Great Basin Water Supply Outlook, February 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-July91 104 121 108 132 167
Woodruff Narrows Rsvr, Abv April-July74 94 112 93 130 199
Montpelier, Nr, Stewart Dam, Blo * April-July137 157 173 95 225 335
Smiths Fork
Border, Nr April-July68 76 87 98 99 122
Logan
Logan, Nr, State Dam, Abv April-July89 98 112 101 122 156
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July32 37 45 105 57 75
Little Bear
Paradise April-July23 28 40 85 51 70

*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-July79 91 108 92 125 160
Rockport Res, Wanship, Nr April-July77 92 113 86 132 183
Coalville, Nr April-July77 94 115 86 136 191
Chalk Ck
Coalville April-July15 20 32 78 38 57
Weber
Echo Reservoir, Echo, At April-July92 108 142 83 177 250
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July6.2 9 11 82 13 18.8
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July18.2 24 29 107 38 44
Weber
Gateway April-July156 210 260 80 350 475
Sf Ogden
Huntsville, Nr April-July37 46 56 100 69 93
Ogden
Pineview Reservoir, Ogden, Nr April-July65 79 102 90 143 186


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-July32 34 39 103 43 51
Big Cottonwood Ck
Salt Lake City, Nr April-July28 31 37 103 41 52
Mill Ck
Salt Lake City, Nr April-July4.3 5 6.1 95 7 8.5
Dell Fk
Little Dell Reservoir April-July3.6 4.6 5.6 102 7 8.4
Lambs Ck
Salt Lake City, Nr April-July3.4 4.1 5.4 102 6.6 8.6
Parleys Ck
Salt Lake City, Nr April-July8.8 10.5 13.9 98 18.1 22
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July1 1.2 1.7 88 2.1 2.9
City Ck
Salt Lake City, Nr April-July5.2 6.1 6.8 88 8.2 10.1
S Willow Ck
Grantsville, Nr April-July2.2 2.5 2.7 87 3.4 4.2


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-July32 40 47 68 58 83
Provo
Woodland, Nr April-July75 84 100 100 117 148
Hailstone, Nr April-July80 92 109 99 126 162
Deer Ck Reservoir April-July86 100 126 99 142 190
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July16.4 19.6 23 74 29 37
West Canyon Ck
Cedar Fort, Nr April-July0.96 1.5 1.8 104 2.2 4.5
Salt Ck
Nephi Powerplant Div, Blo April-July3.8 5.5 7.2 87 9.1 18.7
Jordan
Utah Lake, Provo, Nr April-July179 205 270 83 310 435

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 50.3 174 90 20.7 72 28.9 55.8
untitled Bear River
Bear Lake, Nr Lifton 1031.4 147 79 939.8 134 703.9 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 95 64 9.7 94 10.3 15.3
untitled Weber
Rockport Res, Wanship, Nr 49.0 142 89 27.0 78 34.5 55.2
Echo Reservoir, Echo, At 52.9 114 72 22.5 49 46.3 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 17.2 159 77 14.4 133 10.8 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 41.1 122 83 28.4 84 33.8 49.5
untitled Sf Ogden
Causey Reservoir 5.8 178 81 5.0 154 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 70.1 137 64 51.4 100 51.4 110.1
untitled Provo
Jordanelle Reservoir 266.6 109 83 194.5 80 243.6 320.3
Deer Ck Reservoir 143.7 131 96 112.1 102 110.1 149.7
untitled Dell Fk
Little Dell Reservoir 14.9 -99 73 14.2 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 817.9 109 94 509.3 68 753.0 870.9
untitled
TOTAL 2555.8 126 84 1934.7 95 2029.8 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