Change Detection of Groundwater Level and Quality in Coastal Aquifers of Malabar Region in Kerala, India

A study was conducted to assess the changes in groundwater level and quality for the period 2005-2020 in the coastal aquifer of the Vatakara-Koyilandy stretch in the Kozhikode district of Kerala. Hydrogeochemical analysis of groundwater quality parameters, irrigation water quality analysis and preparation of spatial variability of groundwater level and salinity were used for the study. The Piper diagram was used to track the change in the hydrochemical parameters of groundwater sources in 2005 and 2020 and identify changes in the chemical facies of the groundwater. The Gibbs diagram was used to identify the source of the dissolved ions present in the groundwater in both years. The United States Salinity Laboratory diagram was used to assess the groundwater's suitability for irrigation. The spatial variation of water table elevation and salinity were compared using the ordinary kriging method of interpolation. An increase in seawater intrusion into the wells and a reduction in irrigation water quality was indicated by the change in the Hydrochemical facies, and the shifting of more groundwater samples in the evaporation dominance zone in the Gibbs plot. The spatial variability of groundwater level indicates a reduction in premonsoon in both years. On the North coast, a 4% increase in the area under groundwater level  < 2m. the reduction in the groundwater table on the coast increases the chance of sweater intrusion and thereby increased salinity.  Even though the study area receives heavy rainfall during monsoon and recharging of the coastal aquifer, seawater intrusion progressed landward from 2005 to 2020 during the premonsoon and affected the groundwater level and quality over this period.