Analytical Versus Numerical Estimates of Water- Level Declines Caused by Pumping, and a Case Study of the Iao Aquifer, Maui, Hawaii
Oki DS and Meyer W. 2001. Analytical Versus Numerical Estimates of Water- Level Declines Caused by Pumping, and a Case Study of the Iao Aquifer, Maui, Hawaii. U.S. Geological Survey (USGS) Water Resources Investigations Report. 00-4244. U.S. Geological Survey. Honolulu, Hawaii
Comparisons were made between model calculatedwater levels from a one-dimensional analytical model referred to as RAM (Robust Analytical Model) and those from numerical groundwater flow models using a sharp-interface model code. RAM does not account for the presence of a low-permeability coastal confining unit (caprock), which impedes the discharge of fresh ground water from the aquifer to the ocean, nor for the spatial distribution of ground-water withdrawals from wells, which is significant because water-level declines are greatest in the vicinity of withdrawal wells. Since 1990, RAM has been used by the State of Hawaii Commission on Water Resource Management for establishing sustainable-yield values for the State’s aquifers. Data from the Iao aquifer, which lies on the northeastern flank of the West Maui Volcano and which is confined near the coast by caprock, are now available to evaluate the predictive capability of RAM for this system. However, even before 1996, water levels in the aquifer had declined significantly below those predicted by RAM, and continued to decline in 1997. To halt the decline of water levels and to preclude the intrusion of saltwater into the four major well fields in the aquifer, it was necessary to reduce withdrawal from the aquifer system below the sustainable-yield value derived using RAM. The numerical models performed better for this system.
- Type
- Published Report
- Authors
- Oki, Delwyn; Meyer, William
- Date of Issue
- 2001
- Publisher
- U.S. Geological Survey
- Units
- HALE
- Keywords
- Development, Groundwater, Landscape, Landuse, Maui, Water Quality