Effect of Sea Level Changes on the Groundwater Quality along the Coast of Ernakulam District,Kerala

Sea Level Rise (SLR) is considered as one of the effects of climate change that leads to Salt Water Intrusion (SWI) into the coastal areas around the world, thereby contaminating the groundwater and making it unusable for household and irrigation purposes along the coastal areas. Therefore, this paper is an attempt to analyze the change in sea level and shoreline and the consequent changes on the quality of groundwater in lowland and midland areas of Ernakulam district, Kerala. The tidal gauge data were sourced from the Permanent Service for Mean Sea Level (PSML) to assess the changes in sea level during 1971–2007. Remote sensing data was utilized for estimating the shoreline changes along the coast of the district using Digital Shoreline Analysis System (DSAS). The physical and chemical properties of groundwater were sourced for 27 locations from Central Ground Water Board (CGWB). Ionic ratios were computed to assess the salinity levels in the sampling locations. Sodium percentage (Na%) and potential salinity were computed for determining SWI and the suitability of the groundwater usage for domestic and irrigation purpose. Spatial variation of pH, EC, TDS and ionic ratios were assessed in the GIS environment through IDW interpolation. Findings indicate a rising trend in sea level at the rate of 1.8 mm/yr along the coast of the study area. Shoreline accretion and erosion was also observed at different locations along the coast during 2002–2012, though the rate of change varied across the shoreline. In general, water has shown slight alkaline nature, with pH varying from 7.2 to 8.2 at some locations, particularly along the coast. Higher values of EC and TDS were also observed along the coastal aquifer and may be ascribed to SWI. Sodium percentage (Na%) and potential salinity suggest presence of salt water. However, groundwater in majority of the areas especially away from the coast is good for domestic and irrigation uses. This study showed the groundwater quality deterioration, mainly due to the intrusion of sea water, particularly along the coastal areas of the Ernakulam district.