Great Basin Water Supply Outlook, February 1, 2023

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Patrick Kormos
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Great Basin Summary






*Median of forecasts within each basin.


Bear Basin Conditions




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

Weber Basin Conditions




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

Six Creeks Basin Conditions




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

Utah Lake Basin Conditions




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


Bear Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Bear
Utah April-July102 108 128 117 143 164
Woodruff Narrows Rsvr, Abv April-July88 103 127 118 161 198
Stewart Dam * April-July117 140 168 104 245 315
Smiths Fork
Border, Nr April-July70 77 94 107 104 122
Logan
Logan, Nr, State Dam, Abv April-July74 88 118 111 125 158
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July35 40 49 132 61 77
Little Bear
Paradise April-July34 44 53 136 77 88

*Regulated Forecast, i.e. Observed flow uncorrected for upstream diversion.

Weber Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Weber
Oakley, Nr April-July96 101 124 112 140 170
Rockport Res, Wanship, Nr April-July102 109 135 117 166 205
Coalville, Nr April-July103 109 138 116 171 215
Chalk Ck
Coalville April-July27 34 42 120 57 75
Weber
Echo Reservoir, Echo, At April-July133 145 176 116 225 290
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July10.4 13.6 15.6 122 19.1 25
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July22 32 35 152 46 54
Weber
Gateway April-July250 310 375 136 475 610
Sf Ogden
Huntsville, Nr April-July51 69 78 150 95 117
Ogden
Pineview Reservoir, Ogden, Nr April-July107 122 148 136 195 235


Six Creeks Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Little Cottonwood Ck
Salt Lake City, Nr April-July39 41 46 135 50 58
Big Cottonwood Ck
Salt Lake City, Nr April-July38 42 49 144 51 63
Mill Ck
Salt Lake City, Nr April-July5.9 7.1 8.1 156 9.1 10.5
Dell Fk
Little Dell Reservoir April-July4.9 6.1 6.9 157 8.6 10.1
Lambs Ck
Salt Lake City, Nr April-July5.7 6.9 8.3 193 9.8 11.4
Parleys Ck
Salt Lake City, Nr April-July13.4 17 19.6 170 25 29
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July1.8 2.1 2.4 154 2.9 3.4
City Ck
Salt Lake City, Nr April-July6.4 7.5 8 123 9.4 11
S Willow Ck
Grantsville, Nr April-July0 0 0 0 0 0


Utah Lake Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Spanish Fork
Castilla, Nr April-July47 61 77 143 94 130
Provo
Woodland, Nr April-July95 109 122 127 144 173
Hailstone, Nr April-July105 119 135 127 159 194
Deer Ck Reservoir April-July118 148 171 144 205 270
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July27 36 40 160 44 60
West Canyon Ck
Cedar Fort, Nr April-July1.3 1.9 2.3 132 3.3 6.3
Salt Ck
Nephi Powerplant Div, Blo April-July9.5 14 18.5 237 22 34
Jordan
Utah Lake, Provo, Nr April-July235 330 395 184 475 645

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).

Great Basin End of Month Reservoir Contents (kaf)

EOM
Contents		Percent
EOM
Average		Percent
Usable
Capacity		Last Year
EOM		Last Year
%Average		EOM
Average		Usable
Capacity
untitled Bear
Woodruff Narrows Reservoir, Woodruff, Nr 15.3 53 27 13.5 47 28.9 55.8
untitled Bear River
Bear Lake, Nr Lifton 515.5 73 40 665.1 94 703.9 1302.0
untitled Little Bear
Hyrum Reservoir 9.6 94 63 10.7 104 10.3 15.3
untitled Weber
Rockport Res, Wanship, Nr 43.3 120 79 29.2 81 36.1 55.2
Echo Reservoir, Echo, At 46.6 109 63 23.5 55 42.6 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 9.5 79 42 9.7 80 12.0 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 29.2 88 59 26.6 80 33.3 49.5
untitled Sf Ogden
Causey Reservoir 4.1 103 58 4.3 109 4.0 7.1
untitled Ogden
Pineview Res, Ogden, Nr 46.2 87 42 26.1 49 53.4 110.1
untitled Provo
Jordanelle Reservoir 186.1 86 58 156.7 72 217.6 320.3
Deer Ck Reservoir 84.3 74 56 115.1 101 114.4 149.7
untitled Dell Fk
Little Dell Reservoir 12.9 -99 63 9.4 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 452.6 60 52 508.4 68 753.0 870.9
untitled
TOTAL 1442.4 72 48 1588.9 79 2009.4 3052.8

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 1991-2020 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: Patrick Kormos