New 1981-2010 Averages being used this year.
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Lake Powell Water Supply Outlook, February 1, 2012Lake Powell Water Supply Outlook, February 1, 2012
Contents
Lake Powell Sub-Basin Summaries

*Median of forecasts within each basin.

*Median of forecasts within each basin.

*Median of forecasts within each basin.
Upper Green Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was 100 percent of average
in the Upper Green basin. January
precipitation was 125 percent of average.
Snow:
February 1st snow water equivalent was 100 percent of average in the basin.
--- Upper Green basin
snow
water equivalent plot.
Streamflow:
January streamflow was near 110 percent of average.
Soil Moisture:
Modeled
soil
moisture states indicated near average to above average soil moisture conditions
last fall prior to snow accumulation.
Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation
between La Nina conditions and winter precipitation in the Upper Green basin.
Forecast Summary:
Seasonal precipitation in the Upper Green remains near average as a result of above average and much
above average precipitation in October, November, and January. Snow water equivalent has increased from below average on January 1
to near average due to the above average precipitation in January. It is also important to note that fall soil moisture
conditions were near to above average. As a result, current April through July streamflow volume forecasts increased by
15 to 20 percent and range between 74 and 100 percent of average with a median value of 94 percent.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Yampa/White Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was 70 percent of average
in the Yampa/White basin. January
precipitation was near 60 percent of average.
Snow:
February 1st snow water equivalent was 65 percent of average in the basin.
--- Yampa basin
snow
water equivalent plot.
Streamflow:
January streamflow ranged between 110 and 120 percent of average.
Soil Moisture:
Modeled
soil
moisture states indicated above average to much above average soil moisture conditions
last fall prior to snow accumulation.
Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation
between La Nina conditions and winter precipitation in the Yampa/White basin.
Forecast Summary:
January precipitation was much below average in the Yampa/White basins. As a result of much below average conditions for both
December and January, both seasonal precipitation and snow water equivalent are much below
average. It is also important to note that fall soil moisture conditions were
above to much above average. As a result of another below average month, current April through July streamflow volume
forecasts have decreased by 5 to 10 percent and now range between 62 and 79 percent of average with a median value of 70 percent.
Forecasts are slightly higher than current snow conditions might suggest due to wet antecedent conditions.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Duchesne Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was 85 percent of average
in the Duchesne basin. January
precipitation was 70 percent of average.
Snow:
February 1st snow water equivalent was 65 percent of average in the basin.
--- Duchesne basin
snow
water equivalent plot.
Streamflow:
December streamflow was 115 percent of average.
Soil Moisture:
Modeled
soil
moisture states indicated much above average soil moisture conditions
last fall prior to snow accumulation.
Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation
between La Nina conditions and winter precipitation in the Duchesne basin.
Forecast Summary:
Seasonal precipitation in the Duchesne is below average as a result of much below average and below
average conditions in December and January. Snow water equivalent is also much below average for the
majority of the basin. However, it is important to note that fall precipitation and soil moisture conditions were
much above average. Wet antecedent conditions are resulting in somewhat higher forecasts for the Whiterocks and Uinta river basins.
As a result, current April through July streamflow volume forecasts have decreased by 5 to 10 percent and
range between 54 and 93 percent of average with a median value of 69 percent. Forecasts are slightly higher than current snow conditions
might suggest due to wet antecedent conditions.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Lower Green Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was 80 percent of average
in the Lower Green basin. January
precipitation was 85 percent of average.
Snow:
February 1st snow water equivalent was 55 percent of average in the basin.
--- Lower Green basin
snow
water equivalent plot.
Streamflow:
January streamflow ranged from 120 to 130 percent of average.
Soil Moisture:
Modeled
soil
moisture states indicated near average to above average soil moisture conditions
last fall prior to snow accumulation.
Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation
between La Nina conditions and winter precipitation in the Lower Green basin.
Forecast Summary:
Seasonal precipitation is below average and snow water equivalent is much below average in the Lower Green due to
below average monthly precipitation in November, December, and January. It is also important to note the fall soil moisture
conditions were near to above average. As a result, current April through July streamflow
volume forecasts remain similar to January 1 and range between 56 and 75 percent of average with a median value of 65 percent.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Upper Colorado Mainstem Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation
was near 75 percent of average in the Upper Colorado mainstem basin.
Above average precipitation occured in October but was followed by
two months of much below average precipitation in November and December.
January
precipitation was near normal at 95 percent of average.
Snow:
February 1st snow water equivalent was near 70 percent of average in the basin as a whole.
While it is still below average, it is an improvement from the 60 percent of average
observed on January 1st.
--- Upper Colorado basin
snow
water equivalent plot
Streamflow:
January streamflow was near 110 percent of average.
Soil Moisture:
Modeled
soil
moisture states were above average heading into the winter.
Climate Forecasts:
La Nina climate conditions exist but these do not show a strong correlation with winter
precipitation in the Upper Colorado mainstem basin, and therefore were not influential in the development
of streamflow volume forecasts.
Forecast Summary:
Because of the below average November and, especially, December precipitation, as of February 1 both the
seasonal precipitation and snow water equivalent are below average at 75% and 70%, respectively.
However, due to a very good runoff season last year and a wet October, above average soil moisture conditions
existed in the Upper Colorado mainstem heading into the winter season. As a result of near normal January
precipitation most forecasts are unchanged from last month.
Current April through July streamflow volume
forecasts
range between 70 and 86 percent of average with a median value of 80 percent.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Gunnison Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was 85 percent of
average in the Gunnison Basin. Above average precipitation occured in October. Dry
conditions and much below average precipitation occurred in November and December.
January
precipitation was near to above average in upper Gunnison
and East River Basins, with near to slightly below average precipitation elsewhere.
Snow:
February 1st snow water equivalent was 75 percent of average in the Gunnison basin.
Gunnison Basin
snow
water equivalent plot
Streamflow:
January streamflow volumes ranged from 70 to 90 percent of average.
Soil Moisture:
Modeled
soil
moisture states were above average entering the winter season.
Climate Forecasts:
La Nina climate conditions exist but these do not show a strong correlation with winter
precipitation in the Gunnison Basin, and therefore were not influential in the development
of streamflow volume forecasts.
Forecast Summary:
A wet October was followed by drier condtions in November and December. January precipitation was
near or above average at most locations. Seasonal precipitation was near 85 percent of average as
of February 1st, with a basin snow water equivalent value near 75 percent of average. High runoff
in 2011 and a wet October resulted in above average soil moisture in the Gunnison Basin entering
the winter season. April-July
streamflow runoff volumes changed little
from those issued January 1st and are expected to range between 60 and 80 percent of the 1981-2010
average.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Dolores Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was near 90 percent of average.
Precipitation was above average in October, much below average in November, and near to below average
in December.
January
precipitation ranged from 80 to 95 percent of average.
Snow:
February 1st snow water equivalent was 75 percent of average in the Dolores Basin.
Dolores Basin
snow
water equivalent plot
Streamflow:
January streamflow volumes in the Dolores River Basin were near 65 percent of average.
Soil Moisture:
Modeled
soil
moisture states were near average entering the winter season.
Climate Forecasts:
La Nina climate conditions exist but does not show a strong correlation with winter
precipitation in the Dolores Basin. Therefore, it was not influential in the development
of streamflow volume forecasts.
Forecast Summary:
Near average soil moisture existed in the Dolores River Basin entering the winter
season. Seasonal precipitation was near 90 percent of average on February 1st, with October
the only month with above average precipitation. February 1st snow water equivalent
was 75 percent of average in the Dolores Basin. April-July
streamflow
runoff volumes are expected to range from 65 to 80 percent of the 1981-2010 average.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
San Juan Basin Conditions
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through January
precipitation was near average. October was wet, while November through
December experienced drier than average conditions.
January was dry with a basin average
precipitation near 65 percent.
Snow:
February 1st snow water equivalent for the entire basin was near 75% of average.
Animas River Basin
Snow Plot.
San Juan Basin (above Navajo Reservoir)
Snow Plot.
Streamflow:
Streamflow volumes for January ranged from 60% of average at the Basin outlet to near 90% of average at higher elevations.
Soil Moisture:
Modeled
soil moisture has been updated since January 1st
and was near to above average at highest elevations entering the winter season. Below average soil moisture conditions existed
over the southern half of the basin and in tributaries further downstream.
Climate Forecasts:
La Nina climate conditions exist and a weak to moderate La Nina episode is anticipated to continue through the winter
season. The La Nina climate condition suggests drier than average conditions possible over the San Juan Basin. The
La Nina climate condtion was considered when developing the forecasts.
Forecast Summary:
Seasonal precipitation is near average due to a wet October. Snowpack conditions are below average due to drier
weather November through January. Soil Moisture varied entering the winter season, with near or slightly above
average conditions in high elevations in the northern headwaters, and below average conditions elsewhere.
La Nina climate conditions suggest below average precipitation is possible over the San Juan Basin through spring.
April-July
runoff volumes
are expected to range from 75 to 90 percent of the 1981-2010 average.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.
Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).
Reservoir Monthly Inflow Forecasts






Monthly Streamflows








Precipitation Maps

