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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 58 (1974)

Issue: 7. (July)

First Page: 1435

Last Page: 1435

Title: Simulation Model of Honolulu Basal Aquifer: ABSTRACT

Author(s): R. H. Dale

Article Type: Meeting abstract

Abstract:

A Previous HitmathematicalNext Hit model of the Honolulu aquifer that relates the historical head measurements to the rainfall and pumpage records has been formulated. This work is focused on determining the hydrodynamic relations between the freshwater and saline-water bodies to allow application of the best practices for management of the basal groundwater resource (a body of fresh water that floats on saline groundwater).

The Honolulu aquifer is composed of the basaltic lava flows that form the Koolau Range. These rocks have a value of hydraulic conductivity on the order of 10,000 ft/day (3,000 m/day). The Honolulu coastal-plain sediments conformably overlie the aquifer. The sediments have a low hydraulic conductivity, and restrict the flow of basal groundwater to the ocean. Alluvial deposits that have backfilled Pleistocene valleys cut deep into the aquifer, restrict lateral groundwater flow, and divide the Honolulu aquifer into three reservoirs.

The individual reservoirs are about 10 sq mi (26 sq km) in area. Pumping from each reservoir is restricted to one or two large pumping plants and the freshwater head has been measured by continuous recorders on a single well in each reservoir. The small size of the reservoirs, plus the limited historical data, make it convenient to use each reservoir as a computational cell of the Previous HitmathematicalNext Hit model.

The Previous HitmathematicalTop model was derived by solving the mass-balance equation for discrete time steps for each of the reservoirs. Inflow and outflow elements considered were deep infiltration of rainfall, saltwater flow from the ocean to the underlying saltwater body, flow between the reservoirs, and pumpage. Best estimates of the aquifer parameters were obtained by processing part of the historical records using linear-programming techniques. The estimates of the aquifer parameters were used in the simulation model to compute freshwater head for the remaining part of the historical records. The fit between the historical head and the computed head is good, suggesting that the model could be used as a tool for estimating the effects of alternative management practices.

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Copyright 1997 American Association of Petroleum Geologists