Research On Water Quality Simulation And Water Quality Evaluation Of Dongchang Lake

Lake is one of the major fresh water resources, providing a water supply for the people, playing an invaluable role in the economic development, and being a valuable resources to people's lives. However, as China's economic and social development, domestic sewage and industrial wastewater emissions increased day by day, and a large number of human activities made an adverse impact on the environment. At present the main environmental problem to the lake is eutrophic, especially to city lake. Dongchang Lake in the southwest of Liaocheng City, Shandong Province, around the historic city with a total area of 4.2km~2, is a rare big city lake in the northern part of the Yangtze River. In this paper, in order to research the effective way and measure to prevent and curb and clean up pollution, to realize sustainable use and virtuous circle of water resources, under the actual conditions and status of taking all possible measures, the water quality simulation and the evaluation of simulation results were made to provide evidences for planning and management to environmental quality.There are two parts-water quality simulation and water quality evaluation in this paper. WASP (Water quality analysis simulation program) model was chose in water quality simulation. It was divided into two parts: hydrodynamic model-DYNHYD and water quality model-WASP. It was developed by EPA, and used to analysis and predict the natural and man-made water pollution situation in different environmental policy system. In water quality evaluation, in term of surface water quality standard, scenery and recreation water use standard and lake eutrophication, water quality of Dongchang river was accessed and analyzed by fuzzy pattern recognition model, concentration exponent method and rating method.Firstly, based on the actual water quality data of Dongchang Lake, the evaluation to water quality was made, and the results are the water quality of Dongchang Lake could be classified into IV, and some contaminant indices don't satisfy the requirement of scenery and recreation water use standard, and the water is resulted in eutrophication. Then, on this basis, WASP was used to simulate water quality of Dongchang Lake to test the WASP's feasibility and effectiveness. And the results are that the relative error between the simulated value and measured values was small, and also meets the water quality simulation requirement. Then,the scenario analysis method was used to planning and predicting water quality. There are three main factors affecting water quality of Dongchang Lake-water supply quantity, water supply process, and location of water supply orifice. The water supply quantity was classified into the minimum water supply quantity, the middling water supply quantity and the maximum water supply quantity; the water supply process was classified into focus water filling process and uniform water filling process; the location of water supply orifice was classified into only northeast in use, only southeast in use and two orifice both in use. WASP was used to simulate water quality situation in every project, and the results were analyzed and evaluated. Finally, conclusions were drawn and recommendations to improve water quality were put forward.