Comparing the results of water quality assessment by fuzzy comprehensive evaluantion method and the water quality index: a case study in the Dong Nai river

Abstract

The Dong Nai river is a source of supplying water for Ho Chi Minh city, Bien Hoa city and industrial areas. However, the status of the Dong Nai river has been seriously polluted which were caused by emission sources from urban areas, industrial zones, etc. In this study, the fuzzy comprehensive evaluation model (FCE) based on Entropy weight method was built to calculate pollution levels for 18 monitoring sites of the Dong Nai river with 7 parameters in the period 2005 – 2012. The results of study showed that the water quality of section 1 and section 2 are I level which mean good level. Section 3 is III ranking – medium pollution and section 4 is II ranking – slight pollution. Besides, the study also compared the results of the water quality between FCE and the water quality index (WQI). The results indicated that there isn’t difference between two methods. However, the FCE method is more practical, reasonable and acceptable. FCE was less affected by abnormal values than WQI.