Planning for Idaho’s waterscapes: A review of historical drivers and outlook for the next 50 years

•Southern Idaho exhibits water deficits in summer, northern Idaho maintains water surpluses, these patterns persist under future projections.•Timing of surface runoff in the future is projected to change, despite relatively small overall changes in annual runoff.•Prior appropriation water law can be adaptive if water institutions continue to evolve and adapt to changing circumstances.•Water banking could be expanded to enhance the use of water for its highest beneficial uses for both economic and environmental purposes.•Scenario analysis provides a tool for assessing planning choices for Idaho’s waterscapes.