Study On The Hydrological Response And Ecological Discharge Of The Rivers In The Water Diversion Area During The Initial Operation Of The Hanjiang-to-weihe Water Diversion Project

The Hanjiang-to-Weihe water diversion project in Shaanxi Province is an important water conservancy project to alleviate the shortage of water resources in the region and optimize the allocation of water resources in the Basin.With the water storage operation of the Sanhekou Reservoir,the project transferred water from the reservoir to the water receiving area through the Qinling Water Transport Tunnel,squeezing the ecological water in the downstream,which made the ecological environment of the river downstream of the reservoir face important challenges.Therefore,carrying out research on the hydrological response of water transfer to the downstream reaches of the reservoir and formulating an ecological flow plan can not only maintain and guarantee the ecological function of the river,but also provide important guidance and reference for the reservoir operation.The reaches of the Sanhekou Reservoir downstreams is taken as the research object in this paper.Based on the collected data,a reservoir operation model was established and solved based on the MIKE Basin model,the degree of hydrological change of the river before and after the establishment of the reservoir was calculated,the hydrological response relationship of the river was clarified,the ecological flow plan was formulated and recommended,and the ecological flow guarantee measures were proposed.The main conclusions are drawn as follow:(1)Based on the MIKE Basin,a reservoir operation model was established,the model calibration using design data for water supply,water level,and ecological water,the results of the model were analyzed and compared from the index and objective levels,which verified the rationality and reliability of the MIKE Basin model.(2)Taking the dam site as the control section,analysis of the hydrological rules of the flow sequence before and after the construction of the reservoir shows that after the construction of the database,the average annual flow decreases,the flow period decreases,the flow dispersion increases,and the increasing occurrence of less than average traffic.(3)IHA was selected as the evaluation index,and the degree of change of the hydrological index was calculated based on the range of change method(RVA).It was concluded that the overall degree of hydrological change after the construction of the reservoir was 72.91%,which was highly changed.(4)From the perspective of the connotation of ecological flow,the shortcomings of the current ecological flow plan were answered.7 types of ecological flow plans were designed based on the year's hydrological situation and interannual changes,the ecological flow processes of each plan were obtained by the MIKE Basin model,and the degree of hydrological change of each scheme is calculated based on 33 IHA indicators.(5)Establish an ecological flow evaluation index system,evaluate the set of plans based on the analytic hierarchy process,optimize and recommend the ecological flow plan,give the reservoir operation mode under this plan,and propose ecological flow guarantee measures from the aspects of engineering and non-engineering measures...