24. A Box Model to Quantify Groundwater Discharge Along the Kona Coast of Hawaii Using Natural Tracers

Major islands such as Hawaii typically exhibit conditions favorable for high submarine groundwater discharge (SGD) to the ocean. Quantitative aerial thermal imaging along the leeward Kona coast of Hawaii reveals plumes of relatively cold groundwater discharging from distinct portals along the coastline. Many of these plumes are thought to represent substantial volumes of groundwater discharge. The goal of our tracer work is to quantify groundwater fluxes to the coastal ocean from some of these plumes as a means of calibrating the aerial imaging. We employed coincident mass equations for two tracers (salinity and randon) and water fluxes to develop a mass balance box model for quantifying groundwater discharge. Our results indicate that a small SGD discharge plume emanating from Kahualoa Bay represents water fluxes on the order of thousands of m3/day to the coastal ocean.