Climate and Management Alternatives in Snake River

Basin

Nathan VanRheenen and Richard N. Palmer

Dept. of Civil and Environmental EngineeringUniversity of Washington

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

SIRAS

Considers Major surface water features System uses

e.g., flood control, irrigation, fish, hydropower Groundwater impacts 8 major irrigation districts

Economic Objective Function

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

SnakeSimOperations Model

VICHydrology Model

Changes in Mean Temperature and

Precipitation or Bias Corrected Output

from GCMs

SIRASOptimization Model

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

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 StorageTotal Power

Irrig AreaGW Response

End Storage

GW Response

SIRAS Approach – LP/SLP Decomp

SIRAS Approach – LP/SLP Decomp

1971-1975

1972-1976

1973-1977

1974-1978

1975-1979

1976-1980

1977-1981

71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

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

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