Water Supply Discussion

February 1, 2013 Water Supply Forecast Discussion

The CBRFC geographic forecast area includes the Upper Colorado River Basin,
Lower Colorado River Basin, and Eastern Great Basin.

Seasonal Water Supply Forecasts:

Quick Summary: Some Improvement in the San Juan,Uncompahgre and Salt Rivers
Elsewhere Forecasts Generally Lower

Below average spring and summer April-July streamflow volumes are forecast throughout the
Upper Colorado River Basin and Great Basin. Near median to below median February-May volumes are
expected in the Lower Colorado River Basin.

The highest runoff volumes relative to average are expected in the Great Basin of northern Utah
and Green River Basin of southeast Utah. Lowest volumes relative to average are forecast for the
Blue, Eagle and Roaring Fork Rivers. In the Lower Colorado River Basin highest volumes relative to median
are expected in the Verde Basin with lowest volumes in the Gila Basin

Click here for specific site water supply forecasts

Water Supply Discussion

Weather Synopsis:
The weather pattern during January was dominated by a mostly dry northwest flow over the
CBRFC area. There was a brief but significant event that took place towards the end of January. A moist,
warm southwest flow became established for a few days over the Southern portions of the CBRFC including
most of Arizona, New Mexico and portions of Southern Colorado. This event brought several inches of
precipitation to these areas and resulted in a large increase in snow over the San Juan mountains and
a significant rain event over Arizona.

Image: Mean upper air pattern over the continental U.S. for January 2013 and the mean upper air pattern
for January 26-January 28 2013.

Precipitation and Temperature:
Dry conditions were prevalent over the majority of the forecast area during January due to the
generally dry northwest flow aloft with much of the area showing 70-90 percent of average precipitation.
The moist southwest flow over Arizona, New Mexico and southern Colorado brought up to 6 inches of
precipitation to the area over a 3 day period. Much of the precipitation in Arizona and New Mexico was in
the form of rain and this resulted in some loss of the snowpack below about 7500 feet. The precipitation
over the San Juan Mountains increased the snowpack by up to 50 percent in some areas. October through January
precipitation is generally in the 70-90 percent range with the exception of 90-110 percent in the Verde
River Basin, the Great Basin, and portions of the upper Green river Basin.

Temperatures in January were below average over the entire CBRFC area. The greatest departures from average
(often -8 to -12 degrees ) were in the valleys where inversions were established over most of the northern areas.
Above 7000 feet departures were generally in the -3 to -5 degree range.

Image: January 2013 temperature departure from average

Snowpack:
Snow conditions in early February deteriorated over the northern Great Basin and upper Green Basin,
with some improvement over the San Juan basin and southern portions of the Gunnison basin. In general,
as of February 1st, most SNOTEL sites in the CBRFC area are at or below average.

The map below is a display of SWE at SNOTEL sites as a percent of the 1981-2010 average.

Image: CBRFC Snow Conditions Map as a percent of average for January 2013 and February 2013

Snow in the the Roaring Fork, Blue,and Eagle River Basins continue to record some of the lowest values for
their respective periods of record (red sites on the map below). Several other sites are in the bottom 10 percent
of record (orange on the map). Most SNOTEL sites in this area have periods of record around 30 to 35 years
so they rank near the 2nd or 3rd lowest for this time of year.

Image: CBRFC Snow Percentile Map - sites ranked based on historical record

Click here for river basin snow plots

Soil Moisture:
Soil moisture conditions in the higher elevation headwater areas are important entering the winter,
prior to snowfall, as it influences the efficiency of the snow melt runoff. This fall, modeled soil moisture
conditions were below average througout the upper and lower Colorado Basins. In northern Utah, modeled
soil moisture was closer to average in parts of the Bear, Weber, Provo, Six Creeks, and Duchesne Basins
due to the late October storm and high elevation rainfall. This is also true for some of the upper Green
River Basin headwaters in Wyoming. The generally dry soil moisture conditions elsewhere have influenced
the latest water supply forecasts resulting in a 5-15 percent reduction in the forecast volumes. See the map below
for a more detailed view.

Image: Modeled soil moisture states (as a percent of average) on Dec 31 2012

Streamflow:
Monthly streamflow volumes throughout the CBRFC area in January of 2013 have generally been below average due to the
dry conditions that extend back to the spring of 2012.

Climate Outlook:
The El Nino Southern Oscillation (ENSO) condition is considered neutral and this is expected to continue
through the spring months. The Climate Prediction Center indicates increased chances for below average
precipitation during the Feburary through April period over the southern half of the forecast area, especially
over Arizona and New Mexico.

Image: Climate Prediction Center 3 month precipitation outlook

Conclusion:
Near record low runoff volumes occurred in the spring of 2012 across much of the forecast area. Very dry
conditions with much below average precipitation occurred over most of the area during the September through
November period. This has resluted in much below average modeled soil moisture conditions.

Mild temperatures during the fall also resulted in rainfall with initial storms instead of accumulating snow
at higher elevations. Snow is generally much below average throughout the forecast area with exception of parts
of the Great and Green Basin. As a result streamflow volumes are forecast to be below to much below average as
of February 1st.

End Of Month Reservoir Content Tables
    Green River Basin
    Upper Colorado River Basin
    San Juan River Basin
    Great Salt Lake Basin
    Sevier Basin
    Lower Colorado Basin

Basin Conditons and Summary Graphics
    Green River Basin
    Upper Colorado River Basin
    San Juan River Basin
    Great Salt Lake Basin
    Sevier River Basin
    Lower Colorado Basin