Sensitivity analysis of California water supply: Assessment of vulnerabilities and adaptations By Max Fefer B.S. (University of California, Berkeley) 2016 THESIS Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Civil and Environmental Engineering in the OFFICE OF GRADUATE STUDIES of the UNIVERSITY OF CALIFORNIA DAVIS Approved: Jonathan Herman, Chair Jay Lund Samuel Sandoval-Solis Committee in Charge 2017 i Abstract Long-term changes in climate and population will have significant impacts on California’s freshwater management. Hydro-economic models can address climate change concerns by identifying system vulnerabilities and exploring adaptation strategies for statewide water operations. This thesis combines the new Python implementation of the CALVIN model, a hydro-economic model describing California water resources, with an ensemble of climate scenarios to identify adaptation strategies for managing water in a range of possible climates. A sensitivity analysis is performed by altering the magnitude and the timing of statewide inflows, defined as water availability and winter index respectively, to emulate changes in precipitation and temperature predicted by climate models. Model results show quadratic increases in shortage cost and marginal value of environmental flows, conveyance expansion, and reservoir expansion as water availability decreases. Reservoirs adapt to warmer climates by increasing average storage levels in winter and routing excess runoff to reservoirs downstream with available capacity. Both small and large changes to reservoir operations were observed compared to historical hydrology, showing that no single operating strategy achieves optimality for all reservoirs. Increasing the fraction of winter flow incurs small increases in total shortage cost, showing the state’s ability to manage a changing hydrologic regime with adaptive reservoir operations. ii Table of Contents Abstract ....................................................................................................................... ii Table of Contents ...................................................................................................... iii List of Figures ............................................................................................................. iv List of Tables ............................................................................................................... vi Section 1 – Introduction .............................................................................................. 1 Section 2 – California Background .............................................................................. 5 2.1 California’s water network ............................................................................................................. 5 2.2 CALVIN Model Introduction ....................................................................................................... 6 Section 3 – Methods ..................................................................................................... 9 3.1 Climate Change Modeling in CALVIN ......................................................................................... 9 3.2 Climate Sensitivity Analysis ......................................................................................................... 11 3.3 Removing Infeasibilities ............................................................................................................... 15 3.4 Computational Capacity of Python CALVIN ............................................................................. 16 3.5 Analysis of model outputs ........................................................................................................... 17 Section 4 – CEC GCM Analysis .................................................................................... 18 Section 5 – Sensitivity Analysis Results .................................................................... 22 5.1 – Shortage Cost ............................................................................................................................. 22 5.2 – Water Supply Portfolio ............................................................................................................. 27 5.3 – Reservoir Operations ................................................................................................................ 29 5.3.1 – Reservoirs with major operations shift at -30% WA ............................................................ 30 5.3.2 Gradual Decrease in Storage with decreasing WA .............................................................. 31 5.3.3 Moderate Decrease in Storage with decreasing WA ........................................................... 33 5.4 – Buffering Capacity of San Luis Reservoir ................................................................................ 35 5.5 – Environmental Flows ................................................................................................................ 36 5.6 – Infrastructure Expansion ......................................................................................................... 41 5.6.1 – Reservoir Expansion ........................................................................................................... 41 5.6.2 – Conveyance Expansion ...................................................................................................... 42 5.7 - Mitigation of Delivery Disruption ............................................................................................ 43 Section 6 – Discussion ............................................................................................... 45 6.1 Optimal Reservoir Operations .................................................................................................... 45 6.2 Collaboration for Adaptive Operations .................................................................................... 46 6.3 Modeling Limitations .................................................................................................................. 47 Section 7 – Conclusion ............................................................................................... 49 References ................................................................................................................. 50 iii List of Figures Figure 1. Orders of climate change effects. Adapted from Chalecki and Gleick (1999) and Gain et al. (2012). ................................................................................................................. 2 Figure 2. California regions represented in CALVIN. From Dogan (2015). ............................ 7 Figure 3. Runoff multipliers for CEC scenarios at Shasta Lake inflow .................................. 10 Figure 4. Scenarios varying water availability and winter index developed for sensitivity analysis ..................................................................................... 12 Figure 5. Modified Inflows for Shasta Lake, Lake Oroville, Millerton Lake, and Pine Flat Lake .................................................................................................................................... 14 Figure 6. Modified Inflows for North & South Fork of the American River, Folsom Lake, Trinity Lake, and New Bullards Bar Reservoir ................................................................ 14 Figure 7. Automatic Debug Algorithm for CALVIN ............................................................... 16 Figure 8. Comparing CEC scenarios on WI and WA ............................................................. 20 Figure 9. Total shortage costs across all scenarios ................................................................ 23 Figure 10. Shortage costs by region ......................................................................................... 24 Figure 11. Agricultural/Urban shortage costs by region at -30% WA ................................... 25 Figure 12. Contour plots of Statewide and Upper Sacramento Valley .................................. 26 Figure 13. Contour plots of Lower Sacramento Valley and Delta and San Joaquin South Bay ...................................................................................................................................... 26 Figure 14. Contour plots of Tulare Basin and Southern California ....................................... 27 Figure 15. Statewide monthly average surface reservoir storage ........................................... 29 Figure 16. Lake Shasta average monthly storage .................................................................... 30 Figure 17. Lake McClure and New Don Pedro Reservoir average monthly storage ............. 31 Figure 18. Lake Oroville average monthly storage ................................................................. 32 Figure 19. Folsom Lake and New Bullards Bar Reservoir average monthly storage ............ 33 Figure 20. Trinity Lake average monthly storage ................................................................... 34 iv Figure 21. New Melones Reservoir and Millerton Lake average monthly storage ............... 34 Figure 22. San Luis Reservoir average monthly storage ........................................................ 35 Figure 23. Average monthly dual values for Clear Creek minimum environmental flow requirement at Whiskeytown Reservoir ......................................................................... 36 Figure 24. Quadratic