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.Upper Colorado Water Supply Outlook, June 1, 2010

Upper Colorado Water Supply Outlook, June 1, 2010


Prepared by Brenda Alcorn, Tracy Cox
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Upper Colorado Summary




*Median of forecasts within each basin.


Upper Colorado Mainstem Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was near 90 percent of average in the Upper Colorado mainstem basin. May precipitation was also near 90 percent of average.

Snow:
June 1st snow water equivalent was near 55 percent of average in the basin as a whole. The majority of the remaining snow is above 10,000 feet. The snow peaked in May at 85% of the average seasonal peak.
--- Upper Colorado basin snow water equivalent plot

Streamflow:
May streamflow was near 80 percent of average.

Soil Moisture:
Modeled soil moisture states were near average heading into the winter.

Forecast Summary:
Basin wide precipitation was near average for the month of May. However, some headwater areas received greater amounts of precipitation. June through July streamflow volume forecasts range from 43 to 85 percent of average,with a median value of 69%. April through July streamflow volume forecasts remained the same or increased slightly in certain headwater areas. The Upper Colorado basin April through July streamflow volume forecasts now range from 58 to 85 percent of average, with a median value of 72%.



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

Gunnison Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 95 percent of average in the Gunnison Basin. May precipitation was 60 percent of average.

Snow:
June 1st snow water equivalent was 35 percent of average in the Gunnison Basin. There is still some snow above 11,500 feet with minimal areal extent. The snow peaked above Blue Mesa in early April around 95 percent of the seasonal average.
--- Gunnison basin snow water equivalent plot

Streamflow:
May streamflow was 70 percent of average.

Soil Moisture:
Modeled soil moisture states were below average heading into the winter.

Forecast Summary:
May precipitation was much below average in the Gunnison Basin, as were the monthly streamflow volumes. Also, June 1st snow water equivalent for the Gunnison dropped to 35 percent below average. June through July volume forecasts range from 56 to 69 percent of average, with a median value of 62%. This resulted in a 5 percent decrease to the April through July volume forecasts. The Gunnison Basin April through July forecasts now range between 66 and 86 percent of average, with a median value of 74%.



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

Dolores Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October through May precipitation was 100 percent of average in the entire Dolores Basin. May precipitation was 45 percent of average.

Snow:
June 1st snow water equivalent was 0 percent of average in the Dolores Basin. However, there is still enough snow above 11,500 feet with minimal areal extent for some runoff into June. The snow peaked in early April at about 110 percent of the seasonal average.
--- Dolores basin snow water equivalent plot

Streamflow:
May streamflow was 70 percent of average.

Soil Moisture:
Modeled soil moisture states were below to much below average heading into the winter.

Forecast Summary:
May precipitation was much below average in the Dolores Basin. In addition, the May 1st snow water equivalent was below average at 0%, but still some snow was left above 11,500 feet for runoff into June. June through July volume forecasts range from 30 to 53 percent of average, with a median value of 34%. This resulted in about a 5% decrease in the April through July forecast volumes. The Dolores Basin April through July forecasts now range between 67 and 72 percent of average, with a median value of 69%.



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


Upper Colorado Mainstem Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Colorado
Lake Granby, Granby, Nr April-July16619084215
June-July9612077147
Willow Ck
Willow Ck Res, Granby, Nr April-July39448650
June-July11.1166722
Fraser
Winter Park April-July15.417.48719.4
June-July11138515
Williams Fork
Williams Fork Res, Parshall, Nr April-July69798390
June-July41517562
Muddy Ck
Wolford Mtn Res, Blo April-July32386347
June-July6.1125721
Blue
Dillon Res April-July10512273142
June-July60776597
Green Mtn Res April-July18521075240
June-July11013568163
Colorado
Kremmling, Nr April-July62068579760
June-July32038569460
Eagle
Gypsum, Blo April-July23526579300
June-July12115368190
Colorado
Dotsero, Nr April-July10101120781250
June-July52063070760
Frying Pan
Ruedi Res, Basalt, Nr April-July9511078132
June-July53687190
Roaring Fork
Glenwood Springs April-July50558082665
June-July30037577460
Colorado
Glenwood Springs, Blo April-July15401720801900
June-July8251010721190
Cameo, Nr April-July16701860772070
June-July9001090711300
Plateau Ck
Cameo, Nr April-July80857497
June-July15204332
Colorado
Cisco, Nr April-July31403450743840
June-July13001610632000
Mill Ck
Moab, Nr, Sheley Tun, At April-July2.93.6724.5
June-July1.52.2883.1
Colorado
Lake Powell, Glen Cyn Dam, At April-July44805150655880
June-July21002770603500


Gunnison Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Taylor
Taylor Park Res April-July64807898
June-July32476965
Almont April-July11411872124
June-July63676473
East
Almont April-July12614274160
June-July518269100
Gunnison
Gunnison, Nr April-July24527571310
June-July12615866193
Tomichi Ck
Gunnison April-July44546767
June-July15.3255838
Lake Fork
Gateview April-July879979113
June-July43556369
Gunnison
Blue Mesa Res April-July45050069570
June-July21026061330
Morrow Point Res April-July53054569585
June-July26528062320
Crystal Res April-July58560566635
June-July29031059340
Muddy Ck
Paonia Res, Bardine, Nr March-June68747484
April-July67757486
June-June9.1165926
June-July10.8195830
Nf Gunnison
Somerset, Nr April-July19622072250
June-July628666116
Surface Ck
Cedaredge April-July1112.87515.1
June-July3.85.6677.9
Uncompahgre
Ridgway Res April-July768886102
June-July33456559
Colona April-July9411281135
June-July32505773
Delta April-July83917898
June-July27355642
Gunnison
Grand Junction, Nr April-July10401130721240
June-July38046559580


Dolores Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period
90%
Exceedance
Volume
50%
Exceedance
Volume
Percent
Average
10%
Exceedance
Volume
Dolores
Dolores April-July16818269200
June-July27413660
Mcphee Res April-July21523072250
June-July28443466
San Miguel
Placerville, Nr April-July859572107
June-July33435355
Dolores
Cisco, Nr April-July42541067445
June-July856830104

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






Upper Colorado End of Month Reservoir Contents (kaf)

Usable
Capacity
EOM
Contents
Percent
Usable
Capacity
Last Year
EOM
Last Year
%Capacity
untitled Colorado
Lake Granby, Granby, Nr 490.3 359.6 73 334.6 68
untitled Willow Ck
Willow Ck Res, Granby, Nr 9.1 10.1 111 9.7 106
untitled Williams Fork
Williams Fork Res, Parshall, Nr 96.9 94.3 97 96.4 99
untitled Muddy Ck
Wolford Mountain Reservoir 66.0 67.5 102 66.6 101
untitled Blue
Dillon Res 254.0 259.6 102 260.2 102
Green Mtn Res 146.9 116.1 79 115.7 79
untitled Homestake Ck
Homestake Res 43.0 28.3 66 19.0 44
untitled Frying Pan
Ruedi Res, Basalt, Nr 102.0 86.1 84 88.9 87
untitled Plateau Ck
Vega Res, Collbran, Nr 32.9 33.7 103 34.3 104
untitled Taylor
Taylor Park Res 106.2 80.5 76 102.9 97
untitled Gunnison
Blue Mesa Res 829.5 601.6 73 776.4 94
Morrow Point Res 117.0 112.6 96 112.4 96
Crystal Res 17.5 16.8 96 16.8 96
untitled Muddy Ck
Paonia Res, Bardine, Nr 18.5 16.0 86 15.9 86
untitled Uncompahgre
Ridgway Res 83.2 78.9 95 84.5 102
untitled Dolores
Mcphee Res 381.1 381.4 100 381.4 100
untitled
TOTAL 2794.1 2343.0 84 2515.7 90
Colorado
Lake Powell 24322.0 14405.3 59 14751.2 61
untitled
TOTAL 24322.0 14405.3 59 14751.2 61

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 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: Brenda Alcorn, Tracy Cox