Great Basin Water Supply Outlook, April 1, 2016

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by W.P.Miller, 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-July78 85 94 84 101 114
Woodruff Narrows Rsvr, Abv April-July65 75 83 69 92 117
Montpelier, Nr, Stewart Dam, Blo * April-July69 76 87 48 104 127
Smiths Fork
Border, Nr April-July64 70 79 89 85 92
Logan
Logan, Nr, State Dam, Abv April-July85 87 97 87 106 116
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July30 34 36 84 44 51
Little Bear
Paradise April-July25 30 33 70 41 44

*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-July79 84 89 75 105 119
Rockport Res, Wanship, Nr April-July75 81 88 67 108 127
Coalville, Nr April-July71 77 85 63 105 126
Chalk Ck
Coalville April-July19.1 22 25 61 37 47
Weber
Echo Res, Echo, At April-July88 96 104 61 133 171
Lost Ck
Lost Ck Res, Croydon, Nr April-July6.4 7.1 7.8 58 8.4 10.7
East Canyon Ck
East Canyon Res, Morgan, Nr April-July12.4 13.6 15.2 56 16.9 23
Weber
Gateway April-July150 168 181 56 235 285
Sf Ogden
Huntsville, Nr April-July40 46 50 89 60 74
Ogden
Pineview Res, Ogden, Nr April-July75 85 93 82 111 131


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-July24 26 28 74 31 34
Big Cottonwood Ck
Salt Lake City, Nr April-July18.4 21 22 61 25 30
Mill Ck
Salt Lake City, Nr April-July2.4 2.9 3.1 48 3.6 4.7
Dell Fk
Little Dell Res April-July2.3 2.8 3 55 3.6 5
Parleys Ck
Salt Lake City, Nr April-July5.2 6.7 7.4 52 9 12.7
Emigration Ck
Salt Lake City, Nr April-July1.3 1.5 1.7 41 2.1 2.5
City Ck
Salt Lake City, Nr April-July3.9 4.4 4.9 64 5.6 6.8
S Willow Ck
Grantsville, Nr April-July1.5 1.7 1.9 62 2.3 2.7


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-July21 22 25 36 27 34
Provo
Woodland, Nr April-July67 71 81 81 88 101
Hailstone, Nr April-July73 79 88 80 95 109
Deer Ck Res April-July75 85 95 75 103 119
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July13.5 15 17.1 55 19.9 22
West Canyon Ck
Cedar Fort, Nr April-July0.58 0.96 1.1 64 1.4 2.1
Jordan
Utah Lake, Provo, Nr April-July139 158 173 53 199 215

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 51.1 134 92 51.0 133 38.2 55.8
untitled Bear River
Bear Lake, Nr Lifton 642.8 88 49 702.8 96 731.1 1302.0
untitled Little Bear
Hyrum Reservoir 12.3 94 80 14.2 109 13.0 15.3
untitled Weber
Rockport Res, Wanship, Nr 44.7 119 81 49.9 133 37.6 55.2
Echo Res, Echo, At 38.7 77 52 37.1 74 50.2 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 12.4 111 55 14.5 130 11.2 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 28.5 80 58 30.1 85 35.5 49.5
untitled Sf Ogden
Causey Res 5.3 166 75 7.1 220 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 77.7 124 70 71.0 113 62.7 110.1
untitled Jordanelle Dam
172.2 71 54 206.9 85 242.0 320.3
untitled Provo
Deer Ck Res 138.1 116 92 144.7 121 119.4 149.7
untitled Dell Fk
Little Dell Res 10.9 -99 53 13.0 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 500.9 62 58 569.1 70 812.8 870.9
untitled
TOTAL 1724.6 80 57 1898.2 88 2157.1 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: W.P.Miller, B.Bernard