Assessment of water quality of a river-dominated estuary with hydrochemical parameters: A statistical approach.

Abstract

This study was aimed (1) to evaluate the water quality of Chalakudy river, the fifth longest (145.5 km) river of Kerala (South India), by assessing the general hydrochemical parameters like temperature, dissolved oxygen (DO), salinity and chemical oxygen demand (COD) on a seasonal and spatial basis and (2) to manifest the data using statistical tools like analysis of variance, dendrograms, non-metric multidimensional scaling (nMDS), trellis diagrams, discriminant analysis etc., so as to identify the factors and sources influencing the quality of river water. The sustainability of Chalakudy river estuarine ecosystem is of great significance as thousands of people depend on this particular river, and it is one of the very few rivers in the state of Kerala which is having relics of riparian vegetation in substantial level. DO showed significant differences between estuarine stations and other stations in the trellis diagram. Distribution of COD in water, arranged over seasons showed high seasonal variability at all stations and dendrogram delineated two distinct clusters, representing monsoon and non-monsoon seasons. nMDS drawn to group the stations based on salinity showed two distinct groups of stations (viz. estuarine and riverine). Wider separation (in Canonical discriminant analysis) between estuarine and non-estuarine stations of parameters particularly during nonmonsoon seasons with lower DO, high salinity and high COD indicated higher level of pollution during November to March. Chalakudy town and ferry regions of the riverine stations and the estuarine stations showed considerable levels of pollution.