Hydrogeochemical Assessment of Groundwater Quality and Salinity Intrusion in Coastal Aquifers of Eastern India

Water shortages and degradation of water quality are issues that are escalating globally due to population growth, industrialization, urbanization, and misuse of water, necessitating effective water resources planning and management. This study focuses on assessing groundwater quality along the coastal tract of eastern India, where groundwater is crucial for fulfilling of various water needs. The study further addresses marine-pollution encroachment into the coastal aquifer, emphasizing the need for a thorough water resource quality assessment. Throughout the coastline tract under this study, 61 groundwater samples were randomly collected from hand pumps and excavated wells, and their chemical composition was examined. Water quality parameters such as pH, total dissolved solids (TDS) and electrical conductivity (EC), cations such as calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), and anions such as bicarbonate (HCO3), carbonate (CO3), chloride (Cl) and sulphate (SO4) were determined. Also, hydrogeochemical diagrams, i.e., Piper’s diagram, Chadha’s diagram, Gibbs diagram, and United States Salinity Laboratory (USSL) diagrams were plotted to identify the hydrochemical processes and assess the aquifer salinity. Of the total 61 samples, Chadha’s and Piper's diagrams identified 57.66% and 64.06% of samples, respectively, as Na-Cl water type, confirming the presence of salinity. The Ca concentration ranged from 21.64 to 4868.11 mg L-1, while TDS values ranged from 190 to 7520 mg L-1, with most areas having TDS values below 3000 mg L-1. Chloride values ranged from 24 to 2368 mg L-1. The Simpson ratio/Revelle index, ranging from 0.089 to 56.008, indicated towards occurrence of saltwater intrusion process. The NaCl type water exists at majority of the sampling sites (49.18%), which suggests that seawater mixing is primarily restricted to the coastal zone. Na and K were the dominant cations, making 67% of the ionic composition in water samples. The findings of this study can aid in developing management plans to safeguard aquifers and remediation strategies for groundwater affected by natural and anthropogenic activities.