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

1. Recasting the FutureDeveloping Adaptive Policies Using Optimization and Decision Analysis -A Case for the Snake River Basin- Nathan VanRheenen Richard N. Palmer Civil and Environmental Engineering University of Washington www.tag.washington.edu

2. Goals of Research • What are the long-range impacts of climate change on the managed Snake River system? • Goal: Develop a model that incorporates current and future operating rules and management strategies • Simulation Model of Snake River Basin (SnakeSim) • How can the potential impacts of climate change be mitigated? • Goal: Develop a model that provides the “best” management strategy for SRB users New starting point for policy-makers • Optimization Model of SRB (SnakeOpt)

3. Political Landscape • Many users • Many opinions • Scientific controversy • Established positions • Political activism

4. Political Landscape • No More Ignoring the Obvious – Idaho Sucks Itself Dry – High Country News, 2/95 • “The department has handed out water rights and groundwater permits as if there’s no tomorrow." • "The fish were there first, but they didn’t fill out the (water rights) forms." • Ongoing Issues • Basin Adjudication • Biological Opinions • Groundwater supply uncertainty • Changing water supply needs • Relationship to the Columbia River and the PNW • Uncertainty of future climate and impacts on water resources

5. Snake River Models

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

7. SnakeOpt • Purpose: Develop a model that provides the “best” management strategy for SRB users • Considers • Major surface water features • System uses • e.g., flood control, irrigation, fish, hydropower • Groundwater impacts • 8 major irrigation districts • Economic Objective Function

8. Snake River Basin WR Network

10. SnakeOpt - Approach • Objective Function • Weekly timestep • Maximize Z = Agriculture Revenue ($) + Hydropower Revenue ($) - Flood damages ($) - Environmental Target Penalties • Subject to • Inflows, PET • Water rights • Groundwater availability • Farmland availability, crop values and costs, irrigation efficiency • Energy demand and rates • Infrastructure limitations (reservoir and powerplant capacity, etc.) • Network flow constraints

11. SnakeOpt – Approach • Run model from 1950-1992 • LP/SLP Decomposition • Rolling 5-year window • Step 1 • Maximize over 5 years (260 mo.) • Extract conditions at week 52 • Redefine constraints • Rerun first 52 weeks to determine first year model optimum • Step 2 • Move to 2nd 5-year window • Redefine constraints with Step 1 end conditions • Proceed with 2nd window as per Step 1

12. Comparison to Historical Operation

13. Elev Raised for Energy Lower SW Irrigation Increase GW pumping Drafted for ROR Energy Comparison to Historical Operation

14. Comparison to Historical Operation

15. Drafted for Fish Drafted for Fish Comparison to Historical Operation

16. Earlier runoff Optimized Storage Response

17. Earlier runoff Return to near historic sto Optimized Storage Response

18. Seasonal water availability Optimized SW Diversion Response

19. Higher ET, Less recharge Optimized GW Pumping Response

20. 10% Overall Decrease, Loss of $10 M/yr Optimized Hydropower Response

21. 10% Overall Decrease, Loss of $82 M/yr Optimized Hydropower Response

22. 10% Overall Decrease, Loss of $82 M/yr Optimized Hydropower Response

23. Also Optimized • Surface vs. groundwater use • Cropping area • Crops planted • Environmental flow targets, as desired • 427 rule • Flows at Milner, etc. • Real value is in generating tradeoff curves for testing in simulation tools

24. Example Management Options • Unconstrained system (capacities only) • Flood space preserved • 427 rule (or others) met every year • All reservoirs operated conjunctively • BOR, IP, COE operate own reservoirs optimally • Groundwater not used or used selectively • What areas are you interested in? • Identify locations to optimize sustainable managed recharge

25. Implications • Climate change will negatively impact agriculture productivity, fish flow satisfaction, and energy production But… • If the system is operated in a “more optimal” way, the improvement over historical management far outpaces predicted climate change impacts

26. Implications • Why isn’t the system operated like this now? • Historical precedent • Snake River managed as 2 distinct rivers • Irrigators get the “first fruits” • Belief that extensive groundwater pumping in the upper river is necessary to ensure high flows (vis-à-vis gw discharge) in the lower river • However, users in the Basin may now be receptive to new ideas…

27. SnakeOpt – Potential Future Work Annual Planning Approach • 52-week forecast and 4 years climate change prediction • How much water can irrigators, utilities, and fish get in the next year to ensure a sustainable future? • Where are the tradeoffs?

29. SnakeOpt – The Value of Optimization • What can be learned from an optimization? • Can management alternatives be tested in an optimization? • Why must it be in economic terms? What about “values”? • Can an optimization model “stand alone” or must it be used with a simulation model?