Great Basin Water Supply Outlook, February 1, 2019

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-July80 97 113 101 124 153
Woodruff Narrows Rsvr, Abv April-July60 85 103 85 120 180
Montpelier, Nr, Stewart Dam, Blo * April-July53 68 89 49 140 250
Smiths Fork
Border, Nr April-July55 62 73 82 84 105
Logan
Logan, Nr, State Dam, Abv April-July66 82 95 86 106 138
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July24 31 41 95 53 65
Little Bear
Paradise April-July13.7 22 32 68 47 60

*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-July68 87 104 88 120 154
Rockport Res, Wanship, Nr April-July64 91 113 86 129 179
Coalville, Nr April-July62 89 114 85 131 186
Chalk Ck
Coalville April-July15.5 24 30 73 40 60
Weber
Echo Res, Echo, At April-July76 107 138 81 175 245
Lost Ck
Lost Ck Res, Croydon, Nr April-July5.5 8 12.3 92 14.2 18
East Canyon Ck
East Canyon Res, Morgan, Nr April-July13.1 19 25 93 31 34
Weber
Gateway April-July152 215 270 83 360 480
Sf Ogden
Huntsville, Nr April-July35 41 58 104 71 93
Ogden
Pineview Res, Ogden, Nr April-July55 84 110 97 149 190


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-July30 32 37 97 41 49
Big Cottonwood Ck
Salt Lake City, Nr April-July25 28 35 97 38 48
Mill Ck
Salt Lake City, Nr April-July3.3 4 5 78 5.8 7.2
Dell Fk
Little Dell Res April-July3.6 4.5 5.5 100 6.9 8.2
Lambs Ck
Salt Lake City, Nr April-July2.9 3.5 4.8 91 5.9 7.8
Parleys Ck
Salt Lake City, Nr April-July8.2 9.8 13 92 17.3 21
Emigration Ck
Salt Lake City, Nr April-July1.4 1.9 2.5 63 3.4 5.6
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July1 1.2 1.6 85 2 2.8
City Ck
Salt Lake City, Nr April-July5 5.9 6.6 86 8 9.8
S Willow Ck
Grantsville, Nr April-July2.1 2.3 2.6 84 3.1 3.8


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-July35 49 65 94 78 108
Provo
Woodland, Nr April-July77 85 103 103 118 149
Hailstone, Nr April-July82 95 113 103 128 163
Deer Ck Res April-July90 104 130 102 146 200
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July17.7 21 25 81 31 39
West Canyon Ck
Cedar Fort, Nr April-July0.89 1.4 1.8 101 2.1 3.6
Salt Ck
Nephi Powerplant Div, Blo April-July5.5 8.7 12.1 146 14.1 20
Jordan
Utah Lake, Provo, Nr April-July192 230 320 98 375 485

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 Res, Woodruff, Nr 20.7 72 37 57.3 198 28.9 55.8
untitled Bear River
Bear Lake, Nr Lifton 939.8 134 72 1130.7 161 703.9 1302.0
untitled Little Bear
Hyrum Reservoir 9.7 94 63 9.9 95 10.3 15.3
untitled Weber
Rockport Res, Wanship, Nr 27.0 78 49 54.4 158 34.5 55.2
Echo Res, Echo, At 22.5 49 30 51.4 111 46.3 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 14.4 133 64 18.4 170 10.8 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 28.4 84 57 39.8 118 33.8 49.5
untitled Sf Ogden
Causey Res 5.0 154 70 5.5 171 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 51.4 100 47 71.9 140 51.4 110.1
untitled Jordanelle Dam
194.5 80 61 257.9 106 243.6 320.3
untitled Provo
Deer Ck Res 112.1 102 75 139.4 127 110.1 149.7
untitled Dell Fk
Little Dell Res 14.2 -99 69 15.1 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 509.3 68 58 588.9 78 753.0 870.9
untitled
TOTAL 1934.8 95 64 2425.5 119 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