Vishal K. Mehta

Simulating High-Elevation Hydropower with Regional Climate Warming in the West Slope, Sierra Nevada

Water systems in snowmelt-dominated hydroregions such as Californias Sierra Nevada mountains are sensitive to regional climate change, hydropower systems in particular. In this study, a water resources management model was developed for the upper west slope Sierra Nevada to understand the potential effects of regional climate warming on hydropower at the watershed scale, a scale that has been largely neglected but is important for hydroregional planning. The model is developed with the Water Evaluation and Planning system (WEAP) and includes most water management infrastructure in the study region. Hydropower is simulated assuming historical long-term electricity demand and a spill minimization rule. The method is suitable for simulating generation for most of the main watersheds in the region. To assess the potential effect of climate warming, uniform air temperature increases of 0°C, 2°C, 4°C, and 6°C were considered, with no change in precipitation, to approximate regional warming through 2100. The highly productive northern Sierra Nevada sees large re- ductions in hydropower generation with decreases in annual runoff. The central watersheds see less reduction in annual runoff and can adapt better to changes in runoff timing. Generation in southern watersheds, which are less productive, decreases. Results from this study can help identify which watersheds might easily adapt to climate change, where hydropower is likely to conflict with other uses, and where more detailed operational studies are needed. DOI: 10.1061/(ASCE)WR.1943-5452.0000373.

Exploring scientific information for policy making under deep uncertainty

Each actor evaluating potential management strategies brings her/his own distinct set of objectives to a complex decision space of system uncertainties. The diversity of these objectives and uncertainties requires detailed and rigorous analyses that respond to multifaceted challenges. The utility of this information depends on the accessibility of scientific information to decision makers. This paper demonstrates data visualization tools for presenting scientific results to decision makers in two case studies, La Paz/El Alto, Bolivia, and Yuba County, California. Visualization output from the case studies combines spatiotemporal, multivariate and multirun/multiscenario information to produce information corresponding to the objectives and uncertainties described by key actors. These tools can manage complex data and distill scientific information into accessible formats. Using the visualizations, scientists and decision makers can navigate the decision space and potential objective trade-offs to facilitate discussion and consensus building. These efforts can help identify stable negotiated agreements between different stakeholders. We present a Decision Space Visualization (DSV) that condenses model results to tackle complex water management challenges.DSV enables comparisons between potential management options against many uncertainties.It allows exploring results in meaningful formats for decision makers that answers their most pressing questions.The case studies presented suggests that DSV stimulates active engagement from stakeholders.

Integrating water supply constraints into irrigated agricultural simulations of California

Abstract Simulations of irrigated croplands generally lack key interactions between water demand from plants and water supply from irrigation systems. We coupled the Water Evaluation and Planning system (WEAP) and Decision Support System for Agrotechnology Transfer (DSSAT) to link regional water supplies and management with field-level water demand and crop growth. WEAP-DSSAT was deployed and evaluated over Yolo County in California for corn, rice, and wheat. WEAP-DSSAT is able to reproduce the results of DSSAT under well-watered conditions and reasonably simulate observed mean yields, but has difficulty capturing yield interannual variability. Constraining irrigation supply to surface water alone reduces yields for all three crops during the 1987–1992 drought. Corn yields are reduced proportionally with water allocation, rice yield reductions are more binary based on sufficient water for flooding, and wheat yields are least sensitive to irrigation constraints as winter wheat is grown during the wet season.