New 1981-2010 Averages being used this year. Note: This publication is currently undergoing major revisions. The current publication will be replaced with a new publication based on stakeholder requirements and scientific advances. We expect to begin sharing details on this soon. If you have input on content, format, or publication frequency at any time, please contact us at cbrfc.webmasters@noaa.gov.Lake Powell Water Supply Outlook, January 1, 2012
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 95 percent of average
in the Upper Green basin. December precipitation was 50 percent of average.
Snow:
January 1st snow water equivalent was 75 percent of average in the basin.
--- Upper Green basin snow
water equivalent plot.
Streamflow:
December 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 is near average as a result of much above average precipitation
in October and November. However, snow water equivalent is below average due to much below average
monthly precipitation in December. 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 range
between 65 and 87 percent of average with a median value of 80 percent.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 70 percent of average
in the Yampa/White basin. December precipitation was 30 percent of average.
Snow:
January 1st snow water equivalent was 65 percent of average in the basin.
--- Yampa basin snow
water equivalent plot.
Streamflow:
December streamflow was near 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:
Seasonal precipitation is below average and snow water equivalent is much below average in the Yampa/White basins
as a result of an extremely dry December. It is also important to note that fall soil moisture conditions
were above to much above average. As a result, current April through July streamflow volume forecasts range
between 68 and 83 percent of average with a median value of 75 percent.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 90 percent of average
in the Duchesne basin. December precipitation was 40 percent of average.
Snow:
January 1st snow water equivalent was 65 percent of average in the basin
as a whole.
--- Duchesne basin snow
water equivalent plot.
Streamflow:
December streamflow was 120 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 near average as a result of much above average precipitation
in October and near average precipitation in November. Snow water equivalent is much below average for the
majority of the basin due to much below average monthly precipitation in December. However, the snow water
equivalent for the eastern portion of the basin is near average resulting in somewhat
higher forecasts. It is also important to note that fall soil moisture conditions were
much above average. As a result, current April through July streamflow volume forecasts range between 63 and 104
percent of average with a median value of 80 percent.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 80 percent of average
in the Lower Green basin. December precipitation was 40 percent of average.
Snow:
January 1st snow water equivalent was 40 percent of average in the basin
as a whole.
--- Lower Green basin snow
water equivalent plot.
Streamflow:
December streamflow was near 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 and December. 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 range between 60 and 75 percent of average with a median value of 65 percent.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation
was near 70 percent of average in the Upper Colorado mainstem basin.
The new water year started well with above average precipitation in October;
however, November precipitation was below average and then December
precipitation was just 35 percent of average.
Snow:
January 1st snow water equivalent was near 60 percent of average in the basin as a whole.
--- Upper Colorado basin snow
water equivalent plot
Streamflow:
December 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 January 1 both the
seasonal precipitation and snow water equivalent are much below average at 70% and 60%, 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.
Therefore, current April through July streamflow volume forecasts
range between 72 and 86 percent of average with a median value of 80 percent.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 75 percent of
average in the Gunnison Basin. Above average precipitation occured in October. Dry
conditions and much below average precipitation occurred in November.
December precipitation was also much below average, ranging from
30 percent of average in the East River watershed to 70% of average in the Uncompaghre
watershed. The Gunnison basin-wide average for December was 50%.
Snow:
January 1st snow water equivalent was 65 percent of average in the Gunnison basin.
Streamflow:
December streamflow volumes ranged from 85 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. Seasonal precipitation was
near 75 percent of average as of January 1st, with a basin snow water equivalent value near 65 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, impacting the forecasts. April-July
streamflow runoff volumes are expected to range between 60 and 80 percent of the 1981-2010 average
as of January 1st.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation was 90 percent of average.
Precipitation was above average in October and much below average in November.
December precipitation was near 90% of average.
Snow:
January 1st snow water equivalent was 85 percent of average in the Dolores Basin.
Streamflow:
Many streamflow gages do not function well during the winter. December streamflow volumes in
the Dolores River Basin have been estimated near 60% of average.
Soil Moisture:
Modeled soil
moisture states were near to above 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 to above average soil moisture existed in the Dolores River Basin entering the winter
season. Above average precipitation occurred in October. Precipitation was much below
average in November and near to below average in December. Seasonal precipitation was 90
percent of average on January 1st with snow water equivalent near 85 percent of average.
April-July streamflow runoff volumes are expected to range from 70 to 80
percent of the 1981-2010 average.
The following conditions influenced this month's forecasts:
Precipitation:
Seasonal October through December precipitation is above average due to a wet
October. November was dry with
precipitation amounts generally less than 70 percent of average.
December precipitation was generally below average across much of the Basin, with the exception of a few high
elevation sites that received amounts near or slightly above average.
Snow:
Current snow water equivalent for the entire basin is 85% of average for early January. The Animas basin was near 90% of average
on January 1st and the San Juan above Navajo was near 80 percent of average.
San Juan Basin (above Navajo Reservoir) Snow Plot.
Streamflow:
Streamflow volumes for December ranged from 65% of average at the Basin outlet to near 90% of average at higher elevations.
Soil Moisture:
Modeled soil moisture indicated near to slightly above average soil moisture conditions over the San Juan Basin last fall,
prior to the onset of snow accumulation.
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 above average due to a wet October. Snowpack conditions are below average due to drier
weather in November and December. Soil Moisture was near to slightly above average entering the winter
season. 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 95 percent
of the 1981-2010 average.
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
Green End of Month Reservoir Contents (kaf)
Usable Capacity
EOM Contents
Percent Usable Capacity
Last Year EOM
Last Year %Capacity
untitled
Green
Fontenelle Res, Fontenelle Nr
344.8
207.4
60
210.0
61
Flaming Gorge Res, Flaming Gorge Dam, At
3752.0
3403.7
91
3111.4
83
untitled
Strawberry
Solider Springs,nr
1105.9
978.7
88
975.1
88
Starvation Res, Duchesne, Nr
165.3
142.1
86
141.9
86
untitled
Price
Scofield Res, Scofield, Nr
65.8
48.9
74
22.7
34
untitled
Seeley Ck
Joes Vly Res, Orangeville, Nr
61.6
46.8
76
41.3
67
untitled
Huntington North Reservoir Storage
4.2
3.7
87
2.0
46
untitled
TOTAL
5499.6
4831.3
88
4504.3
82
Upper Colorado End of Month Reservoir Contents (kaf)
Usable Capacity
EOM Contents
Percent Usable Capacity
Last Year EOM
Last Year %Capacity
untitled
Colorado
Lake Granby, Granby, Nr
490.3
412.5
84
427.1
87
untitled
Willow Ck
Willow Ck Res, Granby, Nr
9.1
8.1
88
8.4
92
untitled
Williams Fork
Williams Fork Res, Parshall, Nr
96.9
80.1
83
81.3
84
untitled
Muddy Ck
Wolford Mountain Reservoir
66.0
58.3
88
54.3
82
untitled
Blue
Dillon Res
254.0
240.8
95
219.0
86
Green Mtn Res
146.9
93.8
64
78.3
53
untitled
Homestake Ck
Homestake Res
43.0
23.4
54
37.4
87
untitled
Frying Pan
Ruedi Res, Basalt, Nr
102.0
79.2
78
74.0
73
untitled
Plateau Ck
Vega Res, Collbran, Nr
32.9
16.7
51
11.8
36
untitled
Taylor
Taylor Park Res
106.2
66.7
63
74.3
70
untitled
Gunnison
Blue Mesa Res
829.5
574.1
69
557.0
67
Morrow Point Res
117.0
113.0
97
112.2
96
Crystal Res
17.5
16.4
93
15.6
89
untitled
Muddy Ck
Paonia Res, Bardine, Nr
18.5
0.5
3
1.6
9
untitled
Uncompahgre
Ridgway Res
83.2
68.8
83
66.6
80
untitled
Dolores
Mcphee Res
381.1
290.9
76
275.4
72
untitled
TOTAL
2794.1
2143.2
77
2094.3
75
Colorado
Lake Powell
24322.0
15972.4
66
14469.0
59
untitled
TOTAL
24322.0
15972.4
66
14469.0
59
San Juan End of Month Reservoir Contents (kaf)
Usable Capacity
EOM Contents
Percent Usable Capacity
Last Year EOM
Last Year %Capacity
untitled
Los Pinos
Vallecito Res, Bayfield, Nr
125.4
74.7
60
66.9
53
untitled
San Juan
Navajo Res, Archuleta, Nr
1701.3
1311.4
77
1362.0
80
untitled
Florida
Lemon Res, Durango, Nr
39.8
13.8
35
14.1
35
untitled
TOTAL
1866.5
1399.9
75
1442.9
77
Monthly Streamflows
Precipitation Maps
Definitions
10% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 10% chance of being exceeded. Previously referred to as "Reasonable Maximum Forecast".
50% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 50% chance of being exceeded. Previously referred to as "Most Probable Forecast".
90% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 90% chance of being exceeded. Previously referred to as "Reasonable Minimum Forecast".
Acre-Foot (af):
The volume equal to one acre covered one foot deep (43,560 cubic feet). See kaf below.
Average:
The arithmetic mean. The sum of the values divided by the number of values. Values from 1981-2010 are used for this publication.
Categories:
Much Above Average=Greater than 130%, Above Average=111-130%, Near Average=90-110%, Below Average=70-89%, Much Below Average=Less than 70%.
CBRFC:
Colorado Basin River Forecast Center.
Forecast Period:
The period from April 1 through July 31, unless otherwise noted.
kaf:
Thousand Acre-Feet. See Acre-Foot above.
Inflow:
The volume of water that flows into a reservoir or lake.
Median:
The middle value of an ordered set of values. Half of the values are higher and half of the values are lower. When the set contains an even number of values the median is the average of the two middle numbers.
NOAA:
National Oceanic and Atomospheric Administration.
NWS:
National Weather Service.
Rounding Conventions:
Range
Round to
0-1.99
0.01
2.0-19.9
0.1
20-199
1.0
200-999
5.0
1000+
3 significant digits
Streamflow:
The volume of water that flows past a specific stream site.
Water Year:
The 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends. Thus, the year ending September 30, 2008, is called the "2008 water year."
Additional Information
Water supply forecasts take into consideration present hydrometeorological conditions and use
average basin temperatures and precipitation for the forecast period. As the forecast season progresses,
a greater portion of the future hydrologic and climatic uncertainty becomes known and
monthly forecasts become more accurate. For more information on the tools we use, consult Water Supply Forecasting Tools.
Volume forecasts represent adjusted flows; that is, observed flows with upstream water use
taken into account. Adjusted flows will closely approximate natural or unimpaired flows.
However, not all upstream diversions or impoundments are measured or quantifiable. For specific
adjustments used with each forecast point, consult the Guide to Water Supply Forecasting.
The Water Supply Outlook is issued monthly January through May by the Colorado Basin River
Forecast Center. It represents a coordinated effort between the
National Weather Service, Natural Resources Conservation Service, Bureau of Reclamation, U.S.
Geological Survey and local water district managers.
Note: Data used in this report are provisional and are subject to revision.
For more information, or to be included on the mailing list, please contact:
Colorado Basin River Forecast Center
2242 W North Temple
Salt Lake City, UT 84116
(801) 524-5130
www.cbrfc.noaa.gov
