Priority watershed management areas for groundwater recharge and drinking water protection: a case study from Hawai‘i Island

Worldwide, water utilities and other water users increasingly seek to finance watershed protection and restoration in order to maintain or enhance water quality and quantity important for drinking water supply and other human use. Hydrologic studies which characterize the relative effectiveness of watershed management activities in terms of metrics important to water users are greatly needed to guide prioritization. To address this need, we worked with a local water utility in Hawaiʻi to develop a novel framework for prioritizing investments in native forest protection and restoration for groundwater recharge and applied it in the utility’s priority aquifers and recharge areas. Specifically, we combined land cover and water balance modeling to quantify the 50-year cumulative recharge benefits of: 1) protection of native forest from conversion to non-native forest, and 2) restoration of native forest in non-native grasslands.