Great Basin Water Supply Outlook, February 1, 2017

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by B.Bernard
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-July129 144 160 143 177 195
Woodruff Narrows Rsvr, Abv April-July121 156 177 146 215 275
Montpelier, Nr, Stewart Dam, Blo * April-July295 360 410 225 480 625
Smiths Fork
Border, Nr April-July108 121 134 151 142 173
Logan
Logan, Nr, State Dam, Abv April-July143 160 172 155 185 215
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July65 73 83 193 95 112
Little Bear
Paradise April-July68 77 89 189 107 122

*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-July116 135 152 129 170 194
Rockport Res, Wanship, Nr April-July128 155 175 133 194 235
Coalville, Nr April-July129 157 181 135 200 245
Chalk Ck
Coalville April-July39 50 60 146 72 88
Weber
Echo Res, Echo, At April-July168 210 230 135 275 325
Lost Ck
Lost Ck Res, Croydon, Nr April-July15.1 19.6 23 172 27 34
East Canyon Ck
East Canyon Res, Morgan, Nr April-July23 31 37 137 43 51
Weber
Gateway April-July360 440 500 154 600 680
Sf Ogden
Huntsville, Nr April-July77 90 98 175 113 137
Ogden
Pineview Res, Ogden, Nr April-July179 210 230 204 260 310


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-July40 44 48 126 52 57
Big Cottonwood Ck
Salt Lake City, Nr April-July34 39 44 122 47 57
Mill Ck
Salt Lake City, Nr April-July4.7 5.7 6.6 103 7.5 8.7
Dell Fk
Little Dell Res April-July4.6 5.5 6.6 120 8.1 9
Parleys Ck
Salt Lake City, Nr April-July11.7 13.7 17.5 123 21 25
Emigration Ck
Salt Lake City, Nr April-July3.4 4.6 5.6 140 7.3 9.4
City Ck
Salt Lake City, Nr April-July5.8 7 7.9 103 9.5 11.1
S Willow Ck
Grantsville, Nr April-July2.5 3.1 3.5 113 4 4.9


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-July65 85 96 139 110 153
Provo
Woodland, Nr April-July117 138 148 148 164 186
Hailstone, Nr April-July134 152 164 149 188 210
Deer Ck Res April-July161 190 215 169 230 280
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July35 39 45 145 51 59
West Canyon Ck
Cedar Fort, Nr April-July1.2 1.7 2.1 119 2.5 4.9
Jordan
Utah Lake, Provo, Nr April-July375 450 520 160 580 700

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 50.0 173 90 41.1 142 28.9 55.8
untitled Bear River
Bear Lake, Nr Lifton 578.2 82 44 591.8 84 703.9 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 95 64 9.7 93 10.3 15.3
untitled Weber
Rockport Res, Wanship, Nr 31.6 92 57 36.3 105 34.5 55.2
Echo Res, Echo, At 30.7 66 42 29.5 64 46.3 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 15.1 139 67 11.1 102 10.8 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 25.3 75 51 23.2 69 33.8 49.5
untitled Sf Ogden
Causey Res 5.0 155 71 4.3 132 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 70.5 137 64 54.3 106 51.4 110.1
untitled Jordanelle Dam
188.9 78 59 175.4 72 243.6 320.3
untitled Provo
Deer Ck Res 131.8 120 88 119.5 109 110.1 149.7
untitled Dell Fk
Little Dell Res 12.7 -99 62 10.4 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 387.3 51 44 442.9 59 753.0 870.9
untitled
TOTAL 1524.3 75 50 1539.2 76 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: B.Bernard