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.Lower Colorado Water Supply Outlook, February 1, 2012

Lower Colorado Water Supply Outlook, February 1, 2012


Prepared by T.Cox
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-January precipitation was near 90 percent of average in the Salt River Basin and 85 percent of average in the Verde River Basin.

January precipitation was 15 to 30 percent of average in the Salt and Verde River Basins.

Streamflow:
January streamflow was near 75 percent of median on the Salt and Verde Rivers.

Snow:
February 1st snowpack conditions was 65 percent of average in the Verde River Basin, with condtions in the upper Salt River Basin near 90 percent of average.

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

Soil Moisture:
Modeled soil moisture states are near to below average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Dry conditions in January were consistent with La Nina climate conditions that currently exist. Seasonal precipitation October-January was generally average to below average. La Nina climate conditions suggest below average precipitation over the next few months. Forecast volumes are near 57 percent of median in the Tonto, 59 percent of median in the Verde River Basin and 46 percent of median in the Salt River Basin.




* 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-January precipitation was 95 percent of average.

January precipitation was 30 percent of average.

Streamflow:
January streamflow was 55 percent of median.

Snow:
February 1st snowpack conditions were near 95 percent of average in the upper Gila Basin.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Modeled soil moisture states are near average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Dry conditions in January were consistent with La Nina climate conditions that currently exist. Seasonal precipitation October-January was generally average. La Nina climate conditions suggest below average precipitation over the next few months. Forecast volumes range from 52 to 72 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-January precipitation was 85 percent of average.

January precipitation was 30 percent of average throughout the Little Colorado Basin.

Streamflow:
Minimal streamflow observations exist for January. The January volume on the Little Colorado near Lyman was near 60 percent of median.

Snow:
Basin snowpack conditions on February 1st were near 90 percent of average in the southern Headwaters.

Little Colorado Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Modeled soil moisture states are near to below average at this time.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
The presence of La Nina climate conditions suggest below average precipitation into the spring. Below average seasonal precipitation exists over most of the Little Colorado Basin. February-May streamflow volumes are forecast to range from 43 to 79 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 February-May5013046270
Tonto Ck
Roosevelt, Nr, Gun Ck, Abv February-May3.2205762
Verde
Blo Tangle Ck, Abv Horsehoe Dam February-May238059191


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 February-May17.6367264
Virden, Nr, Blue Ck, Blo February-May19396291
Solomon, Nr, Head Of Safford Vly February-May287158210
San Carlos Res, Coolidge Dam, At February-May174252145
San Francisco
Glenwood, Nr February-May4.1126640
Clifton February-May12316187


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 February-June1.24619.5
Zuni
Black Rock Res, Abv February-May0.070.3790.82
Chevelon Ck
Winslow, Nr, Wildcat Cyn, Blo February-May2.264322

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 1102.9 67 1498.9 91
Horse Mesa 245.0 227.8 93 230.0 94
Mormon Flat 58.0 56.6 98 56.2 97
Stewart Mountain 70.0 65.6 94 67.2 96
Horseshoe 109.2 0.2 0 0.4 0
Bartlett 178.0 73.8 41 157.7 89
untitled
TOTAL 2313.2 1526.8 66 2010.5 87
Little Colorado
Lyman Lake 31.0 10.9 35 20.0 65
Bill Williams
Alamo 1045.0 100.2 10 135.8 13
Agua Fria
Lake Pleasant 1145.0 688.5 60 700.0 61
Gila
San Carlos 885.0 23.1 3 117.3 13
Painted Rock 2476.0 0.1 0 0.0 0
Colorado
Lake Powell 24322.0 15640.0 64 13821.6 57
Lake Mead 27380.0 15022.0 55 10773.0 39
Lake Mohave 1810.0 1627.7 90 1678.2 93
Lake Havasu 619.0 553.9 89 554.3 90
untitled
TOTAL 59713.0 33666.4 56 27800.2 47

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:
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: T.Cox