Application of WQI Technique for the Classification of Water Quality: Mahanadi River-estuarine System,India – A Case Study

Water Quality Index (WQI) plays an important role in interpreting the information on water quality trends of a water body and was used to denote degradation of river water quality. WQI technique was applied for the classification of Mahanadi river-estuarine waters with respect to three major use purposes. WQI representing importance of the variables was studied with respect to suitability of river water for drinking, aquatic lives and irrigation purposes for 31 different stations of the river during six different seasons (pre-monsoon, monsoon and post monsoon during 2001–02 and 2002–03). In the formulation of a WQI, the importance of various parameters (pH, EC (electrical conductance), DO (dissolved oxygen), BOD (biochemical oxygen demand), TDS (total dissolved solids), turbidity, SO4, chloride, nitrate, sodium, calcium, magnesium, alkalinity and hardness) depends on the intend use of water. The results of different WQI produce similar trend but different index values as well as some different remarks. The present study reveals that the water quality of Atherbanki creek irrespective of seasons, is quite unsuitable for all the three purposes, which may be due to the combined impact of municipal effluent from Paradip township, industrial effluents from industries like PPL** and also saline influence. The application of a WQI to the Mahanadi river allows a water quality classification both spatial and temporally, that is reproducible within the river by means of uniform, objective criteria. Such an approach permits the identification of stretches of river that may require urgent measures in order to restore minimal water quality uses for different purposes, and can be applied beyond the Mahanadi river.

From the present observation, it can be concluded that three major townships (Sambalpur, Cuttack and Paradip) in the basin produce negative impact on the Mahanadi river water quality, particularly serious after the city sewage discharge. Effective pollution control measures must be taken in the near future.