qinling Mountains. After combining the results of subregion with the three precipitation indexes, the Qinling-Huaihe region could be spatially divided into six regions, i.e., five major subregions and one transitional subregion, namely, the subregion between Yangtze and Huaihe, the subregion between Huanghe and Huaihe, the subregion at the south of Qinling Mountains, the subregion of west section at the north of the Qinling Mountains and the loess Plateau Region at the north of Qinling Mountains, the subregion of Guanzhong Plain and its nearby regions, and the transitional region between Qinling and Huaihe River in north-south orientation. The discordancy measure test was carried out using the L-moment ratios approach, and the results showed that six subregions divided in this study could be considered as homogeneous regions.
2024, 22(6):1110-1118.
Abstract:
Danjiangkou Reservoir is the key hydraulic project for flood control in Han River basin, and the water source for the Middle Route of South-to-North Water Transfers Project. The design flood of Danjiangkou Reservoir is an important reference for reservoir operation and comprehensive utilization benefits, which was overestimated due to the short-recorded data series and the uncertainty of historical flood information in construction period. Besides, many reservoirs and water transfer projects have been built and put into operation in the upper Hanjaing River basin, which significantly altered the spatiotemporal distribution of streamflow. The Mann-Kendall test indicated a decrease trend for the annual maximum flood series from 1929 to 2023 with the statistical parameters all smaller than 0, which meant that the gauged flood data series was non-stationary. Thus, how to quantitatively estimate design flood of Danjiangkou in operation period has become an urgent scientific and technological challenge. The generalized additive models for location, scale and shape (GAMLSS) model was widely applied in non-stationary flood frequency analysis, which was based on the principle of time-varying moment method and assumed that the location, scale, and shape parameters of probability density function would follow certain mathematical relationship with corresponding covariates. GAMLSS-based time-varying P-Ⅲ distribution method was applied for non-stationary flood frequency analysis for Danjiangkou Reservoir in operation period. The selection of covariates would significantly determine the effectiveness of time-varying model. The reservoir index (IR) was defined with the hydrological characteristics and reservoir storage capacity, which presented superiority in design flood investigation. Meanwhile, diversion index (ID) was first proposed to quantify the influence of water transfer projects with mathematical definition inspired by IR. The IR and ID were selected as covariates to construct the time-varying P-Ⅲ distribution model, and the maximum likelihood estimation method was used to estimate parameters for the single covariate (IR) and the double covariates (IR & ID). Based on the annual maximum flood data series with 441-year historical investigation period (from1583 to 2023), the design flood for Danjiangkou Reservoir in operation period was estimated and compared with original design values. The main conclusions were summarized as follows:(1) The IR and ID were selected as covariates which could conform to the hydrological variation laws objectively. The fitting results of time-varying P-Ⅲ distribution with both covariates could reflect the flood series decreasing trend caused by upstream hydraulic structures. However, there was no significant difference for the time-varying P-Ⅲ distribution fitted with double covariates (IR & ID) or single covariate (R). The influence mainly attributed to upstream reservoirs rather than water transfer projects, since the ID only slightly reduced about 2% design floods in Danjiangkou Reservoir.(2) The estimated 1000-year design flood of Danjiangkou in operation period has been significantly reduced. The flood peak and 7-day flood volumes were 45,000 m3/s and 12.3 billion m3, which were both reduced about 31% compared with the original designed values in construction period. The original designed flood of Danjiangkou Reservoir was overestimated which results in more discarding water and lower refill rate in flood season. Since the estimated design flood of reservoir in operation period has significantly reduced, the reservoir operation water level could be risen with the condition of flood prevention standard unchanged, which could not only generate more hydropower, but also increase the water resource utilization rate as well as reservoir refill rate.
Danjiangkou Reservoir is the key hydraulic project for flood control in Han River basin, and the water source for the Middle Route of South-to-North Water Transfers Project. The design flood of Danjiangkou Reservoir is an important reference for reservoir operation and comprehensive utilization benefits, which was overestimated due to the short-recorded data series and the uncertainty of historical flood information in construction period. Besides, many reservoirs and water transfer projects have been built and put into operation in the upper Hanjaing River basin, which significantly altered the spatiotemporal distribution of streamflow. The Mann-Kendall test indicated a decrease trend for the annual maximum flood series from 1929 to 2023 with the statistical parameters all smaller than 0, which meant that the gauged flood data series was non-stationary. Thus, how to quantitatively estimate design flood of Danjiangkou in operation period has become an urgent scientific and technological challenge. The generalized additive models for location, scale and shape (GAMLSS) model was widely applied in non-stationary flood frequency analysis, which was based on the principle of time-varying moment method and assumed that the location, scale, and shape parameters of probability density function would follow certain mathematical relationship with corresponding covariates. GAMLSS-based time-varying P-Ⅲ distribution method was applied for non-stationary flood frequency analysis for Danjiangkou Reservoir in operation period. The selection of covariates would significantly determine the effectiveness of time-varying model. The reservoir index (IR) was defined with the hydrological characteristics and reservoir storage capacity, which presented superiority in design flood investigation. Meanwhile, diversion index (ID) was first proposed to quantify the influence of water transfer projects with mathematical definition inspired by IR. The IR and ID were selected as covariates to construct the time-varying P-Ⅲ distribution model, and the maximum likelihood estimation method was used to estimate parameters for the single covariate (IR) and the double covariates (IR & ID). Based on the annual maximum flood data series with 441-year historical investigation period (from1583 to 2023), the design flood for Danjiangkou Reservoir in operation period was estimated and compared with original design values. The main conclusions were summarized as follows:(1) The IR and ID were selected as covariates which could conform to the hydrological variation laws objectively. The fitting results of time-varying P-Ⅲ distribution with both covariates could reflect the flood series decreasing trend caused by upstream hydraulic structures. However, there was no significant difference for the time-varying P-Ⅲ distribution fitted with double covariates (IR & ID) or single covariate (R). The influence mainly attributed to upstream reservoirs rather than water transfer projects, since the ID only slightly reduced about 2% design floods in Danjiangkou Reservoir.(2) The estimated 1000-year design flood of Danjiangkou in operation period has been significantly reduced. The flood peak and 7-day flood volumes were 45,000 m3/s and 12.3 billion m3, which were both reduced about 31% compared with the original designed values in construction period. The original designed flood of Danjiangkou Reservoir was overestimated which results in more discarding water and lower refill rate in flood season. Since the estimated design flood of reservoir in operation period has significantly reduced, the reservoir operation water level could be risen with the condition of flood prevention standard unchanged, which could not only generate more hydropower, but also increase the water resource utilization rate as well as reservoir refill rate.
2024, 22(6):1119-1128.
Abstract:
It is of great significance to accurately analyze the influence of human factors on the ecological base flow guarantee of watershed and to develop the quantitative method of ecological base flow guarantee degree. Soil and water assessment tool (SWAT) was employed to simulate river flows, and to compute the ecological base flow guarantee index (IEBFG) for assessing the extent of ecological base flow protection. The analysis was underpinned by the stochastic impacts by regression on population affluence and technology (STIRPAT) model, thus, evaluating the effects of population size, economic development level, technological development level, urbanization level and water consumption level of various industries. In the methodological approach, the SWAT model was utilized to simulate the river runoff within the Qin River basin. While the subsequent calculations of the IEBFG provided a quantifiable measure of the ecological base flow's security. Additionally, the STIRPAT model facilitated an in-depth analysis of the driving factors affecting ecological base flows, categorizing them into demographic, economic, technological, and urban metrics. Results revealed a N-shaped increase trend in the ecological base flow guarantee level within the basin on an annual scale, with a notable decrease in the year 2015, attributed to severe drought conditions. Monthly variations were found to correspond with the seasonal cycles of floods and dry periods within the Qin River. An improvement in ecological base flow guarantee levels were observed from the upstream to downstream sections of the basin. Mainstream sub-basins demonstrated superior ecological base flow protection compared to their tributary counterparts. More than half of the regions within the Qin River basin were classified under "poor" or "relatively poor" categories concerning ecological base flow protection, with an exception in the year 2014, which showed a "normal" status. Among the studied factors, urbanization exhibited the most significant impact on ecological base flow security, followed by technological development, on the other hand the population size and economic growth had less pronounced effects. It is concluded that the urbanization level along with agricultural, industrial and domestic water use has the greatest influence on the ecological base flow guarantee degree, followed by the technological development level, and the population size and economic development level which have relatively little influence on the ecological base flow guarantee degree in the Qinhe River basin. The findings underscore the necessity for integrated approaches in river basin management to balance developmental and ecological needs. The research results provide a basis for ecological base flow protection and coordinated development of the Qinhe River basin, and also provide a way to calculate and evaluate the ecological base flow guarantee degree of other river basins.
It is of great significance to accurately analyze the influence of human factors on the ecological base flow guarantee of watershed and to develop the quantitative method of ecological base flow guarantee degree. Soil and water assessment tool (SWAT) was employed to simulate river flows, and to compute the ecological base flow guarantee index (IEBFG) for assessing the extent of ecological base flow protection. The analysis was underpinned by the stochastic impacts by regression on population affluence and technology (STIRPAT) model, thus, evaluating the effects of population size, economic development level, technological development level, urbanization level and water consumption level of various industries. In the methodological approach, the SWAT model was utilized to simulate the river runoff within the Qin River basin. While the subsequent calculations of the IEBFG provided a quantifiable measure of the ecological base flow's security. Additionally, the STIRPAT model facilitated an in-depth analysis of the driving factors affecting ecological base flows, categorizing them into demographic, economic, technological, and urban metrics. Results revealed a N-shaped increase trend in the ecological base flow guarantee level within the basin on an annual scale, with a notable decrease in the year 2015, attributed to severe drought conditions. Monthly variations were found to correspond with the seasonal cycles of floods and dry periods within the Qin River. An improvement in ecological base flow guarantee levels were observed from the upstream to downstream sections of the basin. Mainstream sub-basins demonstrated superior ecological base flow protection compared to their tributary counterparts. More than half of the regions within the Qin River basin were classified under "poor" or "relatively poor" categories concerning ecological base flow protection, with an exception in the year 2014, which showed a "normal" status. Among the studied factors, urbanization exhibited the most significant impact on ecological base flow security, followed by technological development, on the other hand the population size and economic growth had less pronounced effects. It is concluded that the urbanization level along with agricultural, industrial and domestic water use has the greatest influence on the ecological base flow guarantee degree, followed by the technological development level, and the population size and economic development level which have relatively little influence on the ecological base flow guarantee degree in the Qinhe River basin. The findings underscore the necessity for integrated approaches in river basin management to balance developmental and ecological needs. The research results provide a basis for ecological base flow protection and coordinated development of the Qinhe River basin, and also provide a way to calculate and evaluate the ecological base flow guarantee degree of other river basins.
2024, 22(6):1129-1136.
Abstract:
The construction of cascade reservoirs is a trend and inevitable way for efficient utilization of water resources in the basin. At the same time, the construction and operation of reservoirs have led to the redistribution of non-biological elements such as water and sediment, resulting in changes in the structure and function of river ecosystems. Multiple reservoirs often produce various effects such as summation, synergy, and antagonism along with a complex ecological impact especially in cascade development. The impact of adding new reservoirs has become a key factor in the planning of river cascade development. The river ecosystem is influenced by multiple factors such as water conservancy engineering conditions, climate change, land use, and water intake, which raises difficulty for scientifically quantitfying the role of newly added reservoirs. Xiaolangdi Reservoir is a critical project for controlling the water and sediment processes in the lower reaches of the Yellow River, and since its scheduling, it has jointly worked in conjunction with Sanmenxia Reservoir. Since the scheduling of the Xiaolangdi Reservoir, there have been significant changes in the water and sediment processes in the lower reaches of the Yellow River. To quantify the role played by the Xiaolangdi Reservoir in these changes, the changes in water and sediment conditions in the lower reaches of the Yellow River during the single reservoir period of Sanmenxia Reservoir and the dual reservoir period of Sanmenxia Reservoir and Xiaolangdi Reservoir are quantified. The impact of Xiaolangdi Reservoir is quantitatively evaluated through methods such as trend testing, abrupt change point analysis, and numerical simulation. The results show that the single reservoir period compared with the joint scheduling of Xiaolangdi Reservoir and Sanmenxia Reservoir shortened the duration of low flow events in the lower reaches of the Yellow River, prolonged the duration of high flow events, and caused continuous erosion of the river channel. Compared with the single reservoir period, at the three cross-secions of Huayuankou, Gaocun, and Lijin during the dual reservoir period: the average number of days below the warning flow decreased by more than 90%, and the average number of days above3000 m3/s increased by more than 85%; the duration of high flow pulses during the critical period of fish reproduction (April to June) increased by more than 50%; the annual average sediment yield and average sediment concentration have decreased by more than 70%; the main groove of the cross-sections was deepened and the elevation was reduced.
The role played by Xiaolangdi Reservoir was consistent with the characteristics of changes in water and sediment processes. The scheduling of Xiaolangdi Reservoir increased the number of days with a flow greater than
3000 m3/s by 86%, and reduced the number of days with a flow less than 150 m3/s by 57%. Xiaolangdi Reservoir annually retained an average of 1.50×108m3 of sediment. The sudden change time of sediment concentration at Huayuankou cross-secion is consistent with the operation time of Xiaolangdi Reservoir. Without Xiaolangdi Reservoir, the the lower reaches of the Yellow River would have shifted from an average annual erosion of 130 million t to an average annual sedimentation of 28 million t. After the joint scheduling of Xiaolangdi Reservoir and Sanmenxia Reservoir, the ecological base flow guarantee rate and habitat stability in the lower reaches of the Yellow River have been improved, and the diversity of freshwater fish has been effectively restored.
The construction of cascade reservoirs is a trend and inevitable way for efficient utilization of water resources in the basin. At the same time, the construction and operation of reservoirs have led to the redistribution of non-biological elements such as water and sediment, resulting in changes in the structure and function of river ecosystems. Multiple reservoirs often produce various effects such as summation, synergy, and antagonism along with a complex ecological impact especially in cascade development. The impact of adding new reservoirs has become a key factor in the planning of river cascade development. The river ecosystem is influenced by multiple factors such as water conservancy engineering conditions, climate change, land use, and water intake, which raises difficulty for scientifically quantitfying the role of newly added reservoirs. Xiaolangdi Reservoir is a critical project for controlling the water and sediment processes in the lower reaches of the Yellow River, and since its scheduling, it has jointly worked in conjunction with Sanmenxia Reservoir. Since the scheduling of the Xiaolangdi Reservoir, there have been significant changes in the water and sediment processes in the lower reaches of the Yellow River. To quantify the role played by the Xiaolangdi Reservoir in these changes, the changes in water and sediment conditions in the lower reaches of the Yellow River during the single reservoir period of Sanmenxia Reservoir and the dual reservoir period of Sanmenxia Reservoir and Xiaolangdi Reservoir are quantified. The impact of Xiaolangdi Reservoir is quantitatively evaluated through methods such as trend testing, abrupt change point analysis, and numerical simulation. The results show that the single reservoir period compared with the joint scheduling of Xiaolangdi Reservoir and Sanmenxia Reservoir shortened the duration of low flow events in the lower reaches of the Yellow River, prolonged the duration of high flow events, and caused continuous erosion of the river channel. Compared with the single reservoir period, at the three cross-secions of Huayuankou, Gaocun, and Lijin during the dual reservoir period: the average number of days below the warning flow decreased by more than 90%, and the average number of days above
2024, 22(6):1137-1147.
Abstract:
Since the impoundment of the Three Gorges Reservoir, the nutrient enrichment status of tributary water bodies in the reservoir area significantly deteriorated, transitioning from riverine to lacustrine ecosystems. The reservoir impoundment resulted in reduced flow velocities of tributary water bodies, leading to increased water transparency and nutrient concentrations conducive to the proliferation of increasing in chlorophyll-a mass concentration. Consequently, typical tributaries such as the Xiangxi River in the Three Gorges Reservoir area experienced frequent outbreaks of increasing in chlorophyll-a mass concentration. These recurrent increase in chlorophyll-a mass concentration events not only degraded water quality and aquatic ecosystems but also posed constraints on the sustainable development of society.Correlation analysis, principal component analysis, and grey relational analysis were utilized to identify and validate significant contributors to increase in chlorophyll-a mass concentration. Subsequently, cross-correlation analysis and the Almon distributed lag model were employed to ascertain factors among the major contributors exhibiting time lags and to determine the optimal lag time. Building upon this analysis, an Almon-BP neural network model was developed to forecast the trends of chlorophyll-a mass concentration.The major contributing factors to increase in chlorophyll-a mass concentration at the Xiangxi River Xiakou included dissolved oxygen, pH, air temperature, solar radiation, wind speed, wind direction, turbidity, rainfall, Three Gorges water level difference, and water temperature. Similarly, significant factors at the Pingyikou of the Xiangxi River included dissolved oxygen, pH, air temperature, solar radiation, wind speed, wind direction, turbidity, rainfall, Three Gorges water level difference, water temperature, redox potential, and Three Gorges water level. Among environmental factors at the Xiakou of the Xiangxi River, air temperature, wind speed, solar radiation, pH, and dissolved oxygen exhibited lag effects on increased in chlorophyll-a mass concentration, with optimal lag times ranging from 2 to 7 days, while other environmental factors did not display time lags. Conversely, at the Pingyikou of the Xiangxi River, factors such as water temperature, air temperature, wind speed, rainfall, solar radiation, turbidity, pH, dissolved oxygen, Three Gorges water level difference, redox potential, and Three Gorges water level exhibited lageffects on chlorophyll-a mass concentration, with optimal lag times ranging from 2 to 10 days. Wind direction did not show lag effects.Comparative analysis of three prediction models the BP neural network model considering all environmental factors, the BP neural network model considering only major contributing factors, and the Almon-BP neural network model considering the optimal lag time of major contributors revealed that the Almon-BP neural network model outperformed the corresponding BP models in predicting chlorophyll-a mass concentration in the Xiangxi River, with lower prediction errors. This underscored the efficacy of the Almon-BP neural network model in enhancing the accuracy of chlorophyll-a mass concentration prediction, which was crucial for early warning and mitigating harmful algal bloom occurrences.
Since the impoundment of the Three Gorges Reservoir, the nutrient enrichment status of tributary water bodies in the reservoir area significantly deteriorated, transitioning from riverine to lacustrine ecosystems. The reservoir impoundment resulted in reduced flow velocities of tributary water bodies, leading to increased water transparency and nutrient concentrations conducive to the proliferation of increasing in chlorophyll-a mass concentration. Consequently, typical tributaries such as the Xiangxi River in the Three Gorges Reservoir area experienced frequent outbreaks of increasing in chlorophyll-a mass concentration. These recurrent increase in chlorophyll-a mass concentration events not only degraded water quality and aquatic ecosystems but also posed constraints on the sustainable development of society.Correlation analysis, principal component analysis, and grey relational analysis were utilized to identify and validate significant contributors to increase in chlorophyll-a mass concentration. Subsequently, cross-correlation analysis and the Almon distributed lag model were employed to ascertain factors among the major contributors exhibiting time lags and to determine the optimal lag time. Building upon this analysis, an Almon-BP neural network model was developed to forecast the trends of chlorophyll-a mass concentration.The major contributing factors to increase in chlorophyll-a mass concentration at the Xiangxi River Xiakou included dissolved oxygen, pH, air temperature, solar radiation, wind speed, wind direction, turbidity, rainfall, Three Gorges water level difference, and water temperature. Similarly, significant factors at the Pingyikou of the Xiangxi River included dissolved oxygen, pH, air temperature, solar radiation, wind speed, wind direction, turbidity, rainfall, Three Gorges water level difference, water temperature, redox potential, and Three Gorges water level. Among environmental factors at the Xiakou of the Xiangxi River, air temperature, wind speed, solar radiation, pH, and dissolved oxygen exhibited lag effects on increased in chlorophyll-a mass concentration, with optimal lag times ranging from 2 to 7 days, while other environmental factors did not display time lags. Conversely, at the Pingyikou of the Xiangxi River, factors such as water temperature, air temperature, wind speed, rainfall, solar radiation, turbidity, pH, dissolved oxygen, Three Gorges water level difference, redox potential, and Three Gorges water level exhibited lageffects on chlorophyll-a mass concentration, with optimal lag times ranging from 2 to 10 days. Wind direction did not show lag effects.Comparative analysis of three prediction models the BP neural network model considering all environmental factors, the BP neural network model considering only major contributing factors, and the Almon-BP neural network model considering the optimal lag time of major contributors revealed that the Almon-BP neural network model outperformed the corresponding BP models in predicting chlorophyll-a mass concentration in the Xiangxi River, with lower prediction errors. This underscored the efficacy of the Almon-BP neural network model in enhancing the accuracy of chlorophyll-a mass concentration prediction, which was crucial for early warning and mitigating harmful algal bloom occurrences.
2024, 22(6):1148-1159.
Abstract:
Degradation coefficients are important parameters in water quality models and are commonly used to describe pollutant contents attenuation rate. The research on degradation coefficients primarily focuses on large rivers and plain river networks. There are few quantitative studies on the variability of degradation coefficients in mountain rivers and the calculation errors caused by excessively low pollutant contents. The Dan River, part of the Qin River system in the Yellow River basin, is mountainous and, its watershed is dotted with numerous villages and towns, and the disordered discharge of agricultural and domestic sewage has caused severe non-Point source pollution, creating an urgent need for research on water quality degradation coefficients in mountain rivers. To elucidate the variability of pollutant degradation coefficients in mountain rivers, in-situ water mass tracking was used for field monitoring of the Niucun section of the Dan River to elucidate the variability of pollutant degradation coefficients in mountain rivers. Based on this, the "two-Point method" and "multi-Point method" derived from the first-order reaction kinetics model were used to calculate the degradation coefficients of different pollutants. A one-dimensional advection-diffusion model was used to calculate pollutant prediction values, and the relative error of prediction values was quantitatively studied to evaluate the errors in the calculation process of degradation coefficients. To analyze the impact mechanisms of degradation coefficients in the environment, and to explore the differences in the response mechanisms of mountain river water quality degradation coefficients to different environmental factors compared to plain areas regression and correlation analyses were conducted to understand the relationship between the degradation coefficients and environmental factors in the study area. The results showed that the degradation coefficients calculated for ammonia nitrogen (NH+4-N) in the Niucun section of the Dan River were (0.684±0.486) d?1, for total nitrogen (TN) were (0.518±0.411 d?1, for nitrate nitrogen (NO-3-N) were (0.444±0.280) d?1, for nitrite nitrogen (NO-2-N) were (0.628±0.350) d?1, for chemical oxygen demand (COD) were (0.482±0.343) d?1, for five-day biochemical oxygen demand (BOD5) were (0.491±0.430) d?1, for total phosphorus (TP) were (0.905±0.461) d?1, and for orthophosphate (PO3-4-P) were (1.226±0.612) d?1. Threshold analysis revealed that when the mass concentration of NH+4-N ≥ 0.6 mg/L, and the mass concentrations of TP and PO3-4-P ≥ 0.04 mg/L, the prediction value mass concentration calculation error tends to slow down and remains within a reasonable range. Correlation and regression analyses showed that the main influencing factors for the degradation coefficients were water temperature, potential of hydrogen (pH), oxidation-reduction potential (ORP), and dissolved oxygen (DO). By analyzing the response relationship of hydrological factors to degradation coefficients, it was found that the contact area between the pollutants and the riverbank increased when the flow rate was less than 2.726 m/s, causing the TP degradation coefficient to increase with flow rate. When the flow speed exceeded 0.459 m/s, the residence time of the pollutants on the river surface decreased, causing the TP degradation coefficient to decrease with increasing flow speed. It is concluded that the greater vertical gradient in mountainous areas compresses the horizontal ecological characteristics of rivers, causing the ecological processes in mountain rivers to respond more intensely to hydrological conditions and temperature changes than in flat areas. Compared to plain areas, the water quality degradation coefficients in mountain rivers are higher. Through quantitative analysis of the relative error of prediction values, it was found that below a certain threshold mass concentration, the first-order kinetics model could not simulate molecular diffusion effectively, leading to increased error in the calculation of degradation coefficients. Above a certain mass concentration threshold, the error fluctuations in the calculation results of the degradation coefficients by the first-order kinetics model tended to stabilize and were acceptable. In the Dan River basin, the degradation effect of total phosphorus (TP) was best under moderate flow speeds. The research results are of great significance for the water quality management of the Dan River, providing a reference for understanding the degradation process of pollutants in mountainous rivers and the ecological regulation of dams and gates.
Degradation coefficients are important parameters in water quality models and are commonly used to describe pollutant contents attenuation rate. The research on degradation coefficients primarily focuses on large rivers and plain river networks. There are few quantitative studies on the variability of degradation coefficients in mountain rivers and the calculation errors caused by excessively low pollutant contents. The Dan River, part of the Qin River system in the Yellow River basin, is mountainous and, its watershed is dotted with numerous villages and towns, and the disordered discharge of agricultural and domestic sewage has caused severe non-Point source pollution, creating an urgent need for research on water quality degradation coefficients in mountain rivers. To elucidate the variability of pollutant degradation coefficients in mountain rivers, in-situ water mass tracking was used for field monitoring of the Niucun section of the Dan River to elucidate the variability of pollutant degradation coefficients in mountain rivers. Based on this, the "two-Point method" and "multi-Point method" derived from the first-order reaction kinetics model were used to calculate the degradation coefficients of different pollutants. A one-dimensional advection-diffusion model was used to calculate pollutant prediction values, and the relative error of prediction values was quantitatively studied to evaluate the errors in the calculation process of degradation coefficients. To analyze the impact mechanisms of degradation coefficients in the environment, and to explore the differences in the response mechanisms of mountain river water quality degradation coefficients to different environmental factors compared to plain areas regression and correlation analyses were conducted to understand the relationship between the degradation coefficients and environmental factors in the study area. The results showed that the degradation coefficients calculated for ammonia nitrogen (NH+4-N) in the Niucun section of the Dan River were (0.684±0.486) d?1, for total nitrogen (TN) were (0.518±0.411 d?1, for nitrate nitrogen (NO-3-N) were (0.444±0.280) d?1, for nitrite nitrogen (NO-2-N) were (0.628±0.350) d?1, for chemical oxygen demand (COD) were (0.482±0.343) d?1, for five-day biochemical oxygen demand (BOD5) were (0.491±0.430) d?1, for total phosphorus (TP) were (0.905±0.461) d?1, and for orthophosphate (PO3-4-P) were (1.226±0.612) d?1. Threshold analysis revealed that when the mass concentration of NH+4-N ≥ 0.6 mg/L, and the mass concentrations of TP and PO3-4-P ≥ 0.04 mg/L, the prediction value mass concentration calculation error tends to slow down and remains within a reasonable range. Correlation and regression analyses showed that the main influencing factors for the degradation coefficients were water temperature, potential of hydrogen (pH), oxidation-reduction potential (ORP), and dissolved oxygen (DO). By analyzing the response relationship of hydrological factors to degradation coefficients, it was found that the contact area between the pollutants and the riverbank increased when the flow rate was less than 2.726 m/s, causing the TP degradation coefficient to increase with flow rate. When the flow speed exceeded 0.459 m/s, the residence time of the pollutants on the river surface decreased, causing the TP degradation coefficient to decrease with increasing flow speed. It is concluded that the greater vertical gradient in mountainous areas compresses the horizontal ecological characteristics of rivers, causing the ecological processes in mountain rivers to respond more intensely to hydrological conditions and temperature changes than in flat areas. Compared to plain areas, the water quality degradation coefficients in mountain rivers are higher. Through quantitative analysis of the relative error of prediction values, it was found that below a certain threshold mass concentration, the first-order kinetics model could not simulate molecular diffusion effectively, leading to increased error in the calculation of degradation coefficients. Above a certain mass concentration threshold, the error fluctuations in the calculation results of the degradation coefficients by the first-order kinetics model tended to stabilize and were acceptable. In the Dan River basin, the degradation effect of total phosphorus (TP) was best under moderate flow speeds. The research results are of great significance for the water quality management of the Dan River, providing a reference for understanding the degradation process of pollutants in mountainous rivers and the ecological regulation of dams and gates.
2024, 22(6):1160-1172.
Abstract:
Coastal reservoirs often face water salinization problems, which not only affect their function but also cause severe obstacles to the regional ecosystem and substantial waste of manpower and material resources. To improve the utilization efficiency of reservoirs, several researches have suggested the use of diffuse boundary layer at the sediment-water interface of the water body, as a reaction to hot zone of hydrogeochemical action, which is a key area for controlling the degree of salinization and the type of water quality of the water body. Dissolved oxygen, an important indicator in the evaluation of water quality, is also involved in the transformation of many substances by changing the redox environment. The current study focuses on the spatial and temporal change rules of salt release and the influence of external disturbing forces on the thickness of the diffusion boundary layer. Beidagang Reservoir in Tianjin City was selected as the study area, and field sampling and indoor simulation experiments were combined to investigate the hydrochemical evolution patterns and causative mechanisms of coastal salinized water bodies within the diffuse boundary layer. The results show that there is a diffusion boundary layer of total dissolved solids (TDS) and dissolved oxygen (DO) in the water body during the storage process, and within the diffusion boundary layer there is a high TDS mass concentration zone and a low DO mass concentration zone. The the process of increasing the thickness of the diffusion boundary layer of TDS before and after the test is more stable than that of DO. During the test, the oxygen flux of the water body in the diffuse boundary layer was generally negative, and the salt release flux was mostly positive, while the oxygen depletion reaction and the salt release phenomenon in the diffuse boundary layer in the early stage of the test were the most obvious. The phenomenon of increasing oxygen content appeared in the middle and late stages, at the same time the salts in the diffuse boundary layer were also released to the upper layer of the water body under the effect of the difference in mass concentration, meanwhile the oxygen flux and the salt release flux were finally presented as dynamic and stable. The percentage of water chemical constituents at the upper and lower boundaries of the diffusion boundary layer (DBL) showed obvious clustering, and the relative contents of Na+, Mg2+,SO2-4,and HCO-3, which had obvious stratification phenomena, showed consistency with time.Na+ and SO2-4 showed SWI greater than the DBL,while HCO-3 and Mg2+ showed SWI less than the DBL. Although the upper and lower boundaries of water chemistry of the diffuse boundary layer at each point showed diversified characteristics, Cl?, Mg2+ and Na+ were always the dominant ions in the water chemistry composition. The hydrogeochemistry at the SWI of the water body is more complex as compared to the DBL, and is more ignificantly affected by sulfate dissolution and silicate dissolution . This experimental design is based on the operation of the Beidagang Reservoir and simulates the changes in the hydrochemical characteristics of reservoir at the location of the Diffusion Boundary Layer (DBL) during the impoundment stage. It was found that the interior of the boundary layer is the main reaction area for oxygen depletion and salinity accumulation processes. The DBL serves as a buffer against the overall salinization of the water body. Furthermore, there is a discrepancy in hydrogeochemical roles between the SWI and the DBL. The results of this experiment can provide a reference basis for exploring the material exchange processes within the diffusion boundary layer of coastal salinized water bodies as well as the rational evaluation and prediction of water quality.
Coastal reservoirs often face water salinization problems, which not only affect their function but also cause severe obstacles to the regional ecosystem and substantial waste of manpower and material resources. To improve the utilization efficiency of reservoirs, several researches have suggested the use of diffuse boundary layer at the sediment-water interface of the water body, as a reaction to hot zone of hydrogeochemical action, which is a key area for controlling the degree of salinization and the type of water quality of the water body. Dissolved oxygen, an important indicator in the evaluation of water quality, is also involved in the transformation of many substances by changing the redox environment. The current study focuses on the spatial and temporal change rules of salt release and the influence of external disturbing forces on the thickness of the diffusion boundary layer. Beidagang Reservoir in Tianjin City was selected as the study area, and field sampling and indoor simulation experiments were combined to investigate the hydrochemical evolution patterns and causative mechanisms of coastal salinized water bodies within the diffuse boundary layer. The results show that there is a diffusion boundary layer of total dissolved solids (TDS) and dissolved oxygen (DO) in the water body during the storage process, and within the diffusion boundary layer there is a high TDS mass concentration zone and a low DO mass concentration zone. The the process of increasing the thickness of the diffusion boundary layer of TDS before and after the test is more stable than that of DO. During the test, the oxygen flux of the water body in the diffuse boundary layer was generally negative, and the salt release flux was mostly positive, while the oxygen depletion reaction and the salt release phenomenon in the diffuse boundary layer in the early stage of the test were the most obvious. The phenomenon of increasing oxygen content appeared in the middle and late stages, at the same time the salts in the diffuse boundary layer were also released to the upper layer of the water body under the effect of the difference in mass concentration, meanwhile the oxygen flux and the salt release flux were finally presented as dynamic and stable. The percentage of water chemical constituents at the upper and lower boundaries of the diffusion boundary layer (DBL) showed obvious clustering, and the relative contents of Na+, Mg2+,SO2-4,and HCO-3, which had obvious stratification phenomena, showed consistency with time.Na+ and SO2-4 showed SWI greater than the DBL,while HCO-3 and Mg2+ showed SWI less than the DBL. Although the upper and lower boundaries of water chemistry of the diffuse boundary layer at each point showed diversified characteristics, Cl?, Mg2+ and Na+ were always the dominant ions in the water chemistry composition. The hydrogeochemistry at the SWI of the water body is more complex as compared to the DBL, and is more ignificantly affected by sulfate dissolution and silicate dissolution . This experimental design is based on the operation of the Beidagang Reservoir and simulates the changes in the hydrochemical characteristics of reservoir at the location of the Diffusion Boundary Layer (DBL) during the impoundment stage. It was found that the interior of the boundary layer is the main reaction area for oxygen depletion and salinity accumulation processes. The DBL serves as a buffer against the overall salinization of the water body. Furthermore, there is a discrepancy in hydrogeochemical roles between the SWI and the DBL. The results of this experiment can provide a reference basis for exploring the material exchange processes within the diffusion boundary layer of coastal salinized water bodies as well as the rational evaluation and prediction of water quality.
2024, 22(6):1173-1180.
Abstract:
The vertical dual-directional pumping system is more and more widely used in plain region because it can meet the two operating conditions of pumping station drainage and irrigation. Due to the closed space at the other end of the inlet and outlet flow channel, “dead water area” will be formed at the other end of the vertical dual-directional pumping system. The water flow has backflow in both vertical and horizontal directions, which makes the flow pattern in the bidirectional flow channel more disordered. At the same time, there will be phenomena such as defluidization and backflow, which may lead to the structural vibration of the unit and the unstable operation of the pump station. The pressure fluctuation is one of main factors impacting on the operational stability of vertical dual-directional pumping system, and the pressure pulsation amplitude and frequency of the pump device are the key indicators to measure the stability of the system, so that the study on the similarity laws between model and protype systems of this pump system is necessary. The pressure fluctuations of model and protype pumping systems were predicted with 3D unsteady simulation under various operational conditions, taking an example of one vertical dual-directional pumping station. The corresponding fluctuations in the model test system and protype pumping station were measured with sensors installed in the same locations. Finally, the similarity laws were analyzed. The result showed that the numerical simulation predicted pressure fluctuations and the test results have pressure fluctuations peaks at 3, 6, and 9 times the rotation frequency. The variation law of the pressure fluctuations deviation between the protype and the model was basically consistent with the variation law of the head and efficiency characteristics. The numerical simulation predicted pressure fluctuations were similar to the test results. And the pressure fluctuations amplitude predicted by the numerical simulation were slightly larger than the test value. The pressure fluctuations amplitude and frequency calculation results of the prototype pump system were highly similar to the calculation results of the model pump system. There was little difference between the model numerical simulation and the model test in the prediction of the main frequency amplitude of the pressure fluctuations. The amplitude at the secondary main frequency was relatively small, and the relative deviation was large. Comparing the pressure fluctuations prediction and measured amplitude of the protype and model pump systems, the test value of the model test was the closest to the test amplitude of the prototype pump system. However, the test of the model pump system was affected by many interference factors, so the spectrum of the test pulsation signal was much richer than that of the prototype pump system. Under high flow conditions, the deviation between the protype and model pressure fluctuations values increases, and the deviation between head and efficiency also increases. The deviation between the protype and model measurement was about 3% while the deviation between the protype measurement and simulation was close to 16% under main frequency. These results indicated that there was a certain correlation between the pressure fluctuations value and the external characteristics of the pump system. The pressure fluctuations of the prototype pump system can be predicted by numerical simulation. The model pump system can be used to convert the calculation results, and the deviation was very small. Compared with protype measurement the simulation and model test were tending towards safety so that they can meet the requirement of engineering design and operation.
The vertical dual-directional pumping system is more and more widely used in plain region because it can meet the two operating conditions of pumping station drainage and irrigation. Due to the closed space at the other end of the inlet and outlet flow channel, “dead water area” will be formed at the other end of the vertical dual-directional pumping system. The water flow has backflow in both vertical and horizontal directions, which makes the flow pattern in the bidirectional flow channel more disordered. At the same time, there will be phenomena such as defluidization and backflow, which may lead to the structural vibration of the unit and the unstable operation of the pump station. The pressure fluctuation is one of main factors impacting on the operational stability of vertical dual-directional pumping system, and the pressure pulsation amplitude and frequency of the pump device are the key indicators to measure the stability of the system, so that the study on the similarity laws between model and protype systems of this pump system is necessary. The pressure fluctuations of model and protype pumping systems were predicted with 3D unsteady simulation under various operational conditions, taking an example of one vertical dual-directional pumping station. The corresponding fluctuations in the model test system and protype pumping station were measured with sensors installed in the same locations. Finally, the similarity laws were analyzed. The result showed that the numerical simulation predicted pressure fluctuations and the test results have pressure fluctuations peaks at 3, 6, and 9 times the rotation frequency. The variation law of the pressure fluctuations deviation between the protype and the model was basically consistent with the variation law of the head and efficiency characteristics. The numerical simulation predicted pressure fluctuations were similar to the test results. And the pressure fluctuations amplitude predicted by the numerical simulation were slightly larger than the test value. The pressure fluctuations amplitude and frequency calculation results of the prototype pump system were highly similar to the calculation results of the model pump system. There was little difference between the model numerical simulation and the model test in the prediction of the main frequency amplitude of the pressure fluctuations. The amplitude at the secondary main frequency was relatively small, and the relative deviation was large. Comparing the pressure fluctuations prediction and measured amplitude of the protype and model pump systems, the test value of the model test was the closest to the test amplitude of the prototype pump system. However, the test of the model pump system was affected by many interference factors, so the spectrum of the test pulsation signal was much richer than that of the prototype pump system. Under high flow conditions, the deviation between the protype and model pressure fluctuations values increases, and the deviation between head and efficiency also increases. The deviation between the protype and model measurement was about 3% while the deviation between the protype measurement and simulation was close to 16% under main frequency. These results indicated that there was a certain correlation between the pressure fluctuations value and the external characteristics of the pump system. The pressure fluctuations of the prototype pump system can be predicted by numerical simulation. The model pump system can be used to convert the calculation results, and the deviation was very small. Compared with protype measurement the simulation and model test were tending towards safety so that they can meet the requirement of engineering design and operation.
2024, 22(6):1180-1190.
Abstract:
Global countries have proposed the goal of achieving carbon neutrality due to increasing climate change and human activity interference in natural systems. Water resources are fundamental for the survival and sustainability of human life and are essential for socioeconomic development and ecological protection. They play a pivotal role in achieving carbon neutrality, fostering a harmonious relationship between people and nature, and supporting sustainable development efforts. The water resources of water transfer projects were used to solve water scarcity in water-receiving areas and to change the regional ecosystem function and carbon cycle model. The Jiangsu-Shandong section of the East Route of the South-to-North Water Transfers Project (ER-SNWTP) in China contained many essential energy, chemical, and agricultural production bases along its route. Thus, exploring the spatial-temporal evolution of carbon storage and its influencing factors in the study area could accelerate the establishment of ecological functional zones for water resources, facilitate the rational and optimal allocation of water and carbon resources, and provide a scientific reference for achieving carbon neutrality and promoting high-quality regional development. Carbon neutrality was combined with water resource management. The CA-Markov model was used to predict the spatial patterns of land use and cover in 2025 under the natural variation scenario (S1) and ER-SNWTP scenario (S2) based on the land use and land cover change (LUCC) of the ER-SNWTP from 2005 to 2020. The InVEST model carbon module simulated carbon stocks and predicted carbon stocks under the two scenarios based on the corrected carbon density values derived from regional temperature and precipitation data. The Geo-detector was utilized to assess the influence of different driving factors and identify the primary elements that impacted variations in carbon stocks within the study area. The results revealed that land use changes from 2005 to 2015 included continuous expansion of built-up land and a reduction in forestland and grassland. There was a trend of growth in water area from 2015 to 2020. Under the ER-SNWTP scenario, the expansion of built-up land was curbed, and the reductions in forestland and grassland were alleviated, leading to a significant increase in water areas compared to the natural variation scenario. From 2015 to 2025, carbon stock decreased by 1,228.35×104t under the natural variation scenario, while it increased by 262.84×104t under the ER-SNWTP scenario. In addition, the water resource allocation of ER-SNWTP affected the spatial distribution of carbon stocks. In the northeast region, particularly in the Binzhou and Dongying areas with large water transfer volumes, the increase in carbon stocks was significant. Land use had the highest explanatory power and driving force for spatial variation in carbon stocks. The interaction factor analysis exhibited the strongest interaction factor after 2005 with "land use ∩ nighttime lights", indicating that the interaction between socio-economic factors and land use factors gradually amplified the impact on the spatial variation of carbon stocks. The results suggested that the implementation of the ER-SNWTP caused significant changes in water quantity in the receiving area. The ER-SNWTP replenished a large amount of water resources in water-scarce areas, greatly improving the regional water resource carrying capacity and providing a foundation for the sustainable development of the ecosystem and human production and life in water-receiving areas. Consequently, stricter requirements were proposed for the management of water-diversion projects and ecosystems. In the future, a scientific mechanism for optimal management of carbon and water resources should be established, optimizing land use patterns. More attention should be paid to the construction of ecological civilization while boosting economic development. Promoting an ecological compensation system, specifically a carbon ecological compensation system for inter-basin water transfer, is also encouraged.
Global countries have proposed the goal of achieving carbon neutrality due to increasing climate change and human activity interference in natural systems. Water resources are fundamental for the survival and sustainability of human life and are essential for socioeconomic development and ecological protection. They play a pivotal role in achieving carbon neutrality, fostering a harmonious relationship between people and nature, and supporting sustainable development efforts. The water resources of water transfer projects were used to solve water scarcity in water-receiving areas and to change the regional ecosystem function and carbon cycle model. The Jiangsu-Shandong section of the East Route of the South-to-North Water Transfers Project (ER-SNWTP) in China contained many essential energy, chemical, and agricultural production bases along its route. Thus, exploring the spatial-temporal evolution of carbon storage and its influencing factors in the study area could accelerate the establishment of ecological functional zones for water resources, facilitate the rational and optimal allocation of water and carbon resources, and provide a scientific reference for achieving carbon neutrality and promoting high-quality regional development. Carbon neutrality was combined with water resource management. The CA-Markov model was used to predict the spatial patterns of land use and cover in 2025 under the natural variation scenario (S1) and ER-SNWTP scenario (S2) based on the land use and land cover change (LUCC) of the ER-SNWTP from 2005 to 2020. The InVEST model carbon module simulated carbon stocks and predicted carbon stocks under the two scenarios based on the corrected carbon density values derived from regional temperature and precipitation data. The Geo-detector was utilized to assess the influence of different driving factors and identify the primary elements that impacted variations in carbon stocks within the study area. The results revealed that land use changes from 2005 to 2015 included continuous expansion of built-up land and a reduction in forestland and grassland. There was a trend of growth in water area from 2015 to 2020. Under the ER-SNWTP scenario, the expansion of built-up land was curbed, and the reductions in forestland and grassland were alleviated, leading to a significant increase in water areas compared to the natural variation scenario. From 2015 to 2025, carbon stock decreased by 1,228.35×104t under the natural variation scenario, while it increased by 262.84×104t under the ER-SNWTP scenario. In addition, the water resource allocation of ER-SNWTP affected the spatial distribution of carbon stocks. In the northeast region, particularly in the Binzhou and Dongying areas with large water transfer volumes, the increase in carbon stocks was significant. Land use had the highest explanatory power and driving force for spatial variation in carbon stocks. The interaction factor analysis exhibited the strongest interaction factor after 2005 with "land use ∩ nighttime lights", indicating that the interaction between socio-economic factors and land use factors gradually amplified the impact on the spatial variation of carbon stocks. The results suggested that the implementation of the ER-SNWTP caused significant changes in water quantity in the receiving area. The ER-SNWTP replenished a large amount of water resources in water-scarce areas, greatly improving the regional water resource carrying capacity and providing a foundation for the sustainable development of the ecosystem and human production and life in water-receiving areas. Consequently, stricter requirements were proposed for the management of water-diversion projects and ecosystems. In the future, a scientific mechanism for optimal management of carbon and water resources should be established, optimizing land use patterns. More attention should be paid to the construction of ecological civilization while boosting economic development. Promoting an ecological compensation system, specifically a carbon ecological compensation system for inter-basin water transfer, is also encouraged.
15 Research and application progress of grouting materials for advance pretreatment of headrace tunnel
2024, 22(6):1181-1188.
Abstract:
Most headrace tunnels are in high mountains and valleys with complex hydrological and special geological conditions. During the construction of the headrace tunnel, water inrush often occurs when suffering from unfavorable geological bodies. Pre-grouting is a significant technical means to prevent such occurrence of geological disasters. However, under the condition of high pressure and large flow dynamic water, the pre-treatment grouting materials can not meet the needs of the site, therefore it's of absolute importance to improve its dynamic water performance. Various inorganic grouting materials have been developed to realize high-performance pre-grouting, such as cement, microfine cement, and water glass, or organic grouting materials, such as polyurethane and epoxy. However, among the aforementioned grouting materials, cement hardening requires a long time, and epoxy and polyurethane are expensive. Besides, due to the high pressure, large flow rate, and rapid velocity water inrush environment, grouting materials face the issues of being washed out, diluted, and dispersed, resulting in difficulty of slurry condensation, low mechanical strength, and poor long-term water plugging effect of consolidated body. Therefore, improving the performance of pre-grouting materials under dynamic water conditions is urgent. Cement, polyurethane, and epoxy grouting materials have been commonly used for advanced pretreatment. Researchers have recently tried to improve the anti-scouring ability, mechanical properties, and durability of cement grouts by adding anti-washout admixtures, nanomaterials, and mineral admixtures to grout mix constituents. In addition, phosphate cement grouting materials have been developed to plug water quickly. Therefore, to promote the application of polyurethane grouting materials in ultra-high velocity dynamic water environments, hydroxypropyl methylcellulose has been added to water-soluble polyurethane slurry to improve its retention rate in flowing water. The relationship between density, mechanical behavior, and microstructure evolution of polyurethane has been researched. The time-varying effect of the permeability of epoxy slurry has become a focus when facing high-pressure and low-permeability geological bodies. In addition to commonly used pre-grouting materials, a superabsorbent polymer grouting material based on self-volume expansion by physical water adsorption has been developed. The latest research on cement, polyurethane, epoxy resin, and superabsorbent polymer grouting materials was reviewed. Based on this, the main problems requiring deep exploration in the future are recommended from three aspects: the development of special cement grouting materials, the development of polyurethane, which is low cost, foaming body with high strength, strong resistance to water inrush, and polyurethane-modified by inorganic materials.
Most headrace tunnels are in high mountains and valleys with complex hydrological and special geological conditions. During the construction of the headrace tunnel, water inrush often occurs when suffering from unfavorable geological bodies. Pre-grouting is a significant technical means to prevent such occurrence of geological disasters. However, under the condition of high pressure and large flow dynamic water, the pre-treatment grouting materials can not meet the needs of the site, therefore it's of absolute importance to improve its dynamic water performance. Various inorganic grouting materials have been developed to realize high-performance pre-grouting, such as cement, microfine cement, and water glass, or organic grouting materials, such as polyurethane and epoxy. However, among the aforementioned grouting materials, cement hardening requires a long time, and epoxy and polyurethane are expensive. Besides, due to the high pressure, large flow rate, and rapid velocity water inrush environment, grouting materials face the issues of being washed out, diluted, and dispersed, resulting in difficulty of slurry condensation, low mechanical strength, and poor long-term water plugging effect of consolidated body. Therefore, improving the performance of pre-grouting materials under dynamic water conditions is urgent. Cement, polyurethane, and epoxy grouting materials have been commonly used for advanced pretreatment. Researchers have recently tried to improve the anti-scouring ability, mechanical properties, and durability of cement grouts by adding anti-washout admixtures, nanomaterials, and mineral admixtures to grout mix constituents. In addition, phosphate cement grouting materials have been developed to plug water quickly. Therefore, to promote the application of polyurethane grouting materials in ultra-high velocity dynamic water environments, hydroxypropyl methylcellulose has been added to water-soluble polyurethane slurry to improve its retention rate in flowing water. The relationship between density, mechanical behavior, and microstructure evolution of polyurethane has been researched. The time-varying effect of the permeability of epoxy slurry has become a focus when facing high-pressure and low-permeability geological bodies. In addition to commonly used pre-grouting materials, a superabsorbent polymer grouting material based on self-volume expansion by physical water adsorption has been developed. The latest research on cement, polyurethane, epoxy resin, and superabsorbent polymer grouting materials was reviewed. Based on this, the main problems requiring deep exploration in the future are recommended from three aspects: the development of special cement grouting materials, the development of polyurethane, which is low cost, foaming body with high strength, strong resistance to water inrush, and polyurethane-modified by inorganic materials.
2024, 22(6):1189-1195.
Abstract:
The North Ship Lock of Binhai hub is a permanent structure for navigation between Huaihe River and Tongyu River with the ship lock level of grade II. The design of normal water level difference requires the water conveyance time to be 6 ~ 8 min. The design of high water level difference (5.99 m and 7.19 m head difference) requires the water conveyance time to be 9 ~ 12 min. The ship lock is subjected to two-way head action with the maximum forward water level difference of 7.19 m, and the maximum reverse water level difference of 1.91 m. To construct the ship lock the operation safety and water conveyance efficiency of the ship lock are the key technical problems to be solved. In order to ensure the safe and efficient operation along with providing technical references for the safe and reliable operation of the ship lock, the physical model test was used to study the hydraulic characteristics of the centralized water conveyance system of the North Ship Lock of the Binhai hub. According to the provisions and requirements of the “Design Code for filling and Emptying Systems of Shiplocks (JTJ 306-2001)” and the “Technical Code of Modelling Test for Port and Waterway Engineering (JTS/T 231—2021)”, the weight and force scale of the original model was 27000, the flow velocity and time scale was 5.48, and the flow scale was 4 929.5. The overall physical model of the ship lock with a scale of 1∶30 was established. The side wall of the lock chamber, the water conveyance corridor and the inlet and outlet sections of the upper and lower lock heads were all made of polyethylene plastic plates. Reservoirs were set up in both upstream and downstream, and 2.3 m×2.5 m horizontal grooves were arranged in the reservoir to stabilize the upstream and downstream water levels. The hydraulic characteristics of the water conveyance process of the lock, the flow pattern in the lock chamber, the pressure change characteristics at the top of the water conveyance corridor and bollard force for ships moored in lock chambers under different valve opening time were analyzed by experiments, and the rationality of the overall layout design of the water conveyance system was verified. When the operating head was not greater than 5.99 m, the continuous opening time of the double-sided uniform speed of the filling valve is 7 min. When the operating head was greater than 5.99 m, the continuous opening time of the double-sided uniform speed of the filling valve is 9 min. In each operating water level combination, the continuous opening time of the double-sided uniform speed of the discharge valve is 7 min. When the upper lock head valve was continuously opened bilaterally for water filling for 6 to 9 min, the minimum instantaneous pressure at the top of the upper lock head water conveyance corridor was 2.57 mH2O. When the lower lock head valve was continuously opened bilaterally for water discharge for 6 to 9 min, the minimum instantaneous pressure at the top of the lower lock head water conveyance corridor was ?0.26 mH2O. Under different water head conditions, the water level of the lock chamber rose and fell smoothly, the surface was calm, and there was no unfavorable flow pattern such as vortex and bubble vortex in the lock chamber, and as a whole flow pattern of the lock chamber was better. Under the recommended valve operation mode, the hydraulic characteristics of the lock, the pressure characteristics of the water conveyance corridor and bollard force for ships moored in lock chambers meet the specifications and design requirements.
The North Ship Lock of Binhai hub is a permanent structure for navigation between Huaihe River and Tongyu River with the ship lock level of grade II. The design of normal water level difference requires the water conveyance time to be 6 ~ 8 min. The design of high water level difference (5.99 m and 7.19 m head difference) requires the water conveyance time to be 9 ~ 12 min. The ship lock is subjected to two-way head action with the maximum forward water level difference of 7.19 m, and the maximum reverse water level difference of 1.91 m. To construct the ship lock the operation safety and water conveyance efficiency of the ship lock are the key technical problems to be solved. In order to ensure the safe and efficient operation along with providing technical references for the safe and reliable operation of the ship lock, the physical model test was used to study the hydraulic characteristics of the centralized water conveyance system of the North Ship Lock of the Binhai hub. According to the provisions and requirements of the “Design Code for filling and Emptying Systems of Shiplocks (JTJ 306-2001)” and the “Technical Code of Modelling Test for Port and Waterway Engineering (JTS/T 231—2021)”, the weight and force scale of the original model was 27000, the flow velocity and time scale was 5.48, and the flow scale was 4 929.5. The overall physical model of the ship lock with a scale of 1∶30 was established. The side wall of the lock chamber, the water conveyance corridor and the inlet and outlet sections of the upper and lower lock heads were all made of polyethylene plastic plates. Reservoirs were set up in both upstream and downstream, and 2.3 m×2.5 m horizontal grooves were arranged in the reservoir to stabilize the upstream and downstream water levels. The hydraulic characteristics of the water conveyance process of the lock, the flow pattern in the lock chamber, the pressure change characteristics at the top of the water conveyance corridor and bollard force for ships moored in lock chambers under different valve opening time were analyzed by experiments, and the rationality of the overall layout design of the water conveyance system was verified. When the operating head was not greater than 5.99 m, the continuous opening time of the double-sided uniform speed of the filling valve is 7 min. When the operating head was greater than 5.99 m, the continuous opening time of the double-sided uniform speed of the filling valve is 9 min. In each operating water level combination, the continuous opening time of the double-sided uniform speed of the discharge valve is 7 min. When the upper lock head valve was continuously opened bilaterally for water filling for 6 to 9 min, the minimum instantaneous pressure at the top of the upper lock head water conveyance corridor was 2.57 mH2O. When the lower lock head valve was continuously opened bilaterally for water discharge for 6 to 9 min, the minimum instantaneous pressure at the top of the lower lock head water conveyance corridor was ?0.26 mH2O. Under different water head conditions, the water level of the lock chamber rose and fell smoothly, the surface was calm, and there was no unfavorable flow pattern such as vortex and bubble vortex in the lock chamber, and as a whole flow pattern of the lock chamber was better. Under the recommended valve operation mode, the hydraulic characteristics of the lock, the pressure characteristics of the water conveyance corridor and bollard force for ships moored in lock chambers meet the specifications and design requirements.
2024, 22(6):1196-1204.
Abstract:
Long-distance water conveyance projects are essential in solving northern China's water resource shortage problem. However, the complex water transport conditions caused by river icing in winter seriously affect the channel's water transport capacity and the project's safe operation. Balancing the safety issues with water delivery efficiency has become a significant challenge for engineering water delivery operations. Increasing the surface water temperature to delay ice formation is possible by utilizing a mobile aeration device and this ensures the safety of winter operations and enhances the water conveyance capacity of the long-distance water conveyance project. However, as an active measure to increase the winter water delivery capacity of channel engineering, its working adaptability and disturbance heating effect still lack targeted research. To reflect the changes in water characteristics under aeration operation, computational fluid dynamics numerical simulation could be used as a reliable means of fluid research. The solid-fluid-thermal coupling technology is used to simulate the rotation of spiral blades and aeration. Simultaneously considering the heat exchange between water and atmosphere, the changes in water temperature caused by changes in the flow field are calculated. During the simulation, overlapping grid technology is introduced to optimize the dynamic grid calculation, ensuring computational efficiency and accuracy. The initial velocity distribution, temperature distribution, device operating speed, and operating path of the fluid through user-defined functions are set. Two different calculation schemes are designed to simulate and analyze the water characteristics under different aeration speeds, aeration depths, longitudinal distances, and walking speeds. The average temperature change curve and the average water surface temperature distribution map are drawn. The changes in water characteristics under different device parameters are changed and flow operating conditions are pushed, providing a basis for device parameters and operational design. The results are as follows: (1) Increasing the aeration rate within the safe allowable range can enhance the mixing effect of water. The aeration rate characterizes the size of the aeration amount. A higher aeration rate results in more significant disturbance to the water body and a higher increase in water surface temperature. (2) The aeration depth can increase the upper limit of temperature increase. A higher deep-water temperature can cause a greater temperature to increase as well. The disturbance caused by deeper aeration has a greater resistance to water pressure. In the case of insufficient aeration, the disturbance caused by deep aeration will gradually flatten with the upward migration of water flow. Considering the influence of slope, a depth of 1.5 m is recommended as the appropriate device parameter. (3) The optimal walking distance for operation is 2 m. Expanding the distance can increase the range of disturbed water surface, and secondary mixing will be carried out in local areas to increase water surface temperature. However, excessive longitudinal distance can lead to the appearance of low-temperature fault zones, which is not conducive to improving the efficiency of turbulent flow heating. (4) The trend of the effect of walking speed on temperature increases first weakens and then strengthens. When the speed is less than 2 m/s, the slower walking speed results in higher local aeration and a more substantial temperature mixing effect. After the speed exceeds 2 m/s, the acceleration of the speed causes the device to undergo secondary disturbance on the walking path. The improvement of the warming effect is more significant than the weakening effect caused by the reduction of local aeration.
Long-distance water conveyance projects are essential in solving northern China's water resource shortage problem. However, the complex water transport conditions caused by river icing in winter seriously affect the channel's water transport capacity and the project's safe operation. Balancing the safety issues with water delivery efficiency has become a significant challenge for engineering water delivery operations. Increasing the surface water temperature to delay ice formation is possible by utilizing a mobile aeration device and this ensures the safety of winter operations and enhances the water conveyance capacity of the long-distance water conveyance project. However, as an active measure to increase the winter water delivery capacity of channel engineering, its working adaptability and disturbance heating effect still lack targeted research. To reflect the changes in water characteristics under aeration operation, computational fluid dynamics numerical simulation could be used as a reliable means of fluid research. The solid-fluid-thermal coupling technology is used to simulate the rotation of spiral blades and aeration. Simultaneously considering the heat exchange between water and atmosphere, the changes in water temperature caused by changes in the flow field are calculated. During the simulation, overlapping grid technology is introduced to optimize the dynamic grid calculation, ensuring computational efficiency and accuracy. The initial velocity distribution, temperature distribution, device operating speed, and operating path of the fluid through user-defined functions are set. Two different calculation schemes are designed to simulate and analyze the water characteristics under different aeration speeds, aeration depths, longitudinal distances, and walking speeds. The average temperature change curve and the average water surface temperature distribution map are drawn. The changes in water characteristics under different device parameters are changed and flow operating conditions are pushed, providing a basis for device parameters and operational design. The results are as follows: (1) Increasing the aeration rate within the safe allowable range can enhance the mixing effect of water. The aeration rate characterizes the size of the aeration amount. A higher aeration rate results in more significant disturbance to the water body and a higher increase in water surface temperature. (2) The aeration depth can increase the upper limit of temperature increase. A higher deep-water temperature can cause a greater temperature to increase as well. The disturbance caused by deeper aeration has a greater resistance to water pressure. In the case of insufficient aeration, the disturbance caused by deep aeration will gradually flatten with the upward migration of water flow. Considering the influence of slope, a depth of 1.5 m is recommended as the appropriate device parameter. (3) The optimal walking distance for operation is 2 m. Expanding the distance can increase the range of disturbed water surface, and secondary mixing will be carried out in local areas to increase water surface temperature. However, excessive longitudinal distance can lead to the appearance of low-temperature fault zones, which is not conducive to improving the efficiency of turbulent flow heating. (4) The trend of the effect of walking speed on temperature increases first weakens and then strengthens. When the speed is less than 2 m/s, the slower walking speed results in higher local aeration and a more substantial temperature mixing effect. After the speed exceeds 2 m/s, the acceleration of the speed causes the device to undergo secondary disturbance on the walking path. The improvement of the warming effect is more significant than the weakening effect caused by the reduction of local aeration.
18 The influence and improvement of curved water flow on the flow pattern downstream of bridge piers
2024, 22(6):1205-1213.
Abstract:
In practical engineering, bridge piers are frequently located within the influence of bending water flow. When there is a deviation in the flow upstream of the bridge pier, the low-velocity area created by the shedding of vortices downstream of the bridge pier interacts with the deviation flow. This leads to a highly uneven distribution of flow velocity downstream, posing a hazard to the downstream slopes and related buildings. To improve the disturbance of flow pattern downstream of the bridge pier caused by curve flow, a method of k-ω SST 3D numerical simulation and physical model test were established based on ANSYS Fluent. The influence of different pier tail shapes on downstream velocity distribution was studied, and the causes of downstream deviation were analyzed. The findings indicated that when the incoming flow upstream shifted and the relative velocity difference between the shifted flow and the low-velocity area behind the pier increased, it led to an increase in turbulence in the downstream flow. Enhancing the design of the downstream end of the pier can improve the distribution of velocity downstream. The length of the tail end of the pier had a positive correlation with the steady flow effect, while the radius of the arc at the front end of the pier had a negative correlation with the steady flow effect in the scope of this study. The research results can reference related projects such as bridge pier construction in curved water flow.
In practical engineering, bridge piers are frequently located within the influence of bending water flow. When there is a deviation in the flow upstream of the bridge pier, the low-velocity area created by the shedding of vortices downstream of the bridge pier interacts with the deviation flow. This leads to a highly uneven distribution of flow velocity downstream, posing a hazard to the downstream slopes and related buildings. To improve the disturbance of flow pattern downstream of the bridge pier caused by curve flow, a method of k-ω SST 3D numerical simulation and physical model test were established based on ANSYS Fluent. The influence of different pier tail shapes on downstream velocity distribution was studied, and the causes of downstream deviation were analyzed. The findings indicated that when the incoming flow upstream shifted and the relative velocity difference between the shifted flow and the low-velocity area behind the pier increased, it led to an increase in turbulence in the downstream flow. Enhancing the design of the downstream end of the pier can improve the distribution of velocity downstream. The length of the tail end of the pier had a positive correlation with the steady flow effect, while the radius of the arc at the front end of the pier had a negative correlation with the steady flow effect in the scope of this study. The research results can reference related projects such as bridge pier construction in curved water flow.
2024, 22(6):1214-1223,1238.
Abstract:
The Guangdong Water Resources Allocation Project around Beibu Gulf integrates a large-flow, high-power centrifugal pump system. This project is part of the national water resources comprehensive plan and is among the 150 major water conservancy projects aimed at addressing the water shortage in western Guangdong, particularly in the Leizhou Peninsula. The centrifugal pump used in this project operates under prolonged sandy conditions, which causes significant and unpredictable erosion issues. This study analyzes the erosion characteristics caused by sediment-laden water within the centrifugal pump. Sediment parameters, including particle mass concentration and size, were determined based on data collected from the West River. The solid-liquid two-phase flow within the centrifugal pump was investigated using the Euler-Lagrange method. The Oka erosion model was employed to predict the erosion characteristics of the pump's flow-through components. Numerical simulations were conducted to understand the head conditions on the erosion patterns and impact of various sediment parameters within the pump. Sediment parameters, such as particle mass concentration levels and sizes, were selected based on the typical conditions found in the West River. The influence of different operational head conditions on the pump's erosion characteristics and simulating conditions that varied from the design head to the lowest and highest head conditions was also examined. The results revealed that under typical sediment conditions, the pressure distribution within the centrifugal pump showed no significant difference between sediment-laden and clean water conditions, while low-mass concentration sediment had minimal impact on the internal flow field of the pump. However, operating the pump outside the design head condition resulted in a substantial increase in both the erosion area and intensity. Specifically, the erosion intensity at the lowest head condition was approximately three times higher than that under the design head condition. Sediment mass concentration primarily affected the erosion intensity, while sediment particle size influenced the distribution of the severely worn areas. With increasing sediment mass concentration, the erosion area and intensity on the impeller front cover increased, but the location of the severely worn area did not change significantly. Conversely, with increasing sediment particle size, the erosion area on the impeller front cover decreased, but the location of the severely worn area shifted noticeably. The study's simulations showed that larger particles tend to move towards the pressure side of the impeller blades, causing more significant erosion in those regions.This study demonstrated that sediment mass concentration and particle size are critical factors influencing the erosion characteristics of centrifugal pumps. The findings provide valuable insights into the erosion mechanisms within such pumps, offering guidance for their operation and maintenance under sandy conditions. The results indicate that to minimize erosion and enhance pump longevity, careful consideration of sediment parameters and operational head conditions is essential. By understanding the effects of these parameters, operators can optimize pump performance and reduce maintenance costs. This research contributes to optimizing pump design and operation, ensuring more reliable and efficient performance in sediment-laden environments. Future studies could further explore the development of erosion-resistant materials and coatings to enhance the durability of centrifugal pumps used in similar settings.
The Guangdong Water Resources Allocation Project around Beibu Gulf integrates a large-flow, high-power centrifugal pump system. This project is part of the national water resources comprehensive plan and is among the 150 major water conservancy projects aimed at addressing the water shortage in western Guangdong, particularly in the Leizhou Peninsula. The centrifugal pump used in this project operates under prolonged sandy conditions, which causes significant and unpredictable erosion issues. This study analyzes the erosion characteristics caused by sediment-laden water within the centrifugal pump. Sediment parameters, including particle mass concentration and size, were determined based on data collected from the West River. The solid-liquid two-phase flow within the centrifugal pump was investigated using the Euler-Lagrange method. The Oka erosion model was employed to predict the erosion characteristics of the pump's flow-through components. Numerical simulations were conducted to understand the head conditions on the erosion patterns and impact of various sediment parameters within the pump. Sediment parameters, such as particle mass concentration levels and sizes, were selected based on the typical conditions found in the West River. The influence of different operational head conditions on the pump's erosion characteristics and simulating conditions that varied from the design head to the lowest and highest head conditions was also examined. The results revealed that under typical sediment conditions, the pressure distribution within the centrifugal pump showed no significant difference between sediment-laden and clean water conditions, while low-mass concentration sediment had minimal impact on the internal flow field of the pump. However, operating the pump outside the design head condition resulted in a substantial increase in both the erosion area and intensity. Specifically, the erosion intensity at the lowest head condition was approximately three times higher than that under the design head condition. Sediment mass concentration primarily affected the erosion intensity, while sediment particle size influenced the distribution of the severely worn areas. With increasing sediment mass concentration, the erosion area and intensity on the impeller front cover increased, but the location of the severely worn area did not change significantly. Conversely, with increasing sediment particle size, the erosion area on the impeller front cover decreased, but the location of the severely worn area shifted noticeably. The study's simulations showed that larger particles tend to move towards the pressure side of the impeller blades, causing more significant erosion in those regions.This study demonstrated that sediment mass concentration and particle size are critical factors influencing the erosion characteristics of centrifugal pumps. The findings provide valuable insights into the erosion mechanisms within such pumps, offering guidance for their operation and maintenance under sandy conditions. The results indicate that to minimize erosion and enhance pump longevity, careful consideration of sediment parameters and operational head conditions is essential. By understanding the effects of these parameters, operators can optimize pump performance and reduce maintenance costs. This research contributes to optimizing pump design and operation, ensuring more reliable and efficient performance in sediment-laden environments. Future studies could further explore the development of erosion-resistant materials and coatings to enhance the durability of centrifugal pumps used in similar settings.
2024, 22(6):1224-1238.
Abstract:
Sustainable water resource use and food security are fundamental to society's sustainability. Likewise, crop production is a prerequisite for guaranteeing food security. Heilongjiang Province is an essential commercial grain production base in China and has an important strategic position in ensuring national food security. It is located in one of the world's three major soil belts, recognized as the world's golden growth for maize. According to statistics, in 2021, the sown area of maize in Heilongjiang Province was about 652.4×104hm2, accounting for 44.8% of the total sown area of grain in the province, and its output accounted for 37.7% of the national total maize production. The main planting areas of maize in the province are concentrated in the Qiqihar, Suihua, and Harbin regions, which are all in the Songnen Plain region of Heilongjiang Province. However, the region has undergone significant environmental changes due to the trend of aridification, and water scarcity is a severe problem that limits maize growth and development processes. In addition, numerous studies have shown that drought often occurs during the reproductive period of maize and that in dry years, maize production can be increased through scientifically sound irrigation measures, while in years of high-water availability, when precipitation can satisfy maize water demand, care needs to be taken to avoid over-irrigation that leads to wasted water resources and crop damage.Based on 60 years of long-term historical meteorological data, the modified AquaCrop model was used to simulate maize yields under different rain-fed and irrigated scenarios for different precipitation year types at each typical site in the Songnen Plain. Water use efficiency and irrigation water use efficiency were further computed to assess the efficiency of water resource use under different precipitation year types. Finally, the data were spatially interpolated using ArcGIS, and the results were visualized as maps to better understand maize yield and water use in different regions. The results show that in arid years, the irrigation combination of seedling stage - jointing (20 mm), jointing stage - pulling stage (60 mm), and pulling stage - filling stage (60 mm) was the best irrigation scheme. The yield of maize was 11.33 and 10.23 t/hm2, and the average EWU was 2.35 and 2.16 kg/m3, respectively. Irrigation can alleviate the effects of drought on yield. The optimal irrigation scheme in a typical water year was the soxion-filling period (60 mm). Still, the irrigation yield only increased by 0.1 t/hm2, and the average EWU only increased by 0.028 kg/m3. If the seedlings could emerge neatly, irrigation would not be allowed in an average water year. In wet years, precipitation can meet the water demand of maize without irrigation. For normal and wet years, rain-fed agriculture can obtain a similar yield to EWU. Therefore, irrigation strategies should be differentiated according to hydrological years. Irrigation should not be done in wet years to save water resources, and adequate water should be required in dry years, especially in the key growth stages of maize during jointing–pumping, and pumping-filling. In addition, planting dates need to be adjusted to climate change trends to make the most of natural precipitation and reduce irrigation needs. Future studies should comprehensively consider the effects of climate change, soil moisture, and maize variety improvement to provide a theoretical basis for formulating a reasonable and effective maize irrigation system, coping with climate change and water shortage challenges, and ensuring food security. Conclusion: The AquaCrop model can effectively simulate the growth process of maize in the Songnen Plain. During the critical growth stages of maize, timely and appropriate irrigation can ensure the crop receives sufficient water, reduce yield loss, and improve Water Use Efficiency (EWU). However, over-irrigation can lead to a decrease in both. As yields increase,EWU may decline because higher yields may require more water. In arid years, the optimal irrigation schemes are 20 mm from the seedling to the jointing stage, 60 mm from the jointing to the tasseling stage, and 60mm from the tasseling to the filling stage. In dry years, the optimal schemes are 60 mm during the jointing to tasseling stage and 60 mm during the tasseling to filling stage. Precipitation is sufficient in normal and wet years to meet the maize’s water needs. No irrigation is required. This study can provide a theoretical basis for developing a more rational and effective maize irrigation system in the Songnen Plain of Heilongjiang Province, thereby better addressing the challenges of climate change and water scarcity and ensuring food security.
Sustainable water resource use and food security are fundamental to society's sustainability. Likewise, crop production is a prerequisite for guaranteeing food security. Heilongjiang Province is an essential commercial grain production base in China and has an important strategic position in ensuring national food security. It is located in one of the world's three major soil belts, recognized as the world's golden growth for maize. According to statistics, in 2021, the sown area of maize in Heilongjiang Province was about 652.4×104hm2, accounting for 44.8% of the total sown area of grain in the province, and its output accounted for 37.7% of the national total maize production. The main planting areas of maize in the province are concentrated in the Qiqihar, Suihua, and Harbin regions, which are all in the Songnen Plain region of Heilongjiang Province. However, the region has undergone significant environmental changes due to the trend of aridification, and water scarcity is a severe problem that limits maize growth and development processes. In addition, numerous studies have shown that drought often occurs during the reproductive period of maize and that in dry years, maize production can be increased through scientifically sound irrigation measures, while in years of high-water availability, when precipitation can satisfy maize water demand, care needs to be taken to avoid over-irrigation that leads to wasted water resources and crop damage.Based on 60 years of long-term historical meteorological data, the modified AquaCrop model was used to simulate maize yields under different rain-fed and irrigated scenarios for different precipitation year types at each typical site in the Songnen Plain. Water use efficiency and irrigation water use efficiency were further computed to assess the efficiency of water resource use under different precipitation year types. Finally, the data were spatially interpolated using ArcGIS, and the results were visualized as maps to better understand maize yield and water use in different regions. The results show that in arid years, the irrigation combination of seedling stage - jointing (20 mm), jointing stage - pulling stage (60 mm), and pulling stage - filling stage (60 mm) was the best irrigation scheme. The yield of maize was 11.33 and 10.23 t/hm2, and the average EWU was 2.35 and 2.16 kg/m3, respectively. Irrigation can alleviate the effects of drought on yield. The optimal irrigation scheme in a typical water year was the soxion-filling period (60 mm). Still, the irrigation yield only increased by 0.1 t/hm2, and the average EWU only increased by 0.028 kg/m3. If the seedlings could emerge neatly, irrigation would not be allowed in an average water year. In wet years, precipitation can meet the water demand of maize without irrigation. For normal and wet years, rain-fed agriculture can obtain a similar yield to EWU. Therefore, irrigation strategies should be differentiated according to hydrological years. Irrigation should not be done in wet years to save water resources, and adequate water should be required in dry years, especially in the key growth stages of maize during jointing–pumping, and pumping-filling. In addition, planting dates need to be adjusted to climate change trends to make the most of natural precipitation and reduce irrigation needs. Future studies should comprehensively consider the effects of climate change, soil moisture, and maize variety improvement to provide a theoretical basis for formulating a reasonable and effective maize irrigation system, coping with climate change and water shortage challenges, and ensuring food security. Conclusion: The AquaCrop model can effectively simulate the growth process of maize in the Songnen Plain. During the critical growth stages of maize, timely and appropriate irrigation can ensure the crop receives sufficient water, reduce yield loss, and improve Water Use Efficiency (EWU). However, over-irrigation can lead to a decrease in both. As yields increase,EWU may decline because higher yields may require more water. In arid years, the optimal irrigation schemes are 20 mm from the seedling to the jointing stage, 60 mm from the jointing to the tasseling stage, and 60mm from the tasseling to the filling stage. In dry years, the optimal schemes are 60 mm during the jointing to tasseling stage and 60 mm during the tasseling to filling stage. Precipitation is sufficient in normal and wet years to meet the maize’s water needs. No irrigation is required. This study can provide a theoretical basis for developing a more rational and effective maize irrigation system in the Songnen Plain of Heilongjiang Province, thereby better addressing the challenges of climate change and water scarcity and ensuring food security.
2024, 22(6):1239-1248.
Abstract:
In arid and semi-arid regions, the scarcity of water resources represents a significant challenge to agricultural development. The demand for water during different stages of crop growth and development varies, necessitating the identification of lower limit irrigation indexes for each reproductive period. This approach provides a scientific foundation for the establishment of optimal irrigation control indexes in arid and semi-arid areas, facilitating the advancement of greenhouse-based agriculture. In this experiment, greenhouse tomato was used as the research object, and a field experiment was carried out in Helan County, Ningxia. Three key water control periods were set up (the lower limits of irrigation at each growth stage were 60%, 65% and 70% of the field moisture capacity (θf), and the seedling stage was uniformly set to 55% of the field moisture capacity), and a total of 7 water treatments were established to investigate the impact of varying lower limits of water during each fertility period on the growth, biomass, yield, and quality of greenhouse tomato. The entropy-weighted TOPSIS comprehensive evaluation method was utilized to optimize a reasonable lower limit of soil moisture control in each fertility period of greenhouse tomato. The field experiment demonstrated that the trends in plant height, stem thickness, and the average number of nodes under different treatments were consistent. The T4 treatment (which maintained the lower limit of water control at 55%, 65%, 65%, 70%, and 65% during each fertility period) exhibited the greatest average daily growth in plant height, reaching a maximum value of 230 cm by mid-November, with an average daily growth rate of 2.58 cm/d; The T2 treatment (which maintained the lower limit of water control at 55%, 60%, 70%, 65%, and 65% during each fertility period) exhibited the largest stem thickness of 13.39 mm, The T3 treatment (which maintained the lower limit of water control at 55%, 70%, 70%, 65%, and 65% during each fertility period) the greatest average daily increase in stem thickness, at 0.13 mm per day. Leaf area index (LAI) increased and then decreased during the reproductive period, with the T3 treatment being the largest at 4.43. The dry weight of the entire plant exhibited a range of 101.74 g to 161.01 g during the flowering stage and a range of 147.27 g to 203.92 g during the fruiting stage. The control treatment (CK) exhibited the highest dry weight, with values of 161.01 g and 203.92 g, respectively; The yield ranking analysis indicated that the yield was larger when the lower limit of soil moisture was higher during the fruiting bloom period, T1(which maintained the lower limit of water control at 55%, 65%, 60%, 70%, and 65% during each fertility period) had the highest yield of 35.58 t/ hm2, which was 36.7% higher than the control. The quality of the tomatoes produced in the greenhouse was superior when the lower limit of irrigation during the fruiting bloom period was set at 65% to 70%, the T2 treatment exhibited the highest soluble sugar content, at 8.61%, while the T3 treatment demonstrated the highest lycopene content, at 4.40 mg/(100 g). The comprehensive analysis indicated that the appropriate lower limit of irrigation could lead to higher yield, and the appropriate lower limits of soil water control for tomatoes in different growth stages of autumn delayed cropping facilities were as follows: the seedling stage, the flowering and fruiting stage, the early fruiting stage, the peak fruiting stage, and the late fruiting stage were 55% θf(where θf represents the field water-holding rate), 70% θf, 60%θf, 65%θf, and 65% θf, respectively. The findings of this study may inform the development of optimal and practical irrigation strategies for the cultivation of tomatoes in facilities, thereby providing scientific evidence to support the advancement of local greenhouse agriculture.
In arid and semi-arid regions, the scarcity of water resources represents a significant challenge to agricultural development. The demand for water during different stages of crop growth and development varies, necessitating the identification of lower limit irrigation indexes for each reproductive period. This approach provides a scientific foundation for the establishment of optimal irrigation control indexes in arid and semi-arid areas, facilitating the advancement of greenhouse-based agriculture. In this experiment, greenhouse tomato was used as the research object, and a field experiment was carried out in Helan County, Ningxia. Three key water control periods were set up (the lower limits of irrigation at each growth stage were 60%, 65% and 70% of the field moisture capacity (θf), and the seedling stage was uniformly set to 55% of the field moisture capacity), and a total of 7 water treatments were established to investigate the impact of varying lower limits of water during each fertility period on the growth, biomass, yield, and quality of greenhouse tomato. The entropy-weighted TOPSIS comprehensive evaluation method was utilized to optimize a reasonable lower limit of soil moisture control in each fertility period of greenhouse tomato. The field experiment demonstrated that the trends in plant height, stem thickness, and the average number of nodes under different treatments were consistent. The T4 treatment (which maintained the lower limit of water control at 55%, 65%, 65%, 70%, and 65% during each fertility period) exhibited the greatest average daily growth in plant height, reaching a maximum value of 230 cm by mid-November, with an average daily growth rate of 2.58 cm/d; The T2 treatment (which maintained the lower limit of water control at 55%, 60%, 70%, 65%, and 65% during each fertility period) exhibited the largest stem thickness of 13.39 mm, The T3 treatment (which maintained the lower limit of water control at 55%, 70%, 70%, 65%, and 65% during each fertility period) the greatest average daily increase in stem thickness, at 0.13 mm per day. Leaf area index (LAI) increased and then decreased during the reproductive period, with the T3 treatment being the largest at 4.43. The dry weight of the entire plant exhibited a range of 101.74 g to 161.01 g during the flowering stage and a range of 147.27 g to 203.92 g during the fruiting stage. The control treatment (CK) exhibited the highest dry weight, with values of 161.01 g and 203.92 g, respectively; The yield ranking analysis indicated that the yield was larger when the lower limit of soil moisture was higher during the fruiting bloom period, T1(which maintained the lower limit of water control at 55%, 65%, 60%, 70%, and 65% during each fertility period) had the highest yield of 35.58 t/ hm2, which was 36.7% higher than the control. The quality of the tomatoes produced in the greenhouse was superior when the lower limit of irrigation during the fruiting bloom period was set at 65% to 70%, the T2 treatment exhibited the highest soluble sugar content, at 8.61%, while the T3 treatment demonstrated the highest lycopene content, at 4.40 mg/(100 g). The comprehensive analysis indicated that the appropriate lower limit of irrigation could lead to higher yield, and the appropriate lower limits of soil water control for tomatoes in different growth stages of autumn delayed cropping facilities were as follows: the seedling stage, the flowering and fruiting stage, the early fruiting stage, the peak fruiting stage, and the late fruiting stage were 55% θf(where θf represents the field water-holding rate), 70% θf, 60%θf, 65%θf, and 65% θf, respectively. The findings of this study may inform the development of optimal and practical irrigation strategies for the cultivation of tomatoes in facilities, thereby providing scientific evidence to support the advancement of local greenhouse agriculture.
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