IntermtnClimateSummaryJan2008

• Title: Intermountain West Climate Summary
• Date: 1/22/2008
• Description: Water Availability Task Force Meeting Report
• Basin: Statewide
• Drought Mitigation - Doc Type: Reports

INTERMOUNTAIN WEST CLIMATE SUMMARY, JANUARY 2008

Wyoming Water Availability

Snowpack is the primary determinant of water supply
estimates from December-April 1. Statewide snowpack is
lowest is the Little Wind River basin in the southwest at 65%
of average and highest in the Little Snake River basin in the
south at 107% of average (Figure 8a). According to Wyoming
State Climatologist, Steve Gray, snowpack has increased
in all basins 5-15 percentage points in the last few weeks.
Sno\vpack in the Lo\ver North Platte River basin in southeast-
ern Wyoming has near-average January 1 snow accumulation
(90% of average) for the first time in several years. La Nina
conditions are currently present in the Equatorial Pacific and
are associated with increased precipitation in the northwest
US into northern Wyoming. Snowpack in the northern portion
of the state is near or above average and is consistent with
conditions in previous La Nina years.
Reservoir storage is below average, ranging from a low
of 46% of average in the North Platte basin to a high of 96%
of average in the Green River basin, according to the NRCS.
Reservoir storage in Boysen, Flaming Gorge, Buffalo Bill,
Seminoe, and Fontenelle reservoirs are 104%,81 %,65%,
62%, and 61 % of average, respectively. According to initial
streamflow projections from the CBRFC, statewide spring
and summer streamflows are expected to be belo\v average
ranging from 91 % of average in the Upper Yellowstone basin
to a low of 59% of average in the Belle Fouche basin. Pro-
jected April-July inflow into Fontenelle and Flaming Gorge
reservoirs are 81 % and 74% of average, respectively.

Notes
Figure 8a, (NRCS), shows the SWE as a percent of average
for each of the major river basins in Wyoming. According to
the WY NRCS, "The Surface Water Supply Index" (SWSI
- Figure 8b) is computed using only surface water supplies
for each drainage basin. The computation includes reservoir
storage, if applicable, plus the runoff forecast. The index is
purposely created to resemble the Palmer Drought Index, with
normal conditions centered near zero. Adequate and exces-
sive supply has a positive number and deficit water supply
has a negative value. The SWE does not use soil moisture
and precipitation forecast, but the runoff forecast may include
these values."

Legend
> 4.0 Extremely Wet
3.0 Very Wet
2.0 Moderately Wet
1.0 Slightly Wet
0.5 Incipient Wet Spell
0.0 Near Normal
- 0.5 Incipient Dry Spell
- 1.0 Mild Drought
- 2.0 Moderate Drought
- 3.0 Severe Drought
< - 4.0 Extreme Drought

Figure 8b. Wyoming Surface Water Supply Index as of
January 1, 2008 (Wyoming NRCS).

\/ A . . .lib ;1, I' ~.'

_... T't;t.ct~.. ..~ - - ~
~2D . w ~~ 'Y ~~ &~:;.
Current S~ow _ _ 7 ~ ~'" . ~
W.ater Equlv"s J }J~'" .A,
'" ''''Il~ TiT
'0/0 ot Normal ' '~~ . V
.t. ~ 16CP~ "f ! \t
.t. 140-16~ Y,i
il. 12(1..139'% __ F
- '-" -. J

\._ ~CheYBIUIIJ
~~l,o ~. II
Ji~ ill ~

- ~~ ~,~

.. 100..1'19%
r;; B0-89%

..,
V
T
rg

Figure 8a. Current snow water equivalent (SWE) as
a percent of normal for SNOTEL sites in Wyoming
as of January 2, 2008, (NRCS).

On the Web
For current maps of SWE as a percent of normal (Figure 8a), visit: http://www.wcc.nrcs.usda.gov/gis/snow.html.
For current SNOTEL data and plots of specific sites, visit: http://www.wcc.nrcs.usda.gov/snotel/.
The Wyoming SWSI (Figure 8b), along with more data about current water supply conditions for the state can be found at:
http://www.wrds.uwyo.edu/wrds/nrcs/nrcs.html.
For monthly State Basin Outlook Reports on water supply conditions and forecasts for WY river basins, visit: http://www.
wcc. nrcs. usda.gov/cgibin/bor. pI.
Wyoming Water Resource Data system's drought page is located at: http://www.wrds.uwyo.edu/wrds/wsc/dtf/drought.html.
Article in the Billings Gazette, "Wyoming snowpack improves," January 8, 2008, available at URL: http://www.billingsga-
zette. n etl arti cles/2 008/01 108/n ews/wy om i n g/30-s nowpa ck. txt?C F I D =596826& C FT 0 KE N =e58 b 7 c5562 Od 77 b6-64A5 E F 71-
FF33-87D 1-F703COC52BD2145F.

.... 60..79%
., 40..59%

.. 1-:38"m

+ 0%

· Unavailable'';'

RECENT CONDITIONS 111