Great Salt Lake Water Supply Outlook, June 1, 2021

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

Contents

Great Salt Lake 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-July42 48 55 49 56 63
June-July14 20 27 41 28 35
Woodruff Narrows Rsvr, Abv April-July16.8 26 28 23 29 36
June-July0.8 10.4 12.4 22 13.2 20
Montpelier, Nr, Stewart Dam, Blo * April-July16 19.1 21 12 23 33
June-July8.1 11.2 13.1 14 15.1 25
Smiths Fork
Border, Nr April-July34 40 44 49 46 54
June-July15 21 25 50 27 35
Logan
Logan, Nr, State Dam, Abv April-July36 40 43 39 44 48
June-July13 17 20 33 21 25
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July11.4 13.9 15.5 36 16.4 19.4
June-July3 5.5 7.1 44 8 11
Little Bear
Paradise April-July4.5 4.7 4.8 10 5.5 7.3
June-July0.1 0.3 0.43 4 1.1 2.9

*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-July40 45 46 39 49 55
June-July12.3 17.5 18.4 29 21 27
Rockport Res, Wanship, Nr April-July30 34 35 27 39 43
June-July6.4 10.5 11.4 18 15.4 19.2
Coalville, Nr April-July30 34 35 26 36 43
June-July4.2 8.5 9.2 15 10.4 17.2
Chalk Ck
Coalville April-July5 5.7 6.1 15 6.5 8
June-July1.2 1.9 2.3 15 2.7 4.2
Weber
Echo Reservoir, Echo, At April-July32 37 40 23 43 49
June-July3.6 8.6 11.6 15 14.6 21
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July2.9 3.1 3.2 24 3.3 4
June-July0.28 0.48 0.59 20 0.68 1.4
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July8 8.7 9.1 34 9.5 11.2
June-July1.4 2.1 2.5 30 2.9 4.6
Weber
Gateway April-July56 57 58 18 65 90
June-July6 7 8.4 8 15 40
Sf Ogden
Huntsville, Nr April-July11 13.9 14.2 25 15 18
June-July1.2 4 4.3 31 5.1 8.1
Ogden
Pineview Reservoir, Ogden, Nr April-July17.5 18.3 18.7 17 21 27
June-July2 2.8 3.2 14 5.5 11.5


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-July15.6 17.2 18.3 48 19.8 22
June-July7 8.6 9.7 40 11.2 13.8
Big Cottonwood Ck
Salt Lake City, Nr April-July12.1 13 13.9 39 15.5 17.1
June-July4 4.9 5.8 30 7.4 9
Mill Ck
Salt Lake City, Nr April-July1.3 1.6 1.9 29 2.2 2.6
June-July0.2 0.5 0.77 23 1.1 1.5
Dell Fk
Little Dell Reservoir April-July0.93 1 1.2 21 1.5 1.9
June-July0.07 0.18 0.29 22 0.65 1
Lambs Ck
Salt Lake City, Nr April-July0.72 0.89 0.99 19 1.2 1.6
June-July0.1 0.27 0.37 16 0.6 1
Parleys Ck
Salt Lake City, Nr April-July2.5 2.8 2.9 20 2.9 4
June-July0.5 0.75 0.94 20 0.94 2
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.27 0.33 0.37 19 0.41 0.62
June-July0.05 0.11 0.15 26 0.19 0.4
City Ck
Salt Lake City, Nr April-July1.4 1.8 2 26 2.4 3.1
June-July0.3 0.7 0.92 26 1.3 2
S Willow Ck
Grantsville, Nr April-July0.96 1.1 1.3 42 1.5 1.7
June-July0.2 0.35 0.55 33 0.71 0.9


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-July10 11.5 12.7 18 13.5 15.7
June-July2.5 4 5.2 22 6 8.2
Provo
Woodland, Nr April-July30 32 34 34 37 44
June-July8.5 10.5 12.5 27 15.5 22
Hailstone, Nr April-July30 32 35 32 37 44
June-July8.6 10.6 14 27 15.2 23
Deer Ck Reservoir April-July30 33 35 28 37 42
June-July6.3 9.3 10.9 20 13.3 18.3
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July5.9 7 7.5 24 8.2 9.8
June-July2.5 3.6 4.1 23 4.8 6.4
West Canyon Ck
Cedar Fort, Nr April-July0.05 0.06 0.07 4 0.08 0.13
June-July0.04 0.05 0.06 7 0.07 0.12
Salt Ck
Nephi Powerplant Div, Blo April-July1.2 1.4 1.8 21 2.2 3
June-July0.22 0.38 0.73 24 1.2 2
Jordan
Utah Lake, Provo, Nr April-July77 85 89 27 98 108
June-July14.7 23 27 21 36 46

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 Salt Lake 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 14.3 30 26 46.7 99 47.1 55.8
untitled Bear River
Bear Lake, Nr Lifton 923.4 111 71 1122.4 135 829.8 1302.0
untitled Little Bear
Hyrum Reservoir 13.3 91 87 14.6 100 14.6 15.3
untitled Weber
Rockport Res, Wanship, Nr 33.5 66 61 54.7 108 50.8 55.2
Echo Reservoir, Echo, At 33.1 49 45 65.4 98 67.0 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 15.7 90 70 22.6 130 17.4 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 36.9 81 75 49.0 107 45.8 49.5
untitled Sf Ogden
Causey Reservoir 7.0 101 100 7.1 101 7.0 7.1
untitled Ogden
Pineview Res, Ogden, Nr 60.2 61 55 100.9 103 97.9 110.1
untitled Provo
Jordanelle Reservoir 228.6 79 71 309.9 107 290.9 320.3
Deer Ck Reservoir 119.9 90 80 146.5 110 133.8 149.7
untitled Dell Fk
Little Dell Reservoir 12.2 -99 60 16.5 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr -9999.0 -99 -99 841.3 100 844.2 870.9
untitled
TOTAL 1486.0 93 69 2780.9 114 1602.0 2181.9

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: Brent.Bernard, Patrick Kormos