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.Green Water Supply Outlook, June 1, 2012

Green Water Supply Outlook, June 1, 2012


Prepared by Ashley Nielson
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Green Summary




*Median of forecasts within each basin.


Upper Green Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 80 percent of average in the Upper Green basin as a whole. May precipitation was 45 percent of average. May was the third month in a row with much below average precipitation.

Snow:
On June 1st, only two SNOTEL locations in the Upper Green had any remaining snow. The snow water equivalent for these two sites was 25 percent of average. As of June 5th, these locations have melted out. It is important to note that the highest measuring location is at 9800 feet in the Upper Green; however, the basin extends to elevations up to 13,000 feet. Nearly half of the basin is not represented by the SNOTEL network. It is possible there is still small amounts of remaining snow at the highest elevations.
--- Upper Green basin snow water equivalent plot.

Streamflow:
May streamflow was near 70 percent of average.

Soil Moisture:
Modeled soil moisture states indicated near average to above average soil moisture conditions last fall prior to snow accumulation.

Climate Forecasts:
Climate forecasts were not a factor because there is not a strong correlation between La Nina conditions and winter precipitation in the Upper Green basin.

Forecast Summary:
The Upper Green had above average and much above average precipitation in October, November, January, and February. However, warm and dry conditions persisted from March through May resulting in decreased snow accumulation and early snowmelt. As a result of the warm and dry spring, the seasonal runoff forecasts have been continually reduced since March. Current April through July streamflow volume forecasts in the Upper Green have decreased by 5 to 15 percent since May. Forecasts for locations on the North Slope of the Uintas are in the bottom three of the historical record. April through July forecasts now range between 47 and 83 percent of average with a median value of 65 percent.



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

Yampa/White Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 60 percent of average in the Yampa/White basin. May precipitation was near 25 percent of average. May was the third month in a row with much below average precipitation.

Snow:
The snow had melted out of nearly all the SNOTEL measuring locations by June 1st. Many of these locations had record or near record early melt out dates.
--- Yampa basin snow water equivalent plot.

Streamflow:
May streamflow was 40 percent of average over the basin as a whole.

Soil Moisture:
Modeled soil moisture states indicated above average to much above average soil moisture conditions last fall prior to snow accumulation.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Yampa/White basin.

Forecast Summary:
Near average precipitation in October and November was followed by multiple months, with the exception of February, of much below average precipitation and above normal temperatures. These conditions lead to decreased snow accumulation and record early snowmelt in the Yampa River Basin. As a result of the unseasonably warm and dry spring, seasonal runoff forecasts have continually decreased since March. Current April through July streamflow volume forecasts in the Yampa have decreased by 10 to 20 percent since May. Many of the April through July forecasts are in the bottom five of the historical record. April through July forecasts now range between 25 and 53 percent of average with a median value of 38 percent.



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

Duchesne Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 70 percent of average in the Duchesne basin. May precipitation was 15 percent of average. May was the third month in a row with much below average precipitation.

Snow:
The snow had melted out of nearly all the SNOTEL measuring locations by June 1st. Many of these locations had record or near record early melt out dates.
--- Duchesne basin snow water equivalent plot.

Streamflow:
May streamflow was near 70 percent of average over the basin as a whole. However, some low elevation locations had monthly volumes less than 50 percent of average.

Soil Moisture:
Modeled soil moisture states indicated much above average soil moisture conditions last fall prior to snow accumulation.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Duchesne basin.

Forecast Summary:
A wet October was followed by multiple months of below to much below average precipitation in the Duchesne basin. Warm and dry conditions persisted from March through May resulting in decreased snow accumulation and early snowmelt. As a result of the unseasonably warm and dry spring, seasonal runoff forecasts have continually decreased since March. Current April through July streamflow volume forecasts in the Duchesne have again decreased by 10 to 20 percent April through July forecasts now range between 11 and 56 percent of average with a median value of 44 percent.



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

Lower Green Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 70 percent of average in the Lower Green basin. May precipitation was 10 percent of average. May was the third month in a row with much below average precipitation.

Snow:
The SNOTEL locations have been melted out since late April in the Lower Green. All of the snow in the Lower Green has melted. Many of these locations had record or near record early melt out dates.
--- Lower Green basin snow water equivalent plot.

Streamflow:
May streamflow was near 45 percent of average over the basin as a whole.

Soil Moisture:
Modeled soil moisture states indicated near average to above average soil moisture conditions last fall prior to snow accumulation.

Climate Forecasts:
Climate forecasts were not a factor in the forecasts because there is not a strong correlation between La Nina conditions and winter precipitation in the Lower Green basin.

Forecast Summary:
A wet October was followed by multiple months of below to much below average precipitation,with the exception of February, in the Lower Green. Warm and dry conditions persisted from March through May resulting in decreased snow accumulation and early snowmelt. As a result of the unseasonably warm and dry spring, seasonal runoff forecasts have continually decreased since March. Current April through July streamflow volume forecasts in the Lower Green have again decreased by 10 to 15 percent. Many of the forecasts in the Lower Green are in the bottom five of the historical record. April through July forecasts now range between 15 and 43 percent of average with a median value of 36 percent.



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


Upper Green Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Green
Daniel, Nr, Warren Bridge, At April-July16218375220
June-July8410563140
Pine Ck
Fremont Lk, Abv April-July68828498
June-July41557271
New Fork
Big Piney, Nr April-July22026575315
June-July10715059200
Green
Fontenelle Res, Fontenelle Nr April-July39049068615
June-July16026055385
Big Sandy
Farson, Nr April-July34428152
June-July11.1195629
Green
Green River, Wy, Nr April-July37547565600
June-July15225052375
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30336137
June-July2.1519.29.2
Viva Naughton Res April-July32364943
June-July1516.112
Blacks Fork
Robertson, Nr April-July40455152
June-July3.9915.316.2
Ef Smiths Fork
Stateline Res, Robertson,nr April-July10.712.84716.2
June-July0.87317.36.4
Green
Flaming Gorge Res, Flaming Gorge Dam, At April-July45056057695
June-July16127045405


Yampa/White Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Yampa
Stagecoach Rsvr, Abv April-July5.15.7256.8
June-July0.371112.1
Steamboat Springs April-July10511745134
June-July9.72218.539
Elk
Milner, Nr April-July15217053194
June-July17352359
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July20212924
June-July019.64
Yampa
Maybell, Nr April-July32537040430
June-July327519.2136
Little Snake
Slater, Nr April-July67734783
June-July2.7913.618.9
Savery, Nr April-July9810931132
June-July1.1128.935
Lily, Nr April-July10511734142
June-July1.61410.439
White
Meeker, Nr April-July9711441137
June-July15.2322255
Watson, Nr April-July8710236129
June-July15302257


Duchesne Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Big Brush Ck
Vernal, Nr, Red Fleet Res, Abv April-July7.28.54010.5
June-July0.672224
Ashley Ck
Vernal, Nr April-July17.9224429
June-July1.962512.5
West Fork Duchesne
Vat Diversion, Blo April-July6.584310.6
June-July0.351.819.44.4
Duchesne
Tabiona, Nr April-July44555171
June-July5.5162732
Rock Ck
Upper Stillwater Res April-July34415551
June-July8.7163426
Mountain Home, Nr April-July39475358
June-July9.8183229
Currant Ck
Currant Ck Res April-July5.15.9307.6
June-July00.810.82.5
Strawberry
Solider Springs,nr April-July5.5610.78.5
June-July00.53.23
Starvation Res, Duchesne, Nr April-July19.6242128
June-July0.03410.88
Duchesne
Duchesne, Nr, Knight Div, Abv April-July8410253128
June-July14.6332959
Lake Fork
Moon Lake Res, Mtn Home, Nr April-July29365545
June-July8.2153524
Yellowstone
Altonah, Nr April-July28345642
June-July8.5153723
Whiterocks
Whiterocks, Nr April-July18.7244431
June-July3.892616.5
Uinta
Neola, Nr April-July29385147
June-July10193828
Duchesne
Myton April-July849831119
June-July0.05148.435
Randlett, Nr April-July8910428129
June-July0157.340


Lower Green Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
White
Blo Tabbyune Ck, Soldier Summit, Nr April-July1.82.314.83.1
June-July0.060.514.71.4
Fish Ck
Scofield, Nr, Reservoir, Abv April-July8.9103313.2
June-July0.71.818.65
Price
Scofield Res, Scofield, Nr April-July11.512.73115.1
June-July0.481.712.64.1
Green
Green River, Ut April-July10401240421510
June-July20040026665
Huntington Ck
Electric Lake April-July3.74.3325.3
June-July0.20.816.71.8
Power Plant, Blo April-July15.118.24322
June-July3.973311
Seeley Ck
Joes Vly Res, Orangeville, Nr April-July19223929
June-July0.61412.510.4
Ferron Ck
Ferron, Nr April-July13.615.54118.3
June-July1.53.516.76.3
Muddy Ck
Emery, Nr April-July5.26.9359.3
June-July0.892.5214.9

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).

Reservoir Monthly Inflow Forecasts






Green End of Month Reservoir Contents (kaf)

Usable
Capacity
EOM
Contents
Percent
Usable
Capacity
Last Year
EOM
Last Year
%Capacity
untitled Green
Fontenelle Res, Fontenelle Nr 344.8 227.3 66 120.0 35
Flaming Gorge Res, Flaming Gorge Dam, At 3752.0 3107.7 83 3150.2 84
untitled Strawberry
Solider Springs,nr 1105.9 987.0 89 1046.3 95
Starvation Res, Duchesne, Nr 165.3 152.1 92 128.0 77
untitled Price
Scofield Res, Scofield, Nr 65.8 50.8 77 48.9 74
untitled Seeley Ck
Joes Vly Res, Orangeville, Nr 61.6 55.8 91 35.4 58
untitled Huntington North Reservoir Storage
4.2 3.3 79 4.0 94
untitled
TOTAL 5499.6 4584.0 83 4532.8 82

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: Ashley Nielson