Study On Theory And Application Of Optimal Allocation For Eco-Environmental Water Requirements In The Urban Rivers

With the acceleration of the urbanism, water environment in the urban is becoming worse and worse. It is a new challenge for the environmental managers to manage and protect the urban water environment effectively. In this paper, the environmental water requirements of the urban rivers have been discussed from multi-dimension of theory analysis, mathematic modelling, computational simulation and the real-world application, which could support sciencitifcly the improvement of water environment.Based on a great deal of the literatures about eco-environmental water requirements of the urban rivers in the domestic and oversea, its theory has been researched comprehensively, which includes the concept, theory foundation, investigative category and features. And then the composition of environmental water requirements has been defined based on the functioning of the rivers. The eco-environmental water requirements of the urban rivers has been defined as the necessary water amount in the river to maintain the well-balanced ecological structures and the basic water environmental functions undestroyed with the setting standards of water functions. The research of eco-environmental water requirements has been performed based on the enviro-ecology theory, water cycle principle and water environment carrying capacity theory. The composing of the eco-environmental water requirements of the urban rivers includes water quantities for aquatic inhabit, sand transportation, water-salt balance, dilution and self-purification, evaporation and seeping supplement. The flow rate from rainfall-runoff might be looked upon the supply to the urban rivers. In this charter, the calculating formulas of the above modeling have been established, and the integrated formula, too. The theorical environmental water requirements for the Liming River-basin in Daqing City have been studied. As a result, the eco-environmental water requirements change spacially and temporally, and the average water amount needed in the three river sections is 4.50 m~3/s, 3.80 m~3/s and 4.59 m~3/s, respectively.The optimal allocation system of the eco-environmental water requirements has been established on the basis of its theory research. The connotation, mechanism, principle, dominating tasks and suitable conditions for application of the optimal allocation of the eco-environmental water requirements for improving water environment have analyzed. A fuzzy multi-objective programming modeling for the optimal allocation of environmental water requirements has been developed, and genetic algorithm has been used to sovle it. For the oprimal allocation of environmental water requirements, gerenal benefit loss and assimilative capacity should be considered besides the water quantity objective. Through the operation of the multi-objective programming modeling, the optimal water allocation for Liming River, that is 3.07m~3/s, has been obtained, which is cut down 33.1% from the theory water needed.In order to maintain the effect of environmental water allocation to improve the water environment, the pollutants surround should be controlled effectively. Therefore, the further modeling for optimal environmental water allocation has been established based on the grey theory and the planning of wastewater treatment plants in the river basin. In this modeling, the pollutants removel efficency of each plant and the water distribution from each reservoir and lake are looked upon the decision variables, and the minimum of the total cost is regarded as the decision objective, which include the establishment and operation cost of wastewater treatment plants and the water distribution cost from the reservoirs. At the some time, the solution of the modeling using by genetic alghrothm has been studied. The modeling based the grey theory and the planning of wastewater treatment plants has been applied to optimize the water environment management in the Liming River basin, and the satisfied results have been obtained.To research eco-environmental water requirements allocation in the wide scope and verify the effect of the project timely, the water environment simulation system based on object-oriented techniques has been established. The physical entities of the river basin and the conceptual entities of its water quality simulation and control have been represented through objects. Their basic attributes and methods have been developed. The physical entities include the correlative rivers, lakes, reservoirs and wastewater treatment plants, and the conceptual entities include the low flow frequency object, hydrodynamics simulation object, water quality object, water quality simulation object, water pollution control strategies object and the water quality estimation object. The network modeling of water environment has been established based on the directed acycling graph theory. The run mechanism and simulation algorithm has been developed. The general design of the simulation system of water environment improvement has been done, which makes up of water quantity simulation, water quality simulation and water pollution control strategies simulation. Preliminary design of the database has been done.