Monthly variations of some hydrographic parameters in the Rushikulya Estuary, east coast of India

Abstract

Monthly variations of temperature, salinity, dissolved oxygen (DO), pH and transparency in the Rushikulya Estuary, Orissa, India were studied over two annual cycles (January 1988-December 1989) at 5 stations covering the entire stretch of the estuary. Each of these hydrographic parameters showed significant spatial and seasonal variations. The water temperature was mostly influenced by atmospheric temperature rather than the ingress and outgress of seawater into and from the estuary. Salinity variations were more conspicuous than the other parameters analysed. The surface water salinity ranged from 1.0 to 34.7 x 10/3 during 1988, from 1.0 to 35.7 x 10/3 during 1989. Vertical salinity gradient was prominent only in July during the first year and from July to September in the second year. Annual cycle of salinity is unimodal with peak in April/May and low in August/September. The spatial and seasonal distribution of DO showed considerable variability