Flood control.
Determine the principles
(1) The principle of ecological priority
Rivers are the center of the evolution and convergence of a variety of animals and plants in China, with rich vegetation biodiversity, and assume important functions such as water source protection, water conservation and biodiversity conservation. Therefore, the determination of ecological water demand is requiredIn accordance with the requirements of protection, the relationship between economic and social development and water ecology and environmental protection, the relationship between current interests and long-term interests, and the ecological security of water source areas should be guaranteed.
(2) The principle of scientific reasonableness
The river system should be taken as a whole, the water resources conditions of the basin, the needs of ecological protection, and the current situation and demand of water resources development and utilization should be comprehensively considered, and the different functions of the river and the allocation of water for living, production, and ecology should be coordinated as a whole, and the water resources endowment conditions of the water diversion rivers should be fully considered, and the ecological water volume of the water diversion rivers should be reasonably determined to ensure the scientificity and operability of the results.
(3) The principle of coordination
The proposed ecological water quantity should be coordinated with the relevant plans such as the comprehensive planning of the river basin and the results of the ecological water volume proposed by the environmental impact assessment of the hydropower station.
Ecological protection objects
According to the relevant national and provincial planning and zoning requirements for the ecological environment positioning and protection of the water diversion area, combined with the investigation of the current situation of the river water ecological environment, and from the perspective of maintaining the ecological security of the river basin and region, the ecological units that have direct hydraulic connection with the river and are of great significance to the water ecological protection of the river basin are selected as the water ecological protection objectives at the basin level, mainly including aquatic organisms in the river, river valley vegetation, wetlands, etc.
3. Ecological water demand
The ecological flow of rivers and lakes is the flow rate (water volume, water level) and its process that need to be retained in rivers and lakes to meet the water quality requirements to maintain the structure and function of water ecosystems such as rivers and lakes. The ecological environment water demand in the river includes ecological base flow, sensitive ecological flow, and annual ecological water volume. Among them, the ecological base flow is the bottom line flow that needs to be retained to maintain the function of the river water ecosystem. Sensitive ecological flow refers to the demand for water flow processes in a specific period of time in order to maintain certain components or functions in the river and lake ecosystems. The annual ecological water volume refers to the amount of water required to maintain the good ecological condition of the river, and the annual water volume value is generally calculated according to the ecological environment function corresponding to the protection objectives, and the annual water volume value is obtained after calculating the water required to maintain the good ecological condition of the river in different periods.
The Code for Calculating Water Demand for Ecological Environment of Rivers and Lakes (SL T 712-2021) points out that the design guarantee rate of ecological base flow should not be less than 90%, and the guarantee rate of ecological flow in sensitive periods should be determined according to the functional needs of sensitive objects, combined with the law of regional hydrological changes and ecological characteristicsIn principle, the design guarantee rate of ecological water volume in different periods and throughout the year should not be less than 50%., among othersIn principle, the guarantee rate of the value of the basic ecological flow at different times of the year and the annual value should not be less than 75%.In principle, the design guarantee rate of the target ecological flow should not be less than 50%.
4. Selection of calculation method
According to the requirements of standards and specifications such as the Code for the Calculation of Water Demand for the Ecological Environment of Rivers and Lakes (SL T 712-2021) and the Guidelines for the Preparation of Ecological Protection and Restoration Planning of Rivers and Lakes (SL 709-2015), the calculation methods are divided into three categories, the main = that is, the hydrological method, the hydraulic method, and the ecological hydraulics method. According to the hydrological and ecological environment characteristics of the river, through the analysis of the scope of application of each calculation method, Q is generally usedmethod, Tennant method and the driest moon flow method in the past ten years were used to calculate the ecological base flow, and the ecological hydraulic radius method, the average water depth flow method, the Tennant method and the habitat simulation method were used to calculate the sensitive ecological flow.
Disaster-stricken projects include water diversion projects, irrigation projects, water supply projects, flood control and drainage projects.