The Water Quality Simulation And Evaluation Research Based On GIS In The Lower Reaches Of Wei River

Wei River comes from WeiYuan County in Gansu Province. It is not only the first level tributary of Yellow River, but also "mother river" of Guanzhong plain in Shaanxi Province, which has made tremendous contributions in all ages for the development of Guanzhong region. In recent years, with the rapid regional development of industy, population and urbanization, the contradiction between economic growth and environmental protection is becoming increasingly conspicuous, which has caused a certain extent limit of regional development.This paper combined GIS technology with water quality research method, taking Seg Xianyang to Seg Tongguan in the lower reaches of Wei River as the research object, then carried out the simulation, evaluation and analysis of Wei River water pollution: Selecting COD as the factor, simulated the water quality of the study area with WASP. Choosing DO, BOD₅ and COD_Mn, as the factors, evaluated the water quality synthetically in the method of fuzzy synthesis. This paper made integrated application of GIS and water quality models, analyzed the simulation and evaluation result, and studied COD space-time distribution characteristic and change trend. With the water quality model will GIS application of Wei River water quality, the integrated evaluation results of simulation and analysis, the research of Wei River main pollutant concentration, the space-time distribution of COD and water quality change trend in the past 10 years, then according to the results analyzed the causes of the pollution in lower reaches of Wei River deeply, and also explored the targeted control suggestions.According to the water environment characteristics in lower reaches of Wei River, this paper chose WASP and fuzzy synthesis to do the simulation and evaluation, applied GIS technology in WASP water simulation, and used GIS to analyze the water quality space-time changes in study area, so that the characteristic and trend could be reflected more visualized, intuitively and exactly. The combination of technologies provided a new idea for Wei River basin pollution research. In the process of using "GIS technology + WASP water simulation program", through the model parameters creation, rates making, procedures running, and results verifying, the simulations were executed, results as follows: COD concentration were closed with rainfall distribution in a year, in high water period COD kept with steady low concentration, with rainfall gradually reduced COD concentration raised, and reached the max in spring and winter. COD general trend was high in west and low in east, and the worst places were Xi'an-Xianyang area and Weinan region. Based on the simulation this paper used "GIS technology + fuzzy synthesis" to establish membership functions and weighting factor so that the evaluation could success, the results as follows: with no useable function, the water quality of study area is inferior V quality in every segment, and each single water quality factor was also over the V level standard. The east water was slightly better than the west, and the worst areas were Xi'an-Xianyang and Weinan area, which should be the key management objects. According to the above results and the specific situation of Wei River, the main reasons were that ecological water scarcity in main stream, huge difference of rainfall distribution between months, unreasonable industrial development, pollution control and sewage purification measures unfavorable, lack of scientific management and so on. Also this paper put forward nichetargeting suggestions, such as to optimize the industrial structure and accelerate the wastewater treatment engineering construction, to establish scientific management mechanism, to build "Digital Wei River", to increase the social consciousness and so on.