1. 2006 Water Resources Outlook for Idaho and the Western U.S.
JISAO Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
October, 2006
Alan F. Hamlet
Andy Wood
Dennis P. Lettenmaier

2. Background

3. Background: Forecast System Schematic
NCDC met. station obs. up to 2-4 months from current
local scale (1/8 degree) weather inputs
soil moisture
snowpack
Hydrologic model spin up
SNOTEL Update
streamflow, soil moisture,
snow water equivalent, runoff
25th Day, Month 0
1-2 years back
LDAS/other real-time met. forcings for spin-up gap
Hydrologic forecast simulation
Month
INITIAL STATE
SNOTEL
/ MODIS*
Update
ensemble forecasts
ESP traces (40)
CPC-based outlook (13)
NCEP GSM ensemble (20)
NSIPP-1 ensemble (9)
* experimental, not yet in real-time product

4. Background: Hydrology Model

5. Background: Estimating Initial Conditions SNOTEL assimilation
Assimilation Method
weight station OBS’ influence over VIC cell based on distance and elevation difference
number of stations influencing a given cell depends on specified influence distances
spatial weighting function
elevation
weighting
function
SNOTEL/ASP
VIC cell
distances “fit”: OBS weighting increased throughout season
OBS anomalies applied to VIC long term means, combined with VIC-simulated SWE
adjustment specific to each VIC snow band
important point(s):
the approach attempts to make use of forecast skill from 2 sources:
better understanding of synoptic scale teleconnections and the effects of persistence in SSTs on regional climate, as reproduced in coupled ocean-atmosphere models;
the macroscale hydrologic model yields an improved ability to model the persistence in hydrologic states at the regional scale (more compatible with climate model scales than prior hydrologic modeling).
Climate forecasts with monthly and seasonal horizons are now operationally available, and if they can be translated to streamflow, then they may be useful for water management.

6. Background: Streamflow Forecast Locations
California
Columbia R. basin
in development:
Colorado R.,
Upper Rio Grande
Snake R. basin

7. Linkage to Reservoir Models
Streamflow
Forecast
Bias Correction
Storage
Ensemble
Reservoir Model
Observed Reservoir
Contents
Demand Scenarios

8. Recap of Water Year 2005

9. Observed Nino3.4 anomally

10. Natural Flows at Milner 1928-1989

11. Simulated Natural Flow at Milner (Oct ESP Nino3.4 between +0.2 and +1.2) (data from period)
Natural Streamflow (KAF)
WY 2005

12. http://www. hydro. washington

13. http://www. hydro. washington

15. Probability of Exceedence Plot for Natural Flow at Milner from WY 2005 Forecast

16. System Storage Forecast from SnakeSim:
Jackson Lake
Palisades
Island Park
Ririe
American Falls
Lake Walcott
Nino3.4 anomaly between 0.2 and 1.2 C
Demand aligned with water cond.
October 1 Spin Up
Active Reservoir Storage (kaf)
Obs. System
Storage Oct 1, 2005

17. Outlook for Water Year 2006

18. Winter Climate Forecasts Dominate Hydrologic State Variables Dominate
April 1 SWE (mm)
Winter Climate
Forecasts Dominate
Hydrologic State
Variables Dominate
June
December
March
Range =16.7%
of ensemble
summer mean

20. Initial Soil Moisture Conditions
Oct 1, 2004

21. UW West Wide Seasonal Hydrologic Forecast System

22. UW West Wide Seasonal Hydrologic Forecast System

23. Used range:
Jan3.4 >= -0.4
Jan3.4 <= 0.6

24. Used range:
Jan3.4 >= 0.0
Jan3.4 <= 0.6

25. Natural Flows at Milner 1928-1989

26. Natural Streamflow (KAF)
Climatology of Naturalized Streamflow in the Snake River at Milner
Milner
Climatology
Natural Streamflow (KAF)

27. Natural Streamflow (KAF)
Red = long term mean
Blue = ensemble mean
Gray = ensemble members
Black = range of observations
WY 2006

28. Natural Streamflow (KAF)
Red = long term mean
Blue = ensemble mean
Gray = ensemble members
Black = range of observations

29. PDO ENSO Forecast for Milner Assuming “Neutral PDO Years”
And Nino3.4 between -0.4 and 0.6
Natural Streamflow (KAF)

30. System Storage Forecast from SnakeSim:
Jackson Lake
Palisades
Island Park
Ririe
American Falls
Lake Walcott
Nino3.4 anomaly between -0.4 and 0.6 C
Demand aligned with water cond.
October 1 Spin Up
Active Reservoir Storage (kaf)

31. Summary of 2006 Forecast
Current soil moisture on Oct, 2005 is relatively wet in southern Idaho, and relatively dry in northern Idaho.
ENSO neutral conditions are likely in WY 2006, with forecast Nino3.4 anomalies ranging from about 0.0 to 0.6 in mid winter.
Probability distributions for streamflow in ENSO neutral years are similar in character to the climatology overall. The central tendency of the WY 2006 streamflow forecast at Milner is near the long term mean for both ENSO and PDO/ENSO composites. Risks of very high or very low flows are somewhat reduced, but very high and low flow events have occurred for similar ENSO/PDO conditions in the past.
Carryover storage in the upper Snake reservoirs is improved from last year, and the reservoir system forecast suggests peak reservoir storage levels of about 3000 KAF in April or May, 2006, and carryover storage in Sept, 2006 of about 1000 KAF.

32. Climate Change Planning Activities
Snake River Planning Data Resources
Weekly time step surrogate observations and climate change streamflow scenarios for the Snake basin are currently available:
ftp://ftp.hydro.washington.edu/pub/hamleaf/snakesim/
USBR planning study for the Flathead
Draft daily flow scenarios are completed
Preliminary reservoir model analysis in progress
New GCM Scenarios from the IPCC 4th Assessment
CIG Climate Change Reports and White Papers for King Co. Planning Meeting and Puget Sound Action Team

33. Overview of Experimental Energy-Related Forecasting Products

34. Covariation of Normalized PNW and CA Hydropower Production
California hydropower is less than 10% of total CA demand, but may play a significant role in energy trading on short time scales.

35. Probability of Exceedance for Spring Surplus Energy Resources in the PNW
Voisin, N., A. F. Hamlet, L. P. Graham, D. W. Pierce, T. P. Barnett, and D. P. Lettenmaier, 2005: The role of climate forecasts in western U.S. power planning, Journal of Applied Meteorology (accepted).