A study of saltwater intrusion in the Kallada River, southwest coast of Kerala, India.

Munroe Island in Kollam District of Kerala is a typical backwater village situated at the confluence of the Ashtamudi backwater and the Kallada River system. It is an amalgamation of eight small islands with a total area of 13.4 km². Salinity intrusion has been a serious threat in the downstream areas of Kallada River for more than one and half decades, affecting the groundwater quality of Munroe Island. The present study focuses on the seasonal variation in physico-chemical characteristics of the underground water system of Munroe Island and Kallada River with special reference to saline water intrusion. Physico-chemical analysis of ground water revealed that samples were unsuitable for drinking due to higher content of Na, Ca, and K. Microbiological analysis of island groundwater showed the presence of coliform and E. coli bacteria above the permissible limit. Results indicated a significant correlation between salinity and major anions viz., Cl^- and SO₄² and cations viz., Mg, Na, Ca, and K of both river surface and island groundwater. In the present study it is clearly evident the occurrence of saltwater intrusion in Kallada River from Ashtamudy Lake and the its severity become higher during premonsoon season. The results also indicated that the salinity increase in Kallada River has a negative impact on island groundwater quality. The paper also suggests suitable management strategies for overcoming the saltwater intrusion thereby upgrading island sustainability. [ABSTRACT FROM AUTHOR]