Scenarios are plausible and provocative stories about the future that help us think about long-term changes and consequences. Yahara 2070 is a set of scenarios about Wisconsin's Yahara Watershed, which are intended to help local decision makers and communities discuss how changes in land use, climate, and human demands could impact freshwater and the many natural benefits people need for their well-being. This presentation discusses the "why" and "how" of Yahara 2070 and long-term thinking in general. Yahara 2070 is a part of the Water Sustainability and Climate project at the University of Wisconsin-Madison, a multi-year research endeavor funded by the National Science Foundation.