Understanding Freshwater Availability on Maui Under Projected Future Climate Conditions

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Demand for freshwater on the island of Maui is expected to increase by 45 percent between 2015 and 2035. Wetter and drier climate scenarios impact the availability of groundwater to meet this demand. 

To help evaluate the availability of fresh groundwater under projected future climate conditions and changing agricultural irrigation practices, estimates of groundwater recharge are needed. Scientists used a water-budget model with a daily computation interval to estimate groundwater recharge for three different scenarios: (1) present day; (2) wetter than present day; and (3) drier than present day. End-of-century climate projections were selected to capture the full range of projected rainfall conditions in the peer-reviewed literature.

Results indicate that projected changes in rainfall account for most of the projected changes in recharge. Also, projected changes in reference evapotranspiration and forest-canopy evaporation can account for a substantial part of the projected changes in recharge for certain land covers.

Mair, Alan, Johnson A.G., Rotzoll, Kolja, and Oki, D.S., 2019, Estimated groundwater recharge from a water-budget model incorporating selected climate projections, Island of Maui, Hawai‘i: U.S. Geological Survey Scientific Investigations Report 2019–5064, 46 p., https://doi.org/10.3133/sir20195064.