Lake Powell Water Supply Outlook, February 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 147 175 71 205 260
Pine Ck
Fremont Lk, Abv April-July47 58 70 71 80 95
New Fork
Big Piney, Nr April-July97 143 195 55 240 320
Green
Fontenelle Reservoir, Fontenelle, Nr April-July187 305 400 55 510 715
Big Sandy
Farson, Nr April-July18 26 32 62 38 52
Green
Green River, Wy, Nr April-July185 315 405 55 520 740
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July21 26 32 59 40 57
Viva Naughton Reservoir April-July26 32 41 55 53 82
Blacks Fork
Robertson, Nr April-July30 39 48 54 63 89
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July10.5 12.9 15 58 19.5 25
Green
Flaming Gorge Reservoir April-July265 385 500 51 660 990


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-July8 10.5 13 57 16 19
Steamboat Springs April-July80 117 143 55 173 220
Elk
Milner, Nr April-July135 176 215 67 250 300
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July18.2 30 41 56 50 60
Yampa
Maybell, Nr April-July300 420 530 57 630 790
Little Snake
Slater, Nr April-July50 72 94 60 114 143
Dixon, Nr April-July93 141 177 51 230 305
Lily, Nr April-July86 138 179 52 235 310
Yampa
Deerlodge Park April-July380 550 710 57 845 1060
White
Meeker, Nr April-July120 140 160 57 190 235
Watson, Nr April-July121 141 161 58 195 255


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-July7.8 10.5 12.4 59 15.2 21
Ashley Ck
Vernal, Nr April-July16.5 21 25 50 30 49
West Fork Duchesne
Vat Diversion, Blo April-July4.7 7.1 8.6 46 9.7 16.4
Duchesne
Tabiona, Nr April-July38 48 63 58 70 91
Rock Ck
Upper Stillwater Reservoir April-July26 35 43 58 49 75
South Fork Rock Ck
Docs Div, Blo April-July2 2.6 3.5 48 4.5 5.9
Rock Ck
Mountain Home, Nr April-July32 42 51 58 59 90
Currant Ck
Currant Ck Reservoir April-July4.1 5.7 8.2 41 10.9 18.4
Strawberry
Strawberry Reservoir, Soldier Springs April-July10.8 18.1 25 35 30 49
Starvation Reservoir, Duchesne, Nr April-July27 41 50 45 60 96
Duchesne
Duchesne, Nr, Knight Div, Abv April-July70 92 114 59 132 177
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July22 29 35 53 40 59
Yellowstone
Altonah, Nr April-July22 30 35 57 40 55
Whiterocks
Whiterocks, Nr April-July16.1 23 28 52 31 50
Uinta
Neola, Nr April-July20 30 41 55 45 68
Duchesne
Myton April-July49 92 125 38 153 270
Randlett, Nr April-July60 102 135 35 164 295


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-July1.5 3.7 6.2 40 7.7 9.6
Fish Ck
Scofield, Nr, Reservoir, Abv April-July8.4 11.6 14.5 48 18 26
Price
Scofield Reservoir, Scofield, Nr April-July10.6 14.9 18.3 45 23 34
Green
Green River, Ut April-July920 1180 1450 49 1820 2700
Huntington Ck
Electric Lake April-July3.6 4.3 5.2 39 5.8 11.3
Power Plant, Blo April-July17.4 19.3 21 53 23 35
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July15.1 22 27 48 31 47
Ferron Ck
Ferron, Nr April-July8.3 14.4 20 53 22 37
Muddy Ck
Emery, Nr April-July4.9 7 8 40 9 13.5


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 125 150 68 200 250
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July12 20 28 60 43 58
Fraser
Winter Park April-July9.5 12.5 15 77 18 21
Williams Fork
Williams Fork Reservoir, Parshall April-July43 53 63 66 81 100
Muddy Ck
Wolford Mountain Reservoir April-July13 21 29 54 40 52
Blue
Dillon Reservoir April-July65 87 108 66 134 160
Green Mtn Reservoir April-July115 150 180 65 225 275
Colorado
Kremmling, Nr April-July330 440 550 64 730 910
Eagle
Gypsum, Blo April-July130 165 200 60 265 330
Colorado
Dotsero, Nr April-July540 710 880 63 1150 1420
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July60 76 92 66 116 140
Roaring Fork
Glenwood Springs April-July320 385 450 65 575 700
Colorado
Glenwood Springs, Blo April-July900 1150 1400 66 1700 2150
Cameo, Nr April-July980 1240 1500 64 1950 2400
Plateau Ck
Cameo, Nr April-July20 33 46 37 73 100
Colorado
Cisco, Nr April-July1700 2150 2600 59 3350 4100
Lake Powell, Glen Cyn Dam, At April-July1750 2570 3300 46 4200 6000


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 64 72 73 88 105
Almont April-July80 97 115 74 135 160
East
Almont April-July85 110 130 71 160 195
Gunnison
Gunnison, Nr April-July165 210 255 69 315 380
Tomichi Ck
Gunnison April-July20 30 40 54 60 80
Lake Fork
Gateview April-July60 77 94 76 116 138
Gunnison
Blue Mesa Reservoir April-July320 395 470 70 590 710
Morrow Point Reservoir April-July345 430 510 69 635 765
Crystal Reservoir April-July375 475 570 68 710 850
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June24 32 40 42 56 74
April-July24 32 40 41 56 74
Nf Gunnison
Somerset, Nr April-July105 135 160 54 210 265
Surface Ck
Cedaredge April-July4 5.4 6.8 40 10.4 14
Uncompahgre
Ridgway Reservoir April-July42 52 62 61 80 98
Colona April-July47 62 76 55 103 130
Delta April-July22 35 48 42 75 102
Gunnison
Grand Junction, Nr April-July600 740 880 59 1140 1400


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-July73 108 135 55 165 220
Mcphee Reservoir April-July79 120 150 51 185 245
San Miguel
Placerville, Nr April-July41 58 70 55 83 109
Dolores
Cisco, Nr April-July122 192 255 45 320 415


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 74 180 230
Carracas, Nr April-July180 225 260 68 310 400
Navajo Reservoir, Archuleta, Nr April-July275 380 450 61 540 730
Farmington April-July360 495 600 55 710 945
Bluff, Nr April-July325 460 570 52 710 945
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July31 38 43 80 50 62
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July33 41 49 75 61 72
Little Navajo
Oso Div Dam,bl,chromo,nr April-July2.6 3.6 4.5 59 5.7 7.8
Piedra
Arboles, Nr April-July65 93 120 57 140 189
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July72 91 110 57 139 172
Animas
Durango April-July135 193 230 55 270 340
Florida
Lemon Reservoir, Durango, Nr April-July17 23 30 55 37 49
La Plata
Hesperus April-July5.2 7.6 10 43 13.2 18.1
Mancos
Mancos, Nr April-July6.5 10 12 39 16.7 24

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 153.5 102 45 176.6 118 150.1 344.8
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 7.9 48 21 22.5 136 16.6 38.3
Blacks Fork
Meeks Cabin 4.2 36 14 10.1 87 11.5 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 3.7 66 27 5.8 104 5.6 13.9
untitled Green
Flaming Gorge Reservoir 3151.0 103 84 3273.6 107 3050.5 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 920.2 139 83 959.4 145 659.9 1105.9
Starvation Reservoir, Duchesne, Nr 144.0 104 87 145.0 104 138.8 165.3
untitled Rock Ck
Upper Stillwater Reservoir 9.1 105 29 20.3 235 8.6 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 12.1 50 33 27.9 114 24.4 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 15.8 88 61 20.7 114 18.0 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 32.8 110 50 51.5 172 29.9 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 38.4 98 61 47.3 121 39.3 62.5
untitled Huntington Ck
Electric Lake 19.3 101 61 23.9 125 19.2 31.5
untitled
TOTAL 4511.9 108 79 4784.8 115 4172.4 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 407.3 116 83 436.3 124 352.2 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 7.5 95 83 8.6 108 8.0 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 69.3 109 72 76.3 119 63.8 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 53.5 120 81 50.8 114 44.6 66.0
untitled Blue
Dillon Reservoir 210.3 94 83 227.8 102 223.2 254.0
Green Mtn Reservoir 72.2 89 49 71.9 89 81.1 146.9
untitled Homestake Ck
Homestake Reservoir 40.3 126 94 41.2 129 31.9 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 60.2 83 59 73.2 101 72.4 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 5.3 42 16 15.0 119 12.6 32.9
untitled Taylor
Taylor Park Reservoir 65.1 97 61 74.1 111 66.9 106.2
untitled Gunnison
Blue Mesa Reservoir 400.1 78 48 554.0 108 514.6 829.5
Morrow Point Reservoir 105.9 95 90 107.1 96 111.4 117.0
Crystal Reservoir 15.6 102 89 14.8 97 15.3 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 1.7 41 10 3.8 90 4.2 16.7
untitled Uncompahgre
Ridgway Reservoir 53.2 77 64 65.3 94 69.2 83.0
untitled Dolores
Mcphee Reservoir 167.9 62 44 288.3 106 270.9 381.1
untitled
TOTAL 1735.4 89 62 2108.5 109 1942.5 2792.1


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 38.4 60 31 78.2 123 63.5 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1064.6 81 63 1307.8 100 1310.4 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 10.7 51 27 17.5 84 20.9 39.8
untitled
TOTAL 1113.7 80 60 1403.5 101 1394.7 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