water stream over rocks


Assessment of Groundwater Availability in the Volcanic-Rock Aquifers of Oahu, Hawaii

Assessment of Groundwater Availability in the Volcanic-Rock Aquifers of Oahu, Hawaii

National Institute for Water Resources, Water Resources Research Institute Program

3/1/2014 - 2/28/2016

The volcanic-rock aquifers of Oahu supply freshwater to 70 percent of Hawaii’s population and most of other needs, including commerce, industry, and U.S. military. The resident population on the island has been increasing while freshwater resources are limited. Because the aquifers are small and are surrounded by saltwater, they have a restricted capacity to store groundwater and are thus particularly susceptible to impacts from human activity, through land- use changes or excessive withdrawals, and climate change (Izuka 2013). Availability of fresh groundwater is limited by the desire to avoid adverse effects on water resources, such as lowering water tables, saltwater intrusion, and depletion of streamflow and submarine groundwater discharge. Quantifying these effects is therefore critical for a successful groundwater management. The last regional assessment of the water resources in the volcanic-rock aquifers of Oahu was completed during the 1990s (Hunt 1996, Nichols et al. 1996). Since then however, new technologies (computer power, modeling software) and new analysis techniques have been developed, recharge and hydrogeologic information have been updated, and the need to consider effects of climate change has increased. This warrants a revised assessment of the current groundwater availability, of the likely impacts of natural and anthropogenic factors on such availability, and of the effects of these factors on water resources in the future. The study will utilize a numerical modeling approach of newly available recharge and hydrogeologic information to (1) improve understanding of the most developed regional groundwater-flow system in the main islands of Hawaii, (2) update knowledge of the availability and sustainability of Oahu’s groundwater resources, and (3) provide insight into the impacts of human activity and climate change on groundwater resources.

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