Submarine Groundwater Discharge in the Indian Context

In India, the demand for freshwater resources is increasing every year because of population rise and rapid economic development. This warrants the imminent need for better evaluation of all the available sources of freshwater and their discharge–recharge mechanisms for planning sustainable development strategies in the country. Among different sources, groundwater constitutes about 97% of the earth’s liquid freshwater in the hydrologic cycle. It has now been realized that as part of the hydrologic cycle, a significant amount of groundwater flows directly into the sea through porous rocks and sediments¹. This component is called submarine groundwater discharge (SGD). In a study carried out in the southern United States using ²²⁶Ra as tracer², it was reported that the contribution of SGD in the coastal waters of the area could be comparable to the observed discharge from rivers³. Although India has an extensive coastline of about 7500 km, except selected case studies^4–10, no systematic efforts have hitherto been made to assess SGD flux to its receiving coastal waters. As the country is undergoing rapid economic development in the recent years, it is high time that the scientific community make efforts to estimate the quantity and quality of SGD flux to the Indian seas for planning and development of its freshwater potential.