Estimating Hydraulic Properties of Volcanic Aquifers Using Constant-Rate and Variable-Rate Aquifer Tests

In recent years the ground-water demand of the population of the island of Maui, Hawaii, has significantly increased. To ensure prudent management of the ground-water resources, an improved understanding of ground-water flow systems is needed. At present, large-scale estimations of aquifer propertie...

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Bibliographic Details
Published in:Journal of the American Water Resources Association 2007-04, Vol.43 (2), p.334-345
Main Authors: Rotzoll, Kolja, El-Kadi, Aly I., Gingerich, Stephen B.
Format: Article
Language:English
Subjects:
aquifer characteristics
aquifer pumping test
Earth sciences
Earth, ocean, space
Exact sciences and technology
ground-water hydrology
ground-water management
Hawaii island aquifer
Hydrogeology
Hydrology. Hydrogeology
kriging
step-drawdown test
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Summary:In recent years the ground-water demand of the population of the island of Maui, Hawaii, has significantly increased. To ensure prudent management of the ground-water resources, an improved understanding of ground-water flow systems is needed. At present, large-scale estimations of aquifer properties are lacking for Maui. Seven analytical methods using constant-rate and variable-rate withdrawals for single wells provide an estimate of hydraulic conductivity and transmissivity for 103 wells in central Maui. Methods based on constant-rate tests, although not widely used on Maui, offer reasonable estimates. Step-drawdown tests, which are more abundantly used than other tests, provide similar estimates as constant-rate tests. A numerical model validates the suitability of analytical solutions for step-drawdown tests and additionally provides an estimate of storage parameters. The results show that hydraulic conductivity is log-normally distributed and that for dike-free volcanic rocks it ranges over several orders of magnitude from 1 to 2,500 m/d. The arithmetic mean, geometric mean, and median values of hydraulic conductivity are respectively 520, 280, and 370 m/d for basalt and 80, 50, and 30 m/d for sediment. A geostatistical approach using ordinary kriging yields a prediction of hydraulic conductivity on a larger scale. Overall, the results are in agreement with values published for other Hawaiian islands.
ISSN:1093-474X
1752-1688
DOI:10.1111/j.1752-1688.2007.00026.x