Abstract
Abstract 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.
Highlights
Due to colour change and taste differences of water in most of the wells, pure drinking water availability is scarce in the panchayat
No systematic scientific studies were conducted so far to determine the occurrence of salt water intrusion, this study aims to scientifically prove the severity and occurrence of salt water intrusion occurring at various seasons, its impact on Munroe island ground water quality, and suggesting suitable management strategies for overcoming the current environmental degradation of island
The lowlying areas of the Munroe island are facing a serious threat of water upwelling, salinity problems, poor drinking water quality and agricultural failure for more than one and half decades
Summary
The amount of fresh water on the earth is limited, and its quality is under constant pressure. The lack of water quality adversely affect the health of living beings (Balwant et al 2016). Environmental factors such as the occurrence of highly soluble or weathered minerals, distance to the marine environment, aridity, terrestrial primary productivity, ambient temperature, the weathering reaction kinetics, and quality of unpolluted waters influence the river water chemistry (Gibbs 1970). The process of saltwater intrusion is the phenomenon of the sea and river water mixing, and the estuarine stratification is the combination of small-scale turbulent diffusion and large-scale variation of the field of island constituting velocities, not constant either in time, space, and direction (Antony & Ignatius 2016)
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