Climate Change and Water Resources Challenge in California

1. Climate Change and Water Resources Challenge in California Francis I Chung, Ph.D., P.E. Department of Water Resources

2. Outline • Challenges in Water Management • CALSIM, DSM2, and CVGSM • Interfacing CALSIM with DSM2 • Impacts of Climate Change on Water Resources • Inputs for CALSIM and DSM2

3. Water In California • Population • Agriculture • Projected Water Shortage

4. Two Possible Strategies to Cope with Climate Change • Prevent or Minimize • Define Cause and Effect • Implement Prescriptive Actions • Adapt • Define Possible Consequences with Probabilities • Devise Adaptive Actions to Minimize Negative Impact

6. Challenges in Water Resources • Water Supply • Floods and Droughts • Sea Level Rise • Crop ET • Groundwater • Ecosystem • Water Quality • Power Generation

7. Comparison of CALSIM and DSM2

8. California’s Major Water Projects State Water Project Central Valley Project (Federal) Local Figure from Bulletin 160-98

9. DSM2 CA • Output • Flow • Stage (water level) • Salinity • Other water quality • constituents Relationship between Model Outputs CALSIM Global Climate Models • Output • Reservoir operations • Project deliveries • Delta inflows and • exports • Output • Precipitation • Snowmelt • Soil Moisture • Evapotranspiration • Temperature Outputs shaded blue provide input to the next model.

10. CALSIM

11. State Water Project Central Valley Project (Federal) Local Statewide CVP & SWP Water Allocation ModelCALSIM

12. CALSIM • General-purpose water resource systems model • Developed by DWR’s Bay-Delta Office and the Bureau of Reclamation • Accounts for system operational objectives, physical constraints, legal and institutional agreements and/or statutes • It is a simulation model that uses a daily or monthly time step to look at reservoir release decisions and surface water allocations

13. Salinity Constraints • CALSIM uses an Artificial Neural Network (ANN) to compute Delta salinity • ANN relates flow (inflow and exports) to salinity • ANN was trained on historical data • ANN runs in a few minutes or less

14. Groundwater modeling • Groundwater elevations are simulated using multiple-cells • Multiple cell model emulates CVGSM, a quasi-3D non-steady finite element model of the Central Valley • Darcy’s law used for subsurface flow and stream-aquifer interaction • Unconfined (single) layer in Sacramento basin, and Confined/Unconfined (multiple) layers in San Joaquin basin • Multiple cell model calibrated against CVGSM • Continuity equations for multiple cell model imbedded directly as constraints in CALSIM

17. Calsim Hydrology • Hydrology is the time series estimate of Central Valley water supplies for areas tributary to the Delta at a future level of land use development • Historical 1922-1994 trace of precipitation (monthly) • Land use categories: Ag (crops), Urban, Native, and Riparian vegetation • Demands for water are land use based using consumptive use model • Local accretions calculated using a water budget for each area at a historical level and then modifying it for future land use level Depletion Study Areas

18. DSM2

19. Redding San Francisco LosAngeles San Diego Bay-Delta System Sacramento DSM2 Domain Sacramento River Stockton San Joaquin River San Francisco Bay-Delta detail image from CALFED

20. QUAL HYDRO Delta Geometry Initial Hydrodynamic Conditions Martinez Tide Delta Inflows and Exports Delta Island Consumptive Use Withdrawals and Return Flows Delta Structure Operations Delta Geometry Initial EC Conditions Delta Hydrodynamic Conditions Martinez EC EC in Delta Inflows EC in Agriculture Return Flows Delta EC Running DSM2 to Simulate Delta Conditions

21. DSM2 Grid Image from USBR GIS Group

22. Spring Spring Spring Neap Neap Moon Phases Design Repeating Tide vs. Realistic Tide

23. Interfacing CALSIM with DSM2

24. 72-year Hydrology CALSIM Project Island Operations 2020 Demands DSM2-HYDRO Delta Barriers Martinez Tide DSM2-QUAL DSM2-PTM EC DOC Particle Transport / Fate

25. Inputs for CALSIM and DSM2

26. Calsim Input: Time • Monthly or Daily Time-step • Level of development • Agricultural acreage, growing season, etc. • Urban population • 1922-98 hydrologic events (adjusted to level of development)

27. Calsim Input: Physical Constraints • System representation • Reservoir storage & outlet capacities • Export capacities • Canal, conveyance and river capacities

28. Calsim Input: Hydrologic Inflows • Reservoir inflows • Streams • Precipitation/evaporation • Local flows • Surface-groundwater interaction • Return flows • Forecasting

29. Calsim Input: Regulatory Constraints & Agreements • Minimum in-stream flows • Export reductions • Delta salinity standards • Temperature standards • Delta cross channel operation • COA: Coordinated operations agreement • CVPIA b(2) protections • EWA protections

30. Calsim Input: Operating Rules • Allocation priorities • Reservoir operations (flood control, rule-curve, carryover, balancing) • Project demands/allocation procedure • Non-project demands

31. Sacramento River Sacramento Tributaries Consumptive Use Redding Stockton Tidal Stage San Francisco Exports San Joaquin River San Francisco Los Angeles San Diego DSM2 Boundary Conditions HYDRO Flow Velocity Water Levels QUAL Constituent concentrations Bay-Delta detail image from CALFED

32. Sacramento River • Sacramento Yolo Bypass Eastside Streams MartinezTidal Stage Delta Island Consumptive Use • Martinez Exports San Joaquin River DSM2 HYDRO Boundary Conditions • Tidal flows from the ocean • Represented by stage (water level) at Martinez • Calculated from astronomical tide • Inflows from major tributaries • Precipitation and runoff are reflected in inflows, but are not directly input into DSM2 • Provided by CALSIM simulation results or historical data • Exports and diversions • Federal, state, and local diversions • Delta Cross Channel Operations • Provided by CALSIM simulation results or historical data • Delta Island Consumptive Use (DICU) • Agricultural diversions • Agricultural return flows • Computed from a DICU model Delta Cross Channel • Stockton

33. DSM2 QUAL Boundary Conditions Sacramento River • Boundary conditions are required for each constituent simulated • Conservative constituents (e.g. EC) • Non-conservative constituents (e.g. DO) • Concentration of each constituent at each inflow boundary • Ocean (represented at Martinez) Provided by historical data or estimates from an Artificial Neural Network (ANN) • Tributary rivers and streams Provided by historical data or other estimates • Agricultural return flows • Typically EC is simulated and then converted to other constituents due to lack of field data • Sacramento Yolo Bypass Eastside Streams Ocean sources Delta Island Return Flows • Martinez • Stockton San Joaquin River

34. Concluding Remarks • Key Models on Water Management are available in California • Inputs to Models are needed to account for climate change • Scientific Uncertainties on Inputs need to be identified • Operating rules need to be developed to account for adapted operations

35. Francis Chung, Ph.D., P.E. chung@water.ca.gov 916-653-5924 http://modeling.water.ca.gov Contact Information