Ground‐Water Model for a Thick Fresh‐Water Lens

Abstract

The Pearl Harbor aquifer, an important ground‐water resource for southern Oahu, Hawaii, contains an enormous fresh‐water lens, up to 300 m (1,000 ft) thick, floating above saline water. The upper boundary of the fresh‐water lens is confined near the coast and phreatic inland, whereas its lower boundary is not confined. A finite‐difference flow model was used to simulate the Pearl Harbor aquifer system. The location of the fresh‐water/salt‐water interface, which constitutes the lower boundary of the flow system model, was estimated by Hubbert's formula. Known geohydrologic boundaries and aquifer parameters were also simulated. First, formation of the lens by filling the aquifer with fresh water from natural recharge was simulated to reconstruct the initial conditions before exploitation of the lens and to partially calibrate the model against the hydraulic‐head distribution in 1879. The model then was calibrated fully by simulating the lens’reponse to actual historical pumping patterns covering a time span of 100 years (1880 to 1980). Simulated heads compared favorably with the observed heads over time and space. The calibrated flow model may serve as a useful tool in the management of the Pearl Harbor aquifer.

Noble gases and coupled heat/fluid flow modeling for evaluating hydrogeologic conditions of volcanic island aquifers

“…Reported water-table elevations for volcanic oceanic island aquifers range from low-altitude, low-gradient regional water tables that are located near sea level at great depth beneath the island's interior to high-altitude, high-gradient water tables (Liu et al, 1983;Jackson and Lenat, 1989;Gingerich and Oki, 2000). Low-altitude water tables in Hawaii were first reported by Meinzer (1930) and termed ''basal ground-water'' (Fig.…”

Occupancy and habitat use of the endangered Akikiki and Akekee on Kauai Island, Hawaii

“…5  Groundwater head levels in Pearl Harbor, which supplies over 60% of Oahu's municipal water, 6,7 declined by half since 1910. 8 Estimates of `Iao valley's groundwater, which supplies a majority of Maui's municipal water, declined dramatically since the 1990s. 9  Lawsuits over stream water diversions continue for decades across the state, from Wailua 10 and Hanapepe, 11 Kaua`i 12 to Waiāhole, O`ahu 13 and East Maui.…”

Ground Water

“…In several recent research efforts (Dagan and Bear, 1968;Liu et al, 1983), numerical modeling techniques were used to investigate the flow and salinity transport in coastal aquifers. It was concluded that the evolution of the zone of diffusion may be more important in the management of coastal aquifers than the traditional sustainable yield approach.…”