Study On Calculation Of Ecological Water Demand Of Typical Gate-controlled Rivers And Lakes Based On Different Targets

Water conservancy projects such as sluice and dam in rivers and lakes play a very important role in flood control,power generation and water resources utilization,etc.,and sluice and dam construction will also change the hydrological process of rivers and lakes,thus affecting the ecological environment of rivers and lakes to some extent.Ecological water demand is a key index to guarantee the structure,ecological function,service function and special function of the river and lake ecosystem and to realize the healthy and sustainable utilization of water resources.The research and calculation of river and lake ecological water demand under the influence of sluice and dam is the basis and premise of scientific management of river and lake water resources,restoration of water ecosystem and other health protection work.This paper takes the wuhan section of tongshun river and the Huayang Lakes area in the middle and lower reaches of the Yangtze river as examples.Based on the different natural environmental conditions and protection objectives of the wuhan section of the tongshun river and the Huayang Lakes area,suitable calculation and research methods were selected to study the typical ecological water demand.In order to provide reference for the calculation and analysis of the ecological water demand of other similar flood-controlled rivers and lakes in the middle and lower reaches of the Yangtze river.The main research contents and results are as follows:(1)Summarize the basic characteristics of rivers and lakes ecosystems and the connotation of ecological water demand,and analyze the ecological water demand goals and ecological water demand calculation methods and their applicability.The river and lake ecosystem consists mainly of non-biological environments and organisms.River ecosystems have four-dimensional structural features of vertical,horizontal,vertical and temporal,while lake ecosystems have three-dimensional structural features of lateral,vertical and temporal.According to the characteristics and structural characteristics of river and lake ecosystems,the service functions of river and lake ecosystems mainly include habitat function,corridor function and environmental purification function.The definition of ecological water demand in rivers and lakes is sorted out.The ecological flows of rivers and lakes are divided into narrow and broad.The ecological water demand target of rivers and lakes can be divided into two levels:firstly,the goal of satisfying the morphological stability of rivers and lakes and the ecological water demand level of natural functions;secondly,the goal of meeting the functional ecological water demand level of human society.(2)By analyzing the water system,hydrological characteristics and the status of water ecological environment in the Wuhan section of Tongshun River,it is clarified that the ecological water demand target of the Wuhan section of Tongshun River should meet the morphological stability and natural functions of the river system.On the basis of Mike11 one-dimensional hydrodynamic simulation,according to the artificially calculated trial flow sequence to avoid the shortage of long-sequence measured data,the wet-week method and ecological hydraulic method based on the basic elements of river habitat are used to calculate,and the calculation results show that The ecological flow in the typical section of the Wuhan section is 26m~3/s,and the corresponding ecological water level is between 15.96-20.05m.The calculation results determine the minimum threshold of ecological water demand in the Wuhan section of Tongshun River.(3)By analyzing the characteristics of rivers,lakes,hydrology and water environment of Huayang Lakes area,it is considered that the ecological water demand research in Huayang Lakes area is the ecological water demand level goal of satisfying human social function.Through the correlation analysis between water quality and water level,it is considered that when the water level in the lake area is below 13.5m,the water level in the lake area will improve the water quality of the lake area.When the water level in the lake area is higher than 13.5m,the relationship between water quality and water level is not obvious.Based on the analysis results of water quality and water level process and the initial control scheme of sluice gate,Mike two-dimensional water-hydrodynamic mathematical model was used to carry out multi-scheme calculation between 12m and 13.5m.The calculation results show that the ecological water demand process control plan of Huayang Lakes area based on water quality improvement target should be controlled to 13.5m from October to February,and the water level should be controlled to 11.8m from March to April.