Nathan VanRheenen Rick Palmer Civil and Environmental Engineering University of Washington Attention Snake River Water Users: You Really Can Have It All! ( or Maybe You Can’t) -Optimization as a means to better long-term water policies in the Snake River Basin- CIG Weekly Seminar Series – Nov 16, 2004

Overview Research Goals Setting Model intro Model inputs Model approach and processes Model output On deck

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 (SIRAS)

Setting - 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

Snake River Basin WR Network

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 SIRAS Optimization Model

SIRAS Snake River Basin Integrated Water Resources Allocation System Purpose: Identify the “best” management strategy for SRB users Considers Major surface water features (94% of system storage) System uses e.g., flood control, irrigation, fish, hydropower Groundwater impacts 8 major irrigation districts Economic Objective Function

SIRAS Inputs Streamflow PET Precipitation Crop coefficient Groundwater response

SIRAS Inputs - Streamflows

SIRAS Inputs – GW Discharge Change

SIRAS Inputs - PET

SIRAS Inputs – Precip

SIRAS Inputs - Crops Available Crops: AlfalfaMean, BarleyFeed, BarleyMalt, Beans, CornField1, CornField2, CornSweet1, CornSweet2, Onions, Pasture, Potatoes, Sugarbeets, WheatSpringHard, WheatSpringSoft Crop Coefficient (K) dictates water needs through growing cycle (K is nonlinear) Crop Water Use (PET crop )= K crop * PET ref(alfalfa) Irrig Need = Acres * (PET crop – Precip)

SIRAS Approach and Processes

SIRAS Approach – Obj Function 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

SIRAS Approach – 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

SIRAS Approach – LP/SLP Decomp 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

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

SIRAS Output

SIRAS Output – Storage Upper Snake, Base Case, Traces

SIRAS Output – Storage Elev Raised for Energy

SIRAS Output – Storage Dworshak, Base Case, Traces

SIRAS Output – Storage Max Hydro Eff Drafted for Fish

SIRAS Output – Releases for Fish Supplemental releases to meet Lower Granite targets 427 TAF rule is met every year

SIRAS Output – Releases for Fish Bulk of fish releases are from Jackson-Palisades complex So, why is that?

SIRAS Output – Hydropower Jackson capacity is very low (9.8 MW), so better off drafting for other uses (fish, ROR hydropower, ag)

SIRAS Output – Hydropower

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

SIRAS Output – Irrigation Total Diversions in largest district GW pumping in largest district

SIRAS Output – Irrigation Total Diversions in second largest district GW pumping in second largest district

SIRAS –Management Options Unconstrained system (capacities only) Flood space preserved 427 rule (or others) met every year All reservoirs operated conjunctively BOR, IP, COE hydropower not conjunctive Groundwater not used or used selectively

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…

Feasibility testing of optimal rules in SnakeSim Annual planning 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 – Future Work

SIRAS – 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?

Optimizing Sleeping, Eating, Diaper changing, Marriage, and (oh, yeah) a Dissertation, with Triplets and a Two-Year Old Subtitle: I Sleep at Red Lights