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, February 1, 2009

Great Basin Water Supply Outlook, February 1, 2009


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

Snow Water Equivalent & Precipitation - January precipitation in the Great Basin was above average at 119%.. Snow conditions throughout the northern basin improved slightly (5%-10%) with indexed snow totals of 95% in the Weber and Ogden basins, 96% in the Provo basin, 92% in the Bear River basin and 105% in the Six Creeks basin. Seasonal precipitation for the Great Basin Salt Lake Basin was 106% of average and overall snow water equivalents are 94% of average.

Soil Moisture & Streamflow - Soil moisture grids from our ESP model remain below to much below average in all headwater regions, which tends to lower April through July volume forecasts. Currently we have no gridded information in the Bear River drainage. Streamflows for selected points in each of the Great Basins 4 main drainages were 86% of average.

Short Term Precipitation Forecasts - Weather guidance from National Weather Service models are predicting wet conditions during the first 5-10 days with several storms for both northern and southern Utah. Short term CPC guidance shows the possibility of above average precipitation for the second week of February.

General Discussion - Longer range predictions from NOAA's Climate Prediction Center are now factoring in a weak La Nina episode, predicted to last through the spring of 2009. Please reference the web link above for further details and effects within the Great Basin. Volumetric forecasts were largely unchanged in the Bear River Basin with the median forecast being 85% of average. In the Weber, Provo and Six Creeks drainages, forecasts remained within 5% of their January 1st numbers at or near average.



*Median of forecasts within each basin.


Bear Basin Conditions

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Bear River drainage improved slightly during January. Monthly precipitation was 109% of average and snow water equivalent increased to 92% of average. Seasonal precipitation is currently 101% of average.

Soil Moisture & Streamflow - We currently have no modelled soil moisture information for the Bear River. Observed streamflows for January were estimated for Bear at the UT/WY State line at 86% of average. Observed flows on the Logan River nr Logan above State Dam were 86% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period wet weather during the next 8-10 days in the Great Basin region. Short term CPC guidance shows the possibility of above average precipitation and below normal temperatures for the second week of February.

General Discussion - Volumetric forecast for April through July were held steady or raised slightly ranging from 54% at Bear nr Montpelier to 86% of average at the Utah, Wyoming State line.



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

Weber Basin Conditions

Snow Water Equivalent and precipitation - Conditions in the Weber and Ogden River River basins were above average for January 2009. Monthly precipiation totalled 125% of average. Snow water equivalent numbers rose by 5% to end the month at 95% of average. Seasonal precipiation is currently 99% of average.

Soil Moisture & Streamflow - Soil moisture conditions were below average in the upper Weber basin during January, varying between 70-89% of average. Observed streamflows for the month were 87% of average for the Weber at Oakley.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period wet weather during the next 8-10 days in the Great Basin region. Short term CPC guidance shows the possibility of above average precipitation and below normal temperatures for the second week of February.

General Discussion - Volumetric forecast in the Weber were all raise slightly due to the overall improvement in snow and precipitation conditions ranging from 89% at Echo Reservoir to 94% at East Canyon Reservoir.



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

Six Creeks Basin Conditions

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Six Creeks basins improved the most of any of the Great Basin Salt Lake region basins during January. Monthly precipitation totalled 140% of average and snow water equivalent increased to 105% of average. Seasonal precipitation now totals 114% of average.

Soil Moisture & Streamflow - Streamflows in Big and Little Cottonwood Canyons were 67% of average. These flow numbers are indicative of the low soil moisture conditions that prevail along the Wasatch front. Soil moisture grids currently range from 50%-90% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period wet weather during the next 8-10 days in the Great Basin region. Short term CPC guidance shows the possibility of above average precipitation for the second week of February.

General Discussion - Volumetric forecast were raise slightly for all points in the Six Creeks basin due to the increase in SWE and monthly precipitation. Forecast now range from 87% at Emigration Creek near Salt Lake City to 98% at Little Cottonwood Canyon near Salt Lake City.



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

Utah Lake Basin Conditions

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Utah Lake drainages improved during January. Monthly precipiation totalled 131% and snow water equivalent numbers increased to 96% of average. Seasonal precipitation now totals 106% of average.

Soil Moisture & Streamflow - Streamflows for Spanish Fork near Castilla and Provo at Woodland combined were 105% of average. These are the best streamflow number in the group of basins and are indicative of the warm, liquid precipitation event that occured at the end of the month. Soil moisture grids along the Provo River range from 50-90 percent of average. The Spanish Fork drainage ranges from 70%-99% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period wet weather during the next 8-10 days in the Great Basin region. Short term CPC guidance shows the possibility of above average precipitation for the second week of February.

General Discussion - Volumetric forecast for Utah Lake and associated rivers were raised this month due to the improvement in overall conditions. Forecast now range from 90% at Provo near Hailstone to 94% at American Fork near the UP Power Plant.



* 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-July579786137
Woodruff Narrows Res April-July6311778171
Big Ck
Randolph, Nr April-July2.34.2866.1
Smiths Fork
Border, Nr April-July588885118
Bear
Montpelier, Nr, Stewart Dam, Blo April-July4014054330
Logan
Logan, Nr, State Dam, Abv April-July5510583155
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv April-July15.7418564


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-July6711190155
Rockport Res, Wanship, Nr April-July5912090181
Coalville, Nr April-July6212490186
Chalk Ck
Coalville April-July14.1419168
Weber
Echo Res, Echo, At April-July5916089260
Lost Ck
Lost Ck Res, Croydon, Nr April-July6.4169126
East Canyon Ck
East Canyon Res, Morgan, Nr April-July10.2299448
Weber
Gateway April-July8532090555
Sf Ogden
Huntsville, Nr April-July23578991
Ogden
Pineview Res, Ogden, Nr April-July4712090193
Wheeler Ck
Huntsville, Nr April-July2.45.7909


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-July27399853
Big Cottonwood Ck
Salt Lake City, Nr April-July24379750
Mill Ck
Salt Lake City, Nr April-July2.76.59310.3
Dell Fk
Little Dell Res April-July0.268812.3
Parleys Ck
Salt Lake City, Nr April-July5.314.88924
Emigration Ck
Salt Lake City, Nr April-July0.343.9877.5
City Ck
Salt Lake City, Nr April-July3.17.89012.5
Vernon Ck
Vernon, Nr April-June0.381.4953
S Willow Ck
Grantsville, Nr April-July1.63.41065.2


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-July187091158
Provo
Woodland, Nr April-July549491144
Hailstone, Nr April-July569890151
Deer Ck Res April-July5911390157
American Fork
American Fork, Nr, Up Pwrplnt, AbvApril-July14.2309446
Jordan
Utah Lake, Provo, Nr April-July13030592480

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 Reservoir Contents (kaf)

Usable
Capacity
EOM
Contents
Percent
Usable
Capacity
Last Year
EOM
Last Year
%Capacity
untitled Bear
Woodruff Narrows Res 55.8 43.0 77 25.0 45
untitled Bear Lake
Lifton, St. Charles, Nr 1302.0 254.9 20 237.9 18
untitled Little Bear
Hyrum Res Abv 15.3 10.5 69 11.1 73
untitled Willard Reservoir Storage
215.0 92.0 43 63.2 29
untitled Sf Ogden
Causey Res 7.1 4.5 63 4.1 58
untitled Ogden
Pineview Res, Ogden, Nr 110.1 49.9 45 40.4 37
untitled Lost Ck
Lost Ck Res, Croydon, Nr 22.5 16.0 71 13.0 58
untitled Weber
Rockport Res, Wanship, Nr 60.9 45.3 74 30.7 50
Echo Res, Echo, At 73.9 44.6 60 37.7 51
untitled East Canyon Ck
East Canyon Res, Morgan, Nr 49.5 36.1 73 27.3 55
untitled Jordanelle Dam
311.0 231.1 74 228.5 73
untitled Provo
Deer Ck Res 149.7 112.5 75 70.5 47
untitled Jordan
Utah Lake, Provo, Nr 870.9 747.0 86 747.5 86
untitled
TOTAL 3243.7 1687.4 52 1536.9 47

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 1971-2000 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