Great Basin Water Supply Outlook, March 1, 2017

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by 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-July149 163 176 157 189 205
Woodruff Narrows Rsvr, Abv April-July160 190 215 178 245 300
Montpelier, Nr, Stewart Dam, Blo * April-July440 510 555 305 630 730
Smiths Fork
Border, Nr April-July144 155 171 192 179 199
Logan
Logan, Nr, State Dam, Abv April-July180 205 220 198 235 255
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July85 102 110 256 118 130
Little Bear
Paradise April-July86 102 116 247 128 145

*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-July137 152 164 139 181 205
Rockport Res, Wanship, Nr April-July164 179 197 149 220 255
Coalville, Nr April-July170 186 210 157 235 265
Chalk Ck
Coalville April-July56 64 74 180 81 107
Weber
Echo Res, Echo, At April-July230 250 280 164 320 385
Lost Ck
Lost Ck Res, Croydon, Nr April-July24 31 34 254 38 42
East Canyon Ck
East Canyon Res, Morgan, Nr April-July25 33 42 156 52 60
Weber
Gateway April-July450 550 625 192 730 800
Sf Ogden
Huntsville, Nr April-July87 105 120 214 131 148
Ogden
Pineview Res, Ogden, Nr April-July196 230 265 235 295 330


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-July46 49 52 137 58 60
Big Cottonwood Ck
Salt Lake City, Nr April-July38 43 47 131 52 58
Mill Ck
Salt Lake City, Nr April-July5 6 7 109 8 8.8
Dell Fk
Little Dell Res April-July5.2 6.6 7.2 131 8.7 10.2
Parleys Ck
Salt Lake City, Nr April-July12.8 16.3 18.9 133 23 26
Emigration Ck
Salt Lake City, Nr April-July4.1 5.4 6.5 163 7.7 9.9
City Ck
Salt Lake City, Nr April-July6.5 7.3 8.6 112 9.9 11.8
S Willow Ck
Grantsville, Nr April-July2.9 3.3 4 129 4.4 5.2


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-July84 101 121 175 133 151
Provo
Woodland, Nr April-July140 155 168 168 183 200
Hailstone, Nr April-July171 186 197 179 215 230
Deer Ck Res April-July230 250 275 217 290 315
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July44 49 53 171 59 65
West Canyon Ck
Cedar Fort, Nr April-July1.5 2.6 3.4 193 4.5 6.7
Jordan
Utah Lake, Provo, Nr April-July520 570 650 200 710 760

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 55.3 176 99 43.8 139 31.4 55.8
untitled Bear River
Bear Lake, Nr Lifton 664.4 93 51 610.7 86 713.0 1302.0
untitled Little Bear
Hyrum Reservoir 10.3 92 67 9.8 88 11.2 15.3
untitled Weber
Rockport Res, Wanship, Nr 34.7 99 63 41.2 118 34.8 55.2
Echo Res, Echo, At 36.7 77 50 33.4 70 47.9 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 16.3 152 73 11.4 107 10.7 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 30.7 90 62 25.2 74 34.0 49.5
untitled Sf Ogden
Causey Res 4.7 147 67 4.7 146 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 60.0 113 54 60.8 115 53.0 110.1
untitled Jordanelle Dam
193.6 80 60 172.7 72 241.2 320.3
untitled Provo
Deer Ck Res 144.9 127 97 128.9 113 113.9 149.7
untitled Dell Fk
Little Dell Res 13.1 -99 64 10.6 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 450.9 57 52 475.4 61 784.7 870.9
untitled
TOTAL 1702.7 82 56 1618.2 78 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: B.Bernard