Lower Colorado Water Supply Outlook, March 1, 2019

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
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




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Gila Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Little Colorado Basin Conditions




Snow Water Equivalent in 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
70%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Median
30%
Exceedance
Volume
10%
Exceedance
Volume
Salt
Roosevelt, Nr January-May395 465 530 171 630 710
March-May225 295 360 150 460 540
Tonto Ck
Roosevelt, Nr, Gun Ck, Abv January-May84 96 114 271 144 185
March-May37 49 67 305 97 138
Verde
Tangle Ck, Blo, Horseshoe Dam, Abv January-May370 415 480 306 565 660
March-May163 210 275 257 360 455


Gila Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
70%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Median
30%
Exceedance
Volume
10%
Exceedance
Volume
Gila
Gila, Nr January-May47 53 61 109 77 101
March-May23 29 37 109 53 77
Virden, Nr, Blue Ck, Blo January-May56 65 72 95 89 112
March-May27 36 43 100 60 83
Solomon, Nr, Head Of Safford Vly January-May86 104 117 85 150 187
March-May47 65 78 88 111 148
San Carlos Res, Coolidge Dam, At January-May77 91 104 109 138 184
March-May27 41 54 102 88 134
San Francisco
Glenwood, Nr January-May10.7 12.9 14.6 70 19.8 26
March-May5.1 7.3 9 59 14.2 20
Clifton January-May31 37 45 74 58 79
March-May14.1 20 28 74 41 62


Little Colorado Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
70%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Median
30%
Exceedance
Volume
10%
Exceedance
Volume
Little Colorado
Lyman Lk, Abv, St. Johns, Nr January-June2.9 3.4 3.9 55 5.3 7
March-June2.4 2.9 3.4 57 4.8 6.5
Zuni
Black Rock Res, Abv January-May0.25 0.3 0.36 77 0.65 1.1
March-May0.19 0.24 0.3 130 0.59 1
Chevelon Ck
Winslow, Nr, Wildcat Cyn, Blo January-May29 34 38 273 46 62
March-May10.9 16.2 20 144 28 44

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)

EOM
Contents
Percent
EOM
Average
Percent
Usable
Capacity
Last Year
EOM
Last Year
%Average
EOM
Average
Usable
Capacity
Salt
Roosevelt 832.9 87 50 946.0 99 953.2 1653.0
Horse Mesa 237.8 103 97 231.1 100 231.1 245.1
Mormon Flat 53.6 99 93 55.5 102 54.3 57.9
Stewart Mountain 65.6 104 94 64.4 102 63.0 69.8
Horseshoe 99.6 208 91 12.4 26 47.8 109.2
Bartlett 147.1 122 83 85.5 71 120.3 178.2
untitled
TOTAL 1436.8 98 62 1395.0 95 1469.7 2313.2
Bill Williams
Alamo 120.8 76 12 108.9 69 158.3 1045.0
Agua Fria
Lake Pleasant 779.0 106 90 722.0 98 734.3 869.9
Gila
San Carlos 71.7 18 8 68.7 17 404.1 875.0
Colorado
Lake Powell 9277.9 54 38 13345.8 78 17054.6 24322.0
Lake Mead 10670.5 52 41 10707.3 52 20575.4 26120.0
untitled
TOTAL 20919.8 54 39 24952.7 64 38926.8 53231.9

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