Estimating groundwater inputs from Sankarabarani River Basin, South India to the Bay of Bengal evaluated by Radium (226Ra) and nutrient fluxes

Abstract

Sankarabarani river basin gains significance due to presence of major industrial, agricultural, urban development and tourist related activities has influenced the water quality in the estuarine environment. Investigations about river water quality has been attempted but not more studies focus about the evaluation of groundwater discharge a significant process that connects groundwater and the coastal seawater have been attempted. For the present study, radium (226Ra) a naturally occurring isotope was measured at three locations and used as effective tracers for estimating the groundwater discharge along with nutrient inputs to the Bay. Groundwater samples representing north east monsoon (December, 2017) has been collected during tidal variation in three locations (Location A- away from the coast towards inland, Location B-intermediate between Location A and the coast and Location C-at the estuary). 226Ra mass balance calculated groundwater fluxes irrespective of tidal variations were 2.27×108 m3/d, 2.19×108 m3/d and 5.22×107m3/d for A, B and C locations respectively. The nutrients like Dissolved inorganic nitrogen (DIN), Dissolved inorganic Phosphate (DIP) and Dissolved Silica (DSi) were found to be influencing the coastal groundwater by contributing fluxes to the sea of about 679.33 T mol/day. The study suggests increasing radium and nutrient fluxes to the Bay altering the coastal ecosystems would result in surplus algal blooms creating hypoxia.