AbstractThis article discusses the design and implementation of the Hawai'i Groundwater Recharge Tool, an application for providing data and analyses of the impacts of land‐cover modifications and changes in precipitation on groundwater‐recharge rates for the island of O'ahu. This application uses simulation data based on a set of 29 land‐cover types and 2 precipitation conditions to provide users with real‐time recharge calculations for interactively defined land‐cover modifications. The tool provides two visualizations, representing the land cover for the island and the resultant groundwater‐recharge rates, and a set of metrics indicating the changes to groundwater recharge for relevant areas to present a set of easily interpretable outcomes based on user‐defined scenarios. Users have varying degrees of control over the granularity of data input and output, allowing for the quick production of a roughly defined scenario, or more precise land‐cover definitions. These modifications can be exported for further analysis. Heuristics are used to provide a responsive user interface and performant integration with the database containing the full set of simulation data. This tool is designed to provide user‐friendly access to the information on the impacts of land‐cover and precipitation changes on groundwater‐recharge rates needed to assist in making data‐driven decisions.