Submarine Groundwater Discharge (SGD): Impacts, challenges, limitations, and management recommendations

Judicial use of submarine groundwater discharge (SGD) can be a potential water resource for countries facing water scarcity. Very few studies report the fluxes of SGD into the oceans, especially from those countries that are located in the tropics and facing water scarcity. Another dimension of the SGD is its potential to control the biogeochemical cycles of nutrients and trace metals and the anthropogenic impact on the oceans. This work attempts to give an overview of the challenges and limitations involved in achieving the above. We have reviewed 1628 published literature that reported SGD in different contexts in the last 21 years (the Year, 2000 to this date). Several studies exist in bits and pieces across the world's coastline, with different methodologies adopted for identifying and quantifying the SGD. This compilation has attempted to extract these findings and listed the challenges and limitations in estimating the SGD fluxes. Significant challenges in quantifying the discharge include inconsistent sampling strategies adopted by researchers, uncertainties in modeling, spatio-temporal variations in discharge, extreme weather conditions, and difficulty in quantifying discharge at inaccessible areas (mangroves, large tidal flats, etc.). Some limitations discussed in this work include insufficient knowledge of coastal aquifer data, geology, and lack of historical hydrological data. Based on the critical analysis of the published literature, we recommend a few solutions that can provide a better resolution in the quantification of SGD. Decision makers and water conservation professionals will benefit from this work as they can suitably plan the water management, pollution control, and sustainable extraction of the SGD. We suggest strategies calling for assessments of SGD in areas of potentially significant discharge and developing new monitoring networks and strict policies for groundwater usage.