Hydrogeochemical investigations to assess groundwater and saline water interaction in coastal aquifers of the southeast
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RESEARCH ARTICLE
Hydrogeochemical investigations to assess groundwater and saline water interaction in coastal aquifers of the southeast coast, Tamil Nadu, India Prakash Raja 1,2 & Srinivasamoorthy Krishnaraj 1 & Gopinath Selvaraj 3 & Saravanan Kumar 4 & Vinnarasi Francis 1 Received: 17 January 2020 / Accepted: 15 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Groundwater and saline water interaction is the most common processes in the coastal aquifers that alters the quality of aquifer waters. The quaternary alluvium aquifer system is a significant water resource of southeast coastal Tamil Nadu that provides water supplies for industrial, agriculture, and domestic utilities. Hydrogeochemical investigations were attempted to analyze groundwater–saline water interactions for which a total of three hundred and sixty samples representing surface water, pore water, and groundwater samples collected from three significant locations (location A, B, and C) and analyzed for major ion concentrations. Piper plot infers surface and pore water samples representing saline water type (Na-Cl) in all the three locations due to tidal variation and sand dominant surface layer. Groundwater samples represent (Ca-HCO3) type at location A due to fresh groundwater discharge, mixed or subterranean estuary (Ca, Mg-Cl, HCO3) at location B due to conversion of freshwater (CaHCO3) at low tide to saline water (Na-Cl) at high tide, and saline (Na-Cl) water at location C due to proximity and influence of tides. The Cl−/HCO3− vs. Cl− plot represents two water types, such as fresh groundwater (0.5) and strongly affected by seawater intrusion (6.6). The plot (Ca2++Mg2+)/(K++Na+) vs. log Cl− represents freshwater in location A, mixing in location B, and saline water in location C. Groundwater samples observed to be fresh in location A (20.0 km away from the coast), recirculated in location B (9.0 km away from the coast), and saline in location C (0.5 km away from the coast). Keywords Freshwater . Subterranean estuary . Saline water . Hydrochemical facies . Ionic ratio plots
Introduction Coastal aquifers over the world are facing severe threats caused by human influences due to urbanization, industrialization, agriculture, and natural processes such as fresh groundwater discharge and seawater intrusion (Liu et al. Responsible Editor: Xianliang Yi * Prakash Raja [email protected] 1
Department of Earth Sciences, Pondicherry University, Puducherry 605014, India
2
Department of Geology, Bharathidasan University, Khajamalai Campus, Trichy 620 023, India
3
Institute of Geophysics, Universidad Nacional Autónoma de México, 04510 Mexico City, CP, Mexico
4
Department of Civil Engineering, Indian Institute of Sciences, Bangalore 560 012, India
2017; Najib et al. 2017). Seawater intrusion is mainly due to significant evaporation, excess groundwater pumping, rapid sea-level rise, and density-driven forces (Mondal et al. 2010; Kim et al. 2017). Freshening of coastal aquifers is mainly due to processes like prec
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