Great Basin Water Supply Outlook, June 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-July126 138 140 125 145 152
June-July83 95 97 147 102 109
Woodruff Narrows Rsvr, Abv April-July127 142 146 121 150 158
June-July60 75 79 139 83 91
Montpelier, Nr, Stewart Dam, Blo * April-July137 160 163 90 169 200
June-July51 74 77 85 83 114
Smiths Fork
Border, Nr April-July77 83 84 94 87 92
June-July44 50 51 102 54 59
Logan
Logan, Nr, State Dam, Abv April-July103 113 117 105 119 130
June-July57 67 71 116 73 84
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July49 54 56 130 55 59
June-July18 23 25 154 24 28
Little Bear
Paradise April-July56 59 62 132 62 66
June-July12.2 14.8 17.5 151 17.8 22

*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-July121 128 132 112 140 154
June-July75 82 86 134 94 108
Rockport Res, Wanship, Nr April-July138 148 153 116 163 181
June-July73 83 88 138 98 116
Coalville, Nr April-July147 158 161 120 172 190
June-July73 84 87 138 98 116
Chalk Ck
Coalville April-July47 50 51 124 55 60
June-July18.8 22 23 146 27 32
Weber
Echo Reservoir, Echo, At April-July190 200 205 120 225 245
June-July90 100 106 141 124 147
Lost Ck
Lost Ck Reservoir, Croyden, Nr April-July16.8 17.6 17.7 132 18.6 19.8
June-July2 2.8 2.9 100 3.8 5
East Canyon Ck
East Canyon Reservoir, Morgan, Nr April-July34 35 36 133 38 40
June-July7.9 9.2 10.5 125 11.9 14.3
Weber
Gateway April-July410 430 440 135 465 485
June-July135 155 162 147 188 210
Sf Ogden
Huntsville, Nr April-July71 78 81 145 85 86
June-July12 19 22 158 26 27
Ogden
Pineview Reservoir, Ogden, Nr April-July168 176 177 157 185 195
June-July30 38 39 170 47 57


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-July45 49 51 134 54 56
June-July32 36 38 158 41 43
Big Cottonwood Ck
Salt Lake City, Nr April-July38 42 45 125 47 49
June-July22 26 29 151 31 33
Mill Ck
Salt Lake City, Nr April-July5.4 5.9 6.5 102 7 7.3
June-July2.6 3.1 3.7 112 4.2 4.5
Dell Fk
Little Dell Reservoir April-July5 5.4 6 109 6.2 6.5
June-July0.5 0.9 1.5 112 1.7 2
Lambs Ck
Salt Lake City, Nr April-July6.5 6.9 7.2 136 7.5 8.2
June-July2.2 2.6 2.9 126 3.2 3.9
Parleys Ck
Salt Lake City, Nr April-July15.1 17.4 19.3 136 21 23
June-July1.6 3.8 5.7 121 7.2 9
Emigration Ck
Salt Lake City, Nr April-July3.2 3.6 4.1 103 4.6 5.1
June-July0.5 0.9 1.4 123 1.9 2.4
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July1.7 1.9 2.1 111 2.2 2.4
June-July0.2 0.4 0.54 0 0.65 0.85
City Ck
Salt Lake City, Nr April-July7.6 8.3 8.8 114 9.4 10.2
June-July3.6 4.3 4.8 133 5.4 6.2
S Willow Ck
Grantsville, Nr April-July3 3.4 3.8 123 4 4.5
June-July1.1 1.5 1.9 113 2.1 2.6


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-July106 119 126 183 133 142
June-July27 40 47 196 54 63
Provo
Woodland, Nr April-July116 126 138 138 144 151
June-July65 75 87 185 93 100
Hailstone, Nr April-July135 145 154 140 161 169
June-July70 80 89 171 96 104
Deer Ck Reservoir April-July167 178 188 148 198 210
June-July84 95 105 191 115 125
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July38 43 46 148 48 50
June-July25 30 33 182 35 37
West Canyon Ck
Cedar Fort, Nr April-July3 3.3 3.5 199 3.7 4
June-July1.6 1.9 2.1 256 2.3 2.6
Salt Ck
Nephi Powerplant Div, Blo April-July15.5 18.5 20 241 22 24
June-July6 9 10.5 339 12.5 14.5
Jordan
Utah Lake, Provo, Nr April-July510 580 610 188 635 680
June-July160 230 260 205 285 330

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 49.9 106 90 51.0 108 47.1 55.8
untitled Bear River
Bear Lake, Nr Lifton 1109.9 134 85 1192.9 144 829.8 1302.0
untitled Little Bear
Hyrum Reservoir 14.1 96 92 14.5 99 14.6 15.3
untitled Weber
Rockport Res, Wanship, Nr 45.9 90 83 54.7 108 50.8 55.2
Echo Reservoir, Echo, At 66.2 99 90 70.5 105 67.0 73.9
untitled Lost Ck
Lost Ck Reservoir, Croyden, Nr 23.0 132 102 21.6 124 17.4 22.5
untitled East Canyon Ck
East Canyon Reservoir, Morgan, Nr 49.9 109 101 48.3 106 45.8 49.5
untitled Sf Ogden
Causey Reservoir 7.1 102 101 7.0 100 7.0 7.1
untitled Ogden
Pineview Res, Ogden, Nr 110.9 113 101 107.5 110 97.9 110.1
untitled Provo
Jordanelle Reservoir 273.3 94 85 314.4 108 290.9 320.3
Deer Ck Reservoir 146.5 110 98 140.0 105 133.8 149.7
untitled Dell Fk
Little Dell Reservoir 16.2 -99 79 16.2 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 762.5 90 88 638.4 76 844.2 870.9
untitled
TOTAL 2659.3 109 88 2660.7 109 2446.2 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