Great Basin Water Supply Outlook, March 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-July97 112 122 109 143 159
Woodruff Narrows Rsvr, Abv April-July85 104 121 100 143 189
Montpelier, Nr, Stewart Dam, Blo * April-July76 99 114 63 174 275
Smiths Fork
Border, Nr April-July57 61 76 85 81 96
Logan
Logan, Nr, State Dam, Abv April-July82 92 101 91 116 138
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July33 40 47 109 62 69
Little Bear
Paradise April-July25 39 45 96 59 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-July87 95 122 103 138 156
Rockport Res, Wanship, Nr April-July91 102 136 103 161 184
Coalville, Nr April-July89 102 141 105 168 192
Chalk Ck
Coalville April-July24 36 45 110 61 80
Weber
Echo Res, Echo, At April-July107 137 178 104 230 275
Lost Ck
Lost Ck Res, Croydon, Nr April-July8 10.7 14.3 107 17.7 19.9
East Canyon Ck
East Canyon Res, Morgan, Nr April-July19 25 33 122 42 49
Weber
Gateway April-July215 260 325 100 455 540
Sf Ogden
Huntsville, Nr April-July49 64 78 139 93 104
Ogden
Pineview Res, Ogden, Nr April-July98 117 148 131 184 210


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-July35 39 46 121 48 52
Big Cottonwood Ck
Salt Lake City, Nr April-July30 37 42 117 47 53
Mill Ck
Salt Lake City, Nr April-July4.1 4.9 6.3 98 7 8
Dell Fk
Little Dell Res April-July4 5.1 6.7 122 7.4 9.1
Lambs Ck
Salt Lake City, Nr April-July3.7 4.7 6.3 119 7 8.4
Parleys Ck
Salt Lake City, Nr April-July9.9 12.4 17.4 123 19.3 23
Emigration Ck
Salt Lake City, Nr April-July1.7 2.4 3.8 95 4.5 6.2
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July1.1 1.5 1.9 99 2.3 2.8
City Ck
Salt Lake City, Nr April-July5.1 6.1 7.2 94 8 9.4
S Willow Ck
Grantsville, Nr April-July2 2.3 3.1 100 3.4 3.9


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-July52 70 90 130 102 120
Provo
Woodland, Nr April-July88 108 119 119 130 145
Hailstone, Nr April-July98 115 130 118 143 161
Deer Ck Res April-July117 138 160 126 174 195
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July27 33 38 123 42 46
West Canyon Ck
Cedar Fort, Nr April-July0.85 1.5 2.3 131 3.5 5
Salt Ck
Nephi Powerplant Div, Blo April-July8.7 12.8 17.6 212 20 27
Jordan
Utah Lake, Provo, Nr April-July255 340 400 123 460 530

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 22.0 70 39 57.7 183 31.4 55.8
untitled Bear River
Bear Lake, Nr Lifton 952.2 134 73 1109.9 156 713.0 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 88 64 11.9 106 11.2 15.3
untitled Weber
Rockport Res, Wanship, Nr 29.5 85 53 55.1 158 34.8 55.2
Echo Res, Echo, At 26.5 55 36 56.7 118 47.9 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 14.7 137 65 18.8 175 10.7 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 29.8 88 60 41.2 121 34.0 49.5
untitled Sf Ogden
Causey Res 5.6 174 79 6.0 187 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 55.6 105 50 76.2 144 53.0 110.1
untitled Jordanelle Dam
193.8 80 61 256.2 106 241.2 320.3
untitled Provo
Deer Ck Res 120.5 106 81 145.1 127 113.9 149.7
untitled Dell Fk
Little Dell Res 14.4 -99 70 15.2 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 549.6 70 63 614.0 78 784.7 870.9
untitled
TOTAL 2009.5 97 66 2448.8 118 2079.1 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