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Groundwater Availability in the Haiku, Honopou, and Makawao Areas, Northeast Maui, Hawaii
Phase 1 -- Groundwater Recharge

Project Chief: Adam G. Johnson
Project Period: June 2011 through June 2014
Cooperator: Maui County Department of Water Supply
Location: Island of Maui

Problem

Between 1970 and 2006, the resident population on the island of Maui, Hawaii has increased over 250 percent. Groundwater demand for domestic supply also has increased significantly during this period. Demand for water provided by the Maui County Department of Water Supply in the Upcountry area is expected to increase from about 7.2 million gallons per day in 2005 to 8.8 Mgal/d in 2030 and demand in the Wailuku area is expected to increase from about 22 Mgal/d in 2005 to 34 Mgal/d in 2030. The general area locally referred to as “Upcountry” includes Makawao and adjacent areas on the northwest slopes of Haleakala.

The Haiku, Honopou, and Makawao Aquifer Systems of northeast Maui are potential source areas for meeting this additional demand, with the Haiku Aquifer System being the most desirable because of its lower altitude and proximity to the areas of need. However, development of additional water supply from parts of the Haiku aquifer is subject to compliance with the East Maui Water Development Plan Consent Decree which was issued in 2003. Among the items that must be addressed are an evaluation of the effects of groundwater withdrawal on streamflow and the collection of additional data to support the current understanding that the groundwater system has a perched aquifer above a typical freshwater lens system rather than a system having an aquifer fully saturated to several hundred feet above sea level.

Additional concerns for the Upcountry area include the effects of additional pumping on existing private wells and the lack of up-to-date recharge estimates for the Haiku, Honopou, and Makawao Aquifer Systems.

Objectives

The objective of Phase 1 of the study is to estimate the spatial distribution of groundwater recharge for the Haiku, Honopou, and Makawao Aquifer Systems. Additionally, an approach for the later phases of the groundwater availability study will be developed as part of this phase of the study. Later phases will include 1) design of a new well and a monitoring plan to help gather evidence about the nature of the high-level groundwater body in the study area, and 2) use of a numerical groundwater model to evaluate the effects of additional withdrawals on streamflow, coastal discharge, and salinities in public and private wells in the study area.

Relevance and Benefits

The results from this study are necessary to properly manage groundwater in the State of Hawaii. The study is consistent with the mission of the USGS Science Strategy to provide citizens, communities, natural-resource managers, and policymakers with a clearer knowledge of the status of their water resources. By providing estimates of current groundwater recharge and analyses of the effects of land-use and climate change on recharge to aquifers that provide public water supply and support fragile ecosystems, this study broadly supports three of the six science directions in the USGS Science Strategy, including (1) a water census of the United States, (2) understanding ecosystems and predicting ecosystem change, and (3) climate variability and change.

Approach

A GIS-based water-budget model will be developed for this study to estimate the spatial distribution of long-term recharge. Several scenarios will be examined, including possible future land use and drought. Results from this study will be published in the USGS Scientific Investigations Report series and made available on the internet.

Progress

Gathered information on precipitation, fog, irrigation, runoff, pan evaporation, soils, and historical land cover and prepared datasets that will be used as input to the water-budget model. Modified the water-budget model code used in Engott and Vana (2007) to determine the spatial distribution recharge. Completed report documenting the study approach and findings.

Publication

Johnson, A.G., Engott, J.A., and Bassiouni, Maoya, 2014, Spatially distributed groundwater recharge estimated using a water-budget model for the Island of Maui, Hawai‘i, 1978–2007: U.S. Geological Survey Scientific Investigations Report 2014–5168, 53 p.

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Page Last Modified: Tuesday, 07-Apr-2015 23:03:38 EDT