To help natural resource planners and managers evaluate the balances and tradeoffs between these ecosystem services and make informed decisions in light of changing environmental conditions, Eastern Threat Center scientists have developed a web-based assessment tool known as the Water Supply Stress Index (WaSSI) model. WaSSI can predict how climate, land cover, and human population change may impact water availability and carbon sequestration at the watershed level and across the lower 48 United States, Mexico, Rwanda, and Burundi. WaSSI users can select and adjust temperature, precipitation, land cover, and water use factors to simulate an unlimited number of global change scenarios for user-determined timeframes through 2100. Simulation results are available as downloadable maps, graphs, and data files that users can apply to their unique information and project needs.