As the questions of climate change has moved from “if” it is happening to “how” it is changing our environment, it has become important to have regional assessment designs to allow us to better understand how changes are occurring now and in the future. The authors are using the Precipitatation Runoff Modeling System (PRMS) to assess the potential effects of long-term climate change on 15 basins representing different hydroclimatic regions in the United States.