Lake Powell Water Supply Outlook, June 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-July142 158 169 69 184 210
June-July90 106 117 70 132 158
Pine Ck
Fremont Lk, Abv April-July47 56 63 64 69 79
June-July31 40 47 62 53 63
New Fork
Big Piney, Nr April-July110 132 154 43 184 225
June-July56 78 100 39 130 170
Green
Fontenelle Reservoir, Fontenelle, Nr April-July265 305 345 48 400 480
June-July135 175 215 45 270 350
Big Sandy
Farson, Nr April-July18.1 21 24 46 27 35
June-July10 13 16 47 19.3 27
Green
Green River, Wy, Nr April-July255 295 335 46 395 475
June-July130 173 210 44 270 350
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July22 24 26 48 29 34
June-July6 7.9 10.5 40 12.8 18
Viva Naughton Reservoir April-July30 32 35 47 38 44
June-July6 8.2 11.2 36 13.8 20
Blacks Fork
Robertson, Nr April-July40 44 48 54 53 62
June-July14 17.5 22 37 27 36
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July13.1 14.6 16.2 62 17.5 20
June-July5 6.5 8.1 46 9.4 12
Green
Flaming Gorge Reservoir April-July305 350 395 40 460 555
June-July135 180 225 38 290 385


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-July6.5 7.7 8.5 37 9.3 11.3
June-July1 2.2 3 35 3.8 5.8
Steamboat Springs April-July90 100 110 42 123 142
June-July20 30 40 34 53 72
Elk
Milner, Nr April-July137 150 162 51 177 200
June-July45 58 70 44 85 110
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July16.7 16.9 17.2 24 17.3 20
June-July0.5 0.75 1 10 1.1 4
Yampa
Maybell, Nr April-July270 295 325 35 360 415
June-July72 97 130 33 165 220
Little Snake
Slater, Nr April-July61 66 71 46 77 85
June-July14 18.5 24 36 30 38
Dixon, Nr April-July80 90 95 28 111 130
June-July15 25 30 22 46 65
Lily, Nr April-July83 94 99 29 114 133
June-July15 26 31 23 46 65
Yampa
Deerlodge Park April-July330 375 415 33 465 550
June-July80 127 165 33 215 300
White
Meeker, Nr April-July88 95 103 37 115 128
June-July30 37 45 31 57 70
Watson, Nr April-July82 91 100 36 112 125
June-July30 39 48 35 60 73


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-July5.8 7 7.5 36 8.5 10
June-July1.4 2.6 3.1 34 4.1 5.6
Ashley Ck
Vernal, Nr April-July14.6 18.5 19.6 39 21 23
June-July4.2 8.1 9.2 38 10.6 12.5
West Fork Duchesne
Vat Diversion, Blo April-July3.9 5 5.5 30 5.7 6.2
June-July0.74 1.8 2.3 25 2.5 3
Duchesne
Tabiona, Nr April-July37 42 45 42 47 49
June-July12.2 17.2 20 33 22 24
Rock Ck
Upper Stillwater Reservoir April-July32 35 38 51 43 44
June-July8.6 11.6 14.6 31 19.5 21
South Fork Rock Ck
Docs Div, Blo April-July1.8 2.3 2.4 33 2.6 3.2
June-July0.73 1.2 1.3 27 1.6 2.1
Rock Ck
Mountain Home, Nr April-July38 44 46 52 48 55
June-July12.4 18.4 20 36 22 29
Currant Ck
Currant Ck Reservoir April-July3 3.5 4.1 21 5 5.7
June-July0.32 0.82 1.4 19 2.3 3
Strawberry
Strawberry Reservoir, Soldier Springs April-July8 9.4 10.1 14 12 16
June-July1.4 2.8 3.5 15 5.4 9.4
Starvation Reservoir, Duchesne, Nr April-July9.5 12.5 14.2 13 17.4 27
June-July0.55 3.5 5.2 14 8.4 18
Duchesne
Duchesne, Nr, Knight Div, Abv April-July75 85 89 46 95 104
June-July25 35 39 34 45 54
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July20 25 27 41 29 34
June-July7.1 12.1 14.1 33 16.1 21
Yellowstone
Altonah, Nr April-July20 25 26 43 29 33
June-July8.2 13.2 14.2 35 17.4 21
Whiterocks
Whiterocks, Nr April-July15 20 21 39 22 26
June-July6.2 11.5 12.1 36 13.3 17.2
Uinta
Neola, Nr April-July19 23 27 36 28 32
June-July8.9 12.9 16.8 34 17.8 22
Duchesne
Myton April-July62 74 76 23 80 93
June-July6.8 19 21 12 25 38
Randlett, Nr April-July66 78 81 21 85 98
June-July11.6 24 27 13 31 44


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-July0.81 0.9 1 6 1.1 2
June-July0.29 0.38 0.48 14 0.58 1.5
Fish Ck
Scofield, Nr, Reservoir, Abv April-July3.5 4 4.3 14 4.7 5.4
June-July0.57 1.1 1.4 14 1.8 2.5
Price
Scofield Reservoir, Scofield, Nr April-July5 5.3 5.5 13 6 7
June-July0.64 0.94 1.1 9 1.6 2.6
Green
Green River, Ut April-July790 870 955 32 1070 1270
June-July320 400 485 31 600 800
Huntington Ck
Electric Lake April-July1.8 2.3 2.4 18 2.5 2.7
June-July0.35 0.85 0.95 20 1.1 1.3
Power Plant, Blo April-July10 12 13.6 34 14.5 16.9
June-July6.3 8.3 9.9 50 10.8 13.2
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July8 10.6 11 20 11.5 13.4
June-July5 7.6 8 25 8.5 10.4
Ferron Ck
Ferron, Nr April-July7.9 9.7 9.9 26 10.5 12.3
June-July1.8 3.6 3.8 18 4.4 6.2
Muddy Ck
Emery, Nr April-July3.3 3.6 3.8 19 4 5.1
June-July1.2 1.6 1.7 14 1.9 3


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-July140 155 170 77 185 200
June-July62 77 92 63 107 122
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July26 29 33 70 37 40
June-July2.1 5.1 9.1 43 13.1 16.1
Fraser
Winter Park April-July13 14.5 16 82 17.5 19
June-July8.5 10 11.5 81 13 14.5
Williams Fork
Williams Fork Reservoir, Parshall April-July50 56 62 65 68 74
June-July27 33 39 60 45 51
Muddy Ck
Wolford Mountain Reservoir April-July20 22 25 46 28 31
June-July1.2 3.2 6.2 32 9.2 12.2
Blue
Dillon Reservoir April-July68 78 88 54 98 108
June-July36 46 56 51 66 76
Green Mtn Reservoir April-July120 135 150 55 165 180
June-July63 78 93 51 108 123
Colorado
Kremmling, Nr April-July420 470 520 60 570 620
June-July180 230 280 53 330 380
Eagle
Gypsum, Blo April-July120 135 155 46 175 190
June-July53 68 88 41 108 123
Colorado
Dotsero, Nr April-July620 695 770 55 845 920
June-July260 335 410 49 485 560
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July70 77 85 61 93 100
June-July36 43 51 57 59 66
Roaring Fork
Glenwood Springs April-July280 315 350 51 385 420
June-July161 196 230 51 265 300
Colorado
Glenwood Springs, Blo April-July920 1040 1160 55 1280 1400
June-July425 545 665 51 785 905
Cameo, Nr April-July950 1070 1200 51 1330 1450
June-July445 565 695 49 825 945
Plateau Ck
Cameo, Nr April-July22 26 30 24 35 40
June-July0.48 4.5 8.5 17 13.5 18.5
Colorado
Cisco, Nr April-July1400 1600 1800 41 2000 2200
June-July560 760 960 41 1160 1360
Lake Powell, Glen Cyn Dam, At April-July1280 1570 1800 25 2090 2530
June-July450 735 970 26 1260 1700


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-July48 53 58 59 63 68
June-July25 30 35 56 40 45
Almont April-July65 72 80 52 88 95
June-July34 41 49 52 57 64
East
Almont April-July70 80 90 49 100 110
June-July35 45 55 52 65 75
Gunnison
Gunnison, Nr April-July125 145 165 45 185 205
June-July63 83 103 48 123 143
Tomichi Ck
Gunnison April-July16 20 24 32 28 32
June-July3 7 11 30 15 19
Lake Fork
Gateview April-July50 57 65 53 73 80
June-July26 33 41 51 49 56
Gunnison
Blue Mesa Reservoir April-July250 280 310 46 340 370
June-July112 142 172 45 200 230
Morrow Point Reservoir April-July260 295 330 45 365 400
June-July118 153 188 46 225 260
Crystal Reservoir April-July290 325 360 43 395 430
June-July133 168 205 46 240 275
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June15 16.5 18 19 20 22
April-July15 16.5 18 19 20 22
June-June0.41 1.9 3.4 15 5.4 7.4
June-July1.9 3.4 4.9 17 7 9
Nf Gunnison
Somerset, Nr April-July90 100 110 37 120 130
June-July28 38 48 42 58 68
Surface Ck
Cedaredge April-July3.5 4.2 5 30 5.8 6.5
June-July0.14 0.84 1.6 22 2.4 3.1
Uncompahgre
Ridgway Reservoir April-July38 43 48 48 53 58
June-July19 24 29 45 34 39
Colona April-July40 46 52 38 61 70
June-July18.9 25 31 38 40 49
Delta April-July24 28 32 28 36 40
June-July2.9 6.9 10.9 19 14.9 18.9
Gunnison
Grand Junction, Nr April-July410 470 530 36 590 650
June-July150 210 270 39 330 390


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-July64 68 73 30 80 89
June-July15 19 24 26 31 40
Mcphee Reservoir April-July67 71 76 26 83 92
June-July15 19 24 25 31 40
San Miguel
Placerville, Nr April-July42 47 50 39 53 59
June-July21 26 29 39 32 38
Dolores
Cisco, Nr April-July87 90 91 16 95 105
June-July13 16 17 9 21 31


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-July115 122 128 60 133 140
June-July27 34 40 42 45 52
Carracas, Nr April-July183 193 205 54 215 230
June-July47 57 69 44 80 95
Navajo Reservoir, Archuleta, Nr April-July300 315 335 46 355 380
June-July50 64 83 29 104 130
Farmington April-July390 420 450 41 495 535
June-July90 120 153 33 195 235
Bluff, Nr April-July360 395 420 38 460 505
June-July75 107 134 30 175 220
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July30 32 34 63 36 38
June-July8 9.5 11.7 51 13.8 15.5
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July34 36 39 60 41 44
June-July10 11.2 14.6 49 16.8 20
Little Navajo
Oso Div Dam,bl,chromo,nr April-July3.1 3.2 3.3 43 3.4 3.5
June-July0.3 0.4 0.5 25 0.61 0.7
Piedra
Arboles, Nr April-July84 88 94 45 100 107
June-July17 21 27 36 33 40
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July95 104 110 57 117 127
June-July31 40 46 46 53 63
Animas
Durango April-July147 160 176 42 190 210
June-July57 70 86 39 100 121
Florida
Lemon Reservoir, Durango, Nr April-July22 23 25 45 27 29
June-July5.5 7.2 8.8 33 11 13
La Plata
Hesperus April-July7 7.5 8 35 8.5 9.3
June-July1.7 2.2 2.7 32 3.2 4
Mancos
Mancos, Nr April-July7.9 8 8.6 28 8.8 9.9
June-July1 1 1.6 16 1.9 3

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 151.6 92 45 203.5 124 164.0 334.0
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 18.8 64 49 31.4 107 29.4 38.3
Blacks Fork
Meeks Cabin 16.6 67 56 28.1 113 24.9 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 8.3 73 60 14.3 127 11.3 13.9
untitled Green
Flaming Gorge Reservoir 3148.8 103 84 3227.6 105 3071.5 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 903.4 126 82 1003.1 140 716.0 1105.9
Starvation Reservoir, Duchesne, Nr 152.8 99 92 164.6 106 154.8 165.3
untitled Rock Ck
Upper Stillwater Reservoir 21.5 137 69 18.2 116 15.7 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 13.8 48 38 38.2 134 28.6 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 17.2 73 67 23.4 100 23.4 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 33.3 69 51 58.9 121 48.5 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 37.6 73 60 55.8 108 51.6 62.5
untitled Huntington Ck
Electric Lake 18.0 76 57 26.9 113 23.8 31.5
untitled
TOTAL 4541.6 104 80 4894.2 112 4363.6 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 403.7 111 82 483.1 133 363.6 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 7.4 83 81 8.9 100 8.9 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 73.0 100 75 88.3 121 73.0 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 65.0 109 98 65.9 110 59.9 66.0
untitled Blue
Dillon Reservoir 222.9 96 88 245.6 106 232.7 254.0
Green Mtn Reservoir 71.5 80 49 108.5 121 89.8 146.9
untitled Homestake Ck
Homestake Reservoir 19.6 79 46 29.2 118 24.8 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 68.9 88 68 79.3 102 78.0 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 17.4 57 53 25.8 84 30.8 32.9
untitled Taylor
Taylor Park Reservoir 70.1 94 66 85.9 115 74.7 106.2
untitled Gunnison
Blue Mesa Reservoir 350.0 61 42 549.7 96 575.3 827.9
Morrow Point Reservoir 113.1 100 97 106.5 94 113.2 117.0
Crystal Reservoir 17.1 102 97 17.4 104 16.7 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 15.7 100 94 15.7 100 15.7 16.7
untitled Uncompahgre
Ridgway Reservoir 61.4 87 74 67.9 96 70.7 83.0
untitled Dolores
Mcphee Reservoir 189.0 54 50 283.4 81 347.8 381.1
untitled
TOTAL 1765.6 81 63 2261.2 104 2175.6 2790.6
Colorado
Lake Powell 8366.4 46 34 12238.5 67 18186.3 24322.0
untitled
TOTAL 8366.4 46 34 12238.5 67 18186.3 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 56.6 76 45 95.1 128 74.0 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1044.6 77 62 1296.8 95 1361.0 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 13.2 55 33 19.8 82 24.1 39.8
untitled
TOTAL 1114.4 76 60 1411.7 97 1459.0 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