Lake Powell Water Supply Outlook, March 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-July138 173 195 80 220 260
Pine Ck
Fremont Lk, Abv April-July49 59 73 74 80 91
New Fork
Big Piney, Nr April-July104 150 205 58 250 315
Green
Fontenelle Reservoir, Fontenelle, Nr April-July280 375 480 66 575 745
Big Sandy
Farson, Nr April-July19 26 32 62 38 52
Green
Green River, Wy, Nr April-July280 395 480 66 575 745
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July25 30 37 69 45 60
Viva Naughton Reservoir April-July32 40 48 65 61 87
Blacks Fork
Robertson, Nr April-July33 43 53 60 67 87
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July11.6 15.1 17 65 19.9 25
Green
Flaming Gorge Reservoir April-July330 460 555 57 710 995


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 11 13.5 59 16 20
Steamboat Springs April-July104 138 160 62 190 240
Elk
Milner, Nr April-July165 205 240 75 270 330
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July26 36 46 63 55 72
Yampa
Maybell, Nr April-July370 505 600 64 705 870
Little Snake
Slater, Nr April-July74 99 115 74 130 167
Dixon, Nr April-July142 192 225 65 260 355
Lily, Nr April-July139 190 230 67 270 365
Yampa
Deerlodge Park April-July475 670 825 67 960 1200
White
Meeker, Nr April-July124 145 160 57 188 245
Watson, Nr April-July124 147 161 58 193 260


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-July6.9 9.6 11.9 57 13.1 19
Ashley Ck
Vernal, Nr April-July14.6 18.1 24 48 27 40
West Fork Duchesne
Vat Diversion, Blo April-July4.6 6.6 7.8 42 10.1 12.2
Duchesne
Tabiona, Nr April-July43 52 61 56 73 84
Rock Ck
Upper Stillwater Reservoir April-July28 36 43 58 52 60
South Fork Rock Ck
Docs Div, Blo April-July2 2.8 3.4 47 4.2 5.3
Rock Ck
Mountain Home, Nr April-July34 43 51 58 62 72
Currant Ck
Currant Ck Reservoir April-July4.4 5.5 7.3 37 9.9 12.9
Strawberry
Strawberry Reservoir, Soldier Springs April-July11.3 16 23 32 26 39
Starvation Reservoir, Duchesne, Nr April-July30 36 44 39 56 77
Duchesne
Duchesne, Nr, Knight Div, Abv April-July77 97 113 58 134 150
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July20 28 35 53 40 49
Yellowstone
Altonah, Nr April-July21 29 35 57 40 50
Whiterocks
Whiterocks, Nr April-July14 18.6 26 48 29 38
Uinta
Neola, Nr April-July18.7 28 38 51 44 58
Duchesne
Myton April-July56 88 120 36 153 210
Randlett, Nr April-July66 98 128 33 163 230


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-July1.7 3.7 5 32 6.5 9
Fish Ck
Scofield, Nr, Reservoir, Abv April-July9.8 12.3 14.5 48 18 25
Price
Scofield Reservoir, Scofield, Nr April-July12.3 15.5 18.3 45 23 33
Green
Green River, Ut April-July1060 1320 1600 54 2000 2500
Huntington Ck
Electric Lake April-July4 4.6 5.2 39 5.7 10.3
Power Plant, Blo April-July18.2 19.1 21 53 22 34
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July18 23 27 48 31 44
Ferron Ck
Ferron, Nr April-July9.8 16.3 20 53 24 35
Muddy Ck
Emery, Nr April-July5.4 7.1 8 40 9.3 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-July105 135 165 75 205 245
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July15 23 31 66 43 55
Fraser
Winter Park April-July10.5 13 15 77 17.5 20
Williams Fork
Williams Fork Reservoir, Parshall April-July45 54 63 66 79 95
Muddy Ck
Wolford Mountain Reservoir April-July18 25 33 61 44 55
Blue
Dillon Reservoir April-July70 89 108 66 129 150
Green Mtn Reservoir April-July120 150 180 65 215 255
Colorado
Kremmling, Nr April-July380 480 580 67 730 880
Eagle
Gypsum, Blo April-July140 170 200 60 260 320
Colorado
Dotsero, Nr April-July630 770 910 65 1150 1400
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July65 80 100 72 115 140
Roaring Fork
Glenwood Springs April-July350 410 470 68 565 660
Colorado
Glenwood Springs, Blo April-July1000 1200 1400 66 1700 2110
Cameo, Nr April-July1100 1300 1500 64 1900 2300
Plateau Ck
Cameo, Nr April-July22 34 46 37 69 92
Colorado
Cisco, Nr April-July1700 2100 2550 57 3150 3800
Lake Powell, Glen Cyn Dam, At April-July1820 2510 3400 47 4100 5900


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 63 71 72 84 97
Almont April-July85 97 110 71 130 150
East
Almont April-July90 110 130 71 155 180
Gunnison
Gunnison, Nr April-July180 215 255 69 305 360
Tomichi Ck
Gunnison April-July19 29 39 53 55 71
Lake Fork
Gateview April-July55 72 88 72 109 130
Gunnison
Blue Mesa Reservoir April-July330 395 460 68 560 660
Morrow Point Reservoir April-July350 420 500 68 600 700
Crystal Reservoir April-July400 480 560 67 680 800
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June22 31 40 42 54 70
April-July22 31 40 41 54 70
Nf Gunnison
Somerset, Nr April-July105 130 160 54 200 250
Surface Ck
Cedaredge April-July3.7 5.2 6.7 40 9.3 12
Uncompahgre
Ridgway Reservoir April-July40 51 62 61 78 94
Colona April-July44 59 74 54 99 124
Delta April-July20 33 46 41 71 96
Gunnison
Grand Junction, Nr April-July580 730 880 59 1110 1340


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-July65 94 118 48 145 198
Mcphee Reservoir April-July72 105 132 45 165 235
San Miguel
Placerville, Nr April-July40 55 67 52 79 108
Dolores
Cisco, Nr April-July109 185 225 40 275 400


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-July96 121 141 66 161 197
Carracas, Nr April-July164 205 245 64 285 345
Navajo Reservoir, Archuleta, Nr April-July245 335 415 56 485 650
Farmington April-July310 440 555 50 650 870
Bluff, Nr April-July275 430 545 50 650 850
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July29 34 41 76 46 55
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July31 39 47 72 55 63
Little Navajo
Oso Div Dam,bl,chromo,nr April-July2.3 3 4.3 57 5.4 6.5
Piedra
Arboles, Nr April-July63 92 115 55 137 185
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July65 95 115 59 130 170
Animas
Durango April-July123 185 220 53 255 320
Florida
Lemon Reservoir, Durango, Nr April-July16 23 30 55 37 47
La Plata
Hesperus April-July5.2 6.9 9.5 41 11.7 17.1
Mancos
Mancos, Nr April-July5.3 8.6 10.8 35 14.1 22

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 131.6 103 39 147.3 115 127.6 334.0
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 8.1 54 21 23.1 153 15.1 38.3
Blacks Fork
Meeks Cabin 5.0 41 17 11.0 89 12.3 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 3.8 71 28 5.7 107 5.4 13.9
untitled Green
Flaming Gorge Reservoir 3145.1 104 84 3225.3 107 3015.6 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 925.3 140 84 961.3 146 660.2 1105.9
Starvation Reservoir, Duchesne, Nr 152.3 105 92 153.4 106 144.5 165.3
untitled Rock Ck
Upper Stillwater Reservoir 4.6 60 15 20.1 262 7.6 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 13.1 49 36 28.9 109 26.6 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 16.1 87 63 21.1 114 18.5 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 34.4 112 52 51.7 169 30.6 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 38.2 95 61 47.8 119 40.2 62.5
untitled Huntington Ck
Electric Lake 19.0 101 60 23.4 124 18.8 31.5
untitled
TOTAL 4496.7 109 79 4720.1 114 4123.0 5689.6


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 381.0 115 78 416.3 125 332.0 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 7.7 94 85 8.9 108 8.2 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 67.1 107 69 75.1 120 62.4 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 53.0 120 80 50.6 114 44.2 66.0
untitled Blue
Dillon Reservoir 203.9 93 80 228.2 104 219.3 254.0
Green Mtn Reservoir 69.8 95 48 70.3 96 73.5 146.9
untitled Homestake Ck
Homestake Reservoir 23.6 77 55 41.3 134 30.7 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 58.7 86 58 70.9 104 67.9 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 5.7 43 17 15.3 116 13.2 32.9
untitled Taylor
Taylor Park Reservoir 63.7 97 60 72.8 111 65.7 106.2
untitled Gunnison
Blue Mesa Reservoir 400.9 83 48 537.0 111 482.2 827.9
Morrow Point Reservoir 106.3 96 91 107.4 97 111.1 117.0
Crystal Reservoir 15.8 100 90 15.7 100 15.8 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 2.2 48 13 5.0 108 4.7 16.7
untitled Uncompahgre
Ridgway Reservoir 53.7 77 65 66.0 95 69.4 83.0
untitled Dolores
Mcphee Reservoir 167.3 61 44 286.7 105 272.3 381.1
untitled
TOTAL 1680.5 90 60 2067.6 110 1872.6 2790.6
Colorado
Lake Powell 9225.6 54 38 12011.5 70 17054.6 24322.0
untitled
TOTAL 9225.6 54 38 12011.5 70 17054.6 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 40.7 64 32 79.9 126 63.5 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1051.9 81 62 1294.8 100 1292.2 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 10.8 51 27 17.4 83 21.0 39.8
untitled
TOTAL 1103.4 80 59 1392.1 101 1376.7 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