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Lower Colorado Water Supply Outlook, January 1, 2010


Prepared by G. Smith
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Lower Colorado Summary






*Median of forecasts within each basin.


Salt Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation was near 60 percent of average.
December precipitation was 125 percent of average in the Salt Basin, and near 150 percent in the Verde Basin.

Streamflow:
December streamflow ranged from 60 to 90 percent of median.

Snow:
January 1st snowpack conditions were 210 percent of average in the Verde Basin and 110 percent of average in the upper Salt.

Salt River Basin Snow Plot.
Verde River Basin Snow Plot.

Soil Moisture:
Modeled soil moisture states were drier compared to this time last year.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
Despite below average seasonal precipitation and drier soils, the presence of El Nino climate conditions combined with above average snowpack resulted in January-May volume forecasts between 90 and 110 percent of median.



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Gila Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation was near 60 percent of average.
December precipitation ranged from 80 to 100 percent of average.

Streamflow:
December streamflow ranged from 45 to 75 percent of median.

Snow:
Basin snowpack conditions were near average as of January 1st.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Modeled soil moisture states were wetter in the San Francisco drainage, but vary in comparsion to last year in the upper Gila Basin.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
Below average seasonal precipitation and below median streamflow in December support forecast volumes much lower than those indicated. Significant weight was placed on the El Nino climate condition, and a wetter pattern developing. This resulted in January-May forecast volumes between 90 and 110 percent of median.



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Little Colorado Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-December precipitation was near 50 percent of average.
December precipitation ranged from 70 to 145 percent of average.

Streamflow:
December streamflow was near 30 percent (or less) of median.

Snow:
Basin snowpack conditions were near 130 percent of average in the southern Headwaters.

Little Colorado Southern Headwaters Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Modeled soil moisture states were slightly drier compared to this time last year.

Climate Forecasts:
El Nino climate conditions suggest increased chances for precipitation in this area. The El Nino influence was accounted for in generation of these forecasts.

Forecast Summary:
Below average seasonal precipitation and below median streamflow in December support forecast volumes much lower than those indicated. Significant weight was placed on the El Nino climate condition, and a wetter pattern developing. The El Nino influence combined with an above average snowpack resulted in January-May forecast volumes between 100 and 125 percent of median



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.


Salt Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Median		10%
Exceedance
Volume
Salt
Roosevelt, Nr January-May14735091685
Tonto Ck
Roosevelt, Nr, Gun Ck, Abv January-May11.660107172
Verde
Blo Tangle Ck, Abv Horsehoe Dam January-May85230105485


Gila Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Median		10%
Exceedance
Volume
Gila
Gila, Nr January-May3864107115
Virden, Nr, Blue Ck, Blo January-May4490108190
Solomon, Nr, Head Of Safford Vly January-May9615091380
San Carlos Res, Coolidge Dam, At January-May63115120425
San Francisco
Glenwood, Nr January-May162710058
Clifton January-May396491169


Little Colorado Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Median		10%
Exceedance
Volume
Little Colorado
Lyman Lk, Abv, St. Johns, Nr January-June4.5912218
Woodruff January-May0.8411122
Rio Nutria
Ramah, Nr January-May13.51139.9
Zuni
Black Rock Res, Abv January-May0.81.91284
Cebolla Ck
Ramah Res January-May0.51.91114.4
East Clear Ck
Blue Ridge Res, Pine, Nr January-May5.51911133
Clear Ck
Winslow, Nr January-May153510393
Chevelon Ck
Winslow, Nr, Wildcat Cyn, Blo January-May91910948
Walnut Ck
Lake Mary January-May1.4612010.6

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).

Lower Colorado End of Month Reservoir Contents (kaf)

Usable
Capacity		EOM
Contents		Percent
Usable
Capacity		Last Year
EOM		Last Year
%Capacity
Salt
Roosevelt 1653.0 1254.0 76 1594.9 96
Horse Mesa 245.0 218.2 89 236.1 96
Mormon Flat 58.0 55.9 96 55.5 96
Stewart Mountain 70.0 66.2 95 65.3 93
Horseshoe 109.2 22.3 20 20.4 19
Bartlett 178.0 69.9 39 96.8 54
untitled
TOTAL 2313.2 1686.6 73 2069.0 89
Little Colorado
Lyman Lake 31.0 12.2 39 14.2 46
Bill Williams
Alamo 1045.0 123.7 12 152.3 15
Agua Fria
Lake Pleasant 1145.0 560.2 49 520.4 45
Gila
San Carlos 885.0 240.5 27 216.7 24
Painted Rock 2476.0 0.0 0 0.0 0
Colorado
Lake Powell 24322.0 14433.8 59 13540.9 56
Lake Mead 27380.0 11169.0 41 12512.0 46
Lake Mohave 1810.0 1587.6 88 1584.7 88
Lake Havasu 619.0 565.4 91 557.6 90
untitled
TOTAL 59713.0 28692.4 48 29098.7 49

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 1971-2000 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:
RangeRound to
0-1.990.01
2.0-19.90.1
20-1991.0
200-9995.0
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


Hydrologist: G. Smith