Supervisor: Ministry of Water Resources of the People's Republic of China
Sponsor: Nanjing Institute of water resources, China Water Conservancy Society
Chief Editor: Zhang JianYun
Address: No.34, Hujuguan, Nanjing
Post Code: 210024
Tel: 025-85829770
Email: skxjz@nhri.cn
ISSN 1001-6791
CN 32-1309/P
Postal Code:28-146
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2023, 34(4): 481-489.
doi: 10.14042/j.cnki.32.1309.2023.04.001
Abstract:
As a typical cold mountainous region,the Tibetan Plateau (TP) is characterized by complex water cycle processes,including snow and glacier melting,soil freezing and thawing,and rainfall runoff.Driven by global climate change over the past several decades,discharges of the major rivers on the TP have changed significantly,influencing the water resource utilization and ecosystem in the downstream regions.This study analyzed the discharge variations at 12 hydrological stations in six major exoreic TP rivers from 1980 to 2015,including Heihe River,Yellow River,Yangtze River,Lancang River,Nu River,and Yarlung-Tsangpo River.The precipitation variations in six basins were also analyzed based on five datasets.Results show that the runoff of stations located north of Changdu-Jiayuqiao decreased before 1999,and turned into an increasing trend after 1999.The stations located in the South TP had reversed runoff variations.Such variation can be described as a dipole spatiotemporal variation pattern.The precipitation variations over the TP were similar to that of runoff,showing a dipole pattern with reversed variations bounded by 32°N.These findings are helpful for runoff change mechanism understanding and projection under climate change,providing a scientific foundation for water resource management.
As a typical cold mountainous region,the Tibetan Plateau (TP) is characterized by complex water cycle processes,including snow and glacier melting,soil freezing and thawing,and rainfall runoff.Driven by global climate change over the past several decades,discharges of the major rivers on the TP have changed significantly,influencing the water resource utilization and ecosystem in the downstream regions.This study analyzed the discharge variations at 12 hydrological stations in six major exoreic TP rivers from 1980 to 2015,including Heihe River,Yellow River,Yangtze River,Lancang River,Nu River,and Yarlung-Tsangpo River.The precipitation variations in six basins were also analyzed based on five datasets.Results show that the runoff of stations located north of Changdu-Jiayuqiao decreased before 1999,and turned into an increasing trend after 1999.The stations located in the South TP had reversed runoff variations.Such variation can be described as a dipole spatiotemporal variation pattern.The precipitation variations over the TP were similar to that of runoff,showing a dipole pattern with reversed variations bounded by 32°N.These findings are helpful for runoff change mechanism understanding and projection under climate change,providing a scientific foundation for water resource management.
2023, 34(4): 490-498.
doi: 10.14042/j.cnki.32.1309.2023.04.002
Abstract:
Investigating the spatial pattern and temporal variations of potential evaporation is of great importance in understanding the variations of the actual evaporation and water balance in the Tibetan Plateau.Several hydroclimatic and environmental variables display distinct spatial and temporal patterns in the Tibetan Plateau,but the patterns in the potential evaporation remain unclear.In this study,the potential evaporation from 1980 to 2015 was calculated by the Penman equation using the data of 312 stations in the Tibetan Plateau and its surrounding areas.The potential evaporation and its radiation and aerodynamic terms show non-monotonic spatiotemporal variations,but the variations differ between the north and south of the Tibetan Plateau.The mean annual potential evaporation is bound by 32°30'N and shows a "V" shape pattern with latitude:decreasing with latitude in the south region and increasing with latitude in the north.The annual potential evaporation and its radiation term and aerodynamic term all show non-monotonic changes with 1999 as the turning point but the trends substantially differ between the north and south regions.The results reveal the distinct spatial and temporal patterns of the impacts of the westerlies and the Indian monsoon on the potential evaporation.
Investigating the spatial pattern and temporal variations of potential evaporation is of great importance in understanding the variations of the actual evaporation and water balance in the Tibetan Plateau.Several hydroclimatic and environmental variables display distinct spatial and temporal patterns in the Tibetan Plateau,but the patterns in the potential evaporation remain unclear.In this study,the potential evaporation from 1980 to 2015 was calculated by the Penman equation using the data of 312 stations in the Tibetan Plateau and its surrounding areas.The potential evaporation and its radiation and aerodynamic terms show non-monotonic spatiotemporal variations,but the variations differ between the north and south of the Tibetan Plateau.The mean annual potential evaporation is bound by 32°30'N and shows a "V" shape pattern with latitude:decreasing with latitude in the south region and increasing with latitude in the north.The annual potential evaporation and its radiation term and aerodynamic term all show non-monotonic changes with 1999 as the turning point but the trends substantially differ between the north and south regions.The results reveal the distinct spatial and temporal patterns of the impacts of the westerlies and the Indian monsoon on the potential evaporation.
2023, 34(4): 499-509.
doi: 10.14042/j.cnki.32.1309.2023.04.003
Abstract:
Vegetation is a key component of the complex coupled human-nature system,and there is a prominent greening trend in the Yellow River basin (YRB).We used the NOAA Climate Data Record (CDR) of AVHRR Normalized Difference Vegetation Index (NDVI) daily dataset from 1982 to 2020 and applied a land surface phenology method to investigate the differentiation of the human-nature relationship in the YRB from a vegetation perspective.To extract vegetation intra-annual indices,we applied a land surface phenology method that integrates the Savitzky-Golay filter and double logistic fitting,in addition to the traditional annual vegetation index based on annual NDVI series.We analyzed the trend of the inter-annual and intra-annual vegetation indices and summarized the typical types of vegetation changes using k-means clustering.We also conducted an analysis of the driving factors behind the different vegetation changes.Our results demonstrated that the integrated intra-annual indices extraction method is suitable for various vegetation types in the YRB,achieving a high recognition rate of 98%.The spatial and temporal variations in the extracted intra-annual indices revealed differences in ecological engineering and agricultural activities under distinct climatic conditions.We identified five types of ecological engineering-dominated vegetation changes and two types of agricultural-dominated vegetation changes,and found that the significance of agricultural vegetation changes was comparable to that of ecological engineering.Agricultural intensification is a critical factor that cannot be ignored in vegetation research of the YRB.Given the tense relationship between humans and nature,and the severe water-food-ecological contradictions in the YRB,it is crucial to optimize agricultural water use and ensure food security.
Vegetation is a key component of the complex coupled human-nature system,and there is a prominent greening trend in the Yellow River basin (YRB).We used the NOAA Climate Data Record (CDR) of AVHRR Normalized Difference Vegetation Index (NDVI) daily dataset from 1982 to 2020 and applied a land surface phenology method to investigate the differentiation of the human-nature relationship in the YRB from a vegetation perspective.To extract vegetation intra-annual indices,we applied a land surface phenology method that integrates the Savitzky-Golay filter and double logistic fitting,in addition to the traditional annual vegetation index based on annual NDVI series.We analyzed the trend of the inter-annual and intra-annual vegetation indices and summarized the typical types of vegetation changes using k-means clustering.We also conducted an analysis of the driving factors behind the different vegetation changes.Our results demonstrated that the integrated intra-annual indices extraction method is suitable for various vegetation types in the YRB,achieving a high recognition rate of 98%.The spatial and temporal variations in the extracted intra-annual indices revealed differences in ecological engineering and agricultural activities under distinct climatic conditions.We identified five types of ecological engineering-dominated vegetation changes and two types of agricultural-dominated vegetation changes,and found that the significance of agricultural vegetation changes was comparable to that of ecological engineering.Agricultural intensification is a critical factor that cannot be ignored in vegetation research of the YRB.Given the tense relationship between humans and nature,and the severe water-food-ecological contradictions in the YRB,it is crucial to optimize agricultural water use and ensure food security.
2023, 34(4): 510-519.
doi: 10.14042/j.cnki.32.1309.2023.04.004
Abstract:
Aiming at the conflict between the modeling accuracy and the computation time cost faced by existing urban pluvial flood models,a hierarchically nested multi-scale model technique is proposed according to the spatial and temporal characteristics of urban pluvial flooding.Based on a fully distributed model,the fine mesh of the surface model is nested with a larger scaled computation mesh named as the super mesh.The fine mesh is only used to simulate the surface flood where it happens,while the super mesh is used to simulate rainfall runoff where the surface flood doesn't happen yet.The fine mesh and the super mesh switch each other automatically when it is necessary during the simulation.This hierarchically nested multi-scale modeling technique is applied to simulation on the flood event happening under Chengzhuangzi railway bridge in Beijing on August 12,2020.The case study shows that the proposed hierarchically nested multi-scale modeling technique can save plenty of computation time while assuring a comparable simulation result.This study will improve modeling application to large-scale urban pluvial floods.
Aiming at the conflict between the modeling accuracy and the computation time cost faced by existing urban pluvial flood models,a hierarchically nested multi-scale model technique is proposed according to the spatial and temporal characteristics of urban pluvial flooding.Based on a fully distributed model,the fine mesh of the surface model is nested with a larger scaled computation mesh named as the super mesh.The fine mesh is only used to simulate the surface flood where it happens,while the super mesh is used to simulate rainfall runoff where the surface flood doesn't happen yet.The fine mesh and the super mesh switch each other automatically when it is necessary during the simulation.This hierarchically nested multi-scale modeling technique is applied to simulation on the flood event happening under Chengzhuangzi railway bridge in Beijing on August 12,2020.The case study shows that the proposed hierarchically nested multi-scale modeling technique can save plenty of computation time while assuring a comparable simulation result.This study will improve modeling application to large-scale urban pluvial floods.
2023, 34(4): 520-529.
doi: 10.14042/j.cnki.32.1309.2023.04.005
Abstract:
The Wudongde-Baihetan-Xiluodu-Xiangjiaba cascade reservoirs in the lower Jingsha River shoulder the downstream flood control tasks jointly,and the complementary equivalent relationship between the flood prevention storage of these reservoirs is not considered during the planning and design stage.Based on the principle of water balance and the assumption of total flood prevention storage unchanged,the flood prevention storage of cascade reservoirs was aggregated and decomposed.The optimal allocation calculation formulas for two-reservoir and multi-reservoir systems were derived and solved numerically with power generation as the main objective.Results show that the Wudongde and Xiangjiaba reservoirs with relatively small storage allocate about 1.180 and 0.216 billion m3 of the flood prevention storage to the Baihetan and Xiluodu reservoirs respectively,which can generate extra 445 and 32 million kW·h hydropower from July to August for the Wudongde-Baihetan and the Xiluodu-Xiangjiaba aggregation systems.Joint and optimal allocation of flood prevention storage for the four cascade reservoirs can increase 1.037 billion kW·h hydropower annually from July to August,yielding significant economic benefits.
The Wudongde-Baihetan-Xiluodu-Xiangjiaba cascade reservoirs in the lower Jingsha River shoulder the downstream flood control tasks jointly,and the complementary equivalent relationship between the flood prevention storage of these reservoirs is not considered during the planning and design stage.Based on the principle of water balance and the assumption of total flood prevention storage unchanged,the flood prevention storage of cascade reservoirs was aggregated and decomposed.The optimal allocation calculation formulas for two-reservoir and multi-reservoir systems were derived and solved numerically with power generation as the main objective.Results show that the Wudongde and Xiangjiaba reservoirs with relatively small storage allocate about 1.180 and 0.216 billion m3 of the flood prevention storage to the Baihetan and Xiluodu reservoirs respectively,which can generate extra 445 and 32 million kW·h hydropower from July to August for the Wudongde-Baihetan and the Xiluodu-Xiangjiaba aggregation systems.Joint and optimal allocation of flood prevention storage for the four cascade reservoirs can increase 1.037 billion kW·h hydropower annually from July to August,yielding significant economic benefits.
2023, 34(4): 530-540.
doi: 10.14042/j.cnki.32.1309.2023.04.006
Abstract:
Current study incorporates both the watershed and urban areas into a unified spatial context in order to address the problem of coordinated flood forecasting in watershed-urban compound systems.Based on the proposed framework for distinguishing easily generated runoff patterns,a hybrid forecasting model,called GRGM-LSTM,and is developed by coupling the Grid-based Runoff Generation Model (GRGM) with Long Short-Term Memory neural networks (LSTM).The model is tested using 18 observed flood events in the control basin of the Jialu River at Zhongmou station.In addition,the forecast results are compared and analyzed against the Storm Water Management Model (SWMM) and GRGM-SWMM model.The study reveals that:① The relative error and coefficient of determination obtained from the GRGM for simulating runoff are 8.41% and 0.976,respectively.This indicates that considering the spatial distribution of runoff patterns results in more accurate runoff calculations.② For forest period of less than 6 hours,the GRGM-LSTM hybrid model outperforms physical mechanism models such as GRGM-SWMM and SWMM,yielding Nash-Sutcliffe efficiency coefficients greater than 0.8,indicating superior simulation performance.③ However,for a forest period exceeding 6 hours,the GRGM-LSTM hybrid model experiences some accuracy loss,and when the forest period increases to 12 hours,the simulation accuracy of GRGM-SWMM surpasses that of GRGM-LSTM.The research findings can serve as a scientific basis for coordinated management of flood prevention and disaster reduction in watershed-urban areas.
Current study incorporates both the watershed and urban areas into a unified spatial context in order to address the problem of coordinated flood forecasting in watershed-urban compound systems.Based on the proposed framework for distinguishing easily generated runoff patterns,a hybrid forecasting model,called GRGM-LSTM,and is developed by coupling the Grid-based Runoff Generation Model (GRGM) with Long Short-Term Memory neural networks (LSTM).The model is tested using 18 observed flood events in the control basin of the Jialu River at Zhongmou station.In addition,the forecast results are compared and analyzed against the Storm Water Management Model (SWMM) and GRGM-SWMM model.The study reveals that:① The relative error and coefficient of determination obtained from the GRGM for simulating runoff are 8.41% and 0.976,respectively.This indicates that considering the spatial distribution of runoff patterns results in more accurate runoff calculations.② For forest period of less than 6 hours,the GRGM-LSTM hybrid model outperforms physical mechanism models such as GRGM-SWMM and SWMM,yielding Nash-Sutcliffe efficiency coefficients greater than 0.8,indicating superior simulation performance.③ However,for a forest period exceeding 6 hours,the GRGM-LSTM hybrid model experiences some accuracy loss,and when the forest period increases to 12 hours,the simulation accuracy of GRGM-SWMM surpasses that of GRGM-LSTM.The research findings can serve as a scientific basis for coordinated management of flood prevention and disaster reduction in watershed-urban areas.
2023, 34(4): 541-552.
doi: 10.14042/j.cnki.32.1309.2023.04.007
Abstract:
River networks are channels for water flow within the hydrological cycle of a watershed,and their spatial evolution has significant impacts on watershed hydrological processes.Human modifications and reconstructions of river networks have significantly altered their topological structure and functionality.Analysing the structural characteristics and functional responses of evolving river networks is of great importance for their health assessment and management.This study proposes the concept of a "small-world river network" and constructs an assessment framework based on graph theory to analyse the structural characteristics,spatial growth patterns,and functional responses of an evolving river network.The results show that the current river network in the Haihe River basin exhibits small-world characteristics,such as high connectivity,large overall structure,and dense topology,and it shows high network efficiency.The development of the river network has scale-free characteristics,following a growth pattern of node increase and preferential connection,and it is constrained by spatial limitations imposed by "small-scale connections".Compared to the natural river network,the flood control function has increased by 65%,the water supply function has increased by 222%,and the ecological function has decreased by 78%,indicating a tendency towards non-uniform functional changes.The assessment results can provide technical support for the optimal management and planning of river networks in the watershed.
River networks are channels for water flow within the hydrological cycle of a watershed,and their spatial evolution has significant impacts on watershed hydrological processes.Human modifications and reconstructions of river networks have significantly altered their topological structure and functionality.Analysing the structural characteristics and functional responses of evolving river networks is of great importance for their health assessment and management.This study proposes the concept of a "small-world river network" and constructs an assessment framework based on graph theory to analyse the structural characteristics,spatial growth patterns,and functional responses of an evolving river network.The results show that the current river network in the Haihe River basin exhibits small-world characteristics,such as high connectivity,large overall structure,and dense topology,and it shows high network efficiency.The development of the river network has scale-free characteristics,following a growth pattern of node increase and preferential connection,and it is constrained by spatial limitations imposed by "small-scale connections".Compared to the natural river network,the flood control function has increased by 65%,the water supply function has increased by 222%,and the ecological function has decreased by 78%,indicating a tendency towards non-uniform functional changes.The assessment results can provide technical support for the optimal management and planning of river networks in the watershed.
2023, 34(4): 553-561.
doi: 10.14042/j.cnki.32.1309.2023.04.008
Abstract:
To solve the problem of the equation structure becoming more complex in the improved soil conservation service curve number (SCS-CN) model,a SCS-CN model with revised effective precipitation (SCS-CN-REP) is proposed by introducing a revised coefficient after a comparison between the standard SCS-CN model and the improved model.Furthermore,for the complex area with low impact development (LID) in a city,a distributed SCS-CN-REP model was developed based on a hydrological response unit division in which the effects of the LID facility's storage capacity on rainfall-runoff are also considered.Finally,taking the Shuangzi residential district in Beijing City as a study area,the rainfall-runoff is simulated and compared using the distributed SCS-CN-REP model.An analysis of the SCS-CN-REP model showed that when the revised coefficient is 1.0,it is equivalent to the standard model,when the revised coefficient is smaller than 1.0,it is equivalent to the improved model.In essence,the revised coefficient is a limit value of the runoff coefficient varied with the increase in precipitation.The distributed SCS-CN-REP model application results demonstrated that the calculated runoff depth values are in good agreement with the measured values.The determination coefficients and Nash efficiency coefficient are 0.91 and 0.83 when the adopted value of the revised coefficient for permeable surfaces is 1.0,and are 0.92 and 0.91 when the adopted value is less than 1.0.The effects of the latter model are better than the former,indicating that the simulation effect can be effectively improved when the adopted value of the revised coefficient for permeable surfaces is less than 1.0 in the distributed SCS-CN-REP model.
To solve the problem of the equation structure becoming more complex in the improved soil conservation service curve number (SCS-CN) model,a SCS-CN model with revised effective precipitation (SCS-CN-REP) is proposed by introducing a revised coefficient after a comparison between the standard SCS-CN model and the improved model.Furthermore,for the complex area with low impact development (LID) in a city,a distributed SCS-CN-REP model was developed based on a hydrological response unit division in which the effects of the LID facility's storage capacity on rainfall-runoff are also considered.Finally,taking the Shuangzi residential district in Beijing City as a study area,the rainfall-runoff is simulated and compared using the distributed SCS-CN-REP model.An analysis of the SCS-CN-REP model showed that when the revised coefficient is 1.0,it is equivalent to the standard model,when the revised coefficient is smaller than 1.0,it is equivalent to the improved model.In essence,the revised coefficient is a limit value of the runoff coefficient varied with the increase in precipitation.The distributed SCS-CN-REP model application results demonstrated that the calculated runoff depth values are in good agreement with the measured values.The determination coefficients and Nash efficiency coefficient are 0.91 and 0.83 when the adopted value of the revised coefficient for permeable surfaces is 1.0,and are 0.92 and 0.91 when the adopted value is less than 1.0.The effects of the latter model are better than the former,indicating that the simulation effect can be effectively improved when the adopted value of the revised coefficient for permeable surfaces is less than 1.0 in the distributed SCS-CN-REP model.
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- 1Evolution and variation characteristics of the recorded runoff for the major rivers in China during 1956—2018
- 2Quantifying attribution of runoff change for major rivers in China
- 3Progress on disaster mechanism and risk assessment of urban flood/waterlogging disasters in China
- 4Cause analysis of the centennial trend and recent fluctuation of the Yellow River sediment load
- 5Progress in development and utilization of non-conventional water resources in China
- 6Application of Copula functions in hydrology and water resources: a state-of-the-art review
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