WSP11873

• File Number: 8210.137
• Description: Colorado River Basin-Colorado River Basin Organizations/Entities-Colorado River Forecast Committee
• Date: 3/1/1984
• Author: USDA, USDC, NOAA,NWS
• Title: Water Supply Outlook for the Western United States
• Water Supply Pro - Doc Type: Report/Study

GREAT BASIN -- Continued

have increased the expected April-July runoff volumes in
the Humboldt River Basin to 245 percent of normsI. High
Inf lows to both Utah Lake and the Great Salt lake are
likely to push these large boMes of water to higher
levels than last yesr, and to levels not experienced In
almost a century.

February precipitation was generally near or above
normal over the western half of Utah and eastern Nevada.
and below normal along the east slope of the Sierras.
Amounts ranged from 150 percent in the northeast to less
than 50 percent in the southeast. Seasonal
precipitation, October through February, is generally 130
to 170 percent over most of the state except the extreme
Bouthern areas which are less than BO percent.

Snowfall dudng February was generally below normal
with most snowpack percentages decreasing 5 to 15
percent. Some average basin water contents as a percent
of normal include: Bear River, 134 percent; Weber, 138
percent; Ugden, 164 percent; Provo, 124 percent; Upper
Sevier, 112 percent; Lower Sevier, 168 percent; Beaver,
157 percent; Humboldt. 227 percent, and East Slope
Sierras, 120 percent.

Observed streamflow continues to reflect the saturated
soil conditions and high base f low. Six out .of the seven
index stations throughout Utah during the cold February
were running between 150 to 200 percent of normal. The
combined contents of 23 reservoirs in Utah is 3.5 million
acre-feet, 130 percent of average and 87 percent of
capacity. This storage is similar to last year but more
space has been made available on the Weber and Odgen
drainages this year.

The elevation of the Great Salt Lake on Harch 1 was
4,206.70 feet MSL. This is 4.45 feet higher than last
year at this time and is expected to peak at 4.208.00 to
4,209.00 feet HSL early this summer. Utah Lake dropped
0.16 feet since February I and is now 3.2 feet above
compromise, 1. 7 feet higher than last year, and is
expected to rise between 5 and 6 feet above compromise
this spring.

The flood potential for this spring snowmelt continues
to look threatening. April through July forecasts
indicate volumetric amounts only slightly less than those
experienced last year. Spring weather will play a
significant role in the extent of the spring flooding. A
dry and mild temperature pattern would dramatically
reduce the flood potential but a cold wet pattern, like
last year, would produce critical runoff conditions.

With the onset of melt from abundant low elevation
snow. saturated soils and impending spring rains, valley
residents should be alert to aome pooling of water in
poor drainage areas and the possibility of basement
flooding. Also, the threat of rock and mud sUdes are
still very real during the next several months and
susceptible areas should be watched ciosely.

COLORADO BASIN

The Water supply outlook is generally for above normal
runoff, 125 to 155 percent. for the Colorado River above
Lake Powell. However. the lower Colorado River in
Arizona is much below normal with forecast flows less
than 50 percent throughout the Salt. Gila, and Little
Colorado drainages. Streamflow forecasts above Lake
Powell dropped 10 to 20 percent from those issued
February 1 as a result of another dry month.

Precipitation during February was generally less than
50 percent over the Colorado Basin with most of Arizona
receiving none at all. A few areas in the Gunnison
drainage and some headwater areas of the Green River had
near normal amounts. Seasonal precipitation, October
through February. ranges from below normal. 50 to 80
percent in central Arizona and portions of the San Juan
Basin, to greater than ISO percent in portions of western
Colorado and southwest Wyoming.

February snowfall was only SO to 80 percent of normal
in the Upper Colorado. Ouring the last two months. sno'W
surveya lnd~cate a significant reduction in the average
basin snow water content in relation to normal. Some
average basin snowpacks include: Upper Colorado
mainstem, 139 percent; Gunnison. 144 percent; San Juan
Basin, 120 percent; Yampa River, 115 percent; and the
Upper Green River, 83 percent. Host of the snow on the
Arizona watersheds is gone.

High solI saturation and baseflow conditions in the
Upper Colorado are well evidenced by the winter
streamflow on both the Green River and Colorado River.
Since October I, the flow on the Green River has been 1.3
million acre-feet, 205 percent of average, the highest
flow on record dating back to 19l1. Inflow to Lake
Powell for the winter period. December through February,
has been 1.59 million acre-feet, 1'& percent, the highest
on record.

Reservoir storage remains high with the combined
storage of ten major reservoirs above Lake Powell of 0.2
million acre-feet, 70 percent of capacity, 151 percent of
average and nearly the same storage as last year at this
time. Storage in Lake Powell is n.5 million acre-feet,
86 percent of capacity. about 750,000 acre-feet lower
than last year at this time. The April-July inflow
forecast to Lake Powell is 11.3 mllion acre-feet, 151
percent of the 20-year average, 1961-1980.

RIO GRANDE BASIN

The water supply outlook for the Rio Grand Basin is
for snowmelt runoff to range from near normal up to 100
percent of average.

Precipitation for the month of February was much below
normal over all but isolated areas of the basin. Near to
slightly above normal alllOunts were reported in the
extreme upper reaches of the basin in Colorado around Rio
Grande Reservoir and near 1.5 times normal around Red
River in New Mexico. No measureable precipitation was
observed at many of the reporting stations in the
southern half of New Mexico. Seasonal totals (October
through February) have now decreased to range from 60 to
120 percent of normal in the Colorado portion of the
basin, and 50 to 140 percent of normal in New Mexico,
but near twice normal at Roswell in the Pecos Basin.

Basin snowpacks observed around the first of March
continued above normal for this time of the year but have
decreased 10 to 40 percent from last month. In the
Colorado portion of the basin the snowpack is 122 percent
of normal and 129 percent of last year at this time. The
New Mexico snowpack is 133 percent of normal and 105
percent of last year.

Reservoir storage
about 166 percent of
232 percent of normal
are about the same
February.

continues well above average with
normal in storage in Colorado and
in New Mexico. The storage amounts
as observed around the first of

ARKANSAS BASIN

The Arkansas River water supply outlook for the
current season indicates above normal runoff for all of
the basin. Runoff amounts are expected to range from 125
to 160 percent of the 20-year (1961-1980) average.

February precipitation totals were above normal near
the New Mexico border but below normal over the rest of
the basin. October through February seasonal totals now
range from 1.5 to 2 times normal to only half normal in
the southeast.

2

First of March snowpacks were above normal over ail
the basin but percentages were down slighrly from a month
ago north of Salida and unchanged or slightly increased
to the south. Total basin snowpack now averages about

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