Lake Powell Water Supply Outlook, January 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
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Lake Powell Sub-Basin Summaries




*Median of forecasts within each basin.





*Median of forecasts within each basin.







*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 Colorado Mainstem Basin Conditions




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

Gunnison Basin Conditions




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

Dolores Basin Conditions




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

San Juan 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-July114 155 190 78 225 285
Pine Ck
Fremont Lk, Abv April-July48 60 75 77 88 107
New Fork
Big Piney, Nr April-July106 177 210 59 255 375
Green
Fontenelle Reservoir, Fontenelle, Nr April-July187 340 460 63 625 815
Big Sandy
Farson, Nr April-July15.5 26 32 62 38 53
Green
Green River, Wy, Nr April-July185 345 460 63 645 860
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July22 27 36 67 48 64
Viva Naughton Reservoir April-July29 36 47 64 69 96
Blacks Fork
Robertson, Nr April-July32 48 57 64 70 94
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July10.5 13.7 17 65 21 26
Green
Flaming Gorge Reservoir April-July275 415 585 60 800 1190


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 13.1 17 74 19 23
Steamboat Springs April-July86 126 168 65 205 255
Elk
Milner, Nr April-July135 185 250 78 290 330
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July18.2 33 48 66 58 72
Yampa
Maybell, Nr April-July305 445 640 68 755 890
Little Snake
Slater, Nr April-July50 73 110 71 129 157
Dixon, Nr April-July93 145 215 62 250 355
Lily, Nr April-July86 139 220 64 265 400
Yampa
Deerlodge Park April-July380 570 855 69 995 1240
White
Meeker, Nr April-July120 142 190 68 210 250
Watson, Nr April-July121 146 193 69 220 260


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-July7.6 11.6 12.4 59 15.5 21
Ashley Ck
Vernal, Nr April-July15.6 23 25 50 31 52
West Fork Duchesne
Vat Diversion, Blo April-July3.8 7 8.6 46 13.2 17.1
Duchesne
Tabiona, Nr April-July35 52 65 60 82 95
Rock Ck
Upper Stillwater Reservoir April-July25 35 45 61 57 77
South Fork Rock Ck
Docs Div, Blo April-July1.9 2.5 3.8 52 4.9 7.3
Rock Ck
Mountain Home, Nr April-July30 42 51 58 68 94
Currant Ck
Currant Ck Reservoir April-July3.7 5.3 8.4 42 14 19.3
Strawberry
Strawberry Reservoir, Soldier Springs April-July10 19.8 28 39 38 59
Starvation Reservoir, Duchesne, Nr April-July27 42 52 46 78 105
Duchesne
Duchesne, Nr, Knight Div, Abv April-July67 93 118 61 148 189
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July20 29 36 55 46 60
Yellowstone
Altonah, Nr April-July22 29 35 57 42 55
Whiterocks
Whiterocks, Nr April-July15.4 24 28 52 34 53
Uinta
Neola, Nr April-July19.2 30 41 55 51 68
Duchesne
Myton April-July42 79 135 41 195 295
Randlett, Nr April-July53 90 155 40 210 320


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-July1.6 4.8 7.6 49 9.6 13.6
Fish Ck
Scofield, Nr, Reservoir, Abv April-July7.1 11.2 15.7 52 23 28
Price
Scofield Reservoir, Scofield, Nr April-July8.9 14.3 20 49 30 36
Green
Green River, Ut April-July920 1230 1780 60 2170 2920
Huntington Ck
Electric Lake April-July3.2 4.2 5.5 41 8.3 11.1
Power Plant, Blo April-July16.9 18.8 24 60 29 34
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July15.1 21 31 55 37 50
Ferron Ck
Ferron, Nr April-July9 13.9 22 58 29 38
Muddy Ck
Emery, Nr April-July4.9 7.4 8 40 11 16


Upper Colorado Mainstem 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
Colorado
Lake Granby, Granby, Nr April-July95 125 155 70 210 265
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July12 22 32 68 46 60
Fraser
Winter Park April-July9.5 13 16 82 19 22
Williams Fork
Williams Fork Reservoir, Parshall April-July44 56 68 71 86 104
Muddy Ck
Wolford Mountain Reservoir April-July14 23 31 57 45 60
Blue
Dillon Reservoir April-July70 91 112 69 140 170
Green Mtn Reservoir April-July120 155 190 69 240 295
Colorado
Kremmling, Nr April-July335 460 580 67 770 965
Eagle
Gypsum, Blo April-July135 180 220 66 295 370
Colorado
Dotsero, Nr April-July545 750 950 68 1260 1570
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July65 80 100 72 130 160
Roaring Fork
Glenwood Springs April-July330 405 480 70 600 720
Colorado
Glenwood Springs, Blo April-July895 1200 1500 71 1930 2360
Cameo, Nr April-July980 1290 1600 68 2110 2630
Plateau Ck
Cameo, Nr April-July20 33 46 37 78 110
Colorado
Cisco, Nr April-July1800 2250 2700 61 3500 4300
Lake Powell, Glen Cyn Dam, At April-July1780 2660 3800 53 4680 6520


Gunnison 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
Taylor
Taylor Park Reservoir April-July55 65 75 76 95 120
Almont April-July80 95 115 74 150 190
East
Almont April-July80 105 130 71 180 230
Gunnison
Gunnison, Nr April-July160 210 255 69 360 465
Tomichi Ck
Gunnison April-July22 34 46 62 66 87
Lake Fork
Gateview April-July60 78 96 78 118 140
Gunnison
Blue Mesa Reservoir April-July330 400 470 70 610 755
Morrow Point Reservoir April-July365 440 510 69 660 815
Crystal Reservoir April-July410 490 570 68 735 900
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June22 31 41 43 57 74
April-July21 31 41 42 60 80
Nf Gunnison
Somerset, Nr April-July100 130 165 56 220 275
Surface Ck
Cedaredge April-July3.5 5.1 6.8 40 10.6 14.5
Uncompahgre
Ridgway Reservoir April-July40 51 62 61 81 100
Colona April-July45 60 76 55 105 135
Delta April-July24 36 48 42 79 110
Gunnison
Grand Junction, Nr April-July620 760 900 61 1160 1430


Dolores 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
Dolores
Dolores April-July85 114 145 59 178 235
Mcphee Reservoir April-July94 126 170 58 205 285
San Miguel
Placerville, Nr April-July43 62 75 59 89 121
Dolores
Cisco, Nr April-July152 215 300 53 365 515


San Juan 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
San Juan
Pagosa Springs April-July106 138 160 74 184 240
Carracas, Nr April-July180 225 260 68 315 410
Navajo Reservoir, Archuleta, Nr April-July275 380 450 61 575 740
Farmington April-July370 500 610 55 755 950
Bluff, Nr April-July325 470 580 53 725 950
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July31 38 43 80 50 65
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July33 41 49 75 61 76
Little Navajo
Oso Div Dam,bl,chromo,nr April-July2.6 3.6 4.5 59 5.7 8
Piedra
Arboles, Nr April-July65 93 120 57 140 192
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July72 91 110 57 139 175
Animas
Durango April-July140 195 240 58 280 350
Florida
Lemon Reservoir, Durango, Nr April-July17.7 24 31 56 38 51
La Plata
Hesperus April-July5.2 8.3 11 48 13.7 20
Mancos
Mancos, Nr April-July6.5 10.2 14 45 18.4 27

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 188.1 107 55 207.5 118 175.3 344.8
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 8.0 52 21 22.1 143 15.5 38.3
Blacks Fork
Meeks Cabin 3.2 32 11 9.0 87 10.3 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 3.6 62 26 5.8 100 5.8 13.9
untitled Green
Flaming Gorge Reservoir 3156.9 102 84 3327.1 108 3094.9 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 919.1 139 83 954.5 145 659.7 1105.9
Starvation Reservoir, Duchesne, Nr 134.9 101 82 142.3 106 134.1 165.3
untitled Rock Ck
Upper Stillwater Reservoir 9.3 90 30 20.4 196 10.4 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 11.0 49 30 26.5 118 22.4 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 15.4 88 60 20.0 114 17.5 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 31.4 110 48 50.2 176 28.5 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 38.0 96 61 46.7 118 39.7 62.5
untitled Huntington Ck
Electric Lake 19.7 100 63 24.5 125 19.6 31.5
untitled
TOTAL 4538.6 107 80 4856.7 115 4233.8 5700.4


Upper Colorado 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 Colorado
Lake Granby, Granby, Nr 439.8 117 90 454.9 121 375.1 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 7.3 96 81 8.1 107 7.6 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 72.2 109 75 77.6 117 66.5 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 54.4 121 82 51.2 114 45.1 66.0
untitled Blue
Dillon Reservoir 217.8 96 86 227.0 100 226.9 254.0
Green Mtn Reservoir 74.0 82 50 74.2 83 89.8 146.9
untitled Homestake Ck
Homestake Reservoir 40.3 122 94 41.2 125 32.9 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 62.2 81 61 75.6 98 76.8 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 4.9 41 15 14.6 122 12.0 32.9
untitled Taylor
Taylor Park Reservoir 66.3 97 62 75.4 111 68.1 106.2
untitled Gunnison
Blue Mesa Reservoir 396.8 72 48 587.5 107 549.9 829.5
Morrow Point Reservoir 107.8 97 92 108.4 97 111.6 117.0
Crystal Reservoir 16.5 108 94 15.1 98 15.4 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 1.3 31 8 2.5 59 4.2 16.7
untitled Uncompahgre
Ridgway Reservoir 52.9 77 64 64.5 94 68.8 83.0
untitled Dolores
Mcphee Reservoir 167.8 62 44 288.8 107 270.1 381.1
untitled
TOTAL 1782.5 88 64 2166.5 107 2020.8 2792.1
Colorado
Lake Powell 10130.0 57 42 12603.9 71 17744.8 24322.0
untitled
TOTAL 10130.0 57 42 12603.9 71 17744.8 24322.0


San Juan 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 Los Pinos
Vallecito Reservoir, Bayfield, Nr 35.8 58 29 75.4 121 62.1 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1079.5 80 64 1325.7 99 1341.1 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 10.6 51 27 17.6 85 20.7 39.8
untitled
TOTAL 1125.8 79 60 1418.8 100 1423.8 1861.2

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