Great Basin Water Supply Outlook, March 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-July42 68 61 100
Woodruff Narrows Rsvr, Abv April-July28 74 61 110
Montpelier, Nr, Stewart Dam, Blo * April-July5 45 25 125
Smiths Fork
Border, Nr April-July36 58 65 87
Logan
Logan, Nr, State Dam, Abv April-July45 76 68 111
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July19 28 65 44
Little Bear
Paradise April-July10 23 49 41

*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-July39 66 56 100
Rockport Res, Wanship, Nr April-July31 63 50 110
Coalville, Nr April-July26 63 49 110
Chalk Ck
Coalville April-July5 22 54 40
Weber
Echo Res, Echo, At April-July33 85 51 150
Lost Ck
Lost Ck Res, Croydon, Nr April-July1.7 4.5 34 9
East Canyon Ck
East Canyon Res, Morgan, Nr April-July9 17 63 27
Weber
Gateway April-July80 146 46 295
Sf Ogden
Huntsville, Nr April-July13 36 64 50
Ogden
Pineview Res, Ogden, Nr April-July29 68 60 111


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-July18 27 71 38
Big Cottonwood Ck
Salt Lake City, Nr April-July12 25 69 36
Mill Ck
Salt Lake City, Nr April-July1.7 3.8 59 5.5
Dell Fk
Little Dell Res April-July1.8 3.3 60 5.4
Parleys Ck
Salt Lake City, Nr April-July4 9 63 15
Emigration Ck
Salt Lake City, Nr April-July0.9 2.4 60 4.8
City Ck
Salt Lake City, Nr April-July3.3 5.4 70 8.2
S Willow Ck
Grantsville, Nr April-July1.4 2.4 77 3.2


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-July25 40 58 70
Provo
Woodland, Nr April-July45 65 65 97
Hailstone, Nr April-July50 75 68 112
Deer Ck Res April-July50 82 65 125
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July9.5 18 58 31
West Canyon Ck
Cedar Fort, Nr April-July0.3 0.8 45 2
Jordan
Utah Lake, Provo, Nr April-July100 195 60 300

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
8.7 28 16 49.0 156 31.4 55.8
untitled Bear River
Bear Lake, Nr Lifton 902.2 127 69 993.6 139 713.0 1302.0
untitled Little Bear
Hyrum Reservoir 9.8 88 64 12.9 116 11.2 15.3
untitled Weber
Rockport Res, Wanship, Nr 31.0 89 56 39.8 114 34.8 55.2
Echo Res, Echo, At 23.6 49 32 57.8 121 47.9 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 15.6 145 69 20.2 188 10.7 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 28.5 84 57 46.0 135 34.0 49.5
untitled Sf Ogden
Causey Res 4.4 138 63 6.5 201 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 49.4 93 45 87.3 165 53.0 110.1
untitled Jordanelle Dam
184.0 76 57 265.1 110 241.2 320.3
untitled Provo
Deer Ck Res 126.8 111 85 142.9 125 113.9 149.7
untitled Dell Fk
Little Dell Res 11.0 -99 54 11.1 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 753.9 96 87 899.9 115 784.7 870.9
untitled
TOTAL 2138.0 103 70 2621.0 126 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