Cost-Effective Methodology to Quantify the Submarine Groundwater Discharge from Coastal Unconfined Aquifers

Submarine groundwater discharge is a pathway of fresh and recirculated groundwater to the sea. It is recently understood that this phenomenon delivers thirteen times more nutrients to the sea than the river water. This is due to the high residence time of groundwater in the coastal aquifers when compared with the river water. Studies to estimate the discharge in the field is very scarce; therefore, the real magnitude of discharge and the nutrient budget through SGD is still inconclusive. On the other hand, quantifying the SGD rates in a location would help calculate the optimal pumping rate from the coastal aquifer without leading to seawater ingress. Methods available currently to estimate SGD rates are resource intensive and needs dedicated instruments. We suggest a cost-effective methodology using the basic civil engineering survey instruments and fabricated tools to estimate the SGD rates from the coastal aquifer. This method not only estimates the discharge, but it also helps delineate the seawater-freshwater interface in the coastal aquifer and could differentiate between the fresh and recirculated SGD. The limitation of this methodology is that the SGD rates can only be estimated from the coastal unconfined aquifers, not the deeper aquifers.