Decision Scaling Evaluation of Climate Change Driven Hydrologic Risk to the State Water Project Final Report A Collaborative Study of the Hydrosystems Research Group, University of Massachusetts, Amherst and the California Department of Water Resources “Snow White Mountains and Blue Watershed,” Dr. Qinqin Liu, DWR Climate Change Program, 2017 May 2019 Acknowledgments Lead authors Andrew Schwarz1 Patrick Ray2 Wyatt Arnold Contributors Casey Brown3 Sungwook Wi4 Jordi Vasquez Editors Frank Keeley William O’Daly Climate Change Program Management Elissa Lynn John Andrew 1 Delta Stewardship Council (formerly at California Department of Water Resources) 2 University of Cincinnati (formerly at University of Massachusetts, Amherst) 3 University of Massachusetts, Amherst 4 University of Massachusetts, Amherst 2 Contents Acknowledgements .......................................................................................................................................... 2 Contents ............................................................................................................................................................ 3 Figures ............................................................................................................................................................... 4 Tables ................................................................................................................................................................ 6 Abbreviations and Acronyms ............................................................................................................................ 7 Executive Summary ........................................................................................................................................... 8 Recommendations for Future Applications of Decision Scaling ................................................................. 11 Introduction .................................................................................................................................................... 12 Climate Change in California ........................................................................................................................... 13 Observed Trends ........................................................................................................................................ 13 Projections .................................................................................................................................................. 13 Atmospheric Rivers ..................................................................................................................................... 15 Drought ....................................................................................................................................................... 15 Relevant Studies ............................................................................................................................................. 16 Academic Studies of Climate Change Impact on California Water Resources ........................................... 18 Methodology .................................................................................................................................................. 21 Description of Study Area ........................................................................................................................... 23 Generation of Climate Traces ..................................................................................................................... 26 Water Resources System Model ................................................................................................................ 33 Model Verification ...................................................................................................................................... 48 Risk Assessment Results ................................................................................................................................. 51 Exposure ..................................................................................................................................................... 51 Sensitivity ................................................................................................................................................... 51 Risk ............................................................................................................................................................. 60 Vulnerability ............................................................................................................................................... 72 Adaptive Capacity ....................................................................................................................................... 73 Other Considerations and Next Steps ............................................................................................................. 73 References ...................................................................................................................................................... 75 Annex A: GCM Likelihood Function ................................................................................................................ 82 Annex B: Spatial and Temporal Climate Trends .............................................................................................. 83 Annex C: Resource Management Strategies Screening .................................................................................. 91 Annex D: Adaptation Strategies – Seasonal Forecasting Skill ......................................................................... 92 Annex E: Adaptation Strategies – Enhanced Precipitation ............................................................................. 94 Annex F: Adaptation Strategies – Upper Watershed Management ............................................................... 96 Annex G: Adaptive Water Year Typing .......................................................................................................... 102 Annex H: Groundwater Storage and Recovery ............................................................................................. 103 Annex I: Move From CalLite 3.0 to CalSim-III Operations Modeling ............................................................ 106 Figures Figure ES1 Modeling Workflow for Climate Change Vulnerability Assessment ................................................... 9 Figure 1 Mid-Century Conditional Climate Probability Density .......................................................................... 14 Figure 2 Modeling Workflow for Climate Change Vulnerability Assessment ..................................................... 22 Figure 3 California Central Valley System (CVS) and Rim Subbasins .................................................................. 24 Figure 4 State, Federal, and Local Water Infrastructure .................................................................................... 25 Figure 5 Sacramento 4-River Paleo Reconstructed Annual Streamflow ............................................................. 28 Figure 6 CMIP5 Ensemble of GCM Output Projecting Climate Changes by 2050 for the CVS ............................ 29 Figure 7 Trend Slope of Temperature With Less Than 10 Percent Missing Data in 94 Stations ......................... 31 Figure 8 Trend Slope of Temperature With Less Than 20 Percent Missing Data in 145 Stations ....................... 31 Figure 9 Seasonal Warming Patterns for Climate Projections ............................................................................ 32 Figure 10 CalLite 3.0 Schematic .......................................................................................................................... 35 Figure 11 Maps of Three Calibration Sets For the Application of SAC-SMA-DS to the CVS ................................ 39 Figure 12 Input Variables With Strong Correlation to San Joaquin Water Year Type Classification — Historical Observed Data Shown ....................................................................................................................... 42 Figure 13 Pearson Correlation Coefficients of Two Historical Local Inflows (I_BRANANIS and I_MDOTA) With 12 Historical Rim Inflows. .................................................................................................................. 43 Figure 14 Quantile Mapping Procedure Applied to Example California Sub-Basin ............................................ 45 Figure 15 AD_Wilkins: Correlation With Shasta Flow ......................................................................................... 46 Figure 16 AD_SACAME Historical Behavior ........................................................................................................ 46 Figure 17 Estimates of Sea-Level Rise by Degree C ............................................................................................ 47 Figure 18 Validation of CalLite 3.0 Stress Test Modeling Workflow for Total North of Delta Storage ............... 49 Figure 19 Validation of CalLite 3.0 Stress Test Modeling Workflow for Delta Outflow ...................................... 50 Figure 20 Validation of CalLite 3.0 Stress Test Modeling Workflow for SWP Annual Deliveries ........................ 50 Figure 21 Oroville End-of-April Storage System Response Surface ...................................................................