Research On Ecological Regulation For Hydraulic Engineering Based On The Complex Water Resources System

Hydraulic engineering is the important means to achieve the sustainable utilization of water resources. However, the current hydraulic engineering regulations consider little about the eco-environmental water demand, which leads to certain threat to the river ecosystem. In order to realize the harmonious coexistence between human and water and implement the specific requirements of the ecological civilization construction put forward in the Eighteenth National Congress of Communist Party of China, there are still some problems to be solved in the existing research and practice, such as the unknown of ecological effect root, the unclearness of eco-environmental water demand baseline, and the ineffectiveness of ecological regulation method, which need to be carried out research urgently.For the problem of the unknown of ecological effect root, according to the analysis of ecological effect theory, the paper puts forward three-level ecological effects of hydraulic engineering and constructs its quantifiable evaluation index system. For the problem of the unclearness of eco-environmental water demand baseline, the paper comes up with the method of stakeholder’s participation to estimate eco-environmental water demand and the method of the hierarchical water use. For the problem of the ineffectiveness of ecological regulation methods, this paper proposes the two-layer structure method and model for ecological regulation of hydraulic engineering, and studies the optimization regulation schemes of typical hydraulic engineering.The main contents and results are described as follows:(1)Study on evaluation index system for ecological effect of hydraulic engineeringFirstly, from the aspect of whether to be affected by human activities or not, ecological effect is divided into natural ecological effect and social ecological effect, and its comprehensive evaluation index system is preliminarily built. Secondly, the concept of ecological effect of hydraulic engineering is analyzed, and three-level ecological effects of hydraulic engineering are presented, and their interaction are discussed. Thirdly, the quantifiable evaluation index system is constructed. At last, the method is applied to evaluate the ecological effect of large-scale hydraulic engineering in the Weihe River Basin. The results shows that the precipitation decreasing and temperature rising caused by greenhouse effect has a certain impact on the hydrological situation and the background value of water resources, while other index have little impact. Due to the less interference of human activities, the index of the tributary sites in the upstream of hydraulic engineering are close to the natural state. Because of the regulating-storing function of the upstream hydraulic engineering and the changes of natural rhythm of the river, the index of the mainstream sites are significantly changed.1st level ecological effect is the driving force of all ecological effects.(2)Estimation of eco-environmental water demand based on the method of stakeholder’s participationBased on the theory of stakeholders, the paper presents the connotation of the method of stakeholder’s participation. Firstly, select the eco-environmental functional sections based on the eco-environmental functional zoning. Secondly, analyze the general sub-item ecological flow of the river ecological system, and take account into the tributary inflow, water intake from the key sections of the mainstream as well as the water balance principle. Thirdly, make the government departments as the representative of public benefit and eventually determinate the three-level management goals of eco-environmental water demand by stakeholders’ consultation and discussion, which provides the boundary conditions and regulation goals for the ecological regulation. At last, the paper applies the method in the mainstream of the Weihe River Basin in Shannxi province, and analyzes the three-level management goals of eco-environmental water demand of the five key sections, namely Linjiacun, Weijiabu, Xianyang, Lintong and Huaxian. The 1st level management goals for the five key sections are 5.4m3/s, 8.4m3/s,10.0m3/s,12.0m3/s and 12.0m3/s, respectively. The 2nd level management goals are 8.6m3/s,11.6m3/s,15.1m3/s,20.1m3/s and 12.0m3/s, respectively. The 3rd level management goals are 12.8m3/s,23.5m3/s,31.7m3/s,34.3m3/s and 34.1m3/s, respectively.(3)Study on the hierarchical water use under the conditions of competitionBased on the theory of costs and benefits, considering the different sensitivity level between costs and benefits in the different water using stages, the paper presents the connotation of hierarchical water use. The water using process are divided into three grades, namely minimum water demand, suitable water demand and maximum water demand. The priorities for all water users with different levels are determined, which provides the theoretical basis for the rational allocation of water resources and implementation of eco-environmental water demand. Take the nine irrigation areas in the Weihe River Basin as an example, the minimum irrigation water demand in 50%,75%, and 90% frequency years is 1.17 billion m3,1.33 billion m3 and 1.58 billion m3, respectively, and appropriate irrigation water demand in 50%,75%, and 90% frequency years is 2.11 billion m3,2.90 billion m3 and 3.26 billion m3, respectively. The minimum irrigation water demand is 45%～60% of the suitable irrigation water demand. Then the priorities among agricultural water demand, eco-environmental water demand, and intake of hydropower with different levels for Baojixia irrigation area are proposed. The extremely low limit eco-environmental water demand takes the priority over the minimum irrigation water demand, the low limit eco-environmental water demand takes the priority over the appropriate irrigation water demand, and the appropriate eco-environmental water demand comes last(4)Two-layer structure method of ecological regulation of hydraulic engineeringStarting from the water effect relations of complex water resources system, as the real inflow of engineering are affected by the comprehensive effects of the whole river basin water circulation, the paper puts forward the two-layer structure method of ecological regulation of hydraulic engineering. The first layer structure is the complex water resources system simulation based on the theory of dualistic water cycle. The ROWAS is used to simulate the various influence factors impacting on the whole watershed hydrologic cycle, which provides real inflow of engineering and its water supply scope for ecological regulation. The second layer structure is the optimal ecological regulation model of hydraulic engineering, which is develop by the tool of FORTRAN. In order to obtain the maximum water supply meeting the assurance probability of multi-purpose water supply, the model introduces the regulating line to control the multi-purpose water supply, and adopts the PSO to optimize regulating line, which expands the research approaches of ecological regulation.(5)Study on the optimization regulation schemes of hydraulic engineeringTake the Weihe River Basin in Shannxi province as an example, the water simulation model of Weihe River Basin is constructed. Considering the influence factors of the whole watershed hydrologic cycle, the boundary control scenarios of water simulation are set, which provides real inflow and water supply scope for the optimal regulation of Baojixia reservoir and Weijiabu hydro-junction. Considering priorities of water supply targets, regulating line as well as eco-environmental water demand, the regulating strategies are set. The recommendation regulating strategies of Baojixia reservoir and Weijiabu hydro-junction under different boundary control scenarios can be obtained by using the optimization model. The irrigation water supply of optimal regulating is approximately the same with that of conventional regulating, and the probability of the eco-environmental water demand of optimal regulating is higher than that of conventional regulating, which verifies the feasibility of the model.