Study On The Ecological And Power Generation Benefits Effects Of The Hanjiang-to-Weihe River Water Transfers Project On The Water Transfer Area

As an important inter-basin water transfer project,the Hanjiang-to-Weihe River Water Transfers Project in Shaanxi Province,while deploying water resources from the Hanjiang River Basin in southern Shaanxi to the Guanzhong area,alleviating the contradiction between water supply and demand in the area,promoting the optimal allocation of water resources in Shaanxi Province,and improving the ecological environment of the Weihe River Basin,the project will also have constraints and other negative ecological and economic impacts on the transfer area,affecting the economic and social development of the transfer area.This paper addresses the problem of the impact of the water transfer process of the Hanjiangto-Weihe River Water Transfers Project on the ecology of the downstream region and the power generation of the step-station,and uses mathematical statistics and the Mann-Kendall test to study and analyze the change pattern of the multi-year runo ff into the reservoir based on the runoff into the reservoir from 1967.7 to 2021.6.Finally,according to the water transfer process of the Hanjiang-to-Weihe River Water Transfers Project,the ecological water resources value of the downstream power stations and river cross-sections lost after the water transfer was evaluated and calculated by using the energy value analysis method.The main research results are as follows.(1)The intra-annual,inter-annual and trend variation processes of the incoming runoff from the Huangjinxia and Sanhekou reservoirs were analyzed using mathematical statistics and MannKendall trend test.The trends of the two reservoirs were highly synchronized,with extremely uneven intra-annual water distribution and a larger proportion of water in the flood season;the incoming runoff of both reservoirs showed an overall decreasing trend.The characteristic flows corresponding to the characteristic frequencies of the two reservoirs were integrated by the least square approximation method,and the integrated typical years of the two reservoirs were selected,and finally 2011 was selected as the year of abundant water,2009 as the year of flat water,and 2006 as the year of dry water.(2)The process of water diversion in the Hanjiang-to-Weihe River Water Transfers Project was simulated by using ajoint water diversion method from four sources:Jinpen Reservoir in the receiving water area,groundwater,and Huangjinxia and Sanhekou Reservoirs in the water transfer area.In the 49-year simulation,the average annual water supply from Huangjinxia Reservoir was 588 million cubic meters,and the average annual water supply from Sanhekou Reservoir was 447 million cubic meters.In eight years,1972、1990、1991、1997、1998、1999、2002 and 2013,the amount of water diverted was less than 1 billion cubic meters.However,when combined with groundwater and Jinpen Reservoir to regulate water supply,the water demand of the receiving water area can be met.(3)An optimal dispatching model with maximum power generation capacity was established for the downstream power stations of the project and solved using an improved artificial bee colony algorithm.The results show that the multi-year average cross-sectional flows of Shiquan,Xihe,Ankang and Shuhe dams are reduced by 11.6%,10.8%,7.0%and 5.1%after the water transfer of the Hanjiang-to-Weihe River Water Transfers Project.The multi-year average power generation capacity of the terrace power stations decreased by 84 million kW·h,52 million kW·h,169 million kW·h and 43 million kW·h,respectively,or 12.0%,10.5%,7.1%and 5.4%,respectively.(4)The energy value analysis method was used to assess the value of the downstream impact of the water transfer.The loss of power generation benefit of the stepped power station is calculated by the conversion rate of hydroelectric power generation energy value,the energy conversion rate of electricity and the energy value/money ratio of Ankang City,which results in the price of a single unit of regional hydroelectric power generation benefit of 0.457 (?),and the average annual power generation benefit loss of 159 million CNY for the downstream stepped power station;the ecological value of river water resources is evaluated by biodiversity protection,climate regulation,river water self-purification,river water pollution,nutrient accumulation and the ecological value of river water resources is evaluated and calculated through six aspects:biodiversity protection,climate regulation,river water self-purification,river water pollution,nutrient accumulation and purification value,and dilution and purification benefits,and the monetary value of the ecological water resources in Ankang is only 0.22 (?)/m3,and the average annual loss of ecological water resources in the downstream river is 220 million CNY,provide the basis for the measurement of ecological compensation standards for water transfer.