Great Basin Water Supply Outlook, January 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-July78 102 116 104 135 166
Woodruff Narrows Rsvr, Abv April-July62 95 108 89 132 190
Montpelier, Nr, Stewart Dam, Blo * April-July83 124 158 87 210 305
Smiths Fork
Border, Nr April-July51 63 79 89 93 115
Logan
Logan, Nr, State Dam, Abv April-July71 85 104 94 126 154
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July26 34 43 100 53 76
Little Bear
Paradise April-July15.4 24 39 83 46 73

*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-July64 84 102 86 124 161
Rockport Res, Wanship, Nr April-July58 82 103 78 134 186
Coalville, Nr April-July56 82 104 78 138 195
Chalk Ck
Coalville April-July12.4 19.5 32 78 41 61
Weber
Echo Reservoir, Echo, At April-July66 105 135 79 176 265
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July4.6 9.1 11.5 86 13.7 19
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July13.5 19.3 25 93 35 45
Weber
Gateway April-July115 170 260 80 345 475
Sf Ogden
Huntsville, Nr April-July28 42 59 105 66 94
Ogden
Pineview Reservoir, Ogden, Nr April-July45 72 104 92 141 190


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-July26 32 36 95 43 50
Big Cottonwood Ck
Salt Lake City, Nr April-July23 29 34 94 42 54
Mill Ck
Salt Lake City, Nr April-July3 4.4 5.5 86 6.8 8.7
Dell Fk
Little Dell Reservoir April-July2.5 3.8 5.1 93 7.2 8.6
Lambs Ck
Salt Lake City, Nr April-July2.3 3.4 5 94 6.5 8.4
Parleys Ck
Salt Lake City, Nr April-July6 8.9 12.5 88 18 22
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.63 1.1 1.4 73 2.1 2.9
City Ck
Salt Lake City, Nr April-July4 5.1 6.2 81 8.2 9.6
S Willow Ck
Grantsville, Nr April-July2 2.3 2.6 84 3.5 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-July29 39 51 74 68 95
Provo
Woodland, Nr April-July61 83 97 97 118 142
Hailstone, Nr April-July75 98 107 97 138 168
Deer Ck Reservoir April-July79 107 127 100 162 205
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July15.4 19.9 25 81 31 43
West Canyon Ck
Cedar Fort, Nr April-July0.86 1.3 1.6 90 2.2 4.4
Salt Ck
Nephi Powerplant Div, Blo April-July3.5 5.8 7.6 92 10 20
Jordan
Utah Lake, Provo, Nr April-July160 210 290 89 380 490

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 47.8 165 86 20.0 69 28.9 55.8
untitled Bear River
Bear Lake, Nr Lifton 1028.6 147 79 928.2 133 698.8 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 97 64 9.7 96 10.1 15.3
untitled Weber
Rockport Res, Wanship, Nr 46.9 135 85 25.2 72 34.8 55.2
Echo Reservoir, Echo, At 48.9 111 66 19.1 43 44.3 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 17.0 156 76 14.2 130 10.9 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 39.7 119 80 27.2 82 33.3 49.5
untitled Sf Ogden
Causey Reservoir 5.0 161 71 4.3 137 3.1 7.1
untitled Ogden
Pineview Res, Ogden, Nr 69.3 132 63 48.3 92 52.5 110.1
untitled Provo
Jordanelle Reservoir 267.3 109 83 196.9 80 245.9 320.3
Deer Ck Reservoir 137.7 130 92 104.7 99 105.5 149.7
untitled Dell Fk
Little Dell Reservoir 15.4 -99 75 14.0 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 780.8 108 90 468.9 65 720.9 870.9
untitled
TOTAL 2498.9 126 82 1866.4 94 1988.9 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