Great Basin Water Supply Outlook, June 1, 2020

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 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-July90 95 97 87 99 106
June-July37 42 44 67 46 53
Woodruff Narrows Rsvr, Abv April-July61 69 72 60 74 80
June-July15 23 26 46 28 34
Montpelier, Nr, Stewart Dam, Blo * April-July100 117 120 66 125 140
June-July31 48 51 56 56 71
Smiths Fork
Border, Nr April-July70 75 79 89 82 87
June-July32 37 41 82 44 49
Logan
Logan, Nr, State Dam, Abv April-July85 90 93 84 95 102
June-July38 43 46 75 48 55
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July28 30 32 74 33 34
June-July7.7 9.7 11.4 70 12.7 13.7
Little Bear
Paradise April-July19.1 20 21 45 22 24
June-July0.77 1.7 2.7 23 3.7 5.2

*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-July80 87 91 77 96 102
June-July24 31 35 55 40 46
Rockport Res, Wanship, Nr April-July70 75 81 61 86 92
June-July18.4 23 29 45 34 40
Coalville, Nr April-July72 80 84 63 88 94
June-July17 25 29 46 33 39
Chalk Ck
Coalville April-July15 16 17.1 42 17.8 20
June-July1.9 2.9 4 25 4.7 7.4
Weber
Echo Reservoir, Echo, At April-July80 90 97 57 103 111
June-July13 23 30 40 36 44
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July6.5 6.9 7.2 54 7.8 8.1
June-July0.51 0.91 1.2 43 1.8 2.1
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July13.5 14.8 15.5 57 15.7 17.1
June-July1.4 2.7 3.4 40 3.6 5
Weber
Gateway April-July149 165 171 53 176 192
June-July18.6 35 41 37 46 62
Sf Ogden
Huntsville, Nr April-July32 34 36 64 37 40
June-July2.8 4.8 7.2 52 7.5 10.8
Ogden
Pineview Reservoir, Ogden, Nr April-July53 57 58 51 59 64
June-July1.4 5.4 6.6 29 7.6 12.2


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-July26 29 31 82 32 34
June-July12 15 16.8 70 17.9 19.8
Big Cottonwood Ck
Salt Lake City, Nr April-July19.2 21 23 64 25 27
June-July7.2 8.6 10.7 56 13 15
Mill Ck
Salt Lake City, Nr April-July2.8 3.1 3.5 55 3.8 4.4
June-July0.85 1.2 1.6 48 1.9 2.5
Dell Fk
Little Dell Reservoir April-July2.8 3 3.1 56 3.4 3.5
June-July0.15 0.3 0.49 37 0.7 0.85
Lambs Ck
Salt Lake City, Nr April-July2.4 2.6 2.7 51 2.9 3.1
June-July0.65 0.8 0.9 39 1.2 1.3
Parleys Ck
Salt Lake City, Nr April-July6.7 6.9 7.1 50 7.2 7.7
June-July1.5 1.7 1.8 39 2 2.5
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.6 0.65 0.7 37 0.73 0.78
June-July0.12 0.17 0.22 39 0.25 0.3
City Ck
Salt Lake City, Nr April-July3.1 3.4 3.6 47 4 4.4
June-July1.1 1.4 1.6 45 2 2.4
S Willow Ck
Grantsville, Nr April-July1.1 1.4 1.5 50 1.8 2.1
June-July0.3 0.59 0.7 42 0.92 1.3


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-July26 28 29 42 31 32
June-July6 7.5 9.2 38 10.6 12
Provo
Woodland, Nr April-July83 85 89 89 92 98
June-July25 27 31 66 34 40
Hailstone, Nr April-July85 89 92 84 94 100
June-July27 31 34 65 36 42
Deer Ck Reservoir April-July79 85 92 72 100 109
June-July18 24 31 56 39 48
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July11.8 13.1 14.4 46 16 18.2
June-July5.3 6.6 7.9 44 9.5 11.7
West Canyon Ck
Cedar Fort, Nr April-July0.58 0.63 0.66 38 0.71 0.75
June-July0.03 0.08 0.11 13.4 0.16 0.2
Salt Ck
Nephi Powerplant Div, Blo April-July3 3.2 3.5 42 4.1 4.6
June-July0.61 0.85 1.1 36 1.8 2.3
Jordan
Utah Lake, Provo, Nr April-July180 195 215 66 220 230
June-July18.9 34 54 43 61 69

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 46.7 99 84 49.9 106 47.1 55.8
untitled Bear River
Bear Lake, Nr Lifton 1122.4 135 86 1109.9 134 829.8 1302.0
untitled Little Bear
Hyrum Reservoir 14.6 100 96 14.1 96 14.6 15.3
untitled Weber
Rockport Res, Wanship, Nr 54.7 108 99 45.9 90 50.8 55.2
Echo Reservoir, Echo, At 65.4 98 88 66.2 99 67.0 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 22.6 130 100 23.0 132 17.4 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 49.0 107 99 49.9 109 45.8 49.5
untitled Sf Ogden
Causey Reservoir 7.1 101 100 7.1 102 7.0 7.1
untitled Ogden
Pineview Res, Ogden, Nr 100.9 103 92 110.9 113 97.9 110.1
untitled Provo
Jordanelle Reservoir 309.9 107 97 273.3 94 290.9 320.3
Deer Ck Reservoir 146.5 110 98 146.5 110 133.8 149.7
untitled Dell Fk
Little Dell Reservoir 16.5 -99 81 16.2 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 841.3 100 97 762.5 90 844.2 870.9
untitled
TOTAL 2780.9 114 92 2659.3 109 2446.2 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 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