Background and Motivation

ENSO (El Niño Southern Oscillation)ENSO (El Niño Southern Oscillation)

the water year for which the December to February Sea Surface Temperature in the NINO 3.4 region exceeds 0.5 standard deviations above its long-term (1900-1996) mean value.

ENSO is classified in

three states:

Warm (El Niño)

Neutral

Cool (La Niña)

A Warm ENSO year:

The effects of ENSO on PNW winter climate

Warm ENSO (El Niño) : winters tend to be warmer and drier than average. Cool ENSO (La Niña) : winters tend to be cooler and wetter than average.

Source: Climate Impacts Group website

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The Dalles

The effects of ENSO on flood risk for Columbia River Basin

- Warm ENSO

- Neutral ENSO

X - Cool ENSO

The effects of ENSO on storage deficits

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Warm ENSONeutral ENSOCool ENSO

Objective:

Develop ENSO conditioned Flood

Control Curves by Rebalancing Flood

Control and Reservoir Refill

Flood Control Refill

Test Case: The Columbia River Basin

Multi-objective

Reservoir System

Flood Control Hydropower Instream Flow Water Supply Recreation Navigation

The Dalles

Columbia Falls

Bonners Ferry

Method : Optimization – Simulation Method

Optimization Model Develop Optimized Flood

Control Curves

Simulation Model Test and Refine

Proposed Rule Curves

Hydrologic Model Generate Streamflow

for 20th Century

VIC Hydrologic Model

Macroscale Hydrologic Model developed by University of Washington which simulates energy and water balance at large scale at 1/8 degree (Approximately 50 mi2/ Cell)

(Variable Infiltration Capacity Hydrologic Model)

Optimization model developed by the US Army Corps of Engineers

Penalty functions are used to constrain the Columbia River basin system operation

Flood control penalties Flood control penalties Storage penaltiesStorage penalties

HEC-PRM(Hydrologic Engineering Center’s Prescriptive Model)

ColSim

Flood control Hydropower Irrigation Instream flow Navigation Recreation

(Columbia Simulation Model)

Optimization Strategy

Adjust Penalty functions

Classify

Water Years

into Each ENSO

State

Select

Penalty Functions

for Each ENSO State

Generate

Optimized

Flood Rule Curves

for Each ENSO State

Evaluate Flood and

Refill Statistics using

Simulation for Each

ENSO state

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Warm ENSONeutral ENSOCool ENSO

- Warm ENSO

- Neutral ENSO

X - Cool ENSO

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The Dalles

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- Warm ENSO

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Results

Flood Frequency Analysis at Bonners Ferry

- Current Flood Control Curves

- HEC Flood Control Curves

X - ENSO Flood Control Curves

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CurFC HECFC ENSOFC

Warm ENSO

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CurFC HECFC ENSOFC

Neutral ENSO

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CurFC HECFC ENSOFC

Cool ENSO

Flood Frequency Analysis at Columbia Falls

- Current Flood Control Curves

- HEC Flood Control Curves

X - ENSO Flood Control Curves

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CurFC HECFC ENSOFC

Warm ENSO

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CurFC HECFC ENSOFC

Neutral ENSO

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CurFC HECFC ENSOFC

Cool ENSO

Flood Frequency Analysis at The Dalles

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CurFC HECFC ENSOFC

Warm ENSO

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CurFC HECFC ENSOFC

Neutral ENSO

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CurFC HECFC ENSOFC

Cool ENSO

- Current Flood Control Curves

- HEC Flood Control Curves

X - ENSO Flood Control Curves

Storage Deficits

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Hec FC

ENSO FC

Warm ENSO

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Hec FC

ENSO FC

Neutral ENSO

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Hec FC

ENSO FC

Cool ENSO

Flood Control Curves vs. Simulated Storage (a low flow year)

Flood Control Curves vs. Simulated Storage (a high flow year)

Conclusions ENSO conditioned FC rule curves yield lower storage

deficits than Current FC without significantly increasing flood risks

ENSO FC is successfully calibrated using ENSO conditioned flood frequency curves and storage deficit statistics even though each ENSO category has relatively small sample size.

Conclusions ENSO conditioned FC rule curves yield reduced

storage deficits relative to HEC FC

There is no effect of reduced flood space on storage deficits for low flow years because flood control is not the main driver in low flow years.

Conclusions ENSO conditioned FC rule curves yield reduced

storage deficits relative to HEC FC

There is no effect of reduced flood space on storage deficits for low flow years because flood control is not the main driver in low flow years.