IDENTIFICATION AND ESTIMATION OF THE SUBSURFACE GROUNDWATER DISCHARGE INTO THE SOUTH EAST COASTAL WATERS OF INDIA

Subsurface groundwater discharge (SGD) in the coastal Cuddalore region of south east India has been carried out. Measurement for radon, water level, electrical conductivity (EC) and ph in surface water for a total of twenty hours by hourly interval has been carried out and further correlated with tidal values calculated by wx tide 32 software. The SGD measurements were made by using a modified seepage meter. The study reveals a match with water level variation and tide with minor variation due to influx of surface water. Saline discharges, fresh groundwater discharges and surface water mixing processes were identified along the coast. Lower SGD (37.24 – 79.16 cm/day) was observed during fresh groundwater discharge. The study broadly brings out the major geochemical process occurring in this coastal environment zone. The radon measurements indicate the difference in fresh water- groundwater interface in this region. The EC variation has been studied throughout the tidal cycle period and compared with parameters measured in the field like radon, ph and water level. This study identified four cyclic processes that are dominant in the region as saline SGD, fresh water SGD, saline surface water interference and the mixing of fresh uppanar river with sea. The maximum rate of discharge was observed during the saline water discharge period. Further studies are needed focusing on different season of the same area that will give insight into the holistic processes governing this coastal fresh-saline surface water interface. It helps to exactly delineate the influence of SGD on the coastal productivity, which are depleting in the recent years.