Development of Index for Delineation of Potential Submarine Groundwater Discharge Zones Along the Coast

Abstract

Presently, there are limited techniques to identify submarine groundwater discharge (SGD) zones in the coastal regions due to the dynamic and invisible nature of the phenomenon driven by natural and anthropogenic factors. The driving factors for SGD include but are not limited to groundwater potential (hydraulic head), groundwater occurrence (type of aquifer: confined/unconfined), aquifer characteristics (hydraulic conductivity /transmissivity), aquifer thickness, the topography of the area, land use–land cover area, recharge–discharge pattern, sea level rise, dynamics of tides tidally driven oscillations, density-driven convection, and thermal convection. Considering some of the crucial factors, we have tried to develop an index that can help in indicating potential locations for SGD along the coastal regions based on easily accessible data. The most important factors which indicate the potential of SGD are groundwater level with respect to mean sea level (or hydraulic gradient (S)), groundwater occurrence (G), degree of pollution due to seawater intrusion in a coastal aquifer (D), transmissivity (T) or permeability of aquifer (K), and aquifer thickness (A). Based on this understanding of governing factors, the present work proposes SGDTA (highlighted acronym) index model to identify potential locations for SGD. The data required for this model are readily available with various agencies without any detailed investigation, so this index model is advantageous to delineate the potential location prior to a thorough investigation of SGD. Finally, we successfully demonstrate this model's first-hand application by identifying the SGD zones along the Bhavnagar district coast.