A case study of freshwater discharge in porous calcarenite formation in coastal terrace at Manapad, South India

Abstract

The focus of this study is the discharge of freshwater from coastal terraces to coastal areas. A large amount of submarine groundwater discharge (SGD) flow moves toward the sea. The study to determine the flux rate uses geology, grain size, magneto telluric, resistivity and water geochemistry for quality analysis. The research is on the structure of calcite and sandstone composed of high-porosity rocks in the entire terrace. The height of the platform is 45 m, and the high gradient of SGD flows through the porous medium. Rock types and grain studies are used to distinguish estuarine, beach and shallow sea environments. Round quartz grains were found at the top of the terrace in the form of nodules, which is evidence of the uplift of coastal landforms. In the microscopic study, the carbonate rock in the terrace contains calcium and other substances. The calcium substance has fine, medium, coarse grain and ionic properties. Resistivity sounding, 2D resistivity imaging, and magneto telluric technology are to use resistivity changes to determine the connectivity of permeable calcarinite rock and SGD in land and ocean underground discharges. Geochemical phase evolution maps are used to support freshwater and seawater intrusions in research areas. Water flow is calculated using 2D ERI and MT images. Due to the porosity and permeability of the rock, five open-hole wells in the Saint Xavier Cave were discovered, forming a calcarenite structure with a high water flow gradient. This is a useful case study for the purpose of drinking water for coastal people in the system of seepage aquifers.