Climate and Management Alternatives in Snake River Basin

1. Climate and Management Alternatives in Snake River Basin Nathan VanRheenen and Richard N. Palmer Dept. of Civil and Environmental Engineering University of Washington

2. Goals of Research • How can the potential impacts of climate change be best mitigated? • Goal 1: Develop a model that provides a “constrained optimal” management strategy for Snake River Basin users • Goal 2: Incorporate Mid-range forecasts into optimization to guide operations New starting point for policy-makers • Optimization Model of SRB (SIRAS) can serve to illustrate upper bound of benefits associated with management

3. SIRAS • Considers • Major surface water features • System uses • e.g., flood control, irrigation, fish, hydropower • Groundwater impacts • 8 major irrigation districts • Economic Objective Function

4. SIRAS - Approach • LP/SLP Decomposition • Objective Function • Weekly timestep • Maximize Z = Agriculture profit ($) + Hydropower profit ($) - 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

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

7. SnakeOpt – Decomposition Approach • Run model from 1950-1992 • 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

8. SIRAS Approach – LP/SLP Decomp Year 1 Year 2 Year 3 Year 4 Year 5 End Storage Total Power Irrig Area GW Response GW Response Step 1: Optimize over 5 years Step 2: Extract year 1 ending conditions Step 3: Redefine conditions as constraints End Storage Step 4: Optimize year 1 only with new constraints Step 5: Initialize year 2 starting storage and gw responses Step 6: Move to next rolling 5-year block and repeat Steps 1-5 Year 2 Year 3 Year 4 Year 5 Year 6

9. 81 87 89 95 79 83 82 84 86 90 94 78 91 93 96 80 88 85 92 SIRAS Approach – LP/SLP Decomp 1971-1975 1972-1976 1973-1977 1974-1978 1975-1979 1976-1980 1977-1981 72 73 71 74 75 76 77

10. Mid-term Optimization • Forecasting system offers opportunities for informed and science based decision making • Mid-range forecasts provide improved river forecasts • Operating suggestions can be updated as conditions change over the season • Economic objective functions can be modified • Operation relationships of Snake relative to Columbia River can be evaluated

11. Integration • Integration will occur at several levels • Output of optimization model will be more fully tested in SnakeSim to test robustness • Water Markets research effort will provide realistic constraints on transfers • Long-term forecasts will be incorporated into optimization model