Study On Regulation Of Ecological Water Use Based On River Health Assessment In The Mainstream Of Sihe River

As a precious natural resource,river has the dual attributes of ecosystem function and social service function.Healthy river ecology is the requirement of the construction of ecological civilization.Under the background of the impact of climate change and the gradual enhancement of human activities,how to make full use of the limited water resources in the basin and maintain a healthy river ecology requires not only the conventional optimal allocation and dispatching of water resources in the basin,but also the ecological dispatching of the river.The Sihe River is a typical large river across the "hill-plain" in the Yishu Sihe River Basin in Shandong Province,as well as an important water quality guarantee river entering the Nansi Lake.Due to the increase of water diversion and storage in the basin and the imbalance of water use in cities,counties and districts along the river,there are some problems,such as the competition for water in the upper and lower reaches,the sudden decrease in the flow of backbone sections,the deterioration of water quality into Nansi Lake and so on.How to further standardize the water use behavior of the river basin,implement the double control of total amount and intensity,and maintain the ecological health of the river has become an important task of watershed management and regional management.In view of the problems existing in the utilization of water resources in the Sihe River Basin,and based on the analysis of the hydrological characteristics of the Sihe River,this study calculates the ecological flow of the main control sections of the Sihe River and evaluates the health status of the river.Starting with the goal of maintaining the good health level of the river,this paper constructs a hydrological model based on regional water distribution,formulates and puts forward the ecological flow dispatching scheme of the main stream of the Sihe River,in order to promote the sustainable utilization of water resources and the protection of ecological environment in the Sihe River Basin.The main research contents and conclusions are as follows:(1)Through the analysis of the characteristics of runoff change in Sihe River Basin,it is found that all kinds of human activities such as land use and land cover change,water conservancy project construction and so on have had an extremely serious impact on runoff in recent years.The hydrological station of Sihe River Shuyuan was selected as the control section,and the ecological water requirement of the control section was calculated by Tennant method,wetted perimeter method,7Q10 method and Qp method.Through comprehensive comparison and analysis,it is proposed that the minimum ecological flow threshold of the hydrological station section of Shuyuan is 0.09m3,the threshold of ecological flow to maintain river health is 1.66m3 in flood season,and the threshold in non-flood season is 0.2m3/s.Under the conditions of current construction projects and water use,the minimum ecological flow of the Sihe River in the cross section of Shuyuan station is 93.5%,which can basically meet the demand of the minimum ecological flow.The satisfaction degree of ecological flow to maintain river health is 85.0%,including 77.5%in flood season and 88.7%in non-flood season.The satisfaction degree of the ecological flow of maintaining the river health in the cross section of Shuyuan station is relatively low,and the demand of healthy ecological flow can be met through proper regulation and control.(2)In view of the problems existing in the utilization of water resources in the Sihe River Basin,on the basis of the health assessment of the Sihe River,the overall health of the Sihe River is constructed as the target layer.five characteristics of the Sihe River,such as hydrological integrity,chemical integrity,morphological and structural integrity,biological integrity and sustainability of social service functions,are taken as the criterion layer.The Sihe River health assessment system is based on 17 characteristic values,such as ecological flow standard status,water function area standard rate,riparian artificial interference degree,fish retention index,public satisfaction and so on.The Sihe River is divided into four evaluation sections A,B,C and D from upstream to downstream.Through on-the-spot investigation,data mining and expert consultation,each index is scientifically assigned according to the working principle of giving priority to quantitative analysis and supplemented by qualitative analysis.The analytic hierarchy process and entropy method are used to determine the weight of the index,and the improved matter-element extension model is applied to evaluate the health of the backbone reach of the Sihe River.The results show that the Sihe River as a whole is at a good grade level,in which reach An and B are at an excellent level,and section C and D are at a good level.Among the many factors affecting river health,the weight of ecological flow reaching the standard is 0.2129,which plays a key role in maintaining river health.(3)According to the situation of Sihe River water conservancy project,distribution of hydrological stations and administrative division,considering 5 large and medium-sized reservoirs and 11 river sluice dams in the basin,a water resources dispatching model is constructed by using MikeBasin software to simulate and analyze the cross-section ecological flow of Shuyuan hydrological stations in abundant,flat and dry years.The results show that the cross-sectional flow in April,May and June is 0.19m3/s,0.15m3/s and 0.55m3/s,respectively,which can not reach the river healthy ecological flow threshold,and the total water shortage during this period is 3.0326 million m3.The cross-sectional flow in the rainy year and the water year exceeds the ecological flow threshold,so there is no need to regulate and control the ecological flow.In view of the fact that the ecological flow of the cross section of the academy station in the dry year can not be satisfied in some months,three dispatching schemes are constructed by controlling the amount of water discharged under the sluice dam upstream of the cross section and reducing agricultural water consumption,and a long series of water regulation and control simulation is carried out in the Sihe river basin.Finally,the reasonable regulation and control scheme of ecological flow is optimized,and the safeguard measures such as establishing ecological flow monitoring and early warning system mechanism are put forward,which can realize the unified dispatching and management of ecological water.