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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
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Hydrologic Characteristics of the Columbia Basin
Elevation (m)
Avg Naturalized Flow
The Dalles
Flows Originating in Canada
0
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nFeb M
ar AprM
ay Jun Ju
lAug Sep
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Winter Summer
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Ap
r-S
ept F
low
(cfs
)
Effects of the PDO and ENSO on Columbia River Summer Streamflows
Cool CoolWarm Warm
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v
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c
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b
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r
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Jul
Aug
Se
p
Ave
rag
e F
low
(cm
s)
PDO Cold
PDO Warm
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No
v
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c
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Fe
b
Mar
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r
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p
Ave
rag
e F
low
(cm
s)
La Nina
El Nino
0
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10000
15000
20000
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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
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150000
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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
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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
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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
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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
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Overview of Long-Range Forecasting Methodsand Long-Range Forecasts for Water Year 2002
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Global Climate Models
Regional Climate Models
Hydrology Models
WaterResources
Models
Overview of Modeling Linkages
water demand
streamflowtemp precip wind
downscaling
Observed Meteor.Data
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Time Line for 12-month Lead Time Retrospective Forecasts
Climate Forecast
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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
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0
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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
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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
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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
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0
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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
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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
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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
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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
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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
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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
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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
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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)
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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}
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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.
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Effects to System Storage Retrospective Forecast Method
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Trends in Regulated Peak Flow at The Dalles
Completion of Major Dams
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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
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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
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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)
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Effects to System Storage Climate Model Based Forecast Method
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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)
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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
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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.