Evaluation of riverwater quality by entropy

Abstract

As a measure of uncertainty of a system, entropy is employed as an indicator of the influx of pollutants from point as well as non-point sources of pollution to river systems in India. Most of the Indian rivers receive pollutants from municipal and industrial wastes, which are disposed without proper treatment. In addition, non-point source pollution also enters the receiving surface water diffusely at intermittent intervals. In this study, entropy is used to evaluate the water quality at different locations of six river systems in India: Baitarani, Brahmani, Malprabha, Pachin, Gomti and Yamuna. Two water quality variables, viz., dissolved oxygen (DO) and biochemical oxygen demand (BOD) are considered and their entropy values are determined at different locations for all the six river systems. However, due to the non-availability of data for Malprabha and Pachin river systems, entropy for electrical conductivity (Ec) and hardness (as CaCO3) is determined only for Baitarani, Brahmani, Gomti and Yamuna river systems. The results indicate severe water quality conditions in River Yamuna and River Gomti (in the Ganga plains), moderate water quality condition in River Bairatani (eastern river), and marginal water quality conditions in River Brahmani (eastern river), River Malprabha (southern river) and River Pachin (north-eastern river). The entropy variation at different time scales (during 1990–91 and 1995–96) for River Yamuna and Gomti indicates a gradual increasing trend of pollution