Great Basin Water Supply Outlook, June 1, 2018

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-July75 85 89 79 94 104
June-July22 32 36 55 41 51
Woodruff Narrows Rsvr, Abv April-July49 58 63 52 68 81
June-July5.3 14.3 19.3 34 24 37
Montpelier, Nr, Stewart Dam, Blo * April-July58 64 70 38 80 99
June-July2.8 8.6 14.4 15.8 25 44
Smiths Fork
Border, Nr April-July74 81 87 98 90 95
June-July26 33 39 78 42 47
Logan
Logan, Nr, State Dam, Abv April-July85 88 90 81 96 107
June-July35 38 40 66 46 57
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July27 28 30 70 32 36
June-July8.4 9.4 11.8 73 13.4 17.4
Little Bear
Paradise April-July24 26 28 60 31 35
June-July0.87 2.8 4.8 41 7.8 11.8

*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-July51 60 67 57 71 78
June-July8.7 17.7 25 39 29 36
Rockport Res, Wanship, Nr April-July45 52 56 42 60 72
June-July5.3 12.3 16.3 25 20 32
Coalville, Nr April-July47 51 56 42 62 72
June-July5.2 9.7 14.1 22 20 30
Chalk Ck
Coalville April-July11.5 13 14 34 17 22
June-July0.96 2.5 3.5 22 6.5 11.5
Weber
Echo Res, Echo, At April-July57 62 67 39 72 92
June-July5.2 10.2 15.4 21 19.8 40
Lost Ck
Lost Ck Res, Croydon, Nr April-July4 4.2 4.7 35 5.2 6.5
June-July0.3 0.5 0.99 34 1.5 2.8
East Canyon Ck
East Canyon Res, Morgan, Nr April-July8.5 9.5 10.3 38 11.1 13
June-July0.91 1.9 2.7 32 3.5 5.4
Weber
Gateway April-July87 95 108 33 120 160
June-July4.5 12.5 25 23 37 77
Sf Ogden
Huntsville, Nr April-July25 27 28 50 31 35
June-July3.2 5.2 6.5 47 9.2 13.2
Ogden
Pineview Res, Ogden, Nr April-July37 39 41 36 49 62
June-July1.5 3.5 5 22 13.5 26


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-July18.4 22 24 63 25 26
June-July6.9 11 12.2 51 13.4 14.6
Big Cottonwood Ck
Salt Lake City, Nr April-July14.7 16.2 17.4 48 18.2 19.1
June-July4.5 6 7.2 38 8 8.9
Mill Ck
Salt Lake City, Nr April-July1.7 2.1 2.5 39 2.7 2.9
June-July0.25 0.65 1 30 1.3 1.4
Dell Fk
Little Dell Res April-July0.9 1 1.1 19.3 1.2 1.3
June-July0.09 0.19 0.25 18.7 0.35 0.5
Lambs Ck
Salt Lake City, Nr April-July1.3 1.5 1.6 31 1.8 1.9
June-July0.1 0.25 0.4 17.4 0.54 0.69
Parleys Ck
Salt Lake City, Nr April-July3.2 3.7 4 28 4.2 4.6
June-July0.4 0.9 1.2 26 1.5 1.8
Emigration Ck
Salt Lake City, Nr April-July0.7 0.8 0.8 20 0.8 0.91
June-July0.09 0.19 0.19 16.7 0.19 0.3
Red Butte Ck
Ft Douglas, At, Salt Lake City, Nr April-July0.29 0.34 0.39 21 0.44 0.49
June-July0.05 0.1 0.15 0 0.2 0.25
City Ck
Salt Lake City, Nr April-July2.1 2.4 2.6 34 1.8 3
June-July0.65 0.95 1.2 33 0.35 1.6
S Willow Ck
Grantsville, Nr April-July1.2 1.2 1.3 40 1.3 1.4
June-July0.62 0.62 0.63 38 0.65 0.79


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-July11.2 13.2 14.9 22 16 17.2
June-July2 4 5.7 24 6.8 8
Provo
Woodland, Nr April-July50 57 62 62 66 70
June-July5 12 17.2 37 21 25
Hailstone, Nr April-July47 54 61 55 63 67
June-July7 13.5 21 40 23 27
Deer Ck Res April-July53 60 64 50 69 74
June-July4 10.8 14.8 27 19.8 25
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July7.2 8.4 9.2 30 10.1 11.1
June-July2 3.2 4 22 4.9 5.9
West Canyon Ck
Cedar Fort, Nr April-July0.06 0.09 0.12 6.8 0.16 0.2
June-July0.02 0.05 0.08 9.8 0.12 0.16
Salt Ck
Nephi Powerplant Div, Blo April-July0.91 1.1 1.2 14.7 1.4 1.6
June-July0.2 0.35 0.51 16.5 0.7 0.85
Jordan
Utah Lake, Provo, Nr April-July146 161 169 52 177 186
June-July5 20 28 22 36 45

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 51.0 108 91 56.3 120 47.1 55.8
untitled Bear River
Bear Lake, Nr Lifton 1192.9 144 92 1199.9 145 829.8 1302.0
untitled Little Bear
Hyrum Reservoir 14.5 99 95 14.6 100 14.6 15.3
untitled Weber
Rockport Res, Wanship, Nr 54.7 108 99 50.8 100 50.8 55.2
Echo Res, Echo, At 70.5 105 95 73.5 110 67.0 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 21.6 124 96 22.9 132 17.4 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 48.3 106 98 50.1 109 45.8 49.5
untitled Sf Ogden
Causey Res 7.0 100 99 7.2 102 7.0 7.1
untitled Ogden
Pineview Res, Ogden, Nr 107.5 110 98 110.1 112 97.9 110.1
untitled Jordanelle Dam
314.4 108 98 294.5 101 290.9 320.3
untitled Provo
Deer Ck Res 140.0 105 94 142.0 106 133.8 149.7
untitled Dell Fk
Little Dell Res 16.2 -99 79 17.0 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 638.4 76 73 637.5 76 844.2 870.9
untitled
TOTAL 2660.7 109 88 2659.2 109 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