State of the groundwater resources of southern Oahu

Abstract

The aquifers of all of Southern Oahu from Manoa Valley to the Waianae Mountains are hydraulically connected. For convenience the Pearl Harbor region is considered as extending from Red Hill to the Waianae crest and the Honolulu region from Manoa to Red Hill. This arbitrary division has been employed in all hydrologic studies of Southern Oahu. The total natural groundwater flow passing through the Pearl Harbor region lies between 200 and 250 mgd (million gallons per day). This includes infiltration from rainfall and subsurface inflows from the Wahiawa high-level aquifer and from the rift zones of the Koolau and Waianae Ranges. It is reasonable to assign a natural flux of 220 mgd to the Pearl Harbor region for modeling purposes. In Honolulu the natural flux is about 60 mgd.