This study addresses regional adjustments to possible reductions in water availability which may occur with a future climate change. The study assesses potential responses of urban water suppliers to reduced water availability by examining an analogous case of reduced supply in the Denver metropolitan region. In this case the U.S. Environmental Protection Agency's veto of a large surface storage project (the Two Forks dam) prompted water providers in metropolitan Denver to take other actions to ensure adequate future water supply. In some cases, actions taken since the veto process began represent a departure from previous water provider policies. It is argued that similar institutional adjustments may occur due to climate change‐induced reductions in regional water supplies and that useful lessons may be drawn from an analysis of institutional responses to the Two Forks veto. This paper introduces what is envisioned as a long‐term assessment of regional adjustments to reduced future water suppl