Plausible 21st century water management through stakeholder-driven modeling of a water-stressed, agricultural socio-economic system in the American West

In our research on the nexus of food, energy, and water in Idaho's Upper Snake River Basin, we assumed that knowledgeable, engaged leaders in each of these sectors provided the best possible resource for identifying key uncertainties, anticipated societal responses, and appropriate solutions. Through an iterative stakeholder-driven geodesign framework, we identified key actors that control water and nutrient resources, specified climate concerns, cataloged key future uncertainties in the social and natural system, and simulated a suite of alternative futures. Large uncertainties in potential climate regime and resultant availability of irrigation water dramatically change projected cropping and will require a range of stakeholder refereed solutions. Climate scenarios selected ranged from slight increases in water availability to a millennial-scale drought equivalent to the driest 17-year period in the last 1200 years superimposed on anticipated mid-century climatic warming. We simulated water availability for each scenario using a macro-scale hydrologic model implementing several interpretations of prior appropriation water law as enacted through a complex network of regulators. Our scenarios project a range of -3% decrease to +160% increase in unmet demand from irrigated crops relative to the contemporary period when considering climate effects alone. From unmet demand, we used multiple suitability criteria co-created with stakeholders to refine irrigated areas and crop types to match present-day unmet demand, leading to a 17% reduction in irrigated crop lands and significant shifts in crops planted under the millennial scale drought, and up to a 7% increase in irrigated cropland under a scenario with greater water availability and moderately regulated growth of the dairy-based economy. Collaborative stakeholder meetings scheduled for late summer and fall 2019 will identify a suite of impact indicators and scenario specific solutions to meet potential challenges with respect to water and nutrient management.