Seawater intrusion generally occurs when withdrawal of fresh groundwater from coastal aquifers results in declining groundwater levels, facilitating lateral and/or vertical migration of saline water causing deterioration of groundwater quality. Hydro-chemical studies are widely used to determine the interaction between groundwater and saline water/seawater in coastal aquifers. Sea water ingression study was undertaken in the Kelwa-Mahim coastal area in Palghar district. Water quality parameters of water samples from 47 well were also measured using handheld multiparameter instrument. The depth to saline-fresh water interface varied from <1 to 5 m at different locations. The high salinity clay horizons are identified at various depths. Hydro chemical data was analyzed using hill-piper diagrams and statistical plots to understand groundwater-seawater mixing/interaction in the coastal aquifers. In this area NaCl was dominant solvent and MgCl occurred at few locations. Higher EC and TDS were noted in the western part of the area close to the sea. Vertical distribution of ground water salinity indicates that fresh water sea water interface is about 15-20 m.bgl.
