Great Basin Water Supply Outlook, April 1, 2013

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Brent 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




* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Weber Basin Conditions




* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Six Creeks Basin Conditions




* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Utah Lake Basin Conditions




* 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		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Bear
Utah April-July37 57 51 80
Woodruff Narrows Rsvr, Abv April-July20 45 37 80
Montpelier, Nr, Stewart Dam, Blo * April-July2 28 15.4 80
Smiths Fork
Border, Nr April-July29 55 62 75
Logan
Logan, Nr, State Dam, Abv April-July35 65 59 90
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July13.3 24 56 38
Little Bear
Paradise April-July6.3 13.5 29 34

*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		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Weber
Oakley, Nr April-July36 64 54 88
Rockport Res, Wanship, Nr April-July28 51 40 88
Coalville, Nr April-July22 48 37 90
Chalk Ck
Coalville April-July2 15 37 32
Weber
Echo Res, Echo, At April-July30 64 39 110
Lost Ck
Lost Ck Res, Croydon, Nr April-July0.9 3.3 25 7
East Canyon Ck
East Canyon Res, Morgan, Nr April-July6 14.2 53 22
Weber
Gateway April-July51 103 32 210
Sf Ogden
Huntsville, Nr April-July10 20 36 42
Ogden
Pineview Res, Ogden, Nr April-July13 43 38 82


Six Creeks Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Little Cottonwood Ck
Salt Lake City, Nr April-July16 22 58 30
Big Cottonwood Ck
Salt Lake City, Nr April-July11 21 58 29
Mill Ck
Salt Lake City, Nr April-July1.5 2.7 42 4.6
Dell Fk
Little Dell Res April-July1.3 2.4 44 5
Parleys Ck
Salt Lake City, Nr April-July3.5 6 42 11
Emigration Ck
Salt Lake City, Nr April-July0.2 1.3 34 2.8
City Ck
Salt Lake City, Nr April-July3.4 4.6 60 7
S Willow Ck
Grantsville, Nr April-July1.6 2.4 77 3.1


Utah Lake Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Spanish Fork
Castilla, Nr April-July7.8 22 32 45
Provo
Woodland, Nr April-July35 55 55 82
Hailstone, Nr April-July37 62 56 90
Deer Ck Res April-July30 56 44 100
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July7.3 14 45 22
West Canyon Ck
Cedar Fort, Nr April-July0.2 0.62 35 1.7
Jordan
Utah Lake, Provo, Nr April-July69 145 45 250

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 Woodruff Narrows Reservoir Nr Woodruff Ut
12.3 32 22 57.5 151 38.2 55.8
untitled Bear River
Bear Lake, Nr Lifton 920.0 126 71 1030.5 141 731.1 1302.0
untitled Little Bear
Hyrum Reservoir 13.0 99 85 14.2 109 13.0 15.3
untitled Weber
Rockport Res, Wanship, Nr 34.7 92 63 42.1 112 37.6 55.2
Echo Res, Echo, At 28.4 57 38 66.1 132 50.2 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 16.1 144 71 21.4 192 11.2 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 30.7 86 62 48.7 137 35.5 49.5
untitled Sf Ogden
Causey Res 5.4 169 77 5.9 185 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 58.1 93 53 93.5 149 62.7 110.1
untitled Jordanelle Dam
182.4 75 57 266.0 110 242.0 320.3
untitled Provo
Deer Ck Res 135.8 114 91 147.6 124 119.4 149.7
untitled Dell Fk
Little Dell Res 11.3 -99 55 10.9 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 777.6 96 89 865.8 107 812.8 870.9
untitled
TOTAL 2214.5 103 73 2659.3 123 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: Brent Bernard