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Hydrologic Outlook for the Pacific Northwest Andy Wood and Dennis P. Lettenmaier Department of Civil and Environmental Engineering for Washington Water.

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Presentation on theme: "Hydrologic Outlook for the Pacific Northwest Andy Wood and Dennis P. Lettenmaier Department of Civil and Environmental Engineering for Washington Water."— Presentation transcript:

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 Snow water content on April 1 April to August runoff McLean, D.A., 1948 Western Snow Conf. SNOTEL Network Introduction: Hydrologic prediction PNW

4 Technical Advances related to Hydrologic Forecasting 1920s1930s1940s1950s1960s1970s1980s1990s2000s snow survey / graphical forecasts / index methods / i.e., regression computing in water resources aerial snow surveys SNOTEL network ESP method snow cats conceptual hydrologic models

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. ICs Spin-upForecast obs recently observed meteorological data ensemble of met. data to generate forecast ESP forecast hydrologic state

6 Technical Advances related to Hydrologic Forecasting 1920s1930s1940s1950s1960s1970s1980s1990s2000s snow survey / graphical forecasts / index methods / i.e., regression computing in water resources satellite imagery aerial snow surveys desktop computing SNOTEL network ESP method ENSO / seasonal climate forecasts snow cats Internet / real-time data conceptual hydrologic models physical hydrologic models

7 Introduction: Experimental Hydrologic Forecasting

8 Soil Moisture Initial Condition Snowpack 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 targeted statisticse.g., runoff volumes monthly hydrographs streamflow forecast locations

11 Introduction: UW Experimental Hydrologic Forecasting SWESoil MoistureRunoffPrecipTemp 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

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 Puget Sound Drainage Basin How does the WY2005 current year compare to WY1977? WY2005 WY1977

20 3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE WY2005 WY1977

21 3/15 ESP fcst: WY2005 vs. WY1977 Runoff WY2005 WY1977 Puget Sound Drainage Basin Apr-Sep % of avg max80 0.7560 0.5054 0.2549 min45

22 3/15 ESP fcst: WY2005 vs. WY1977 Precip, Temp BC portion of Columbia R. Basin How does the WY2005 current year compare to WY1977? WY2005 WY1977

23 3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE WY2005 WY1977

24 3/15 ESP fcst: WY2005 vs. WY1977 Runoff WY2005 WY1977 BC portion of Columbia R. Basin Apr-Sep % of avg max95 0.7583 0.5078 0.2574 min64

25 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? WY2005 WY1977

26 3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE WY2005 WY1977

27 3/15 ESP fcst: WY2005 vs. WY1977 Runoff Columbia R. basin upstream of The Dalles, OR WY2005 WY1977 Apr-Sep % of avg max88 0.7573 0.5069 0.2565 min55

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 BC portion of Columbia R. Basin How does the WY2005 current year compare to WY1977? WY2005 WY1977

33 3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE WY2005 WY1977

34 3/15 ESP fcst: WY2005 vs. WY1977 Runoff WY2005 WY1977 Snake R. Basin Apr-Sep % of avg max90 0.7571 0.5062 0.2557 min49

35 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

36 3/15 ESP fcst: WY2005 vs. WY1977 SM, SWE WY2005 WY1977

37 3/15 ESP fcst: WY2005 vs. WY1977 Runoff WY2005 WY1977 Yakima R. Basin near Parker, WA Apr-Sep % of avg max61 0.7546 0.5041 0.2539 min31


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