Nathan VanRheenen Richard N. Palmer Civil and Environmental Engineering University of Washington

1. Modeling the Snake River BasinFuture Streamflow Scenarios and System Response for the Snake River Basin-2004 Update- Nathan VanRheenen Richard N. Palmer Civil and Environmental Engineering University of Washington www.tag.washington.edu

2. Goals of the Investigation • What are the long-range impacts of climate change on the management of the Snake River system? • Goal 1: Predict 80+ years of streamflows using appropriate climate and hydrologic models • Goal 2: Model current and future operating rules and management strategies • Snake River Basin water resources system • Current management, Agriculture, Fish, Hydropower, Alternative management, Groundwater • Simulation Model of Snake River Basin (SnakeSim) • How can the potential impacts of climate change be mitigated? • Goal: Identify the “best” management strategy for SRB users • Optimization Model of SRB (SnakeOpt)

3. Summary • Climate change will shift flows dramatically • Current management strategies may need to be changed • Conflicts between environmental and agricultural uses will likely increase

4. Columbia River Basin

5. Snake River Basin • Basin in parts of 7 states • Largest tributary of Columbia River • 1000 miles long • 20 major reservoirs • 14 MAF surface storage • 250 MAF groundwater aquifer • 17 MAF allocated water rights • Agriculture Productivity - 3rd in US • Hydropower, Fish

6. Snake River Basin WR Network

7. Snake River Basin WR Network

8. SnakeSim Model • 23 inflow nodes • 22 reservoirs modeled • 15 MAF total storage (94% of total) • Eastern SRPA • Climate Scenarios Used: • Wet: Hadley 2 2020, 2040 • Dry: Max Plank 2020, 2040 • Mid: Composite 2020, 2040

9. Changes in Mean Temperature and Precipitation or Bias Corrected Output from GCMs SnakeSim Water Resources Model VIC Hydrology Model

10. ~ + 1.7 C ~ + 2.5 C PNW Climate Change Scenarios Trending toward wetter winters and slightly drier summers

11. Predicted Streamflow Impacts

12. Snake System - Inflows • Flows from 1915 – 1992 • weekly, monthly timestep

13. Snake System Inflows – Jackson Lk

14. Snake System Inflows – Jackson Lk

15. Snake System Inflows – Jackson Lk

16. Snake System Inflows – Milner

17. Snake System Inflows – Milner

18. Snake System Inflows – Milner

19. Snake System Inflows – Boise River

20. Snake System Inflows – Boise River

21. Snake System Inflows – Boise River

22. Snake System Inflows – Dworshak R.

23. Snake System Inflows – Dworshak R.

24. Snake System Inflows – Dworshak R.

25. Predicted Groundwater Impacts

26. Predicted Groundwater Impacts • Recharge and discharge change as irrigation patterns change • Decreases in irrigation result in decreases in recharge and discharge • BOR estimates SRPA elevation will decrease 40 feet in next 50 years due to irrigation restrictions • Decreases in precipitation and/or increasing ET decrease recharge and discharge • Impacts of management likely far greater than impacts of climate change on groundwater

27. Predicted Groundwater Impacts Mean Predicted Change in Discharge from the Base Case, Ashton to King Hill

28. SnakeSim Operations Model • Purpose: Measure the projected impacts of climate change on SRB water resources • Considers • Major surface water features • Accepted management practices/rules • System uses • e.g., flood control, irrigation, fish, hydropower • Groundwater/Surface water interactions

29. SnakeSim - Storage

30. SnakeSim - Storage

31. SnakeSim - Storage

32. SnakeSim - Storage

33. Snake System – Implications/Future • Nature of flow shifts due to climate change are significant… • Water quality and fish implications • System operations implications • Need to investigate impacts on water rights system and conjunctive uses (Slaughter and Reading) • ESRP has greater sensitivity to irrigation than to ET • But, “best” mitigation techniques aren’t known