New 1991-2020 Averages being used this year.
Great Basin Water Supply Outlook, May 1, 2022

Great Basin Water Supply Outlook, May 1, 2022

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-July78 84 94 86 101 110
May-July71 77 87 86 94 103
Woodruff Narrows Rsvr, Abv April-July61 67 78 72 85 102
May-July51 57 68 73 75 92
Stewart Dam * April-July44 52 59 37 80 107
May-July30 38 45 36 66 93
Smiths Fork
Border, Nr April-July45 54 59 67 64 68
May-July39 48 53 67 58 62
Logan
Logan, Nr, State Dam, Abv April-July47 55 61 58 65 72
May-July39 47 53 58 57 64
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July14.8 17 18.9 51 21 24
May-July9.2 11.4 13.3 49 15.4 18.3
Little Bear
Paradise April-July9.1 10.5 12.1 31 16.9 20
May-July4.5 5.9 7.5 29 12.3 15.4

*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-July69 77 84 76 93 102
May-July59 67 74 74 83 92
Rockport Res, Wanship, Nr April-July66 73 81 70 91 106
May-July53 60 68 68 78 93
Coalville, Nr April-July64 70 78 66 88 107
May-July50 56 64 63 74 93
Chalk Ck
Coalville April-July15.8 17.1 21 60 24 31
May-July12.2 13.5 17.3 60 20 27
Weber
Echo Reservoir, Echo, At April-July78 85 97 64 109 134
May-July60 67 79 62 91 116
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July4.3 5 6.2 48 6.9 8
May-July2.1 2.8 4 44 4.7 5.8
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July8.8 10 11 48 12 15.9
May-July4.4 5.6 6.6 42 7.6 11.5
Weber
Gateway April-July95 119 133 48 154 196
May-July53 77 91 43 112 154
Sf Ogden
Huntsville, Nr April-July19.1 25 27 52 32 38
May-July9.8 15.9 17.7 49 23 29
Ogden
Pineview Reservoir, Ogden, Nr April-July26 31 36 33 53 59
May-July10.7 11.4 20 29 33 43


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-July19.7 22 23 68 25 29
May-July18.1 20 21 66 23 27
Big Cottonwood Ck
Salt Lake City, Nr April-July19 22 23 68 25 29
May-July16.5 19.7 21 72 23 27
Mill Ck
Salt Lake City, Nr April-July2.9 3.5 3.6 69 4.2 4.9
May-July2.5 3.1 3.2 73 3.8 4.5
Dell Fk
Little Dell Reservoir April-July1.7 2.2 2.3 52 2.7 3.5
May-July0.95 1.5 1.6 41 2 2.8
Lambs Ck
Salt Lake City, Nr April-July1.7 2.5 2.8 65 3.3 4.1
May-July1.2 2 2.3 55 2.8 3.6
Parleys Ck
Salt Lake City, Nr April-July4.3 5.9 6.1 53 7.1 8.9
May-July2.8 4.4 4.6 43 5.6 7.4
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.43 0.5 0.54 35 0.7 1
May-July0.2 0.27 0.31 29 0.47 0.78
City Ck
Salt Lake City, Nr April-July3 3.5 3.6 55 4 5
May-July2.5 3 3.1 56 3.5 4.5
S Willow Ck
Grantsville, Nr April-July0.8 0.95 1 34 1.2 1.5
May-July0.63 0.78 0.86 33 1 1.4


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-July17 20 23 43 25 29
May-July11 14.1 17 40 19 23
Provo
Woodland, Nr April-July66 74 81 84 87 96
May-July55 63 70 82 76 85
Hailstone, Nr April-July70 77 84 79 90 99
May-July58 65 72 77 78 87
Deer Ck Reservoir April-July67 75 83 70 92 111
May-July53 61 69 70 78 97
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July11 12.6 13.1 52 15.2 17.3
May-July10 11.6 12.1 55 14.2 16.3
West Canyon Ck
Cedar Fort, Nr April-July0 0.08 0.09 5 0.15 0.26
May-July0 0.08 0.09 6 0.15 0.26
Salt Ck
Nephi Powerplant Div, Blo April-July2.8 3.2 3.6 46 4 5
May-July2.1 2.5 2.9 47 3.3 4.3
Jordan
Utah Lake, Provo, Nr April-July115 124 136 63 154 182
May-July78 87 99 40 117 145

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 26.9 60 48 26.1 58 45.0 55.8
untitled Bear River
Bear Lake, Nr Lifton 727.3 94 56 952.1 124 770.8 1302.0
untitled Little Bear
Hyrum Reservoir 14.6 105 96 14.6 104 14.0 15.3
untitled Weber
Rockport Res, Wanship, Nr 49.2 118 89 39.8 96 41.6 55.2
Echo Reservoir, Echo, At 39.1 72 53 33.3 62 53.9 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 12.6 85 56 16.0 107 14.9 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 35.2 87 71 36.9 91 40.4 49.5
untitled Sf Ogden
Causey Reservoir 6.9 121 98 5.9 102 5.7 7.1
untitled Ogden
Pineview Res, Ogden, Nr 56.7 68 51 64.6 78 83.1 110.1
untitled Provo
Jordanelle Reservoir 164.1 74 51 211.3 96 220.6 320.3
Deer Ck Reservoir 132.7 104 89 131.7 103 127.3 149.7
untitled Dell Fk
Little Dell Reservoir 10.1 -99 49 11.6 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 531.0 64 61 663.9 80 827.8 870.9
untitled
TOTAL 1796.4 80 59 2196.1 98 2245.2 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