VARIABILITY OF SUBMARINE GROUNDWATER DISCHARGE DURING SPRING AND NEAP TIDAL CYCLES ON THE KONA COAST, HAWAII

Submarine groundwater discharge occurs where fresh and saline ground water discharges to the sea. The magnitude of groundwater discharge can vary due to terrestrial and marine factors, including swell events, sea-level fluctuations, tidal changes, and seasonality in precipitation and groundwater withdrawal. All of these coastal factors affect not just the magnitude but also the salinity of the discharging groundwater. This research aims to analyze changes in submarine groundwater discharge (SGD) at a coastal site during spring and neap tides that occurred on the Kona Coast of the Big Island of Hawaii. We compare SGD and salinity measurements taken in the nearshore water over an eighteen-month period and corresponding observations of salinity and groundwater level in the coastal aquifer. The SGD and salinity patterns found at the coast and in the coastal aquifer can ultimately provide insight into how SGD changes with respect to variation in marine and terrestrial factors on a tidal scale and over a short distance.