1. Modeling the Snake River Basin Future 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 - 3 rd in US Hydropower, Fish

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

10. PNW Climate Change Scenarios ~ + 1.7 C~ + 2.5 C 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

16. Snake System Inflows – Milner

19. Snake System Inflows – Boise River

22. Snake System Inflows – Dworshak R.

25. Predicted Groundwater Impacts

26. 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

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