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Hydrologic Outlook for the Pacific Northwest
Andy Wood
andDennis P. Lettenmaier
Department of Civil and Environmental Engineering
for Washington Water Outlook Workshop
UW Climate Impacts Group
March 21, 2005
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Presentation Outline
1. Introduction: UW Experimental Hydrologic
Forecasting System
2. Water Year 2005 Assessment
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Sn
ow w
ater
con
ten
t on
Ap
ril
1
April to August runoff
McLean, D.A., 1948 Western Snow Conf.
SNOTEL Network
Introduction: Hydrologic prediction
PNW
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Technical Advances related to Hydrologic Forecasting
1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s
snow survey / graphical forecasts /
index methods / i.e., regression
computing in water
resources
aerial snow
surveys
SNOTEL network
ESP method
snow cats
conceptualhydrologic
models
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Introduction: Hydrologic prediction and ESP
NWS River Forecast Center (RFC) approach:
rainfall-runoff modeling(i.e., NWS River Forecast System,
Anderson, 1973 offspring of Stanford Watershed Model, Crawford & Linsley, 1966)
Ensemble Streamflow Prediction (ESP)
• used for shorter lead predictions;• ~ used for longer lead predictions
Currently, some western RFCs and NRCS coordinate their seasonal forecasts, using mostly statistical methods.
ICsSpin-up Forecast
obs
recently observedmeteorological data
ensemble of met. datato generate forecast
ESP forecast
hydrologicstate
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Technical Advances related to Hydrologic Forecasting
1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s
snow survey / graphical forecasts /
index methods / i.e., regression
computing in water
resources
satelliteimagery
aerial snow
surveys desktopcomputing
SNOTEL network
ESP method
ENSO / seasonal climate
forecasts
snow catsInternet / real-time
data
conceptualhydrologic
models
physicalhydrologic
models
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Introduction: Experimental Hydrologic Forecasting
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Introduction: Experimental Hydrologic Forecasting
Soil MoistureInitial
Condition
SnowpackInitial Condition
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Introduction: Merging of SNOTEL obs with model SWE
The pattern of observed SWE values, which are merged with the forecast initial conditions, was in good agreement with the VIC simulated snow state.
The PNW currently has very low snowpack, while the Southwest and California have record high snowpacks.
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Introduction: Experimental Hydrologic Forecasting
targeted statistics e.g., runoff volumes
monthly hydrographs
streamflowforecastlocations
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Introduction: UW Experimental Hydrologic Forecasting
SWE Soil MoistureRunoffPrecip Temp
Mar-05
Apr-05
May-05
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Presentation Outline
1. Introduction: UW Experimental Hydrologic Forecasting
System
2. Water Year 2005 Assessment
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WY2005, Dec. 1 hydrologic conditions
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WY2005, Dec. 1 hydrologic conditions
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WY2005, Jan. 1 hydrologic conditions
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WY2005, Feb. 1 hydrologic conditions
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WY2005, Mar. 1 hydrologic conditions
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3/15 ESP fcst: Basin Average Water Balance
The following series of results are for a March 15 ESP forecast, based on 1960-99 climate traces, compared with climatology
forecast distribution
max
0.75median0.25
min
spinup
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3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp
Puget Sound Drainage Basin
How does the WY2005 current year compare to WY1977?
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 Runoff
WY2005
WY1977
Puget Sound Drainage Basin
Apr-Sep% of avgmax 800.75 600.50 540.25 49min 45
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3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp
BC portion of Columbia R. Basin
How does the WY2005 current year compare to WY1977?
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 Runoff
WY2005
WY1977
BC portion of Columbia R. Basin
Apr-Sep% of avgmax 950.75 830.50 780.25 74min 64
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3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp
Columbia R. basin upstream of The
Dalles, OR
How does the WY2005 current year compare to WY1977?
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 Runoff
Columbia R. basin upstream of The
Dalles, OR WY2005
WY1977
Apr-Sep% of avgmax 880.75 730.50 690.25 65min 55
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Conclusions
Puget Sound regional runoff will be in the lowest quartile: 50% chance of between 49 - 60 % of normal
Columbia R. basin in slightly better shape, but still in lowest quartile: median runoff forecast is 69% of normal
Some other areas, such as the Yakima Basin, are drier than Puget Sound (39-46% of normal runoff)
This has been a rough year for forecasters!
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Questions?
website:
www.hydro.washington.edu / Lettenmaier / Projects / fcst /
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Introduction: Experimental Hydrologic Forecasting
VIC model runoff is routed to streamflow gages, and verified against observations
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Introduction: Seasonal Climate Prediction
e.g., precipitation
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3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp
BC portion of Columbia R. Basin
How does the WY2005 current year compare to WY1977?
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 Runoff
WY2005
WY1977
Snake R. Basin
Apr-Sep% of avgmax 900.75 710.50 620.25 57min 49
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3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp
Yakima R. Basin near
Parker, WA
How does the WY2005 current year compare to WY1977?
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE
WY2005WY1977
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3/15 ESP fcst: WY2005 vs. WY1977 Runoff
WY2005
WY1977
Yakima R. Basin near Parker, WA
Apr-Sep% of avgmax 610.75 460.50 410.25 39min 31