Water Quality Evaluation of South Tiaoxi River Lin'an Section by Improved Fuzzy Analytic Hierarchy Process

The South Tiaoxi river, located in Lin'an city, Zhejiang province, is the origin of Tai Lake. The water quality condition of this river basin has the important meaning to the resident health of Hang-Jia-Hu plain and preventing pollution from Tai Lake. A two-year water monitor was carried out in South Tiaoxi river Lin'an section. Water samples were collected in July 2009, October 2009, January 2010 and April 2010. In order to overcoming the malpractice of previous fuzzy analytic hierarchy process which underestimates the severity of pollution and could not appraise inferior V water quality, an improved fuzzy analytic hierarchy process was established in the study. It was used to eveluated the water quality of South Tiaoxi river Lin'an section and analyze its temporal and spatial variation. Improved fuzzy analytic hierarchy process takes the intermediate value of the upper and lower limits of water quality standards as limited value, "S(i(j))", to compute the degree of membership. It can obtain six membership functions, conforming to the national standards. In this study, TN, TP, NH(3)-N, COD(cr), and DO were selected as main contamination factors. The eveluation results showed that the major pollutant was nitrogen. Nitrogen's weight coefficient reached 0.487.