Volume 20,Issue 5,2022 Table of Contents
2022, 20(5):833-841.
Abstract:
Shandong of the east route of South-to-North Water Transfer Project (Hereinafter referred to as Shandong section) is the main water receiving area of the first phase of the east route of the South-to-North Water Transfer Project, and its water resources ecological security (WRES) research can provide reference for the implementation of subsequent projects. Based on the pressure-state-response (P-S-R) model, an evaluation indicators system of WRES was discussed, and then the spatial-temporal differentiation characteristics of WRES were studied by coupling the projection decision method with modulus similarity and Gini coefficient method.From the perspective of time series, WRES in 14 cities of Shandong section has generally become better year by year, and the comprehensive ranking value has increased from 0.463 1 in 2011 to 0.623 4 in 2019. However, the situation is not optimistic, and there is still a large gap from the ideal state. Among the 126 samples, only 25. 4% had a ranking value of more than 0.6, 6. 3% more than 0.7, and only Dongying reached 0.8 in 2019. Population and economic development are important factors affecting WRES, which also shows that human beings have more and more influence on the water resources system while pursuing the rapid development of economy and society. In 2019, with the exception of Dongying, the response subsystem is better than the pressure subsystem and the state subsystem to varying degrees, especially the lag of the pressure subsystem. The Shandong section is generally facing great pressure on WRES, and it has not been effectively alleviated during the study period. Especially Heze and Zaozhuang, the pressure subsystem of the two cities is in a relatively backward position all the year round. The strong man-made control measures in various cities have alleviated the risks brought by the pressure subsystem to a certain extent, making the level of WRES improve year by year.From the perspective of space, the spatial equilibrium state of Shandong section of east route of South-to-North Water Transfer Project has great differences in 9 indicators, but the interannual variation range is small, which indicates that there are differences among various systems in the Shandong section, but it has maintained a good coordinated development trend as a whole. Comprehensively considering the nine indicators, WRES spatial equilibrium index of Shandong section from 2011 to 2019 is stable at about 0.2, and fluctuates slightly up and down at the critical point of very equilibrium and general equilibrium. However, from the perspective of single indicators, there are significant differences in the investment proportion of water management industry, water consumption per 10 000-yuan GDP, per capita water resources and fertilizer application intensity, and there is no obvious sign of improvement. The multi-year average Gini coefficient of per capita GDP is 0.25, slightly biased towards imbalance, but relatively stable. Population density, 10 000-yuan GDP, industrial sewage discharge, sewage treatment rate and green coverage rate of built-up areas have always been in a very balanced state, especially the sewage treatment rate and green coverage rate of built-up areas are almost absolutely balanced. The impact of human activities, especially water use efficiency, on WRES is becoming more and more prominent. The east route of South-to-North Water Transfer Project has played an important role in promoting the WRES in Shandong.In general, the comprehensive model constructed is practical and effective for temporal evolution and spatial equilibrium analysis. The temporal and spatial differentiation characteristics of WRES in Shandong section can provide some guidance for the formulation and implementation of relevant policies for the follow-up of the east route of South-to-North Water Transfer Project. Besides, the results can also provide reference for other relevant studies and support regional coordinated development and environmental protection.
Shandong of the east route of South-to-North Water Transfer Project (Hereinafter referred to as Shandong section) is the main water receiving area of the first phase of the east route of the South-to-North Water Transfer Project, and its water resources ecological security (WRES) research can provide reference for the implementation of subsequent projects. Based on the pressure-state-response (P-S-R) model, an evaluation indicators system of WRES was discussed, and then the spatial-temporal differentiation characteristics of WRES were studied by coupling the projection decision method with modulus similarity and Gini coefficient method.From the perspective of time series, WRES in 14 cities of Shandong section has generally become better year by year, and the comprehensive ranking value has increased from 0.463 1 in 2011 to 0.623 4 in 2019. However, the situation is not optimistic, and there is still a large gap from the ideal state. Among the 126 samples, only 25. 4% had a ranking value of more than 0.6, 6. 3% more than 0.7, and only Dongying reached 0.8 in 2019. Population and economic development are important factors affecting WRES, which also shows that human beings have more and more influence on the water resources system while pursuing the rapid development of economy and society. In 2019, with the exception of Dongying, the response subsystem is better than the pressure subsystem and the state subsystem to varying degrees, especially the lag of the pressure subsystem. The Shandong section is generally facing great pressure on WRES, and it has not been effectively alleviated during the study period. Especially Heze and Zaozhuang, the pressure subsystem of the two cities is in a relatively backward position all the year round. The strong man-made control measures in various cities have alleviated the risks brought by the pressure subsystem to a certain extent, making the level of WRES improve year by year.From the perspective of space, the spatial equilibrium state of Shandong section of east route of South-to-North Water Transfer Project has great differences in 9 indicators, but the interannual variation range is small, which indicates that there are differences among various systems in the Shandong section, but it has maintained a good coordinated development trend as a whole. Comprehensively considering the nine indicators, WRES spatial equilibrium index of Shandong section from 2011 to 2019 is stable at about 0.2, and fluctuates slightly up and down at the critical point of very equilibrium and general equilibrium. However, from the perspective of single indicators, there are significant differences in the investment proportion of water management industry, water consumption per 10 000-yuan GDP, per capita water resources and fertilizer application intensity, and there is no obvious sign of improvement. The multi-year average Gini coefficient of per capita GDP is 0.25, slightly biased towards imbalance, but relatively stable. Population density, 10 000-yuan GDP, industrial sewage discharge, sewage treatment rate and green coverage rate of built-up areas have always been in a very balanced state, especially the sewage treatment rate and green coverage rate of built-up areas are almost absolutely balanced. The impact of human activities, especially water use efficiency, on WRES is becoming more and more prominent. The east route of South-to-North Water Transfer Project has played an important role in promoting the WRES in Shandong.In general, the comprehensive model constructed is practical and effective for temporal evolution and spatial equilibrium analysis. The temporal and spatial differentiation characteristics of WRES in Shandong section can provide some guidance for the formulation and implementation of relevant policies for the follow-up of the east route of South-to-North Water Transfer Project. Besides, the results can also provide reference for other relevant studies and support regional coordinated development and environmental protection.
2022, 20(5):842-850.
Abstract:
Under the combined effect of climate change and human activities, there is a sharp decline in the Fenhe River runoff, which aggravates the shortage of water resources in the middle and lower Yellow River. To quantify the contribution of climatic factors, vegetation, and human water use to runoff reduction, the evolution above characteristics is carried out from 1981 to 2015 in the Fenhe River basin. A distributed hydrological model and a factor detrending method were used to quantitatively analyze the contribution of the changes in precipitation, net radiation, temperature, leaf area index, and human water use to the runoff reduction. The results revealed that annual precipitation and net radiation showed an insignificant ( p>0.05) increasing and decreasing trend during the study period. The annual temperature and leaf area index (LAI) showed a significant ( p<0.05) increasing trend and human water use showed a significant ( p<0.05) increasing trend. These factors jointly led to a significant ( p<0.05) decrease in annual runoff in the Fenhe river basin. The increase in human water use was the primary factor leading to the reduction of annual runoff. The observed mean annual runoff increased by 27.4% under the trend-free scenario of human water use. Warming and vegetation greening were the main natural factors causing runoff reduction, while the effect of net radiation was limited. Under the trend-free scenarios of the above three factors, the mean annual observed runoff increased by 14.4%, 13.7%, and 2.1%, respectively. The increase in annual precipitation partly alleviated the decrease in the annual runoff. The observed mean annual runoff decreased by 5.3% under the trend-free scenario of annual precipitation. The findings of this research may provide guidelines for water resources management and plan in the Fenhe River basin.
Under the combined effect of climate change and human activities, there is a sharp decline in the Fenhe River runoff, which aggravates the shortage of water resources in the middle and lower Yellow River. To quantify the contribution of climatic factors, vegetation, and human water use to runoff reduction, the evolution above characteristics is carried out from 1981 to 2015 in the Fenhe River basin. A distributed hydrological model and a factor detrending method were used to quantitatively analyze the contribution of the changes in precipitation, net radiation, temperature, leaf area index, and human water use to the runoff reduction. The results revealed that annual precipitation and net radiation showed an insignificant ( p>0.05) increasing and decreasing trend during the study period. The annual temperature and leaf area index (LAI) showed a significant ( p<0.05) increasing trend and human water use showed a significant ( p<0.05) increasing trend. These factors jointly led to a significant ( p<0.05) decrease in annual runoff in the Fenhe river basin. The increase in human water use was the primary factor leading to the reduction of annual runoff. The observed mean annual runoff increased by 27.4% under the trend-free scenario of human water use. Warming and vegetation greening were the main natural factors causing runoff reduction, while the effect of net radiation was limited. Under the trend-free scenarios of the above three factors, the mean annual observed runoff increased by 14.4%, 13.7%, and 2.1%, respectively. The increase in annual precipitation partly alleviated the decrease in the annual runoff. The observed mean annual runoff decreased by 5.3% under the trend-free scenario of annual precipitation. The findings of this research may provide guidelines for water resources management and plan in the Fenhe River basin.
2022, 20(5):851-861.
Abstract:
Domestic water consumption proportion is high in Beijing due to the adjustment of industrial structure in recent years, and domestic water saving has become the focus of urban water resources management. However, previous studies focused more on the impact of per capita water consumption and water saving, while ignoring the group differences in residential water consumption, such as gender, age, education, income, etc. The group differences made diversity in lifestyle, behavior habits, and consciousness, resulting in a large difference in water demand. Therefore, the targeted water-saving measures to improve water use efficiency were proposed based on the analysis of water consumption for residents with different individual characteristics. Questionnaire was used for data collection in Beijing’s households, adential water use habits and their characteristics such as gender and age, but not with income and education. Especially for the habits of showering, toilet flushing, and cooking, there were great differences among residents with different individual characteristics, which led to differences in water consumption for various behaviors. The proportion of water consumption for showering and toilet in households were the largest, and the difference was the most obvious. There was also a striking difference between the water consumption for washing clothes or cooking and individual characteristics, but no significant correlation for personal hygiene or household cleaning. In terms of total residential water consumption, it decreased with the increase of age, and the average water consumption for females was 13% higher than that of males. Young women and old men had the highest and lowest water demand, with average water consumption of 156 L/(person?d) and 118 L/(person?d), respectively. According to the theory of the hierarchical water demand and definition behaviors, the luxury water demand for showering, toilet flushing, personal hygiene, laundry, cooking, and household cleaning in Beijing’s households was more than 48 L/(person?d), 24 L/(person?d), 21 L/(person?d), 12 L/(person?d), 9 L/(person?d)and 2 L/(person?d), respectively. Young women and old men had the highest and lowest luxury water consumption, which the proportion ware 27% and 3%, respectively. The analysis showed that there was a need to focus on improving the efficiency of showering and toilet flushing, which consumed more luxury water. Based on the investigation of water conservation behaviors for residents with different individual characteristics, the water conservation potential of improving the wastewater behaviors was calculated, and the rate of water saving would be increased by 15% to 20%. Among these, the water-saving rate of the elderly was lowest, and the middle young was highest. The water conservation potential results exhibited that the measures and key points of residential water conservation with different characteristics were put forward. The residential water consumption and water saving model were constructed combined with the theory of hierarchical water demand. The total and each behavior against water consumption was analyzed for residents with different individual characteristics. According to the luxury water demand and water conservation potential, the measures and key points for water saving work were put forward, which could provide a theoretical reference for urban water management.
Domestic water consumption proportion is high in Beijing due to the adjustment of industrial structure in recent years, and domestic water saving has become the focus of urban water resources management. However, previous studies focused more on the impact of per capita water consumption and water saving, while ignoring the group differences in residential water consumption, such as gender, age, education, income, etc. The group differences made diversity in lifestyle, behavior habits, and consciousness, resulting in a large difference in water demand. Therefore, the targeted water-saving measures to improve water use efficiency were proposed based on the analysis of water consumption for residents with different individual characteristics. Questionnaire was used for data collection in Beijing’s households, adential water use habits and their characteristics such as gender and age, but not with income and education. Especially for the habits of showering, toilet flushing, and cooking, there were great differences among residents with different individual characteristics, which led to differences in water consumption for various behaviors. The proportion of water consumption for showering and toilet in households were the largest, and the difference was the most obvious. There was also a striking difference between the water consumption for washing clothes or cooking and individual characteristics, but no significant correlation for personal hygiene or household cleaning. In terms of total residential water consumption, it decreased with the increase of age, and the average water consumption for females was 13% higher than that of males. Young women and old men had the highest and lowest water demand, with average water consumption of 156 L/(person?d) and 118 L/(person?d), respectively. According to the theory of the hierarchical water demand and definition behaviors, the luxury water demand for showering, toilet flushing, personal hygiene, laundry, cooking, and household cleaning in Beijing’s households was more than 48 L/(person?d), 24 L/(person?d), 21 L/(person?d), 12 L/(person?d), 9 L/(person?d)and 2 L/(person?d), respectively. Young women and old men had the highest and lowest luxury water consumption, which the proportion ware 27% and 3%, respectively. The analysis showed that there was a need to focus on improving the efficiency of showering and toilet flushing, which consumed more luxury water. Based on the investigation of water conservation behaviors for residents with different individual characteristics, the water conservation potential of improving the wastewater behaviors was calculated, and the rate of water saving would be increased by 15% to 20%. Among these, the water-saving rate of the elderly was lowest, and the middle young was highest. The water conservation potential results exhibited that the measures and key points of residential water conservation with different characteristics were put forward. The residential water consumption and water saving model were constructed combined with the theory of hierarchical water demand. The total and each behavior against water consumption was analyzed for residents with different individual characteristics. According to the luxury water demand and water conservation potential, the measures and key points for water saving work were put forward, which could provide a theoretical reference for urban water management.
2022, 20(5):862-875.
Abstract:
Many studies focus on the application of deep learning in data-driven hydrological models for hydrological forecasting. The recent research progress of deep learning models on hydrological forecasting are reviewed. Deep learning shows new features unseen in non-deep learning data-driven models. It can also help to address some old challenges in hydrological modeling, such as hydrological modeling under the impact of hydraulic projects and uncertainty analysis. Deep learning can be a tool for knowledge discovery. We also describe some studies for the integration of deep learning and domain knowledge in hydrology, including incorporating deep learning in physical mechanism models and physics-guided deep learning. We also highlight the challenges in applying deep learning to hydrological forecasting and propose potential opportunities. This review can provide a useful reference for further research on deep-learning-based hydrological forecasting.
Many studies focus on the application of deep learning in data-driven hydrological models for hydrological forecasting. The recent research progress of deep learning models on hydrological forecasting are reviewed. Deep learning shows new features unseen in non-deep learning data-driven models. It can also help to address some old challenges in hydrological modeling, such as hydrological modeling under the impact of hydraulic projects and uncertainty analysis. Deep learning can be a tool for knowledge discovery. We also describe some studies for the integration of deep learning and domain knowledge in hydrology, including incorporating deep learning in physical mechanism models and physics-guided deep learning. We also highlight the challenges in applying deep learning to hydrological forecasting and propose potential opportunities. This review can provide a useful reference for further research on deep-learning-based hydrological forecasting.
2022, 20(5):876-885.
Abstract:
The dynamic change of groundwater level is an intuitive reflection of groundwater reserve change and basic information for studying the characteristics of groundwater occurrence and evolution. The variation characteristics of water level in a single well are affected by supplementary drainage characteristics and hydrogeological conditions. The water level of distributed wells at different points may have different trends with total groundwater reserve changes in a region. How to obtain representative values which can describe the overall regional water level changes becomes a key problem to be solved urgently. A correlation between the observed water level of multiple wells and the water level calculated by regional groundwater reservoir variables was constructed based on water balance method. The k-means clustering analysis method and Thiessen polygon were used to solve the multi-solution problem caused by the gap between the number of wells and the length of continuous water level observations of a single well. By solving the linear equation, a set of weighting coefficients that can describe the relationship between a single well water level change and the whole area water level change was obtained. These weighting coefficients and water level changes of corresponding wells were used to quickly calculate regional representative groundwater level changes.A new method was calculated and validated by numerical simulation and regional example. The results show that in an ideal example, using the water level variation data of five selected observation points and corresponding weight values, the annual variation of overall water level was 0.23 m. The calculated result was 0.02 m, different from the verified annual water level variation of 0.21 m calculated by the water balance method. In an ideal situation, the new method showed good accuracy and it reached 90.5%. In a typical area, a set of coefficients were obtained by water level data of 8 wells in Dingxing County for 5 consecutive years and groundwater storage variable data. The representative groundwater level change in Dingxing County in 2019 was calculated as 0.16 m by an obtained coefficient. This result was 0.01 m in difference from that of the water balance method, with an accuracy of 93.3%.Based on actual water level monitoring data, a systematic method for calculating representative groundwater level changes was proposed in the new method by combining various methods. The accuracy and practicability of the method were verified by ideal examples and in Dingxing County. In the ideal example, the error of this method was 9.5% compared with that of the water balance method. This error was 6.7% in the calculation result taking Dingxing County as an example. New method can be used to calculate regional representative groundwater level changes. During the experiment, it was found that the new method need to add observation wells to ensure the accuracy of results according to the actual situation in areas with less monitoring data but more observation wells or less well distribution density or uneven distribution. After obtaining a set of weighting coefficients of a single well, the observed water level change values and corresponding coefficients of each well can be directly used to calculate the groundwater level change values of the whole representative groundwater level in the study area. The overall change in regional water level can be evaluated, which greatly reduces the workload of statistics and evaluation.
The dynamic change of groundwater level is an intuitive reflection of groundwater reserve change and basic information for studying the characteristics of groundwater occurrence and evolution. The variation characteristics of water level in a single well are affected by supplementary drainage characteristics and hydrogeological conditions. The water level of distributed wells at different points may have different trends with total groundwater reserve changes in a region. How to obtain representative values which can describe the overall regional water level changes becomes a key problem to be solved urgently. A correlation between the observed water level of multiple wells and the water level calculated by regional groundwater reservoir variables was constructed based on water balance method. The k-means clustering analysis method and Thiessen polygon were used to solve the multi-solution problem caused by the gap between the number of wells and the length of continuous water level observations of a single well. By solving the linear equation, a set of weighting coefficients that can describe the relationship between a single well water level change and the whole area water level change was obtained. These weighting coefficients and water level changes of corresponding wells were used to quickly calculate regional representative groundwater level changes.A new method was calculated and validated by numerical simulation and regional example. The results show that in an ideal example, using the water level variation data of five selected observation points and corresponding weight values, the annual variation of overall water level was 0.23 m. The calculated result was 0.02 m, different from the verified annual water level variation of 0.21 m calculated by the water balance method. In an ideal situation, the new method showed good accuracy and it reached 90.5%. In a typical area, a set of coefficients were obtained by water level data of 8 wells in Dingxing County for 5 consecutive years and groundwater storage variable data. The representative groundwater level change in Dingxing County in 2019 was calculated as 0.16 m by an obtained coefficient. This result was 0.01 m in difference from that of the water balance method, with an accuracy of 93.3%.Based on actual water level monitoring data, a systematic method for calculating representative groundwater level changes was proposed in the new method by combining various methods. The accuracy and practicability of the method were verified by ideal examples and in Dingxing County. In the ideal example, the error of this method was 9.5% compared with that of the water balance method. This error was 6.7% in the calculation result taking Dingxing County as an example. New method can be used to calculate regional representative groundwater level changes. During the experiment, it was found that the new method need to add observation wells to ensure the accuracy of results according to the actual situation in areas with less monitoring data but more observation wells or less well distribution density or uneven distribution. After obtaining a set of weighting coefficients of a single well, the observed water level change values and corresponding coefficients of each well can be directly used to calculate the groundwater level change values of the whole representative groundwater level in the study area. The overall change in regional water level can be evaluated, which greatly reduces the workload of statistics and evaluation.
2022, 20(5):886-901.
Abstract:
With the recent development of nuclear power and increasing demand for uranium resources, groundwater contamination has become a global concern from uranium production. Uranium is highly radioactive and toxic, posing a long-term potential threat to human health and the environment. Compared with other types of uranium contamination, groundwater uranium contamination has a wider spatial extent and generates higher environmental exposure and health risks. The treatment and remediation of groundwater pollution in uranium mines has become an urgent environmental problem. A comprehensive review is conducted of the basic theories, practical examples, and future development prospects of physicochemical, bioremediation and permeable reactive barrier remediation technologies based on a summary of the recent progress and achievements of groundwater pollution treatment and remediation technologies in uranium mining areas at home and abroad. Review results indicate that the physicochemical remediation technology mainly includes chemical remediation technology, electrochemical remediation technology and natural attenuation of aquifers. The application of this technology is very limited, and its treatment products are expensive. In addition to being influenced by the regional groundwater flow field, improper treatment may easily damage the site structure and its physicochemical properties, causing secondary pollution to groundwater. Microbial remediation of uranium-contaminated groundwater can be achieved through different mechanisms of action such as microbial reduction, microbial mineralization, microbial adsorption and microbial enrichment. This remediation technology has its unique advantages in the real-time, field treatment of large contaminated water bodies and is an effective way to address uranium contamination management and sustainable development. Phytoremediation technology is economically viable, technically effective, free of secondary pollution, and less environmentally disturbing for large areas of low concentration uranium contamination, and has been more widely used. Although the permeable reactive barrier technology has been widely used in the remediation of groundwater pollution in uranium mining areas and has achieved certain remediation results. There are still some problems that affect the long-term effectiveness of permeable reactive barrier operation, such as the selection of media materials, clogging of reaction media materials and complex groundwater quality. The current in situ treatment and remediation technologies for groundwater pollution in uranium mining areas are mainly studied in the laboratory, and there is a lack of engineering practice for the treatment and remediation of groundwater pollution in actual uranium mining areas. How to develop green, efficient, and low-carbon treatment and remediation technologies in combination with the hydrogeological conditions and pollution characteristics of actual uranium mining areas is an important development direction for the treatment and remediation of groundwater pollution in uranium mining areas in the future. The 101 species of phytoplankton were detected belonging to 76 genera of 8 phyla, 20 species belonging to 17 genera of diatoms, 26 species belonging to 17 genera of cyanophyta, 45 species belonging to 32 genera of chlorophyta, and 10 species belonging to 10 genera of dinoflagellates, chrysophyta, Cryptophyta, xanthophyta and Euphyta. There were 9 dominant phytoplankton species in Danjiangkou Reservoir, which were Melosira granulosus, Melosira granulata var.angustissima, Microcystis aeruginosa, Pseudanabaena sp, Glenodinium, Oscillatoria sp, Chlamydomonas sp, Cyclotella sp, Chlamydomonas globosa Snow . The average biomass of phytoplankton in Danjiangkou Reservoir in winter, spring, summer and autumn were (0.003±0.001) mg/L, (0.006±0.002) mg/L, (0.129±0.018) mg/L and (0.481±0.029) mg/L, respectively. In Danjiangkou Reservoir, the biomass of phytoplankton at Langhekou site S1 and Nancaojiayuan site S2 was relatively high, while that at Xiaogsanxia site S6 was relatively low. The Shannon-Wiener diversity index ( H '), Pielou evenness index ( J ') and Margalef richness index ( Dm ) of phytoplankton in Danjiangkou Reservoir ranged from 1.76 to 2.53, 0.48 to 0.75 and 1.89 to 3.44. The dominant species of phytoplankton in Danjiangkou Reservoir varied significantly with the season. Diatoms dominated in winter, followed by green algae-dinoalgae-diatoms in spring, and gradually developed into blue algae-green algae-diatoms in summer and autumn, indicating that the eutrophication degree of water in Danjiangkou Reservoir deepened from winter to autumn. The spatial distribution of phytoplankton in Danjiangkou Reservoir was obvious, and the phytoplankton biomass in Hanjiang Reservoir was higher than that in Danjiang Reservoir. The evaluation of diversity index showed that the water in the reservoir area was mild to moderately polluted, and the trophic status of water was higher in summer and autumn, with a certain eutrophication trend, and the risk of bloom was greater. The phytoplankton community structure in Danjiangkou Reservoir was mainly affected by environmental factors such as water temperature, transparency, total nitrogen and total phosphorus, summer, autumn season cyanobacteria, and green algae overgrowth may cause deterioration of water quality of Danjiangkou Reservoir.
With the recent development of nuclear power and increasing demand for uranium resources, groundwater contamination has become a global concern from uranium production. Uranium is highly radioactive and toxic, posing a long-term potential threat to human health and the environment. Compared with other types of uranium contamination, groundwater uranium contamination has a wider spatial extent and generates higher environmental exposure and health risks. The treatment and remediation of groundwater pollution in uranium mines has become an urgent environmental problem. A comprehensive review is conducted of the basic theories, practical examples, and future development prospects of physicochemical, bioremediation and permeable reactive barrier remediation technologies based on a summary of the recent progress and achievements of groundwater pollution treatment and remediation technologies in uranium mining areas at home and abroad. Review results indicate that the physicochemical remediation technology mainly includes chemical remediation technology, electrochemical remediation technology and natural attenuation of aquifers. The application of this technology is very limited, and its treatment products are expensive. In addition to being influenced by the regional groundwater flow field, improper treatment may easily damage the site structure and its physicochemical properties, causing secondary pollution to groundwater. Microbial remediation of uranium-contaminated groundwater can be achieved through different mechanisms of action such as microbial reduction, microbial mineralization, microbial adsorption and microbial enrichment. This remediation technology has its unique advantages in the real-time, field treatment of large contaminated water bodies and is an effective way to address uranium contamination management and sustainable development. Phytoremediation technology is economically viable, technically effective, free of secondary pollution, and less environmentally disturbing for large areas of low concentration uranium contamination, and has been more widely used. Although the permeable reactive barrier technology has been widely used in the remediation of groundwater pollution in uranium mining areas and has achieved certain remediation results. There are still some problems that affect the long-term effectiveness of permeable reactive barrier operation, such as the selection of media materials, clogging of reaction media materials and complex groundwater quality. The current in situ treatment and remediation technologies for groundwater pollution in uranium mining areas are mainly studied in the laboratory, and there is a lack of engineering practice for the treatment and remediation of groundwater pollution in actual uranium mining areas. How to develop green, efficient, and low-carbon treatment and remediation technologies in combination with the hydrogeological conditions and pollution characteristics of actual uranium mining areas is an important development direction for the treatment and remediation of groundwater pollution in uranium mining areas in the future. The 101 species of phytoplankton were detected belonging to 76 genera of 8 phyla, 20 species belonging to 17 genera of diatoms, 26 species belonging to 17 genera of cyanophyta, 45 species belonging to 32 genera of chlorophyta, and 10 species belonging to 10 genera of dinoflagellates, chrysophyta, Cryptophyta, xanthophyta and Euphyta. There were 9 dominant phytoplankton species in Danjiangkou Reservoir, which were Melosira granulosus, Melosira granulata var.angustissima, Microcystis aeruginosa, Pseudanabaena sp, Glenodinium, Oscillatoria sp, Chlamydomonas sp, Cyclotella sp, Chlamydomonas globosa Snow . The average biomass of phytoplankton in Danjiangkou Reservoir in winter, spring, summer and autumn were (0.003±0.001) mg/L, (0.006±0.002) mg/L, (0.129±0.018) mg/L and (0.481±0.029) mg/L, respectively. In Danjiangkou Reservoir, the biomass of phytoplankton at Langhekou site S1 and Nancaojiayuan site S2 was relatively high, while that at Xiaogsanxia site S6 was relatively low. The Shannon-Wiener diversity index ( H '), Pielou evenness index ( J ') and Margalef richness index ( Dm ) of phytoplankton in Danjiangkou Reservoir ranged from 1.76 to 2.53, 0.48 to 0.75 and 1.89 to 3.44. The dominant species of phytoplankton in Danjiangkou Reservoir varied significantly with the season. Diatoms dominated in winter, followed by green algae-dinoalgae-diatoms in spring, and gradually developed into blue algae-green algae-diatoms in summer and autumn, indicating that the eutrophication degree of water in Danjiangkou Reservoir deepened from winter to autumn. The spatial distribution of phytoplankton in Danjiangkou Reservoir was obvious, and the phytoplankton biomass in Hanjiang Reservoir was higher than that in Danjiang Reservoir. The evaluation of diversity index showed that the water in the reservoir area was mild to moderately polluted, and the trophic status of water was higher in summer and autumn, with a certain eutrophication trend, and the risk of bloom was greater. The phytoplankton community structure in Danjiangkou Reservoir was mainly affected by environmental factors such as water temperature, transparency, total nitrogen and total phosphorus, summer, autumn season cyanobacteria, and green algae overgrowth may cause deterioration of water quality of Danjiangkou Reservoir.
2022, 20(5):902-913.
Abstract:
Minqin oasis is a typical desert oasis in arid area with strong independence. A systematic analysis of the relationship between vegetation change and water resources in Minqin oasis has important reference value for the future construction and development of oasis in the Northwest China. The above key issue is analyzed using the Landsat multispectral remote sensing data and water resource data from 1986 to 2020. These results are as follows.The average vegetation coverage of Minqin oasis is low and its spatial distribution is generally high in the oasis and sparse at the edge of the oasis. Its vegetation coverage was generally stable from 1986 to 2020 with some improvements, and the areas with slight improvement were the largest. The oasis area and vegetation coverage showed a strong linear correlation, which demonstrated the technical rationality of defining oasis by vegetation coverage. For the period of 1986-2020, the area of oasis showed an overall increasing trend, which can be divided into three stages, rapid expansion, maintained in an oversized position, and stabilization.From 1986 to 2020, the total amount of available water resources continued to decrease on the whole, and the process is embodied in three stages, slow decrease, rapid decrease and stabilization. Among them, before 2000, groundwater was mainly exploited for water use, and surface runoff continued to decrease and remained at a low level. From 2000 to 2009, the study area began to gradually reduce groundwater exploitation in a large amount, and at the same time constructed some projects to transfer water from other basins. Therefore, water resources show a trend of rapid reduction of groundwater consumption, gradual increase of surface water, and steady reduction of total water consumption. After 2010, the amount of surface water and groundwater exploitation has gradually stabilized, which is the result of great efforts in governance in recent years. The precipitation shows a fluctuating and slowly increasing trend, which is generally stable, but there will be violent fluctuations in different years, which will have a certain impact on the oasis area.By analyzing the situation in different periods,the basic reasons are found for the different response relationship between oasis area and water resources and the indication function of this response relationship on the development status of oasis is put forward. Specifically, the change of the area of Minqin oasis from 1986 to 2020 was affected by the comprehensive influence of water resources and human factors. In the extensive expansion stage before 2000 and the drastic adjustment stage from 2001 to 2009, the relationship between oasis area and water resources showed high disorder, which was the result of man-made forced intervention. After 2010, the amount of water resources and the area of the oasis showed a good response relationship, which is also a reflection of the good development status of the oasis. In addition, the response relationship between precipitation and oasis area can also be verified at a reliable level. The data analysis of the benign development stage of Minqin oasis since 2010 shows that, with the current conditions and level of Minqin oasis, every additional 100 million m 3 of water resources can maintain an oasis area of 277 km 2 and a certain amount of attached ecological restoration areas. Compared with other current research results, the conclusions of this paper are more valuable. This is a preliminary quantitative reference for the bearing capacity of water resources to the scale of oasis when large-scale water transfer to Northwest China and then large-scale development of oases are carried out in the future.
Minqin oasis is a typical desert oasis in arid area with strong independence. A systematic analysis of the relationship between vegetation change and water resources in Minqin oasis has important reference value for the future construction and development of oasis in the Northwest China. The above key issue is analyzed using the Landsat multispectral remote sensing data and water resource data from 1986 to 2020. These results are as follows.The average vegetation coverage of Minqin oasis is low and its spatial distribution is generally high in the oasis and sparse at the edge of the oasis. Its vegetation coverage was generally stable from 1986 to 2020 with some improvements, and the areas with slight improvement were the largest. The oasis area and vegetation coverage showed a strong linear correlation, which demonstrated the technical rationality of defining oasis by vegetation coverage. For the period of 1986-2020, the area of oasis showed an overall increasing trend, which can be divided into three stages, rapid expansion, maintained in an oversized position, and stabilization.From 1986 to 2020, the total amount of available water resources continued to decrease on the whole, and the process is embodied in three stages, slow decrease, rapid decrease and stabilization. Among them, before 2000, groundwater was mainly exploited for water use, and surface runoff continued to decrease and remained at a low level. From 2000 to 2009, the study area began to gradually reduce groundwater exploitation in a large amount, and at the same time constructed some projects to transfer water from other basins. Therefore, water resources show a trend of rapid reduction of groundwater consumption, gradual increase of surface water, and steady reduction of total water consumption. After 2010, the amount of surface water and groundwater exploitation has gradually stabilized, which is the result of great efforts in governance in recent years. The precipitation shows a fluctuating and slowly increasing trend, which is generally stable, but there will be violent fluctuations in different years, which will have a certain impact on the oasis area.By analyzing the situation in different periods,the basic reasons are found for the different response relationship between oasis area and water resources and the indication function of this response relationship on the development status of oasis is put forward. Specifically, the change of the area of Minqin oasis from 1986 to 2020 was affected by the comprehensive influence of water resources and human factors. In the extensive expansion stage before 2000 and the drastic adjustment stage from 2001 to 2009, the relationship between oasis area and water resources showed high disorder, which was the result of man-made forced intervention. After 2010, the amount of water resources and the area of the oasis showed a good response relationship, which is also a reflection of the good development status of the oasis. In addition, the response relationship between precipitation and oasis area can also be verified at a reliable level. The data analysis of the benign development stage of Minqin oasis since 2010 shows that, with the current conditions and level of Minqin oasis, every additional 100 million m 3 of water resources can maintain an oasis area of 277 km 2 and a certain amount of attached ecological restoration areas. Compared with other current research results, the conclusions of this paper are more valuable. This is a preliminary quantitative reference for the bearing capacity of water resources to the scale of oasis when large-scale water transfer to Northwest China and then large-scale development of oases are carried out in the future.
2022, 20(5):914-924.
Abstract:
Phytoplankton can respond quickly to environmental changes caused by water quality parameters, climate and hydrodynamic conditions, and is often used to monitor water quality pollution. Its species composition, the succession of dominant species, and biodiversity can reflect the water ecological environment in the reservoir area. Since the middle route of the South-to-North Water Transfer Project was officially put into operation in 2014, due to the increase of the reservoir capacity area after the dam was raised, many slow flow areas were generated along the bank lines, which caused easily growing algae. Long-term water transfer may change the phytoplankton community structure of Danjiangkou Reservoir, affect the ecological environment around the water source area and cause water quality problems. Therefore, it is particularly important to understand the spatial and temporal distribution characteristics of the phytoplankton community structure in the Danjiangkou Reservoir and evaluate the potential risk of eutrophication. A portable water quality detector (HACH SL1000) was used to measure pH, temperature, conductivity (Cond), ammonia nitrogen (NH4 +-N),nitrite nitrogen (NO2--N), and nitrate nitrogen (NO3--N). Total phosphorus (TP) was measured by ammonium molybdate spectrophotometry GB 11893-1989, total nitrogen (TN) was measured by alkaline potassium persulfate ultraviolet spectrophotometry GB 11892-1989, and transparency (SD) was measured by Plug plate. A 25# plankton net (64 μm) was used to do "∞" zigzagging for 3-5 minutes at a depth of 0.5 m to collect qualitative samples of phytoplankton. A plexiglass water collector was used to collect quantitative samples of phytoplankton at a depth of 0.5 m. The number of phytoplankton was calculated by the eyepiece field method, the biological volume was calculated by morphological characteristics and measured by a microscope. The biomass was calculated by the volume conversion method. Dominance Y, Margalef richness index, Pielou evenness index, and Shannon-Wiener diversity index were selected to calculate phytoplankton community indicators. Typical correspondence analysis (CCA) between phytoplankton and environmental factors was performed using Canoco 4.5 software.
Phytoplankton can respond quickly to environmental changes caused by water quality parameters, climate and hydrodynamic conditions, and is often used to monitor water quality pollution. Its species composition, the succession of dominant species, and biodiversity can reflect the water ecological environment in the reservoir area. Since the middle route of the South-to-North Water Transfer Project was officially put into operation in 2014, due to the increase of the reservoir capacity area after the dam was raised, many slow flow areas were generated along the bank lines, which caused easily growing algae. Long-term water transfer may change the phytoplankton community structure of Danjiangkou Reservoir, affect the ecological environment around the water source area and cause water quality problems. Therefore, it is particularly important to understand the spatial and temporal distribution characteristics of the phytoplankton community structure in the Danjiangkou Reservoir and evaluate the potential risk of eutrophication. A portable water quality detector (HACH SL1000) was used to measure pH, temperature, conductivity (Cond), ammonia nitrogen (NH4 +-N),nitrite nitrogen (NO2--N), and nitrate nitrogen (NO3--N). Total phosphorus (TP) was measured by ammonium molybdate spectrophotometry GB 11893-1989, total nitrogen (TN) was measured by alkaline potassium persulfate ultraviolet spectrophotometry GB 11892-1989, and transparency (SD) was measured by Plug plate. A 25# plankton net (64 μm) was used to do "∞" zigzagging for 3-5 minutes at a depth of 0.5 m to collect qualitative samples of phytoplankton. A plexiglass water collector was used to collect quantitative samples of phytoplankton at a depth of 0.5 m. The number of phytoplankton was calculated by the eyepiece field method, the biological volume was calculated by morphological characteristics and measured by a microscope. The biomass was calculated by the volume conversion method. Dominance Y, Margalef richness index, Pielou evenness index, and Shannon-Wiener diversity index were selected to calculate phytoplankton community indicators. Typical correspondence analysis (CCA) between phytoplankton and environmental factors was performed using Canoco 4.5 software.
9 Evaluation of the performance of GEFSv12 precipitation reforecast dataset in the Huaihe River basin
2022, 20(5):925-934.
Abstract:
Due to the complexity of atmospheric physical processes, numerical weather prediction often suffers from uncertainty. Ensemble forecasts can be used to represent the uncertainty and provide uncertainty information for risk-based decision-making. In recent years, hydrometeorological ensemble forecasting has become widely applied, which uses the ensemble outputs from the numerical weather prediction models to drive the hydrological models. Bias-free, accurate and reliable ensemble precipitation forecasts are important for producing accurate streamflow forecasts. Forecast verification is the process of assessing the quality of forecasts, which involves the investigation of the properties of the joint distribution of forecasts and observations. Objective evaluations of forecast quality can help monitor operational forecasts, assess the specific strengths and weaknesses of forecast systems and support decision-making. Global Ensemble Forecast System, version 12 (GEFSv12), is a new generation of reforecast dataset generated by the National Centers for Environmental Prediction (NCEP). Reforecast dataset is generated by retrospectively re-forecasting weather for previous years using the current dynamical model. It is an important dataset for improving weather predictions. The performance of GEFSv12 precipitation forecasts has not been discussed in the Huaihe River basin, so we evaluated the performance of GEFSv12 precipitation forecasts in the Huaihe River basin in this research. Due to the systematic bias of the raw forecasts, the Bayesian Joint Probability (BJP) model was used to perform statistical post-processing on the raw GEFSv12 reforecasts. The quality of the raw and post-processed GEFSv12 ensemble reforecasts was evaluated in three aspects, i. e. , bias, accuracy and reliability. Verification metrics included Root Mean Squared Error (ERMS), Brier Skill Score ( EBSS), Continuous Ranked Probability Skill Score (ECRPSS), αindex and Reliability Diagram. The main results are as follows:(1) In terms of forecast bias, according to the map of the spatial variation of precipitation and the results of ERMS, raw GEFSv12 precipitation forecasts suffer from a large bias, and have difficulty in reproducing the spatial variability of precipitation within the Huaihe River basin. Statistical post-processing approach can effectively reduce the systematic bias of the raw forecasts. (2) In terms of forecast accuracy, the accuracy of raw GEFSv12 precipitation forecasts is better than that of climatology at lead times of 1-7 days. The accuracy of the raw and post-processed forecasts decreases with lead times. According to the EBSS,when the lead times are up to 6 days, the accuracy of raw GEFSv12 precipitation forecasts for light rain events at some grid cells in the Huaihe River basin is lower than that of climatology. The statistical post-processing approach can improve the forecast accuracy of raw forecasts for light rain at long lead times(≥6 days). According to the ECRPSS, when the lead times are up to 7 days, the accuracy of raw GEFSv12 precipitation forecasts at some grid cells in the Huaihe River basin is lower than that of climatology. The statistical post-processing approach can improve the forecast accuracy of raw forecasts at long lead times(≥7 days). (3) In terms of forecast reliability, according to the αindex and reliability diagram, the raw GEFSv12 precipitation forecasts suffer from overestimation for light and moderate rain events. Statistical post-processing approach can significantly improve forecast reliability.The results show that the raw GEFSv12 forecasts perform well in the Huaihe River basin at lead times of 1-7 days. BJP post-processing approach can effectively reduce the systematic bias of the raw forecasts and increase forecast accuracy and reliability. Post-processed precipitation ensemble forecasts can be applied in further applications such as hydrological ensemble forecasting.
Due to the complexity of atmospheric physical processes, numerical weather prediction often suffers from uncertainty. Ensemble forecasts can be used to represent the uncertainty and provide uncertainty information for risk-based decision-making. In recent years, hydrometeorological ensemble forecasting has become widely applied, which uses the ensemble outputs from the numerical weather prediction models to drive the hydrological models. Bias-free, accurate and reliable ensemble precipitation forecasts are important for producing accurate streamflow forecasts. Forecast verification is the process of assessing the quality of forecasts, which involves the investigation of the properties of the joint distribution of forecasts and observations. Objective evaluations of forecast quality can help monitor operational forecasts, assess the specific strengths and weaknesses of forecast systems and support decision-making. Global Ensemble Forecast System, version 12 (GEFSv12), is a new generation of reforecast dataset generated by the National Centers for Environmental Prediction (NCEP). Reforecast dataset is generated by retrospectively re-forecasting weather for previous years using the current dynamical model. It is an important dataset for improving weather predictions. The performance of GEFSv12 precipitation forecasts has not been discussed in the Huaihe River basin, so we evaluated the performance of GEFSv12 precipitation forecasts in the Huaihe River basin in this research. Due to the systematic bias of the raw forecasts, the Bayesian Joint Probability (BJP) model was used to perform statistical post-processing on the raw GEFSv12 reforecasts. The quality of the raw and post-processed GEFSv12 ensemble reforecasts was evaluated in three aspects, i. e. , bias, accuracy and reliability. Verification metrics included Root Mean Squared Error (ERMS), Brier Skill Score ( EBSS), Continuous Ranked Probability Skill Score (ECRPSS), αindex and Reliability Diagram. The main results are as follows:(1) In terms of forecast bias, according to the map of the spatial variation of precipitation and the results of ERMS, raw GEFSv12 precipitation forecasts suffer from a large bias, and have difficulty in reproducing the spatial variability of precipitation within the Huaihe River basin. Statistical post-processing approach can effectively reduce the systematic bias of the raw forecasts. (2) In terms of forecast accuracy, the accuracy of raw GEFSv12 precipitation forecasts is better than that of climatology at lead times of 1-7 days. The accuracy of the raw and post-processed forecasts decreases with lead times. According to the EBSS,when the lead times are up to 6 days, the accuracy of raw GEFSv12 precipitation forecasts for light rain events at some grid cells in the Huaihe River basin is lower than that of climatology. The statistical post-processing approach can improve the forecast accuracy of raw forecasts for light rain at long lead times(≥6 days). According to the ECRPSS, when the lead times are up to 7 days, the accuracy of raw GEFSv12 precipitation forecasts at some grid cells in the Huaihe River basin is lower than that of climatology. The statistical post-processing approach can improve the forecast accuracy of raw forecasts at long lead times(≥7 days). (3) In terms of forecast reliability, according to the αindex and reliability diagram, the raw GEFSv12 precipitation forecasts suffer from overestimation for light and moderate rain events. Statistical post-processing approach can significantly improve forecast reliability.The results show that the raw GEFSv12 forecasts perform well in the Huaihe River basin at lead times of 1-7 days. BJP post-processing approach can effectively reduce the systematic bias of the raw forecasts and increase forecast accuracy and reliability. Post-processed precipitation ensemble forecasts can be applied in further applications such as hydrological ensemble forecasting.
10 Application of subtractive set pair potential in the determining flood season of Foziling Reservoir
2022, 20(5):935-943.
Abstract:
To effectively characterize the comprehensive influence of uncertain factors such as precipitation and runoff on the determining flood season in the reservoir basin according to experience in the existing method of distinguishing flood season staging based on set pair analysis, a subtraction based set pair situation method was proposed to discriminate the staging results by applying the concept of determining flood season.Taking the flood season staging of Foziling Reservoir as an example, five indexes of rainstorms and floods that can affect the division of flood season were selected. According to the local climate characteristics, the flood season of Foziling Reservoir can be divided into four periods such as the early flood season, the main flood season, the summer and drought season, the late flood season, and the bare flood season.Finally, it is compared with the method of two-element connection number and three-element connection number. The results show that the subtraction based set pair situation method is simple and practical for determining flood season, and the results are reasonable.It is consistent with the conclusion of the set pair analysis method of two-element connection number and three-element connection number, can objectively reflect the situation of the influence of rainstorm and flood characteristics on flood season in Foziling Reservoir, and also can intuitively distinguish the boundary between non-flood season and flood season. The subtraction set pair potential method proposed is reasonable to apply in determining the flood season of reservoirs.
To effectively characterize the comprehensive influence of uncertain factors such as precipitation and runoff on the determining flood season in the reservoir basin according to experience in the existing method of distinguishing flood season staging based on set pair analysis, a subtraction based set pair situation method was proposed to discriminate the staging results by applying the concept of determining flood season.Taking the flood season staging of Foziling Reservoir as an example, five indexes of rainstorms and floods that can affect the division of flood season were selected. According to the local climate characteristics, the flood season of Foziling Reservoir can be divided into four periods such as the early flood season, the main flood season, the summer and drought season, the late flood season, and the bare flood season.Finally, it is compared with the method of two-element connection number and three-element connection number. The results show that the subtraction based set pair situation method is simple and practical for determining flood season, and the results are reasonable.It is consistent with the conclusion of the set pair analysis method of two-element connection number and three-element connection number, can objectively reflect the situation of the influence of rainstorm and flood characteristics on flood season in Foziling Reservoir, and also can intuitively distinguish the boundary between non-flood season and flood season. The subtraction set pair potential method proposed is reasonable to apply in determining the flood season of reservoirs.
2022, 20(5):944-952,965.
Abstract:
Floods in near-dam areas due to spatial and temporally uneven rainfall are often difficult to forecast effectively with conventional forecasting schemes, where the non-uniformity of rainfall at the basin level is an important factor affecting the accuracy of flood forecasting. There have been many studies on sub-basin division methods, but the problem of uneven rainfall distribution has rarely been studied. The spatial distribution of rainfall represented by the location of the storm center is used to refine the sub-basin division, and to improve the accuracy of flood forecasting in the near-dam area.Taking the watershed near-dam area of Wuqiangxi by extracting from the SRTMDEM 90M digital elevation model, and based on the rainfall data, the storm center map was plotted using the inverse distance weighting method. Storm center locations were considered and used to precisely divide the sub-basins. A parameter calibration method combining an automatic selection of the Monte Carlo random sampling model and manual debugging was used in the parameter calibration process. Flood simulations were carried out based on the Xin'anjiang model, while the results were used to compare with those based on the natural sub-basin division method. Twenty historical floods from 2014 to 2020 were selected, of which 13 floods were used for model calibration and 7 floods for model validation. Four floods from 2021 were selected for testing, and the comparative analysis was based on the results of the natural sub-basin flood forecasts and the results of the flood forecasts considering the location of the storm center.The results showed that sub-flood simulation based on natural sub-basins only failed for one flood in terms of flood volume error and two floods in terms of flood peak error, while the sub-flood simulation taking into account the location of the center of the storm for the sub-basins passed in terms of flood volume error and flood peak error for both periods (rate and test). Four flood simulations for 2021 that were used for testing showed the mean value of the coefficient of certainty for the sub-basins considering the location of the storm center was 0.82, which was higher than the mean value of the coefficient of certainty for the sub-basins based on natural sub-basins, which was 0.72. The results of the four flood simulations considering the location of the storm center to divide the sub-basins were within 10% of the peak error and within 20% of the flood volume error, which reached the accuracy standard of Class A. This showed that it was reasonable to divide the sub-basins considering the location of the storm center.A new method is provided for the division of sub-basins in the near-dam area of reservoirs. The method of dividing sub-basins by considering the location of the storm center can be applied to flood forecasting in the near-dam area, thus achieving the effect of improving forecast accuracy, providing a basis for flood control departments to make decisions on disaster prevention and mitigation, and reducing the losses caused by floods in the basin, with significant economic and social benefits.
Floods in near-dam areas due to spatial and temporally uneven rainfall are often difficult to forecast effectively with conventional forecasting schemes, where the non-uniformity of rainfall at the basin level is an important factor affecting the accuracy of flood forecasting. There have been many studies on sub-basin division methods, but the problem of uneven rainfall distribution has rarely been studied. The spatial distribution of rainfall represented by the location of the storm center is used to refine the sub-basin division, and to improve the accuracy of flood forecasting in the near-dam area.Taking the watershed near-dam area of Wuqiangxi by extracting from the SRTMDEM 90M digital elevation model, and based on the rainfall data, the storm center map was plotted using the inverse distance weighting method. Storm center locations were considered and used to precisely divide the sub-basins. A parameter calibration method combining an automatic selection of the Monte Carlo random sampling model and manual debugging was used in the parameter calibration process. Flood simulations were carried out based on the Xin'anjiang model, while the results were used to compare with those based on the natural sub-basin division method. Twenty historical floods from 2014 to 2020 were selected, of which 13 floods were used for model calibration and 7 floods for model validation. Four floods from 2021 were selected for testing, and the comparative analysis was based on the results of the natural sub-basin flood forecasts and the results of the flood forecasts considering the location of the storm center.The results showed that sub-flood simulation based on natural sub-basins only failed for one flood in terms of flood volume error and two floods in terms of flood peak error, while the sub-flood simulation taking into account the location of the center of the storm for the sub-basins passed in terms of flood volume error and flood peak error for both periods (rate and test). Four flood simulations for 2021 that were used for testing showed the mean value of the coefficient of certainty for the sub-basins considering the location of the storm center was 0.82, which was higher than the mean value of the coefficient of certainty for the sub-basins based on natural sub-basins, which was 0.72. The results of the four flood simulations considering the location of the storm center to divide the sub-basins were within 10% of the peak error and within 20% of the flood volume error, which reached the accuracy standard of Class A. This showed that it was reasonable to divide the sub-basins considering the location of the storm center.A new method is provided for the division of sub-basins in the near-dam area of reservoirs. The method of dividing sub-basins by considering the location of the storm center can be applied to flood forecasting in the near-dam area, thus achieving the effect of improving forecast accuracy, providing a basis for flood control departments to make decisions on disaster prevention and mitigation, and reducing the losses caused by floods in the basin, with significant economic and social benefits.
ZHUANG?Jiacheng，XING?Yincong，LI?Yanzhong，LIU?Xiaocong，YANG?Zelong
,
，ZHAO?Zichun，
WANG?Qisu，XIE?Yuchu，WANG?Jie，BAI?Peng，LIU?Changming
2022, 20(5):953-965.
Abstract:
Three Rivers Source is known as the "Chinese Water Tower" because it is an important water source conservation area in China and even in Asia. The change of runoff in the source region of the Yellow River in the Three Rivers Source played a crucial role in the ecological civilization and high-quality development of the Yellow River basin. Thus, it is of great scientific and practical significance to clarify the change of the runoff and its driving factor in the source region. The abcd -snow model coupled with the traditional abcd hydrological model and snowfall-snowmelt module was constructed to improve the traditional abcd model's insufficient simulation of snowmelt runoff in alpine regions. Monthly observed runoff data and the measured meteorological data interpolated by AnuSpline software using more than 2000 meteorological stations from 1980 to 2018. The genetic algorithm was used to calibrate the abcd-snow model parameters. Among them, the data from 1980 to 1999 was used for model calibration, and from 2000 to 2018 was used for model validation. The Nash-Sutcliffe Efficiency, Kling-Gupta Efficiency, root mean square error and BIAS were used as indicators to evaluate the applicability of the abcd-snow model. With the aid of the abcd-snow model, the change dynamics of the runoff in the source region of the Yellow River before and after the ecological protection of the Three Rivers Source was analyzed. The contributions of climate change and human activities to runoff variability were analyzed and quantified based on the detrending method. Results showed that theabcd
-snow model improved runoff simulation performance, and had good applicability in the source region of the Yellow River. The Nash-Sutcliffe Efficiency and Kling-Gupta Efficiency of the
abcd-snow model were above 0.82. Compared with the traditional abcd
model, the accuracy of the abcd-snow model is slightly improved, and the impact of different factors on the runoff change can be more reasonably analyzed. The observed runoff showed an insignificant decrease trend (slope=?0.80, p>0.05), but the runoff from 1980 to 1999 showed a significant decrease (slope=?4.12, p<0.05), and the runoff from 2000 to 2018 showed a significant increase trend (slope=3.16, p<0.05). From 1980 to 1999, the impact of climate change indicate a reduced runoff at a rate of 14.1 mm/a, with a relative contribution rate of 62.8 %. And from 2000 to 2018, climate change caused runoff to increase at a rate of 29.4 mm/a, with a relative contribution rate of 120 %. The contribution of precipitation to runoff change was the largest, with a relative contribution rate of 68.8% from 1980 to 1999 and 124.9% from 2000 to 2018. The contribution of other climatic factors to runoff change was limited, and the absolute value of the relative contribution was within 10%. Human activities reduced the runoff by 8.4 mm from 1980 to 1999, with a relative contribution rate of 37.2%. It decreased by 4.9 mm from 2000 to 2018, with a relative contribution rate of 20%. Climate change was the dominant factor in the change of runoff in the source region of the Yellow River. Among them, precipitation was the main driving factor determining the streamflow variation, and human activities dominated by ecological restoration could significantly reduce river runoff. This study could help to understand the mechanism of the impact of climate change on the runoff change in the Yellow River basin and provide a scientific reference for water resources planning in the basin.
Three Rivers Source is known as the "Chinese Water Tower" because it is an important water source conservation area in China and even in Asia. The change of runoff in the source region of the Yellow River in the Three Rivers Source played a crucial role in the ecological civilization and high-quality development of the Yellow River basin. Thus, it is of great scientific and practical significance to clarify the change of the runoff and its driving factor in the source region. The abcd -snow model coupled with the traditional abcd hydrological model and snowfall-snowmelt module was constructed to improve the traditional abcd model's insufficient simulation of snowmelt runoff in alpine regions. Monthly observed runoff data and the measured meteorological data interpolated by AnuSpline software using more than 2000 meteorological stations from 1980 to 2018. The genetic algorithm was used to calibrate the abcd-snow model parameters. Among them, the data from 1980 to 1999 was used for model calibration, and from 2000 to 2018 was used for model validation. The Nash-Sutcliffe Efficiency, Kling-Gupta Efficiency, root mean square error and BIAS were used as indicators to evaluate the applicability of the abcd-snow model. With the aid of the abcd-snow model, the change dynamics of the runoff in the source region of the Yellow River before and after the ecological protection of the Three Rivers Source was analyzed. The contributions of climate change and human activities to runoff variability were analyzed and quantified based on the detrending method. Results showed that the
2022, 20(5):966-975.
Abstract:
The man-land relationship of the floodplain in the Lower Yellow River is very complex, as it has a dual function of flood control and people’s living. Under the current conditions, there are lots of land use contradictions between flood control, ecology, life, and development leading to slower overall economic development and poorer living conditions. A study on the structure and historical evolution of land use is helpful to accurately understand the interaction between human activity and the natural environment and is of great significance to scientifically promoting the ecological protection and high-quality development of the floodplain in the Lower Yellow River. The spatial-temporal change characteristics and trajectory of land use from 1980 to 2020 were analyzed, and main factors affecting land use change were further explored using a change dynamically, transfer matrix, transfer trajectory map, and Logistic regression model. The results showed that cultivated land was the main land use type in the wide floodplain of the Lower Yellow River accounting for more than 60% of the total area followed by water and construction land. The construction land converged on the continuous large floodplain, and most of them kept a certain distance from the main river channel. From 1980 to 2020, the cultivated land area increased continuously, the water area increased and the construction land area remained stable. From 1990 to 2000, there was a drastic change due to the significant increase in cultivated land area and the significant decrease in water area. There were multi-stage and multi-objective transformation relations among different land use types. Before 2000, the transformation from water to cultivated land was the main model, with an area of 385. 43 km2 (73.65% of the total water area in 1980). But after 2000, the mutual transformation of cultivated land and construction land became dominant. There are 128. 71 km2 of cultivated land transformed into construction land, and meanwhile 129.61 km2of construction land transformed into cultivated land. All of the commonly used factors including temperature, precipitation, soil organic matter content, population density, GDP, county distance, road distance, and river distance could not explain the land use change, which indicated the uniqueness and complexity of the wide beach area in the lower Yellow River. It was suggested that river engineering, floodplain area, and management policy were the main influencing factors of land use change. The construction of river regulation engineering was the reason for the water area decreasing, as it could effectively reduce the wandering range of the main channel (the correlation coefficient of engineering density and water area is ?0.89). The large floodplain was more conducive to attracting population aggregation and was an important factor in the spatial distribution of rural residential areas (the correlation coefficient of floodplain area and rural residential area is 0.98). The policies and regulations of river management, wetland protection, and basic farmland protection constrain the expansion of construction land area and the reduction of the cultivated land area leading to the single land use structure of the wide floodplain (mainly cultivated land). In future, it is necessary to explore land classification management and land use control to promote the rational use and sustainable development of land in the wide floodplain of the lower Yellow River on basis of the natural endowment and river regulation.
The man-land relationship of the floodplain in the Lower Yellow River is very complex, as it has a dual function of flood control and people’s living. Under the current conditions, there are lots of land use contradictions between flood control, ecology, life, and development leading to slower overall economic development and poorer living conditions. A study on the structure and historical evolution of land use is helpful to accurately understand the interaction between human activity and the natural environment and is of great significance to scientifically promoting the ecological protection and high-quality development of the floodplain in the Lower Yellow River. The spatial-temporal change characteristics and trajectory of land use from 1980 to 2020 were analyzed, and main factors affecting land use change were further explored using a change dynamically, transfer matrix, transfer trajectory map, and Logistic regression model. The results showed that cultivated land was the main land use type in the wide floodplain of the Lower Yellow River accounting for more than 60% of the total area followed by water and construction land. The construction land converged on the continuous large floodplain, and most of them kept a certain distance from the main river channel. From 1980 to 2020, the cultivated land area increased continuously, the water area increased and the construction land area remained stable. From 1990 to 2000, there was a drastic change due to the significant increase in cultivated land area and the significant decrease in water area. There were multi-stage and multi-objective transformation relations among different land use types. Before 2000, the transformation from water to cultivated land was the main model, with an area of 385. 43 km2 (73.65% of the total water area in 1980). But after 2000, the mutual transformation of cultivated land and construction land became dominant. There are 128. 71 km2 of cultivated land transformed into construction land, and meanwhile 129.61 km2of construction land transformed into cultivated land. All of the commonly used factors including temperature, precipitation, soil organic matter content, population density, GDP, county distance, road distance, and river distance could not explain the land use change, which indicated the uniqueness and complexity of the wide beach area in the lower Yellow River. It was suggested that river engineering, floodplain area, and management policy were the main influencing factors of land use change. The construction of river regulation engineering was the reason for the water area decreasing, as it could effectively reduce the wandering range of the main channel (the correlation coefficient of engineering density and water area is ?0.89). The large floodplain was more conducive to attracting population aggregation and was an important factor in the spatial distribution of rural residential areas (the correlation coefficient of floodplain area and rural residential area is 0.98). The policies and regulations of river management, wetland protection, and basic farmland protection constrain the expansion of construction land area and the reduction of the cultivated land area leading to the single land use structure of the wide floodplain (mainly cultivated land). In future, it is necessary to explore land classification management and land use control to promote the rational use and sustainable development of land in the wide floodplain of the lower Yellow River on basis of the natural endowment and river regulation.
2022, 20(5):976-987.
Abstract:
Yellow River is the mother river of Chinese nation and is famous for the most sandiness river in the world. The amount and process of water and sediment have changed significantly at present. And the main problem is that the relationship between the runoff and sediment is uncertain. Human activities and climate change are the most important influence factors.Multiple methods had been applied to study the contribution rates of the two factors to runoff-sediment variation in the Yellow River, such as method of the slope changing ratio of cumulative quantity(SCRCQ), separation evaluation method and double-mass curves of precipitation vs runoff (or sediment load), multiple regression analysis, different series of comparative analysis, hydrological method, soil conservation method and separation judgment method, etc. Many scholars had analyzed the driving factors of runoff and sediment change in the Yellow River basin in the past 40 years based on the method above. And the results varied considerably due to the different assumptions of the methods, data sources and the limitations of the test areas. Fuzzy analytic hierarchy process(FAHP) has an advantage in integrating the research advantages of different scholars to a certain extent. The method based on fuzzy mutual judgment matrix belongs to subjective weight distribution method. The main scoring basis of the evaluation system is the representativeness of the investigative areas. Regional representativeness is measured by the representative coefficients. The representative coefficients are determined by the product of sediment transport ratio and area ratio in the middle Yellow River. And the scoring according to the criteria that if one study area is much more important than the other, then the scoring is closer to 1, and closer to 0 otherwise.There is a hypothetical premise that runoff and sediment discharge are only affected by precipitation. So SCRCQ had been adopted to analyze the attribution of runoff-sediment variation in the middle Yellow River to compare the results of FAHP . The contribution rate of climate change calculated by SCRCQ is equal to the ratio of the slope change rate of cumulative runoff (or sediment transport) to the slope change rate of cumulative precipitation. The results of the two methods were compared. It is showed that the contribution of human activities to runoff and sediment change was greater than that of climate change in different ages. The contribution rate of human activities to the runoff and sediment change in the middle reaches of the Yellow River in different years was consistent: the contribution of human activities to the runoff change first decreased and then increased, and that to sediment change first increased, then decreased and then increased. Climate change contributes the opposite.The impact of human activities and climate change on runoff-sediment variation are also discussed. They proved true based on the analysis of the variation of runoff, sediment and precipitation, as well as water reduction by human activities and sediment reduction by water conservancy and conservation measures. In the 1970s, 1980s, 1990s and 2000s, the contribution rates of human activities to runoff reduction were 68%, 64%, 64% and 75%, and that to sediment reduction were 45%, 65%, 59% and 69%, respectively.
Yellow River is the mother river of Chinese nation and is famous for the most sandiness river in the world. The amount and process of water and sediment have changed significantly at present. And the main problem is that the relationship between the runoff and sediment is uncertain. Human activities and climate change are the most important influence factors.Multiple methods had been applied to study the contribution rates of the two factors to runoff-sediment variation in the Yellow River, such as method of the slope changing ratio of cumulative quantity(SCRCQ), separation evaluation method and double-mass curves of precipitation vs runoff (or sediment load), multiple regression analysis, different series of comparative analysis, hydrological method, soil conservation method and separation judgment method, etc. Many scholars had analyzed the driving factors of runoff and sediment change in the Yellow River basin in the past 40 years based on the method above. And the results varied considerably due to the different assumptions of the methods, data sources and the limitations of the test areas. Fuzzy analytic hierarchy process(FAHP) has an advantage in integrating the research advantages of different scholars to a certain extent. The method based on fuzzy mutual judgment matrix belongs to subjective weight distribution method. The main scoring basis of the evaluation system is the representativeness of the investigative areas. Regional representativeness is measured by the representative coefficients. The representative coefficients are determined by the product of sediment transport ratio and area ratio in the middle Yellow River. And the scoring according to the criteria that if one study area is much more important than the other, then the scoring is closer to 1, and closer to 0 otherwise.There is a hypothetical premise that runoff and sediment discharge are only affected by precipitation. So SCRCQ had been adopted to analyze the attribution of runoff-sediment variation in the middle Yellow River to compare the results of FAHP . The contribution rate of climate change calculated by SCRCQ is equal to the ratio of the slope change rate of cumulative runoff (or sediment transport) to the slope change rate of cumulative precipitation. The results of the two methods were compared. It is showed that the contribution of human activities to runoff and sediment change was greater than that of climate change in different ages. The contribution rate of human activities to the runoff and sediment change in the middle reaches of the Yellow River in different years was consistent: the contribution of human activities to the runoff change first decreased and then increased, and that to sediment change first increased, then decreased and then increased. Climate change contributes the opposite.The impact of human activities and climate change on runoff-sediment variation are also discussed. They proved true based on the analysis of the variation of runoff, sediment and precipitation, as well as water reduction by human activities and sediment reduction by water conservancy and conservation measures. In the 1970s, 1980s, 1990s and 2000s, the contribution rates of human activities to runoff reduction were 68%, 64%, 64% and 75%, and that to sediment reduction were 45%, 65%, 59% and 69%, respectively.
2022, 20(5):988-998.
Abstract:
Flow patterns in the closed sump can be very complicated. A sudden start-up or shut-down procedure will drain or flood the closed sump. Longquan pump station belongs to the phase II project of the Central Yunnan Water Diversion Project. The safety and stability of the pumping station operation directly affect the water supply system of the phase II project and further affect the public life and industrial and agricultural production in Kunming. Therefore, it is of great significance to study the closed sump of the pumping station.A three-dimensional (3D) simulation model of closed sump was established by computational fluid dynamics software (Flow-3D) to simulate and analyze the typical hydraulic response of Longquan closed sump. During operation of a pump station, the water level in the closed sump should be within the limit of 5～19.233 m with a stable flow pattern. To ensure the safe operation of the project and verify the rationality of the preliminary design of the closed sump, it is necessary to set up typical working conditions for simulation considering various factors. Four typical working conditions were chosen for analysis, including the sudden start-up and shut-down of the extreme working conditions of the pump. The focus was on whether the sudden drop of water level leads to excessive suction vacuum lift of the pump or whether the sudden surge of water level leads to the top penetration of the closed pump.The simulation results showed that the water level of the closed sump is slightly lower than that of the main canal under design conditions, and the water level difference ranged between 0.003 m to 0.066 m. Under the most unfavorable working conditions, sudden start-up and shut-down of the pump caused the water level to deviate–0.16~+0.10 m according to the designed level. In the water distribution system, the design of the channel-sump connection section affected the flow pattern in the closed sump and the operation efficiency of the pump station. The height setting of the connecting gate chamber and the pump sump must be matched as far as possible to ensure a smooth connection.Based on the analysis following conclusions are made: (1) Because the channel-sump is connected by a short gate chamber, the water level of the closed sump is slightly lower than that of the main channel under design conditions. (2) A sudden start-up and shut-down of the pump caused the water level of the closed sump to drop or surge sharply in a short time. To ensure the super-elevation of closed sump meet the design requirements, the influence of the sudden start-up and shut-down of the pump must be considered in the design. A 1.5 m super-elevation reserved in the preliminary design could meet the requirements of safe operation, which could be used as a reference for other similar engineering designs. (3) In a water distribution system, the closed sump could be used as a surge chamber, which might suppress the water level fluctuation during the hydraulic transition process. Under the most unfavorable working conditions, the sudden drop and surge of the water level could not lead to excessive suction vacuum lift of the pump or the top penetration of the closed pump. Therefore, the preliminary design scheme of this closed sump is feasible. Results of this research can provide technical support for the design and operation of this project, and also provide references for the design and operation scheduling of other similar projects.
Flow patterns in the closed sump can be very complicated. A sudden start-up or shut-down procedure will drain or flood the closed sump. Longquan pump station belongs to the phase II project of the Central Yunnan Water Diversion Project. The safety and stability of the pumping station operation directly affect the water supply system of the phase II project and further affect the public life and industrial and agricultural production in Kunming. Therefore, it is of great significance to study the closed sump of the pumping station.A three-dimensional (3D) simulation model of closed sump was established by computational fluid dynamics software (Flow-3D) to simulate and analyze the typical hydraulic response of Longquan closed sump. During operation of a pump station, the water level in the closed sump should be within the limit of 5～19.233 m with a stable flow pattern. To ensure the safe operation of the project and verify the rationality of the preliminary design of the closed sump, it is necessary to set up typical working conditions for simulation considering various factors. Four typical working conditions were chosen for analysis, including the sudden start-up and shut-down of the extreme working conditions of the pump. The focus was on whether the sudden drop of water level leads to excessive suction vacuum lift of the pump or whether the sudden surge of water level leads to the top penetration of the closed pump.The simulation results showed that the water level of the closed sump is slightly lower than that of the main canal under design conditions, and the water level difference ranged between 0.003 m to 0.066 m. Under the most unfavorable working conditions, sudden start-up and shut-down of the pump caused the water level to deviate–0.16~+0.10 m according to the designed level. In the water distribution system, the design of the channel-sump connection section affected the flow pattern in the closed sump and the operation efficiency of the pump station. The height setting of the connecting gate chamber and the pump sump must be matched as far as possible to ensure a smooth connection.Based on the analysis following conclusions are made: (1) Because the channel-sump is connected by a short gate chamber, the water level of the closed sump is slightly lower than that of the main channel under design conditions. (2) A sudden start-up and shut-down of the pump caused the water level of the closed sump to drop or surge sharply in a short time. To ensure the super-elevation of closed sump meet the design requirements, the influence of the sudden start-up and shut-down of the pump must be considered in the design. A 1.5 m super-elevation reserved in the preliminary design could meet the requirements of safe operation, which could be used as a reference for other similar engineering designs. (3) In a water distribution system, the closed sump could be used as a surge chamber, which might suppress the water level fluctuation during the hydraulic transition process. Under the most unfavorable working conditions, the sudden drop and surge of the water level could not lead to excessive suction vacuum lift of the pump or the top penetration of the closed pump. Therefore, the preliminary design scheme of this closed sump is feasible. Results of this research can provide technical support for the design and operation of this project, and also provide references for the design and operation scheduling of other similar projects.
2022, 20(5):999-1,009.
Abstract:
In order to solve the problems of uneven distribution of water resources, mismatched water and soil resources, and serious shortage of water resources, China has launched many long-distance water diversion projects during recent years. With the implementation of these projects, a large number of headrace tunnels has also been constructed, which is continuously developing and improving the construction methods, and now the shield method has gradually become the main construction method of tunnels. As the shield tunneling is a complex system process influenced by a variety of risk factors, construction risk accidents occur from time to time, resulting in delays of the construction period as well as loss of life and property. Therefore, predicting and analyzing the possible risk path of the shield tunneling of long-distance water conveyance tunnel plays an important role in ensuring the safe construction of the tunnel project.At present, the risk analysis of tunnel shield construction schedule have several limitations. First, the correlation between the risk factors of shield tunneling of headrace tunnel is not considered; Secondly, the existing research results are mostly based on subway and traffic tunnel, and the differences in construction technology and risk management of long-distance headrace tunnel of hydraulic engineering are not considered. This paper takes the shield tunneling of long-distance water conveyance tunnel in the water diversion project of hydraulic engineering as the research object. Statistical analysis are made on a large number of collected data of water diversion tunnel construction cases, and the risk causing indicators and possible risk events are extracted of tunnel engineering shield tunneling. By using interpretative structural model, the causal hierarchy analysis and network topology diagram construction are conducted. Then a prediction model of shield construction risk events based on Bayesian network is established, and the reliability of the model is preliminarily verified through Bayesian network learning.Finally, the risk event prediction model obtained has been applied to the shield construction project of Xixiayuan Chuanqin Tunnel. The reverse diagnosis reasoning technology of Bayesian network is used to calculate the maximum possible path of risk events and determine the key factors leading to risk events in shield construction. The results show that the risk accident path calculated by the model is consistent with the actual construction situation at the current stage of the project. The reliability and applicability of the model are verified, and according to the prediction results of the risk accident path, the guidance is provided for the troubleshooting and governance of the risk hidden dangers in the subsequent construction of Chuanqin Tunnel.Conclusion: (1) The risk path prediction model of tunnel shield construction is established. Through the interpretation of the structural model, the correlation between various risk events that affect the tunnel shield construction progress is determined, and then the Bayesian network model is established, forming an effective method to predict the development trend of the tunnel shield construction risk events through the tunnel shield construction risk factors. (2) The reliability and applicability of the model are verified. Through the application of the shield construction project of Chuanqin Tunnel Project, the predicted result of risk causal chain is consistent with the actual construction situation, and the model can provide real-time decision support for managers. (3) This model can be directly applied to shield tunneling of headrace tunnels with similar construction conditions; for different situations, such as special geological conditions and different shield machines, some parameters of the model need to be appropriately changed, but the model and calculation process established in this paper are applicable.
In order to solve the problems of uneven distribution of water resources, mismatched water and soil resources, and serious shortage of water resources, China has launched many long-distance water diversion projects during recent years. With the implementation of these projects, a large number of headrace tunnels has also been constructed, which is continuously developing and improving the construction methods, and now the shield method has gradually become the main construction method of tunnels. As the shield tunneling is a complex system process influenced by a variety of risk factors, construction risk accidents occur from time to time, resulting in delays of the construction period as well as loss of life and property. Therefore, predicting and analyzing the possible risk path of the shield tunneling of long-distance water conveyance tunnel plays an important role in ensuring the safe construction of the tunnel project.At present, the risk analysis of tunnel shield construction schedule have several limitations. First, the correlation between the risk factors of shield tunneling of headrace tunnel is not considered; Secondly, the existing research results are mostly based on subway and traffic tunnel, and the differences in construction technology and risk management of long-distance headrace tunnel of hydraulic engineering are not considered. This paper takes the shield tunneling of long-distance water conveyance tunnel in the water diversion project of hydraulic engineering as the research object. Statistical analysis are made on a large number of collected data of water diversion tunnel construction cases, and the risk causing indicators and possible risk events are extracted of tunnel engineering shield tunneling. By using interpretative structural model, the causal hierarchy analysis and network topology diagram construction are conducted. Then a prediction model of shield construction risk events based on Bayesian network is established, and the reliability of the model is preliminarily verified through Bayesian network learning.Finally, the risk event prediction model obtained has been applied to the shield construction project of Xixiayuan Chuanqin Tunnel. The reverse diagnosis reasoning technology of Bayesian network is used to calculate the maximum possible path of risk events and determine the key factors leading to risk events in shield construction. The results show that the risk accident path calculated by the model is consistent with the actual construction situation at the current stage of the project. The reliability and applicability of the model are verified, and according to the prediction results of the risk accident path, the guidance is provided for the troubleshooting and governance of the risk hidden dangers in the subsequent construction of Chuanqin Tunnel.Conclusion: (1) The risk path prediction model of tunnel shield construction is established. Through the interpretation of the structural model, the correlation between various risk events that affect the tunnel shield construction progress is determined, and then the Bayesian network model is established, forming an effective method to predict the development trend of the tunnel shield construction risk events through the tunnel shield construction risk factors. (2) The reliability and applicability of the model are verified. Through the application of the shield construction project of Chuanqin Tunnel Project, the predicted result of risk causal chain is consistent with the actual construction situation, and the model can provide real-time decision support for managers. (3) This model can be directly applied to shield tunneling of headrace tunnels with similar construction conditions; for different situations, such as special geological conditions and different shield machines, some parameters of the model need to be appropriately changed, but the model and calculation process established in this paper are applicable.
2022, 20(5):1010-1018.
Abstract:
Monitoring data analysis is an important part of dam health monitoring to ensure the long-term safe operation of the dam. Vertical displacement is one of the main component in dam deformation monitoring. It can reflect the settlement deformation of the dam intuitively. The analysis of vertical deformation law and mechanism of the dam is a key content of data monitoring analysis. The main factors affecting the vertical displacement of the concrete dam are water pressure, temperature, and time-varying, and the influence degree of each factor is different. For the concrete dam with a low water head or little change of water level, the temperature has a greater influence on the vertical displacement, while for the high water head concrete dam, the water pressure has a greater influence than other factors. The effect of water pressure on the vertical displacement of a gravity arch dam is mainly manifested in two aspects: (1) The dam body tilts downstream due to the action of reservoir water pressure, which leads to the upstream surface of the dam body to lift and the downstream surface to sink. (2) The gravity action of the reservoir water causes the settlement of the reservoir plate and the dam foundation, which causes the dam body to tilt upstream, resulting in the upstream surface of the dam body sinking and the downstream surface lifting. The water pressure and temperature influence on deformation at different elevations of Longyangxia arch dam are different, which results in “phase difference” in the vertical displacement of the dam. The reservoir water pressure in the high elevation part is dominant, and the influence of temperature is comparatively small. The foundation of the dam is less affected by external air temperature and is mainly affected by upstream water pressure. Due to the complex interaction between water pressure and temperature in the middle part of the dam, the hysteresis phenomenon of water pressure effect and the abnormal phenomenon of temperature effect appears. The uplift pressure in the upstream and downstream of the curtain at the no.7 and no.8 dam sections foundation is larger than other dam sections, which leads to the large vertical displacement of the no.7 dam foundation. Therefore, the monitoring of seepage and deformation in this section should be strengthened. During the operation of high water levels since 2018, the deformation of the dam body has an obvious response, and the variation trend of the measured vertical displacement of the dam has changed significantly. Although Longyangxia arch dam has operated for more than 30 years, the vertical displacement of some measuring points of the dam still shows a trend of continuous deformation and has not reached a stable state. The settlement rate of no.6, 7 and 8 dam sections at 2 463m elevation is faster, so the observation of these sections should be strengthened. The vertical deformation of Longyangxia arch dam from the no.14 dam section to the right bank foundation is contrary to that of other dam sections at the same elevation, which sinks as the water level rises and lifts when the water level decreases.
Monitoring data analysis is an important part of dam health monitoring to ensure the long-term safe operation of the dam. Vertical displacement is one of the main component in dam deformation monitoring. It can reflect the settlement deformation of the dam intuitively. The analysis of vertical deformation law and mechanism of the dam is a key content of data monitoring analysis. The main factors affecting the vertical displacement of the concrete dam are water pressure, temperature, and time-varying, and the influence degree of each factor is different. For the concrete dam with a low water head or little change of water level, the temperature has a greater influence on the vertical displacement, while for the high water head concrete dam, the water pressure has a greater influence than other factors. The effect of water pressure on the vertical displacement of a gravity arch dam is mainly manifested in two aspects: (1) The dam body tilts downstream due to the action of reservoir water pressure, which leads to the upstream surface of the dam body to lift and the downstream surface to sink. (2) The gravity action of the reservoir water causes the settlement of the reservoir plate and the dam foundation, which causes the dam body to tilt upstream, resulting in the upstream surface of the dam body sinking and the downstream surface lifting. The water pressure and temperature influence on deformation at different elevations of Longyangxia arch dam are different, which results in “phase difference” in the vertical displacement of the dam. The reservoir water pressure in the high elevation part is dominant, and the influence of temperature is comparatively small. The foundation of the dam is less affected by external air temperature and is mainly affected by upstream water pressure. Due to the complex interaction between water pressure and temperature in the middle part of the dam, the hysteresis phenomenon of water pressure effect and the abnormal phenomenon of temperature effect appears. The uplift pressure in the upstream and downstream of the curtain at the no.7 and no.8 dam sections foundation is larger than other dam sections, which leads to the large vertical displacement of the no.7 dam foundation. Therefore, the monitoring of seepage and deformation in this section should be strengthened. During the operation of high water levels since 2018, the deformation of the dam body has an obvious response, and the variation trend of the measured vertical displacement of the dam has changed significantly. Although Longyangxia arch dam has operated for more than 30 years, the vertical displacement of some measuring points of the dam still shows a trend of continuous deformation and has not reached a stable state. The settlement rate of no.6, 7 and 8 dam sections at 2 463m elevation is faster, so the observation of these sections should be strengthened. The vertical deformation of Longyangxia arch dam from the no.14 dam section to the right bank foundation is contrary to that of other dam sections at the same elevation, which sinks as the water level rises and lifts when the water level decreases.
2022, 20(5):1019-1026.
Abstract:
A comprehensive groundwater overdraft control pilot project was launched in Hebei Province, China due to severe groundwater overexploitation problems, and many control measures were implemented including highly efficient irrigation, water source replacement, planting structure adjustment, etc. The performance, implementation difficulty, and investment of different measures vary drastically. To further upscale and promote the pilot project, the comprehensive evaluation of each measure became increasingly important. Many existing studies focus on the evaluation of the overall effect of the project, such as reduced pumping rate, water level change, storage change, etc., but failed to answer the question of the performance and economic efficiency of specific measures. Different research methods had been used synergistically including irrigation on-site tests, household visits, surveys, technical and economic analysis. Comparative experiments on the same crop with different irrigation methods were conducted yearly throughout the whole duration of the project within the pilot and non-pilot areas in Shijiazhuang, Cangzhou, Hengshui, Xingtai and Handan. The water-saving capacity was attained by analyzing the water consumption of traditional irrigation methods, and water-saving irrigation methods. The performance of different control measures for the whole pilot area was calculated based on the groundwater abstraction rate change analysis before and after the comprehensive governance. The input-output ratio of different groundwater overdraft control measures was estimated by calculating the investment per unit of reduced groundwater extraction. The investment equaled the initial investment and the additional cost for the following years. The reduced groundwater extraction could be deduced using the groundwater abstraction rate change from the performance evaluation. The results show that adopted measures played an essential role in alleviating groundwater overdrafts. Taking the wheat-maize planting pattern as an example, the annual saved water per hectare of sprinkling irrigation, rainfed farming, pipe irrigation, integration of water into fertilizer, following, and replacing with non-agriculture crops reached 600-1 200 m3, 2 700 m3, 600-1 200 m3, 600-1 200 m3, 2 700-4 200 m3, 2 400-2 700 m3, respectively, compared to traditional irrigation. The drip irrigation to vegetables could save water up to 2 700 m3per hectare, and 3 900 m3 of water per hectare could be saved by water source replacement. The initial annual investment for water-saving irrigation and water source replacement was 16.7 yuan/m3, while the annual initial investment for replacing the non-agricultural crop, rain-fed farming, and the following was only 8.8, 4.2, and 2.6 yuan/m3, respectively. But the annual investment for the latter three methods in the last year reached 26.5, 20.8, and 12.8 yuan/m3. This concluded that planting structure adjustment and water source replacement have posed an obvious effect on reducing groundwater extraction. The high-efficiency water-saving irrigation and water source replacement methods require relatively high construction investment at the initial stage, making the cost of a single unit higher. The initial investment in planting structure adjustment is relatively small, but the investment of a single unit could reduce extraction increased linearly year by year. By combining the results of the performance evaluation and the input-output ratio of different control measures, the applicable scenarios and priorities could be deduced, which could work as a reference for the management of groundwater overdraft control in the future.
A comprehensive groundwater overdraft control pilot project was launched in Hebei Province, China due to severe groundwater overexploitation problems, and many control measures were implemented including highly efficient irrigation, water source replacement, planting structure adjustment, etc. The performance, implementation difficulty, and investment of different measures vary drastically. To further upscale and promote the pilot project, the comprehensive evaluation of each measure became increasingly important. Many existing studies focus on the evaluation of the overall effect of the project, such as reduced pumping rate, water level change, storage change, etc., but failed to answer the question of the performance and economic efficiency of specific measures. Different research methods had been used synergistically including irrigation on-site tests, household visits, surveys, technical and economic analysis. Comparative experiments on the same crop with different irrigation methods were conducted yearly throughout the whole duration of the project within the pilot and non-pilot areas in Shijiazhuang, Cangzhou, Hengshui, Xingtai and Handan. The water-saving capacity was attained by analyzing the water consumption of traditional irrigation methods, and water-saving irrigation methods. The performance of different control measures for the whole pilot area was calculated based on the groundwater abstraction rate change analysis before and after the comprehensive governance. The input-output ratio of different groundwater overdraft control measures was estimated by calculating the investment per unit of reduced groundwater extraction. The investment equaled the initial investment and the additional cost for the following years. The reduced groundwater extraction could be deduced using the groundwater abstraction rate change from the performance evaluation. The results show that adopted measures played an essential role in alleviating groundwater overdrafts. Taking the wheat-maize planting pattern as an example, the annual saved water per hectare of sprinkling irrigation, rainfed farming, pipe irrigation, integration of water into fertilizer, following, and replacing with non-agriculture crops reached 600-1 200 m3, 2 700 m3, 600-1 200 m3, 600-1 200 m3, 2 700-4 200 m3, 2 400-2 700 m3, respectively, compared to traditional irrigation. The drip irrigation to vegetables could save water up to 2 700 m3per hectare, and 3 900 m3 of water per hectare could be saved by water source replacement. The initial annual investment for water-saving irrigation and water source replacement was 16.7 yuan/m3, while the annual initial investment for replacing the non-agricultural crop, rain-fed farming, and the following was only 8.8, 4.2, and 2.6 yuan/m3, respectively. But the annual investment for the latter three methods in the last year reached 26.5, 20.8, and 12.8 yuan/m3. This concluded that planting structure adjustment and water source replacement have posed an obvious effect on reducing groundwater extraction. The high-efficiency water-saving irrigation and water source replacement methods require relatively high construction investment at the initial stage, making the cost of a single unit higher. The initial investment in planting structure adjustment is relatively small, but the investment of a single unit could reduce extraction increased linearly year by year. By combining the results of the performance evaluation and the input-output ratio of different control measures, the applicable scenarios and priorities could be deduced, which could work as a reference for the management of groundwater overdraft control in the future.
2022, 20(5):1027-1040.
Abstract:
Seasonally frozen soil is widely distributed in Qinghai-Tibet Plateau and soil freeze-thaw events occur frequently in the headstream of Nujiang River. Due to the large altitude difference and the asynchrony of meteorological changes between different regions in the headstream region, the occurrence of freeze-thaw events has different characteristics and certain regularities in time and space.To explore the characteristics of freeze-thaw in seasonally frozen soil, the short-duration freeze-thaw events that occurred in the 5 cm surface soil of 4 typical experimental fields of the headstream region were selected. The connotation of the short-duration freeze-thaw events was clarified and a specific identification method for these events was proposed. The characteristics of events were evaluated and the evaluation was formed by five aspects: The start and end time, the total duration, the total number of times, the cycle frequency, and the intensity. In the intensity evaluation, the Copula function method was used to combine three single indexes of temperature difference, humidity difference, and duration to construct a more comprehensive and efficient comprehensive index, and the two different processes of freeze and freeze-thaw are evaluated separately.The evaluation results showed that from September 1, 2019, to August 31, 2020, the short-duration freeze-thaw events in the 4 typical experimental fields had a maximum difference of 45 days in the start time and 64 days in the end time. The maximum difference in the total duration, the total number of times and the cycle frequency can reach 112 days, 79 times, and 0.058 times/day, respectively. The maximum difference in the cumulative intensity and the maximum intensity can reach 50.991 and 0.034 for the freezing process, 50.991 and 0.034 for the freeze-thaw process.The characteristics of short-duration freeze-thaw events in different geographical locations in the headstream of Nujiang River are different. The events in the middle-altitude area ( 4 500 - 5 000 m.a.s.l.) showed regularity with a longer total duration, higher total number of times, cycle frequency, and accumulation intensity than the events in the low-altitude area (< 4500 m.a.s.l.) and the high-altitude area (> 5 000 m.a.s.l.). High-frequency or high-intensity events can greatly affect or even destroy the soil environment. In this regard, more attention should be paid to freeze-thaw monitoring and protection in the northern part of the basin. Freeze and freeze-thaw were two processes with different intensity effects, and evaluated respectively can avoid the problem of weakened strength. The results are conducive to clarifying the freeze-thaw characteristics of seasonally frozen soil in the plateau alpine region, and reflecting the impact of short-duration freeze-thaw events, providing support for water and soil conservation, frost heaving, thaw collapsing hazards prevention and control in the headstream.
Seasonally frozen soil is widely distributed in Qinghai-Tibet Plateau and soil freeze-thaw events occur frequently in the headstream of Nujiang River. Due to the large altitude difference and the asynchrony of meteorological changes between different regions in the headstream region, the occurrence of freeze-thaw events has different characteristics and certain regularities in time and space.To explore the characteristics of freeze-thaw in seasonally frozen soil, the short-duration freeze-thaw events that occurred in the 5 cm surface soil of 4 typical experimental fields of the headstream region were selected. The connotation of the short-duration freeze-thaw events was clarified and a specific identification method for these events was proposed. The characteristics of events were evaluated and the evaluation was formed by five aspects: The start and end time, the total duration, the total number of times, the cycle frequency, and the intensity. In the intensity evaluation, the Copula function method was used to combine three single indexes of temperature difference, humidity difference, and duration to construct a more comprehensive and efficient comprehensive index, and the two different processes of freeze and freeze-thaw are evaluated separately.The evaluation results showed that from September 1, 2019, to August 31, 2020, the short-duration freeze-thaw events in the 4 typical experimental fields had a maximum difference of 45 days in the start time and 64 days in the end time. The maximum difference in the total duration, the total number of times and the cycle frequency can reach 112 days, 79 times, and 0.058 times/day, respectively. The maximum difference in the cumulative intensity and the maximum intensity can reach 50.991 and 0.034 for the freezing process, 50.991 and 0.034 for the freeze-thaw process.The characteristics of short-duration freeze-thaw events in different geographical locations in the headstream of Nujiang River are different. The events in the middle-altitude area ( 4 500 - 5 000 m.a.s.l.) showed regularity with a longer total duration, higher total number of times, cycle frequency, and accumulation intensity than the events in the low-altitude area (< 4500 m.a.s.l.) and the high-altitude area (> 5 000 m.a.s.l.). High-frequency or high-intensity events can greatly affect or even destroy the soil environment. In this regard, more attention should be paid to freeze-thaw monitoring and protection in the northern part of the basin. Freeze and freeze-thaw were two processes with different intensity effects, and evaluated respectively can avoid the problem of weakened strength. The results are conducive to clarifying the freeze-thaw characteristics of seasonally frozen soil in the plateau alpine region, and reflecting the impact of short-duration freeze-thaw events, providing support for water and soil conservation, frost heaving, thaw collapsing hazards prevention and control in the headstream.
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