Abstract
Submarine groundwater discharge (SGD) is described as submarine inflow of fresh and brackish groundwater from land into the sea. The release of sewages from point and non-point source pollutants from industries, agricultural and domestic activities gets discharged through groundwater to ocean creating natural disparity like decreasing flora fauna and phytoplankton blooms. Hence, to quantify fluxes of SGD in coastal regions is important. Quantification of SGD was attempted in Coleroon estuary, India, using three dissimilar methods like water budget, Darcy law and manual seepage meter. Three seepage meters were installed at two prominent litho units (alluvium and fluvio marine) at a distance of (0–14.7 km) away from Bay of Bengal. The water budget and Darcy law-quantified submarine seepage at a rate of 6.9 × 106 and 3.2 × 103 to 308.3 × 103 m3 year−1, respectively, and the seepage meter quantified seepage rate of 0.7024 m h−1 at an average. Larger seepage variations were isolated from three different techniques and the seepage rates were found to be influenced by hydrogeological characteristics of the litho units and distance from the coast.
Highlights
Submarine groundwater discharge (SGD) is one of the major water conduits that connect the land and ocean in global water cycle
For the SGD estimation by Darcy’s law, the hydraulic conductivity has been calculated for two different aquifers at three different locations, where the seepage meters have been installed
Higher SGD was noted in alluvium formation when compared with the other two fluvio marine formations, which might be due to greater hydraulic conductivity (Table 2) noted in the alluvium formation (Oberdorfer 2003a, b; Simmons et al 1991)
Summary
Submarine groundwater discharge (SGD) is one of the major water conduits that connect the land and ocean in global water cycle. The groundwater discharging from coastal aquifers and/or the incoming saline water contains elevated concentrations of nutrients, inorganic and organic substances and radionuclides triggering the coastal areas towards environmental degradation. In the last few decades, nutrients transporting from land to ocean have increased as a result of anthropogenic activities (Diaz and Rosenberg 1995; Soetaert and Middelburg 2006; Elsdon et al 2009; Ouyang 2012; Wang et al 2014; Gaume et al 2016). Through SGD the continuous loading of nutrients and trace metals alters the water quality resulting in environmental degradation of coastal regions (LaRoche et al 1997; Black et al 2009; Lee et al 2011; Rodellas et al 2015; Trezzi et al 2016). Quantification of SGD is important and a challenging task due to slow, diffuse and heterogeneous nature of the discharge that occurs below the water surface
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