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Scientific Investigations Report 2014–5168

Prepared in cooperation with the County of Maui Department of Water Supply and the State of Hawai‘i Commission on Water Resource Management

Spatially Distributed Groundwater Recharge Estimated Using a Water-Budget Model for the Island of Maui, Hawai‘i, 1978–2007 (ver 2.0, February 2018)

By Adam G. Johnson, John A. Engott, Maoya Bassiouni, and Kolja Rotzoll

Thumbnail of and link to report PDF (13.3 MB)Abstract

Demand for freshwater on the Island of Maui is expected to grow. To evaluate the availability of fresh groundwater, estimates of groundwater recharge are needed. A water-budget model with a daily computation interval was developed and used to estimate the spatial distribution of recharge on Maui for average climate conditions (1978–2007 rainfall and 2010 land cover) and for drought conditions (1998–2002 rainfall and 2010 land cover). For average climate conditions, mean annual recharge for Maui is about 1,309 million gallons per day, or about 44 percent of precipitation (rainfall and fog interception). Recharge for average climate conditions is about 39 percent of total water inflow consisting of precipitation, irrigation, septic leachate, and seepage from reservoirs and cesspools. Most recharge occurs on the wet, windward slopes of Haleakalā and on the wet, uplands of West Maui Mountain. Dry, coastal areas generally have low recharge. In the dry isthmus, however, irrigated fields have greater recharge than nearby unirrigated areas. For drought conditions, mean annual recharge for Maui is about 1,010 million gallons per day, which is 23 percent less than recharge for average climate conditions. For individual aquifer-system areas used for groundwater management, recharge for drought conditions is about 8 to 51 percent less than recharge for average climate conditions. The spatial distribution of rainfall is the primary factor determining spatially distributed recharge estimates for most areas on Maui. In wet areas, recharge estimates are also sensitive to water-budget parameters that are related to runoff, fog interception, and forest-canopy evaporation. In dry areas, recharge estimates are most sensitive to irrigated crop areas and parameters related to evapotranspiration.

  • A GIS data set containing results associated with this report can be accessed here. Note: Google Chrome may not display the metadata of this GIS data set correctly.

This publication is online only

For additional information, contact:
Director,
Pacific Islands Water Science Center
U.S. Geological Survey
Inouye Regional Center
1845 Wasp Blvd., B176
Honolulu, HI 96818

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Suggested citation:

Johnson, A.G., Engott, J.A., Bassiouni, Maoya, and Rotzoll, Kolja, 2018, Spatially distributed groundwater recharge estimated using a water-budget model for the Island of Maui, Hawai`i, 1978–2007 (ver. 2.0, February 2018): U.S. Geological Survey Scientific Investigations Report 2014–5168, 53 p., https://doi.org/10.3133/sir20145168.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Description of Maui

Water-Budget Model

Model Input

Model Exclusions and Limitations

Model Randomness

Water-Budget and Groundwater-Recharge Estimates

Suggestions for Future Study and Additional Data Collection

Summary and Conclusions

References Cited

Figures (12)

Tables (10)


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