In the recent decades, issues of water quality deterioration have been raised by the ecologists and environmentalists. This is a severe problem all over the world. For assessing water quality various methods have been used. Chemical and physical parameters are assessed but it is expensive and time consuming in comparison to biological tools. Flora and fauna present in a particular water body depends on the environmental and the physicochemical factors like temperature, pH, light ,salinity, nitrate ,phosphate, silicate etc. Thus, the biota present in a particular water body indicates the characteristics of the water and it can be used to assess the water quality. As a biological tool diatom have been used extensively. Researchers use various indices to determine the water quality.