Green Water Supply Outlook, May 1, 2021

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Ashley Nielson,Patrick Kormos
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




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Yampa/White Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Duchesne Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Lower Green Basin Conditions




Snow Water Equivalent in Percent of Median.
* 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		70%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		30%
Exceedance
Volume		10%
Exceedance
Volume
Green
Daniel, Nr, Warren Bridge, At April-July126 150 169 69 194 215
May-July113 137 156 69 181 200
Pine Ck
Fremont Lk, Abv April-July46 56 63 64 69 80
May-July45 55 62 65 68 79
New Fork
Big Piney, Nr April-July89 142 170 48 198 255
May-July73 126 154 47 182 240
Green
Fontenelle Reservoir, Fontenelle, Nr April-July225 315 380 52 445 535
May-July173 260 325 51 390 480
Big Sandy
Farson, Nr April-July17.7 22 27 52 32 42
May-July16 20 25 52 30 40
Green
Green River, Wy, Nr April-July220 305 375 51 450 530
May-July170 255 325 51 400 480
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July24 27 31 57 37 44
May-July19 22 26 54 32 39
Viva Naughton Reservoir April-July30 33 37 50 44 55
May-July23 26 30 48 37 48
Blacks Fork
Robertson, Nr April-July32 39 46 52 56 67
May-July30 37 44 52 54 65
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July11.8 13.7 16.2 62 18.9 23
May-July11 12.9 15.4 59 18.1 22
Green
Flaming Gorge Reservoir April-July270 365 450 46 550 670
May-July200 295 380 45 480 600


Yampa/White 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
Yampa
Stagecoach Rsvr, Abv April-July9 10.7 11.7 51 12.7 14.7
May-July5.3 7 8 50 9 11
Steamboat Springs April-July80 95 110 42 132 167
May-July70 85 100 45 122 157
Elk
Milner, Nr April-July134 157 174 54 194 230
May-July115 138 155 53 175 210
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July14.7 18.2 21 29 27 34
May-July9 12.5 15 30 21 28
Yampa
Maybell, Nr April-July260 315 365 39 425 540
May-July220 275 325 42 385 500
Little Snake
Slater, Nr April-July58 69 80 51 92 113
May-July50 61 72 52 84 105
Dixon, Nr April-July106 127 148 43 177 215
May-July88 109 130 44 159 195
Lily, Nr April-July96 122 148 43 177 220
May-July78 104 130 45 159 200
Yampa
Deerlodge Park April-July355 430 510 41 605 755
May-July300 375 455 45 550 700
White
Meeker, Nr April-July106 121 136 49 149 178
May-July85 100 115 47 128 157
Watson, Nr April-July106 124 136 49 151 183
May-July85 103 115 49 130 162


Duchesne 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
Big Brush Ck
Vernal, Nr, Red Fleet Res, Abv April-July6.1 7.6 9.1 43 10 14
May-July5.4 6.9 8.4 46 9.3 13.3
Ashley Ck
Vernal, Nr April-July14.6 17 20 40 22 31
May-July13.6 16 19.3 41 21 30
West Fork Duchesne
Vat Diversion, Blo April-July3.7 4.5 5.5 30 6.2 7.8
May-July3 3.8 4.8 28 5.5 7.1
Duchesne
Tabiona, Nr April-July38 43 50 46 56 59
May-July32 37 44 45 50 53
Rock Ck
Upper Stillwater Reservoir April-July27 33 38 51 43 48
May-July23 29 34 48 39 44
South Fork Rock Ck
Docs Div, Blo April-July1.7 2.3 2.9 40 3.3 3.8
May-July1.4 2 2.6 38 3 3.5
Rock Ck
Mountain Home, Nr April-July33 40 47 53 53 59
May-July28 35 42 50 48 54
Currant Ck
Currant Ck Reservoir April-July2.6 3.5 4.8 24 5.5 7
May-July1.8 2.7 4 23 4.7 6.2
Strawberry
Strawberry Reservoir, Soldier Springs April-July9.8 12 14.5 20 16 17.8
May-July5.7 7.9 10.4 17.9 11.9 13.7
Starvation Reservoir, Duchesne, Nr April-July13 22 30 27 34 40
May-July6.5 15.5 23 25 27 33
Duchesne
Duchesne, Nr, Knight Div, Abv April-July70 87 99 51 110 116
May-July60 77 89 50 100 106
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July19 24 27 41 31 39
May-July17 22 25 40 29 37
Yellowstone
Altonah, Nr April-July19.5 23 26 43 29 37
May-July16.9 20 23 40 26 34
Whiterocks
Whiterocks, Nr April-July14 17.4 22 41 24 30
May-July12.5 15.9 21 41 23 29
Uinta
Neola, Nr April-July18.5 25 30 41 33 46
May-July16.3 23 28 39 31 44
Duchesne
Myton April-July45 64 81 25 96 122
May-July27 46 63 21 78 104
Randlett, Nr April-July53 73 89 23 105 131
May-July34 54 70 20 86 112


Lower Green 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
White
Blo Tabbyune Ck, Soldier Summit, Nr April-July0.7 0.94 1.5 9.5 2 3.5
May-July0.43 0.67 1.2 10.1 1.7 3.2
Fish Ck
Scofield, Nr, Reservoir, Abv April-July6 8.5 10 33 11 12.1
May-July4.8 7.3 8.8 34 9.8 10.9
Price
Scofield Reservoir, Scofield, Nr April-July7.5 10 11.9 29 13 14.3
May-July5.5 8 9.9 28 11 12.3
Green
Green River, Ut April-July710 940 1110 38 1350 1660
May-July550 780 950 37 1190 1500
Huntington Ck
Electric Lake April-July2.1 3 3.5 26 4 5.1
May-July1.7 2.6 3.1 26 3.6 4.7
Power Plant, Blo April-July14 16.1 16.8 42 17.8 20
May-July13.1 15.2 15.9 43 16.9 19.1
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July11 14.9 17.1 31 18.2 24
May-July9.7 13.6 15.8 30 16.9 23
Ferron Ck
Ferron, Nr April-July7 11.2 12.5 33 15.3 19.9
May-July6 10.2 11.5 33 14.3 18.9
Muddy Ck
Emery, Nr April-July3.6 5.2 5.8 29 6.5 7.8
May-July2.9 4.5 5.1 28 5.8 7.1

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).

Green 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 Green
Fontenelle Reservoir, Fontenelle, Nr 125.2 100 37 145.1 116 125.0 334.0
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 11.5 54 30 26.7 125 21.3 38.3
Blacks Fork
Meeks Cabin 8.4 51 28 15.7 95 16.5 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 4.5 69 32 6.6 102 6.5 13.9
untitled Green
Flaming Gorge Reservoir 3178.3 105 85 3207.0 105 3040.4 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 926.2 137 84 986.1 146 676.1 1105.9
Starvation Reservoir, Duchesne, Nr 164.9 109 100 165.1 109 151.9 165.3
untitled Rock Ck
Upper Stillwater Reservoir 4.0 140 13 2.4 84 2.9 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 16.0 58 44 27.3 99 27.6 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 16.7 83 65 21.7 108 20.1 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 36.8 111 56 53.6 162 33.0 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 37.4 94 60 47.8 121 39.6 62.5
untitled Huntington Ck
Electric Lake 18.4 98 58 22.6 121 18.7 31.5
untitled
TOTAL 4548.3 109 80 4727.7 113 4179.6 5689.6

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,Patrick Kormos