Alan F. HamletAndy Wood

Dennis P. Lettenmaier

JISAO Climate Impacts Group and the Department of Civil Engineering

University of WashingtonSeptember, 2001

Hydroclimatology of the Pacific Northwestand Long-Lead Streamflow Forecasts for

the Columbia River Basin for 2002

Hydrologic Characteristics of the Columbia Basin

Elevation (m)

Avg Naturalized Flow

The Dalles

Flows Originating in Canada

0

100000

200000

300000

400000

500000

600000

Oct NovDec Ja

nFeb M

ar AprM

ay Jun Ju

lAug Sep

Milner

Winter Summer

150000

200000

250000

300000

350000

400000

450000

190

0

191

0

192

0

193

0

194

0

195

0

196

0

197

0

198

0

199

0

200

0

Ap

r-S

ept F

low

(cfs

)

Effects of the PDO and ENSO on Columbia River Summer Streamflows

Cool CoolWarm Warm

0

5000

10000

15000

20000

Oct

No

v

De

c

Jan

Fe

b

Mar

Ap

r

May

Jun

Jul

Aug

Se

p

Ave

rag

e F

low

(cm

s)

PDO Cold

PDO Warm

0

5000

10000

15000

20000

Oct

No

v

De

c

Jan

Fe

b

Mar

Ap

r

May

Jun

Jul

Aug

Se

p

Ave

rag

e F

low

(cm

s)

La Nina

El Nino

0

5000

10000

15000

20000

Oct

Nov

Dec Jan

Feb

Mar

Apr

May Jun

Jul

Aug

Sep

Ave

rag

e F

low

(cm

s)

Cool PDO/La Nina

Warm PDO/El Nino

PDO/ENSO Effects

PDO Effects ENSO Effects

Naturalized Flow at The Dalles, OR

150000

200000

250000

300000

350000

400000

450000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Probability of Exceedence

Flo

w (

cfs)

WarmPDO/WarmENSO

WarmPDO/ENSONeut

WarmPDO/CoolENSO

CoolPDO/WarmENSO

CoolPDO/ENSONeut

CoolPDO/CoolENSO

Naturalized Summer Streamflow at The Dalles

0

5

10

15

20

25

30

35O

ct

No

v

De

c

Jan

Fe

b

Mar

Ap

r

May

Jun

Jul

Aug

Se

p

Av

erag

e F

low

(cm

s) Cool PDO

Warm PDO

Cedar at Chester Morse Lake--PDO Effects

0

5

10

15

20

25

30

35O

ct

No

v

De

c

Jan

Fe

b

Mar

Ap

r

May

Jun

Jul

Aug

Se

p

Av

erag

e F

low

(cm

s) La Nina

El Nino

Cedar at Chester Morse Lake--ENSO Effects

Cedar at Chester Morse Lake--PDO/ENSO Effects

0

5

10

15

20

25

30

35O

ct

No

v

De

c

Jan

Fe

b

Mar

Ap

r

May

Jun

Jul

Aug

Se

p

Av

erag

e F

low

(cm

s)

Cool PDO/La Nina

Warm PDO/El Nino

Overview of Long-Range Forecasting Methodsand Long-Range Forecasts for Water Year 2002

Global Climate Models

Regional Climate Models

Hydrology Models

WaterResources

Models

Overview of Modeling Linkages

water demand

streamflowtemp precip wind

downscaling

Observed Meteor.Data

Time Line for 12-month Lead Time Retrospective Forecasts

Climate Forecast

0

100000

200000

300000

400000

500000

600000

700000

J J A S O N D J F M A M J J A S

Estimated Initial Conditions

ForecastEnsemble

Lead time = 12 months

0

100000

200000

300000

400000

500000

600000

700000

800000o

ct

nov

de

c

jan

feb

mar

apr

may jun jul

aug

sep

Month

Str

eam

flo

w (

cfs)

Forecast1

Forecast2

Forecast3

Forecast4

Forecast5

Forecast6

Forecast7

Forecast8

High Climatology

Low Climatology

Observed VirginFlow

1998 cool PDO/warm ENSO

0

100000

200000

300000

400000

500000

600000

700000

800000

oct

nov

dec jan

feb

mar

apr

may jun jul

aug

sep

Month

Str

eam

flo

w (

cfs)

Forecast1

Forecast2

Forecast3

Forecast4

Forecast5

Forecast6

Forecast7

Forecast8

Forecast9

Forecast10

Forecast11

Forecast12

High Climatology

Low Climatology

Observed Virgin Flow

1999 cool PDO/cool ENSO

0

100000

200000

300000

400000

500000

600000

700000

800000o

ct

nov

de

c

jan

feb

mar

apr

may jun jul

aug

sep

Month

Str

eam

flo

w (

cfs)

Forecast1

Forecast2

Forecast3

Forecast4

Forecast5

Forecast6

Forecast7

Forecast8

Forecast9

Forecast10

Forecast11

Forecast12

High Climatology

Low Climatology

Observed Virgin Flow

2000 cool PDO/cool ENSO

0

100000

200000

300000

400000

500000

600000

700000

800000o

ct

nov

de

c

jan

feb

mar

apr

may jun jul

aug

sep

Str

eam

flo

w (

cfs)

Forecast1

Forecast2

Forecast3

Forecast4

Forecast5

Forecast6

Forecast7

Forecast8

Sim Min

Sim Max

Observed Virgin Flow

2001 cool PDO/ENSO neutral

2002 Forecast Construction Details:

•Hindcast hydrologic state for August 1, 2001 based on observed weather data•VIC driving data from August 1- Sept 30 is taken from 15 observed water years from 1949-2000 associated with winter ENSO neutral conditions in the tropics.•This produces 15 forecast ensembles from Oct, 2001 to September, 2002

Experimental Forecasts for 2002 Based on Resampled Observed Driving Data

Raw streamflow forecast ensemble at The Dalles compared to 50-year “observed” min, max and mean monthly simulated

streamflow. All ENSO neutral.

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

mar apr

may jun jul

aug

sep

Flo

w (

cfs) Observed Long Term Mean

Highest Observed

Lowest Observed

Summary of raw streamflow forecast ensemble compared to 50-year “observed” min, max and mean monthly simulated

streamflow {whiskers show 90th and 10th percentiles of forecast}

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

ma

r

apr

ma

y

jun jul

aug

sep

Str

ea

mfl

ow

(c

fs)

Simulated MinSimulated MaxForecast MeanSim Hist Avg

Natural Flow at The Dalles

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

mar apr

may jun jul

aug

sep

Flo

w (

cfs)

Cool PDO/ENSO Neutral Raw Forecast

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

ma

r

apr

ma

y

jun jul

aug

sep

Str

ea

mfl

ow

(c

fs)

Simulated MinSimulated MaxForecast MeanSim Hist Avg

Summary of Cool PDO/ENSO Neutral Raw Forecast

2002 Forecast Construction Details:

•Hindcast hydrologic state for August 1, 2001 based on observed weather data•VIC driving data from August 1, 2001- February 28, 2002 are taken from 20 climate global climate model ensembles.•VIC driving data from March 1- September 30, 2002 are based on median 1953 meteorological data•This produces 20 forecast ensembles from Oct, 2001 to September, 2002

Experimental Climate Model Driven Forecasts for 2002

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

mar apr

may jun jul

aug

sep

Flo

w (

cfs)

Climate Model-Based 20-member streamflow forecast at The Dalles

1953 driving data for March-Sept

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

mar apr

may jun jul

aug

sep

Flo

w (

cfs)

0

200000

400000

600000

800000

1000000

1200000

oct

nov

dec

jan

feb

ma

r

apr

ma

y

jun jul

aug

sep

Str

ea

mfl

ow

(c

fs)

Simulated MinSimulated MaxForecast MeanSim Hist Avg

Summary of raw streamflow forecast ensemble compared to 50-year “observed” min, max and mean monthly simulated

streamflow {whiskers show 90th and 10th percentiles of forecast}

Conclusions:

Typical relationships between categorical PDO/ENSO state and PNW winter climate can be exploited to produce useful long lead time streamflow forecasts for PNW rivers using several methods.

The 2001 drought has produced unusually dry late summer soil conditions in the Columbia River basin, and winter flows in 2002 are expected to be somewhat below average. ENSO neutral conditions for winter 2002 are most likely to produce near normal summer streamflows at The Dalles. Assumption of cool PDO conditions for winter 2002 increases the likelihood of above average flows and decreases the likelihood of below average flows.

Effects to System Storage Retrospective Forecast Method

Trends in Regulated Peak Flow at The Dalles

Completion of Major Dams

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

Ap

r-0

1

Ma

y-0

1

Jun

-01

Jul-

01

Au

g-0

1

Se

p-0

1

Oct

-01

No

v-0

1

De

c-0

1

Jan

-02

Fe

b-0

2

Ma

r-0

2

Ap

r-0

2

Ma

y-0

2

Jun

-02

Jul-

02

Au

g-0

2

Se

p-0

2

Sys

tem

Sto

rag

e (

MA

F)

Observed System Storage Sept 1, 2001

Observed System Storage April 1, 2001

Obs. 1977-1978refill sequence

full

Forecast System Storage: Oct, 2001- Sept, 2002Firm Energy is met in 3 out of 15 simulations (20% reliability)

empty

Summary of System Storage Simulation{whiskers are 10th and 90th percentiles}

15

20

25

30

35

40

45

50

55

Apr

-01

May

-01

Jun-

01

Jul-0

1

Aug

-01

Sep

-01

Oct

-01

No

v-01

Dec

-01

Jan-

02

Feb

-02

Mar

-02

Apr

-02

May

-02

Jun-

02

Jul-0

2

Aug

-02

Sep

-02

Sys

tem

Sto

rag

e (

MA

F) 1977-1978 reference refill

Ensemble Average Energy Shortfalls from ColSimAssociated with Streamflow Forecast

0

100000200000

300000400000

500000600000

700000

Oct

-01

No

v-0

1

De

c-0

1

Jan

-02

Fe

b-0

2

Ma

r-0

2

Av

g E

ne

rgy

Sh

ort

fall

s (

MW

-hr)

Effects to System Storage Climate Model Based Forecast Method

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

Ap

r-0

1

Ma

y-0

1

Jun

-01

Jul-

01

Au

g-0

1

Se

p-0

1

Oct

-01

No

v-0

1

De

c-0

1

Jan

-02

Fe

b-0

2

Ma

r-0

2

Ap

r-0

2

Ma

y-0

2

Jun

-02

Jul-

02

Au

g-0

2

Se

p-0

2

Sys

tem

Sto

rag

e (

MA

F)

Observed System Storage Sept 1

Forecast System Storage: Oct, 2001- Sept, 2002Firm Energy is met in 8 out of 20 simulations (40% reliability)

0100000200000300000400000500000600000700000

Oct

-01

No

v-0

1

De

c-0

1

Jan

-02

Fe

b-0

2

Ma

r-0

2

Av

g E

ne

rgy

Sh

ort

fall

s (

MW

-hr)

Ensemble Average Energy Shortfalls from ColSimAssociated with Streamflow Forecast

Conclusions

Drought conditions in 2001 will increase the likelihood of below average winter flows in 2002 due to reduced soil moistures.

Current reservoir contents and limited summer refill in 2001 will produce high vulnerability to capacity-related hydro system shortfalls in winter 2002, and will likely also prevent complete reservoir refill in summer 2002. Normal “firm” energy production from the hydro system is shown to be about 20-40% reliable in the simulations, with most shortfalls occurring in Jan and Feb.

Reservoir storage in spring 2002 will be comparable to spring 2001.

Expected energy shortfalls (as compared to normal conditions) for winter 2002 are on the order of 850,000 MW-hrs.