This data release contains the input files for the watershed and water-balance models that simulate historic (1990‒2009) and future (2080‒2099) climate conditions on Guam. These simulations are described in the associated Scientific Investigations Report, “Water Resources on Guam—Potential Impacts of and Adaptive Response to Climate Change" by Stephen B. Gingerich, Adam G. Johnson, Sarah N. Rosa, Mathieu D. Marineau, Scott A. Wright, Lauren E. Hay, Matthew J. Widlansky, John W. Jenson, Corinne I. Wong, Jay L. Banner, Victoria W. Keener, and Melissa L. Finucane (https://doi.org/10.3133/sir20195095). The watershed and water-balance models were previously published in “Supporting data for Fena Valley Reservoir watershed and water-balance model, southern Guam” (Rosa and Hay, 2017). Data are provided in two folders: 1) the PRMS_2016_historic_future folder contains the climate by hydrologic response unit (HRU) data files (CBH_files folder) needed to drive each of the modeled regions in southern Guam for the historic and future periods and a README_PRMS_2016_historic_future.txt document that describes the contents of this folder and how to update the previously published model files (Rosa and Hay, 2017) and run the watershed model with the historic and future datasets; and 2) the FVR_2016_historic_future folder contains the input files needed to run the Fena Valley Reservoir water-balance model for the historic and future periods and a README_FVR_2016_historic_future.txt document that describes the contents of this folder and how to execute the water-balance model (Rosa and Hay, 2017) with the historic and future input files.