Water Quality Assessment Study Based On TOPSIS Method

Lanzhou city is the only capital city where the Yellow river goes through in China, the Yellow river is the water resource of Lanzhou city, meantime it also accepted industrial and domestic sewage in Lanzhou, as a result, it is of great significance to assess and study the water environment quality of Lanzhou section of yellow river.The article first analyzed and studied the practice condition of the water quality assessment methods at home and abroad, then compared the water quality assessment work between China and abroad, further more analyzed the shortages of China’s water quality assessment; and then fully analyzed the system theory of water quality assessment; mainly focus on the integrated application of the improved TOP SIS method in water quality assessment; at last some conclusions and suggestions are proposed. The main content includes:(1)Analyzed and summarized the research situation at home and abroad, including the laws and standards related to water environment quality and frequently used water quality assessment methods, as well as the comparisons on water quality assessment work at home and abroad.(2)Summarized the working process and methods of water environment quality assessment. Start with pollution source investigation and assessment, the confirmation of assessment standard and the weight of the factors, as well as the assessing representative value, and establish a more complete water environment quality theory system.(3)On the basis of comparing the frequently used water quality assessment methods at home and abroad, selects the TOPSIS method as the method using to evaluate the water quality of the studying area. Introduces the theory and steps of TOPSIS method and improves it appropriately and uses it on evaluate the water quality of Yellow river, finally compare the evaluate results between the improved TOPSIS method and the traditional TOPSIS method, and find that in some of the sections, the water quality category is slightly worse when using the traditional TOPSIS method than that using the improved TOPSIS method. The evaluation results shows that the water quality category of the three water sections could all reach the Ⅲ class.(4)The pollution trend analysis research of the study area. Overall, the water pollution extent of the three water sections in yellow river Lanzhou section from September2012to September2013shows that the dry season is worse than normal season and wet season; the concentration of some pollutants changes drastically in the wet season, the concentration of most pollutants are bigger in the downstream such as the Baolan bridge section.(5)The theory of the improved TOPSIS method is simple and its calculation is easy, as well as the intuitive results, it also take into account the combined action of the factors in water environment. Therefore the evaluation result is reliable and is of some help to allocating water resources rationally and formulating water quality control objective.