Hydrologic Outlook for the Pacific Northwest

1
Hydrologic Outlook for the Pacific Northwest

• Andy Wood
• and
• Dennis P. Lettenmaier
• Department of Civil and Environmental Engineering
  
• for
• Washington Water Outlook Workshop
• UW Climate Impacts Group
• March 21, 2005

2
Presentation Outline
1. Introduction UW Experimental Hydrologic
Forecasting System 2. Water Year 2005 Assessment
3
Introduction Hydrologic prediction
PNW
Snow water content on April 1
SNOTEL Network
McLean, D.A., 1948 Western Snow Conf.
April to August runoff
4
Technical Advances related to Hydrologic
Forecasting
snow cats
snow survey / graphical forecasts / index methods
/ i.e., regression
computing in water resources
SNOTEL network
ESP method
conceptual hydrologic models
aerial snow surveys
1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 20
00s
5
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.

6
Technical Advances related to Hydrologic
Forecasting
physical hydrologic models
Internet / real-time data
snow cats
snow survey / graphical forecasts / index methods
/ i.e., regression
satellite imagery
computing in water resources
SNOTEL network
ENSO / seasonal climate forecasts
ESP method
conceptual hydrologic models
aerial snow surveys
desktop computing
1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 20
00s
7
Introduction Experimental Hydrologic Forecasting
8
Introduction Experimental Hydrologic Forecasting
Snowpack Initial Condition
Soil Moisture Initial Condition
9
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.
10
Introduction Experimental Hydrologic Forecasting
streamflow forecast locations
monthly hydrographs
targeted statistics
e.g., runoff volumes
11
Introduction UW Experimental Hydrologic
Forecasting
SWE
Soil Moisture
Runoff
Precip
Temp
Mar-05 Apr-05 May-05
12
Presentation Outline
1. Introduction UW Experimental Hydrologic
Forecasting System 2. Water Year 2005 Assessment
13
WY2005, Dec. 1 hydrologic conditions
14
WY2005, Dec. 1 hydrologic conditions
15
WY2005, Jan. 1 hydrologic conditions
16
WY2005, Feb. 1 hydrologic conditions
17
WY2005, Mar. 1 hydrologic conditions
18
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 0.75 median 0.25 min
spinup
19
3/15 ESP fcst WY2005 vs. WY1977 Precip, Temp
WY1977
WY2005
How does the WY2005 current year compare to
WY1977?
Puget Sound Drainage Basin
20
3/15 ESP fcst WY2005 vs. WY1977 SM, SWE
WY1977
WY2005
21
3/15 ESP fcst WY2005 vs. WY1977 Runoff
Apr-Sep of avg max 80 0.75 60 0.50 54 0.25 49 mi
n 45
WY2005
Puget Sound Drainage Basin
WY1977
22
3/15 ESP fcst WY2005 vs. WY1977 Precip, Temp
WY1977
WY2005
How does the WY2005 current year compare to
WY1977?
BC portion of Columbia R. Basin
23
3/15 ESP fcst WY2005 vs. WY1977 SM, SWE
WY1977
WY2005
24
3/15 ESP fcst WY2005 vs. WY1977 Runoff
Apr-Sep of avg max 95 0.75 83 0.50 78 0.25 74 mi
n 64
BC portion of Columbia R. Basin
WY2005
WY1977
25
3/15 ESP fcst WY2005 vs. WY1977 Precip, Temp
WY1977
WY2005
How does the WY2005 current year compare to
WY1977?
Columbia R. basin upstream of The Dalles, OR
26
3/15 ESP fcst WY2005 vs. WY1977 SM, SWE
WY2005
WY1977
27
3/15 ESP fcst WY2005 vs. WY1977 Runoff
Apr-Sep of avg max 88 0.75 73 0.50 69 0.25 65 mi
n 55
Columbia R. basin upstream of The Dalles, OR
WY2005
WY1977
28
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!

29
Questions?
website www.hydro.washington.edu /
Lettenmaier / Projects / fcst /
30
Introduction Experimental Hydrologic Forecasting
VIC model runoff is routed to streamflow gages,
and verified against observations
31
Introduction Seasonal Climate Prediction
e.g., precipitation
32
3/15 ESP fcst WY2005 vs. WY1977 Precip, Temp
WY1977
WY2005
How does the WY2005 current year compare to
WY1977?
BC portion of Columbia R. Basin
33
3/15 ESP fcst WY2005 vs. WY1977 SM, SWE
WY1977
WY2005
34
3/15 ESP fcst WY2005 vs. WY1977 Runoff
Apr-Sep of avg max 90 0.75 71 0.50 62 0.25 57 mi
n 49
WY2005
Snake R. Basin
WY1977
35
3/15 ESP fcst WY2005 vs. WY1977 Precip, Temp
WY2005
WY1977
How does the WY2005 current year compare to
WY1977?
Yakima R. Basin near Parker, WA
36
3/15 ESP fcst WY2005 vs. WY1977 SM, SWE
WY1977
WY2005
37
3/15 ESP fcst WY2005 vs. WY1977 Runoff
Apr-Sep of avg max 61 0.75 46 0.50 41 0.25 39 mi
n 31
WY2005
Yakima R. Basin near Parker, WA
WY1977