New 1981-2010 Averages being used this year.
Note: This publication is currently undergoing major revisions. The current publication will be replaced with a new publication based on stakeholder requirements and scientific advances. We expect to begin sharing details on this soon. If you have input on content, format, or publication frequency at any time, please contact us at cbrfc.webmasters@noaa.gov.Great Basin Water Supply Outlook, June 1, 2012

Great Basin Water Supply Outlook, June 1, 2012


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

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 82 percent of average in the upper Bear Basin. May precipitation was 66 percent of average.

Streamflow:
The Bear River at Utah/Wyoming Stateline last month was 76 percent of average. The regulated inflow to Bear River at Stewart Dam was 6 percent of average. The Logan River above State Dam was estimated at 73 percent of average streamflow.

Snowpack:
As of June 1st the Bear Basin snowpack has melted out in one of the earliest melts we've seen. As of water year 2012 the CBRFC has re-calculated all snow stations to reflect the new 30 year average from 1981-2010.


Upper Bear River Basin Snow Plot.
Bear River Below Woodruff Narrows Reservoir Snow Plot.
Bear River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not a factored into the northern Utah forecasts because there is not a strong correlation between La Nina conditions and winter precipitation.

Forecast Summary:
Overall the winter of 2012 has been drier and warmer than average. Seasonal precipitation throughout the Bear Basin as of June 1 was 82 percent of average. Indexed snow water equivalents on June 1st were zero, indicating that in terms of runoff, the snow is now gone. Streamflow forecast have been reduced significantly since March, as warm temperature and below average precipitation numbers have drastically reduced streamflow volume forecast. The June through July forecasts are now ranked in the top 5 lowest years on record. April through July seasonal volume forecast range from 21 to 56 percent of average with a median volume of 51 percent of average.



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

Weber Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation is 72 percent of average. May precipitation was 52 percent of average.

Streamflow:
The Weber at Oakley gage was estimated to be 67 percent of average. The inflow to Rockport Reservoir was 47 percent of average.

Snowpack:
As of June 1st the snowpack is all but gone except on the highest peaks and runoff has finished. The current snow water equivalent index is zero percent of average. As of water year 2012 the CBRFC has re-calculated all snow stations to reflect the new 30 year average from 1981-2010.

Weber River Basin Snow Plot.
Upper Weber River Basin Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not a factored into the northern Utah forecasts because there is not a strong correlation between La Nina conditions and winter precipitation.

Forecast Summary:
Overall the winter of 2012 has been drier and warmer than average and resulted in very low streamflows. Seasonal precipitation throughout the Weber River Basin as of June 1 was 72 percent of average. Indexed snow water equivalents on June 1st indicated that in terms of runoff, the snow is now gone. Streamflow forecast have been reduced significantly since March, as warm temperature and below average precipitation numbers have drastically reduced streamflow volume forecast. The June through July Weber Basin forecasts ranked in the top 5 lowest historical years on record. April through July seasonal volume forecasts range between 28 and 52 percent of average with a median forecast volume of 37 percent of average. Here's hoping for a wet summer and a much better water year 2013.



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

Six Creeks Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was near 74 percent of average. May precipitation was 46 percent of average.

Streamflow:
May streamflow for City Creek near Salt Lake City was 47 percent of average. Big Cottonwood Creek nr Salt Lake City was 58 percent of average.

Snowpack:
As of June 1st the snowpack are all but gone with only residual snowfields at elevations above 10000 feet. The has now effectively ended in what will be recored in history as one of the earliest melts ever. As of water year 2012 the CBRFC has re-calculated all snow stations to reflect the new 30 year average from 1981-2010.

Six Creeks Headwaters Basins Snow Plot.

Big and Little Cottonwood Canyons Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not factored into the northern Utah forecasts because there is not a strong correlation between La Nina conditions and winter precipitation.

Forecast Summary:
Overall the winter of 2012 has been drier and warmer than average resulting in very low streamflow volumes. Seasonal precipitation throughout the Weber River Basin as of June 1 was 74 percent of average. Indexed snow water equivalents on June 1st indicated that in terms of runoff, the snow is now gone. Streamflow forecast have been reduced significantly since March, as warm temperature and below average precipitation numbers have drastically reduced streamflow volume forecast. Many of the June through July Six Creeks forecasts are now ranked near or in the top 10 lowest years on record. April through July seasonal volume forecasts range between 15 to 55 percent of average with a median forecast of 45 percent of average.



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

Utah Lake Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October thought April seasonal precipitation was 71 percent of average. May precipitation was 34 percent of average.

Streamflow:
Streamflows for the Provo at Woodland were 66 percent of average. Unregulated inflow to Utah Lake was 26 percent of average.

Snowpack:
As of June 1st the snowpack is all but gone and water year 2012 runoff is done. Current snow water equivalent measurements are zero at NRCS SNOTEL stations. As of water year 2012 the CBRFC has re-calculated all snow stations to reflect the new 30 year average from 1981-2010.

Provo River, Utah Lake Drainage Snow Plot.

Soil Moisture:
Modeled Soil Moisture, click on map to zoom.

Climate Forecasts:
Climate forecasts were not factored into the northern Utah forecasts because there is not a strong correlation between La Nina conditions and winter precipitation here.

Forecast Summary:
Overall the winter of 2012 has been drier and warmer than average resulting in significantly below average runoff. Seasonal precipitation throughout the Utah Lake and Provo River Basins as of June 1 was 71 percent of average. Indexed snow water equivalents on June 1st indicated that in terms of runoff, the snow is now gone. Streamflow forecast have been reduced significantly since March, as warm temperature and below average precipitation numbers have drastically reduced streamflow volume forecast. Many of the June through July forecasts are now ranked in the top 10 lowest historical years on record. April through July seasonal volume forecasts now range between 17 and 55 percent of average with a median forecast volume of 45 percent of average.



* 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
UtahApril-July43635683
June-July19213250
Woodruff Narrows Rsvr, Abv April-July28383148
June-July4.5915.836
Montpelier, Nr, Stewart Dam, Blo *April-July28382148
June-July0.977.5102
Smiths Fork
Border, Nr April-July38515763
June-July10204035
Logan
Logan, Nr, State Dam, Abv April-July53686183
June-July14254141
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July15225129
June-July5.874316.5
Little Bear
Paradise April-July1015.43320
June-July1.454310.4

*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-July46615276
June-July7.4223440
Rockport Res, Wanship, Nr April-July37493961
June-July7.3142338
Coalville, Nr April-July34463658
June-July31016.434
Chalk Ck
Coalville April-July914.33519
June-July0.3319.114
Weber
Echo Res, Echo, At April-July45603675
June-July71317.845
Lost Ck
Lost Ck Res, Croydon, Nr April-July34.6346
June-July0.051344.3
East Canyon Ck
East Canyon Res, Morgan, Nr April-July7.99.93711.9
June-July13358.6
Weber
Gateway April-July689128115
June-July111614.877
Sf Ogden
Huntsville, Nr April-July15223929
June-July3.253610.9
Ogden
Pineview Res, Ogden, Nr April-July25484271
June-July183519.5


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-July15.3215527
June-July4.18.53512.9
Big Cottonwood Ck
Salt Lake City, Nr April-July11.3174723
June-July2.55.83010.5
Mill Ck
Salt Lake City, Nr April-July1.62.5394.1
June-July0.61302.1
Dell Fk
Little Dell Res April-July0.91.2221.5
June-July0.060.3220.83
Parleys Ck
Salt Lake City, Nr April-July2.73.7224.7
June-July0.5117.23.8
Emigration Ck
Salt Lake City, Nr April-July0.450.6150.8
June-July0.010.1513.20.72
City Ck
Salt Lake City, Nr April-July2.33.3434.3
June-July0.151.2322.3
Vernon Ck
Vernon, Nr April-July0.250.65441
June-July0.130.18320.46
S Willow Ck
Grantsville, Nr April-July1.11.5482
June-July0.40.6361.1


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-July13202927
June-July1.452127
Provo
Woodland, Nr April-July39545469
June-July9132831
Hailstone, Nr April-July43585573
June-July6.5153237
Deer Ck Res April-July40554570
June-July3122441
American Fork
American Fork, Nr, Up Pwrplnt, AbvApril-July712.23917
June-July242211.2
West Canyon Ck
Cedar Fort, Nr April-July0.10.3170.5
June-July0.090.1518.30.88
Jordan
Utah Lake, Provo, Nr April-July567824100
June-July14272299

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)

Usable
Capacity
EOM
Contents
Percent
Usable
Capacity
Last Year
EOM
Last Year
%Capacity
untitled Bear
Woodruff Narrows Res 55.8 51.6 92 47.0 84
untitled Bear River
Bear Lake, Nr Lifton 1302.0 1057.8 81 769.6 59
untitled Little Bear
Hyrum Res Abv 15.3 14.1 92 11.4 75
untitled Willard Reservoir Storage
215.0 183.6 85 189.6 88
untitled Sf Ogden
Causey Res 7.1 7.1 100 7.3 103
untitled Ogden
Pineview Res, Ogden, Nr 110.1 101.6 92 96.9 88
untitled Lost Ck
Lost Ck Res, Croydon, Nr 22.5 22.6 100 22.0 98
untitled Weber
Rockport Res, Wanship, Nr 60.9 55.4 91 32.2 53
Echo Res, Echo, At 73.9 58.5 79 52.9 72
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 49.5 49.5 100 46.0 93
untitled Dell Fk
Little Dell Res 20.5 11.9 58 15.8 77
untitled Mountain Dell Dam
3.0 1.8 61 1.2 40
untitled Jordanelle Dam
311.0 303.8 98 224.3 72
untitled Provo
Deer Ck Res 149.7 122.9 82 140.4 94
untitled Jordan
Utah Lake, Provo, Nr 870.9 823.7 95 1054.8 121
untitled
TOTAL 3267.2 2866.0 88 2711.5 83

Monthly Streamflows











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