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Reassessment of Groundwater Recharge for Central and West Maui
Project Chief: Adam G. Johnson
Since the last water-budget study of central and west Maui (Engott and Vana, 2007), more detailed rainfall datasets were made available and a refined water-budget model was introduced. These new developments could substantially improve the estimates of groundwater recharge for central and west Maui. The new rainfall datasets are more current and detailed, and the refined water-budget model uses improved methods of estimating fog interception, including forest canopy interception, and the differentiation of native and alien forests.
The objective of this study is to update estimates of the spatial distribution of groundwater recharge in central and west Maui. Daily recharge estimates for current average climatic conditions and land use will be aggregated to determine an average recharge rate for current conditions.
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.
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.
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. Ran model simulations for various scenarios. Completed the study.
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.