Great Basin Water Supply Outlook, April 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-July150 165 175 156 193 205
Woodruff Narrows Rsvr, Abv April-July187 200 220 182 260 295
Montpelier, Nr, Stewart Dam, Blo * April-July530 575 600 330 680 760
Smiths Fork
Border, Nr April-July145 155 163 183 176 190
Logan
Logan, Nr, State Dam, Abv April-July197 210 220 198 235 255
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July85 94 100 233 110 120
Little Bear
Paradise April-July80 86 96 204 112 123

*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-July130 149 168 142 182 200
Rockport Res, Wanship, Nr April-July151 174 200 152 210 240
Coalville, Nr April-July160 179 200 149 230 250
Chalk Ck
Coalville April-July55 60 68 166 80 94
Weber
Echo Res, Echo, At April-July225 250 275 161 295 340
Lost Ck
Lost Ck Res, Croydon, Nr April-July27 30 33 246 36 42
East Canyon Ck
East Canyon Res, Morgan, Nr April-July25 28 33 122 37 45
Weber
Gateway April-July440 480 530 163 600 695
Sf Ogden
Huntsville, Nr April-July90 98 105 188 118 139
Ogden
Pineview Res, Ogden, Nr April-July175 195 210 186 240 270


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-July45 48 51 134 56 59
Big Cottonwood Ck
Salt Lake City, Nr April-July35 42 45 125 49 53
Mill Ck
Salt Lake City, Nr April-July5 5.8 6.4 100 7 8.2
Dell Fk
Little Dell Res April-July4.2 5.1 5.5 100 6.1 7.6
Parleys Ck
Salt Lake City, Nr April-July11 13.4 14.5 102 17 20
Emigration Ck
Salt Lake City, Nr April-July3.5 4.1 4.6 115 5 6.6
City Ck
Salt Lake City, Nr April-July6.8 7.5 8.2 106 9.2 11
S Willow Ck
Grantsville, Nr April-July2.9 3.6 3.7 119 4.4 4.9


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-July85 92 105 152 110 132
Provo
Woodland, Nr April-July148 163 170 170 179 198
Hailstone, Nr April-July170 190 195 177 210 230
Deer Ck Res April-July220 245 255 201 275 305
American Fork
American Fork, Nr, Up Pwrplnt, Abv April-July43 48 51 165 56 60
West Canyon Ck
Cedar Fort, Nr April-July2.1 3 3.3 188 4.5 6.9
Jordan
Utah Lake, Provo, Nr April-July505 570 605 186 645 715

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 48.7 127 87 51.1 134 38.2 55.8
untitled Bear River
Bear Lake, Nr Lifton 809.8 111 62 642.8 88 731.1 1302.0
untitled Little Bear
Hyrum Reservoir 10.5 81 69 12.3 94 13.0 15.3
untitled Weber
Rockport Res, Wanship, Nr 26.7 71 48 44.7 119 37.6 55.2
Echo Res, Echo, At 35.3 70 48 38.7 77 50.2 73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr 15.6 140 69 12.4 111 11.2 22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 37.1 104 75 28.5 80 35.5 49.5
untitled Sf Ogden
Causey Res 7.2 223 101 5.3 166 3.2 7.1
untitled Ogden
Pineview Res, Ogden, Nr 56.1 90 51 77.7 124 62.7 110.1
untitled Jordanelle Dam
215.2 89 67 172.2 71 242.0 320.3
untitled Provo
Deer Ck Res 148.1 124 99 138.1 116 119.4 149.7
untitled Dell Fk
Little Dell Res 12.8 -99 62 10.9 -99 -9999.0 20.5
untitled Jordan
Utah Lake, Provo, Nr 514.3 63 59 500.9 62 812.8 870.9
untitled
TOTAL 1924.6 89 63 1724.6 80 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: B.Bernard