Study On Regulation Of Ecological Basic Flow In Baoji City Segment Of Weihe River

The ecological environment of Weihe River basin showed deterioration trend over the long time. The ecological environment problems of Baoji City segment of Weihe River is particularly prominent, resulting in degradation of the river features, contradiction of water demand and supply become increasingly serious, the sustainable development of economy and society of Baoji is restricted, so it is urgent to address the ecological environment problems. In order to maintain the ecological environment functions of rivers, it is necessary to ensure the ecological basic flow. In practice, traditional benefit-rasing goals (town water supply, irrigation, flood control, power generation, etc.) were mainly considered in previous regional water resources allocation and operation of water project, little or no ecological basic flow and ecological function demand, but also lack of scheduling management experiences considering the ecological objective.Taking the example of Baoji City segment of Weihe River, the optimal allocation of water resources is studied while ecological basic flow is met. Main research contents and results are summarized as follows:1. Several aspects are analyzed including the socio-economic situation in Baoji, water features, water environment, etc., and also the river features and channel functions of Baoji City segment of Weihe River, for the finalization of the ecological basic flow.2. Self-purification flow is Calculated and the recent ecological basic flow is determined. According to the information collected, combined with the actual situation of the study section, self-purification water demand is calculated using the section-beginning control method, the minimum monthly average flow method, mass conservation method. Results show that the self-purification water demand under present situation to be much larger than the standard reaching situation. The self-purification water demand under present situation is 16.3m3/s～ 89.6m3/s, and the self-purification water demand under standard reaching situation is 7.68m3/s～34.7 m3/s. On this basis, combined with the results existing, the ecological basic flow is determined to be 10.0m3/s in this paper.3. The profit and loss evaluation and impact factors analysis about the ecological basic flow are made in this paper. The profit and loss is evaluated under the case of base flow known. And impact factors are analyzed including Baoji Gorge irrigation district water diversion, Weijiabu Hydropower plant water diversion, Baoji irrigation headwork and branch supplement, urban sewage discharge, agricultural and other water-saving factors, which provides the basis for rational allocation of water resources.4. The ecological basic flow control model of Baoji City segment of Weihe River is established and the model is applied. Based on comprehensive analysis of factors, using system optimization theory, the mathematical model is built to realize optimum water allocation while meeting the ecological basic flow demand. And the model is applied in different cases, such as wet year (25%), flat-water year (50%), dry year (75%), three kinds of typical representative years; the different level of assurance of ecological basic flow that the guaranteed rates are 100%,80%,60%; the existing regulation and storage facilities, to consider and not. From Baoji Gorge up-tableland irrigation area, feasible engineering measures and non-engineering measures are put forward, aims to reduce irrigation water and guarantee the ecological basic flow.