SUBMARINE GROUNDWATER DISCHARGE ON THE HAWAIIAN ISLANDS

The Hawaiian Islands capture a range of geologic, land-use, climate, and population gradients. We study submarine groundwater discharge in multiple watersheds across these gradients. In this context we have been investigating the significance of SGD as a terrestrial nutrient pathway to the ocean and the source of the nutrients it carries to the coastal zone. The general trend across the islands is that SGD in the form of total (fresh+brackish) groundwater discharge is 1-4 times larger than surface inputs. Corresponding dissolved inorganic nutrients originate from natural as well as anthropogenic sources (waste water and agriculture) and their coastal fluxes are also dominated by groundwater discharge. These findings suggest that along many shorelines on the islands SGD is not negligible from hydrological and geochemical perspective.

This presentation will illustrate observed trends and our current understanding of SGD through specific case studies.