Development of Water Quality Indexes to Identify Pollutants in Vietnam’s Surface Water

This study presents the first water quality indexes developed to evaluate surface water in Vietnam. The basic water quality index (${\mathrm{WQI}}_B$) can be effectively used to evaluate the spatial and temporal variations of surface water quality as well as to identify water pollutants. The overall water quality index (${\mathrm{WQI}}_O$) can provide additional information, particularly on toxic substances contributing to water pollution. The water quality indexes developed for this paper were applied to the national surface-water quality monitoring data taken from 1999 to 2007. Water pollutants were classified into three subcategories: organic and nutrients, particulates, and bacteria. Surface water in northern and central Vietnam was poor in quality and contained organic matter, nutrients, and bacteria. Water in the southern part was mainly polluted by bacteria. Trend analysis results reveal a deterioration in water quality in those provinces under pressure from rapid population growth, urbanization, and industrialization. Vietnam has established an official policy to ensure comprehensive nationwide water quality monitoring by 2020. The implementation of water quality indexes may provide the guiding data for sustainable water-resources management in Vietnam.