Water Cycle Evolution And Response Characteristicsto Water Scheduling In Middle-lower Heihe River Basin

The water cycle at basin scale is affected by both climate factors and human activities, and it evolves and affects the ecological environment, which in return influences human activities sequentially. Inarid inland river basins, the water resources are scarce and the anthropogenic effects on surface-groundwater movement are quite serious. The effects are sometimes dominant and cause a series of system responses among hydrology, ecology, economy and society consequently. The understanding on basin scale system responses was insufficientduring traditional water resources exploitation, and there lacked comprehensive coordination among ecological, environmental and socioeconomic water uses. These caused river drought, lake shrinkage, wetland disappearance,oasis degradation and water conflicts between different regions, which restricted sustainable basin developmentsignificantly.In the thesis, the second largest inland river in China, Heihe River, was selected as the study area. Theempirical analyses of water resources utilization in the basin were carried out, to investigate the water cycle evolution processes of middle-lowerriver basin through coupled surface-groundwater modeling, and the response characteristics to water resourcesexploitation were studied.Then the optimization model was further developed to studyoptimal water resources allocation and management under current water rights framework in Heihe River Basin(HRB), in order to provide methodology basis for sustainable management of arid river basins.The water cycle evolution history of HRB was reviewed firstly, and the impacts of human activities and water rights management on water cycle were recognized from historic data analysis and test. Secondly, the whole middle-lower HRB water cycle simulation model was developed, by coupling the demand-based surface water model WEAP and groundwater flow model MODFLOW, and the water cycle changes were simulated with history inversion and future scenarios, to analyze the effects of human water utilization and river inflow changes. Then, the aquifer heterogeneity effects on stream-aquifer water exchanges were further discussed with simple Monte Carlo simulation, to reveal the aquifer heterogeneity effects on surface-groundwater transformation. Based on the surface-groundwater simulation model, statistical analysis and data mining methods, the Heihe River mainstream flow response characteristics to different water operations were discussed, as well as the responses to different water utilization scenarios in the sub-basin Taolai River. Finally, the mixed-integer optimization model by integrating quantitative water rights and duration-based water rights was developed, and the optimization method for water allocationwas analyzed in the mixed water rights framework of quantitative water rights allot and duration-based water rights operation in HRB, to determine the optimal water allocation schemes and water resources management strategies.The methods of data analysis and mining, the surface-groundwater simulation model and water allocation optimization model were proposed and applied in HRB, which expanded the research metho ds for basin scale water cycle and water resources management. These are valuable to reveal the basin evolution and management strategy for similar arid inland rivers, and will promote sustainable water resources utilization and ecology conservation in future.