A Comparison of CalSimII and CalSim3: Parallel Application of Two Planning Models

1. A Comparison of CalSimII and CalSim3: Parallel Application of Two Planning Models James Gilbert, PhD (jmgilbert@usbr.gov) Nancy Parker US Bureau of Reclamation, Technical Service Center

2. Outline • Motivation • Model setup and assumptions • CSII and CS3 differencese • What’s in COS? What’s in PA? • Comparing CSII and CS3 • Comparing scenario effects (PA-COS for each CSII and CS3) • What does CS3 tell us that CSII can’t?

3. Motivation: • Transition toward CalSim3 as primary planning tool for CVP and SWP • Identify issues or refinements through comparisons • In other words – start using CalSim3 • What does a recent CalSimII analysis look like in CalSim3? • Test case: implement RoC on LTO scenarios

4. CalSim Background • Long-term water resources planning models for CVP-SWP systems • Assume a constant ‘level of development’ combined with historic hydrology pattern • Monthly time step with layered (‘cycles’) rules within time steps • System represented via LP formulation (constraints, weights, etc) • CalSim3 (CS3) refines spatial resolution and hydrologic representation

5. Water Budget Areas and Demand Units C2VSim Groundwater model Channel and conveyance network CalSim3 network & domain

6. RoC on LTO Scenarios“Reinitiation of Consultation on Long-Term Operations” • Current Operations Study (COS) • Demonstrates applicable criteria for CVP/SWP operations today • Includes D1641 and 2008 USFWS and 2009 NMFS Biological Opinion RPA’s • December 12, 2018 COA decision • Updates to CVP allocation and San Luis operation logic • Proposed Action Study (PA) • Increase operational flexibility through non-operational measures where possible to avoid adverse effects

7. Major Model Assumption Differences

8. Implementation • CalSimII studies were prepared as part of Reclamation’s consultation with Federal fisheries agencies (January 2019) • CalSim3 updated based on review and revisions from DWR, Stantec • Code for COS and PA studies mapped to CalSim3 • Variable names changed where necessary • CalSimII studies set up with historical hydrology (Q0) for consistency with CalSim3

9. Two ways of comparing: • Direct comparisons – do CalSimII and CalSim3 represent each study consistently? • Compare COS to COS, PA to PA • Effects comparisons – do CalSimII and CalSim3 represent the effects of the actions the same way? • Tabulate the difference between PA and COS for each CalSimII and CalSim3 – how do these differences compare?

10. CalSimII – CalSim3 Comparisons • Operations logic mapped between CSII and CS3 • Additional upstream operations in CS3 • Hydrology is different • Spatial refinement • Land-use based demands • Valley floor water budgets more complex • Delta demands and salinity ANN • Closure terms • Expect direct mapping of CalSimII logic to CalSim3 to give the same results?

11. Flow Comparisons

12. Sacramento River at Hood – version comparison: Differences difficult to discern at monthly scale

13. Sacramento R at Hood – version comparison: Annual comparison shows ~330 TAF more flow in CS3 compared to CSII

14. Sacramento R at Hood – version comparison:CS3 monthly average flows higher in Oct, March, May, Aug

15. San Joaquin R at Vernalis – version comparison: High flows are lower in CS3

16. San Joaquin R at Vernalis – version comparison: Monthly average pattern:CS3 most different in October - April

17. Delta Outflow – version comparison:Differences dominated by Sacramento and Eastside inflows

18. Delta Outflow:CSII – CS3 differences are dominated by increased Sacramento and Eastside inflows in CS3

19. Delta Outflow – version comparison:Differences dominated by Sacramento and Eastside inflows

20. Delivery Comparisons

21. CVP SOD Ag Delivery – version comparison:Different demands -> different deliveries

22. CVP SOD Ag Delivery – version comparison:Demand pattern differences throughout year

23. CVP SOD Ag Delivery – scenario comparison:Benefits to delivery in both CSII and CS3

24. CVP SOD Ag Delivery – scenario comparison:Timing of increased PA delivery not the same in CS3

25. Storage Comparisons

26. Folsom – version comparison:Greater dry year drawdowns in CalSim3; Higher storage in average years

27. Folsom – version comparison: CalSim3 storage higher in summer and fall

28. Folsom – scenario comparison: CSII PA has greater storage increase compared to CS3

29. Groundwater Comparisons

30. Groundwater representation is simplified (or absent) in CalSimII • CalSim3 coupled with C2VSim finite element mesh, stream reaches, and pumping/recharge • Groundwater pumping in CS3 has consequences • Explicit spatial representation of drawdown • Stream-groundwater interactions along main waterways

31. SOD Groundwater Pumping – scenario comparisonDelivery increases reduce pumping

32. SOD Stream-Groundwater– scenario comparisonCombination of reduced pumping and different channel flows yields mix of groundwater exchange effects

33. Stream-Groundwater Interactions:Modified Stanislaus flows affect groundwater exchange

34. Summary • Scenario analysis is feasibly implemented in CalSim3 • Differences in CalSim3 analysis result from increased resolution, refined hydrology • Simple mapping of CalSimII code to CalSim3 not sufficient – will need scenario-specific adaptation • The way to make CalSim3 a comparable tool – start using and testing it!

35. Looking ahead… • CalSim3 expands scope of what can be included in scenario analysis • For example: land fallowing impacts to consumptive use and delivery; groundwater as an additional ‘reservoir’ • Ongoing refinements: • Water quality (salinity) in San Joaquin • Allocation and other system logic testing • Tulare expansion (Lauren Thatch’s presentation – next) • The way to make CalSim3 a comparable tool – start using and testing it!

36. James Gilbert USBR – Technical Service Center jmgilbert@usbr.gov Thanks!