Nathan VanRheenen Richard N. Palmer Civil and Environmental Engineering University of Washington Recasting the Future Developing Adaptive Policies Using Optimization and Decision Analysis -A Case for the Snake River Basin-

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)

Political Landscape Many users Many opinions Scientific controversy Established positions Political activism

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

Snake River Models

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

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

Snake River Basin WR Network

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

SnakeOpt – Approach Run model from 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 2 nd 5-year window Redefine constraints with Step 1 end conditions Proceed with 2 nd window as per Step 1

Comparison to Historical Operation

Drafted for ROR Energy Elev Raised for Energy Lower SW Irrigation Increase GW pumping

Comparison to Historical Operation

Drafted for Fish

Optimized Storage Response Earlier runoff

Optimized Storage Response Earlier runoff Return to near historic sto

Optimized SW Diversion Response Seasonal water availability

Optimized GW Pumping Response Higher ET, Less recharge

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

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

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

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

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

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

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…

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?

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?