Lake Powell Water Supply Outlook, June 1, 2020

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-July200 215 225 92 245 265
June-July133 148 158 94 178 200
Pine Ck
Fremont Lk, Abv April-July60 64 72 73 78 90
June-July43 47 55 72 61 73
New Fork
Big Piney, Nr April-July171 186 210 59 235 270
June-July90 105 129 51 156 190
Green
Fontenelle Reservoir, Fontenelle, Nr April-July500 535 590 81 645 735
June-July255 290 345 73 400 490
Big Sandy
Farson, Nr April-July20 22 25 48 28 35
June-July9.7 11.5 14.7 43 17.9 25
Green
Green River, Wy, Nr April-July505 545 600 82 655 745
June-July250 290 345 72 400 490
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30 32 36 67 40 45
June-July7 9.2 13.4 52 17 22
Viva Naughton Reservoir April-July39 42 47 64 51 57
June-July7 9.6 14.5 47 19 25
Blacks Fork
Robertson, Nr April-July67 75 83 93 90 97
June-July25 33 41 69 48 55
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July24 26 28 108 31 32
June-July9 10.7 12.8 72 15.3 17
Green
Flaming Gorge Reservoir April-July650 685 740 76 830 910
June-July320 355 410 68 500 580


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-July19.8 21 23 100 25 27
June-July3 4.5 6.2 72 8 10
Steamboat Springs April-July240 250 260 100 280 300
June-July70 80 90 76 110 130
Elk
Milner, Nr April-July270 285 300 94 320 355
June-July100 114 129 81 150 185
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July67 69 70 96 73 78
June-July2 3.4 4.8 46 7.5 13
Yampa
Maybell, Nr April-July780 815 860 92 935 980
June-July220 255 300 77 375 420
Little Snake
Slater, Nr April-July128 138 147 94 158 168
June-July25 35 44 67 55 65
Dixon, Nr April-July245 260 275 80 300 325
June-July45 60 76 56 99 125
Lily, Nr April-July235 255 270 78 290 320
June-July40 60 75 56 97 125
Yampa
Deerlodge Park April-July980 1040 1130 91 1210 1310
June-July220 280 370 74 450 550
White
Meeker, Nr April-July162 173 185 66 200 220
June-July60 71 83 58 100 120
Watson, Nr April-July145 158 175 63 190 210
June-July60 73 90 65 105 125


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-July11 11.9 13 62 14.4 15.7
June-July2.1 3 4.1 46 5.5 6.8
Ashley Ck
Vernal, Nr April-July25 28 30 60 33 35
June-July6.5 9 11.5 48 14 16.5
West Fork Duchesne
Vat Diversion, Blo April-July12 13 14 75 15 16.5
June-July2.5 3.5 4.5 48 5.5 7
Duchesne
Tabiona, Nr April-July74 82 87 81 92 100
June-July25 33 38 63 43 51
Rock Ck
Upper Stillwater Reservoir April-July61 66 70 95 76 81
June-July25 30 34 72 40 45
South Fork Rock Ck
Docs Div, Blo April-July4.8 5.1 5.5 75 5.9 6.3
June-July2 2.3 2.7 55 3.1 3.5
Rock Ck
Mountain Home, Nr April-July72 77 80 91 84 92
June-July33 38 41 73 45 53
Currant Ck
Currant Ck Reservoir April-July12.5 13.3 14 70 14.8 15.5
June-July1.7 2.5 3.2 43 4 4.7
Strawberry
Strawberry Reservoir, Soldier Springs April-July18 19.9 21 30 24 26
June-July4.1 6 7.1 30 10 12
Starvation Reservoir, Duchesne, Nr April-July40 46 50 45 53 56
June-July8.9 15 18.9 50 22 25
Duchesne
Duchesne, Nr, Knight Div, Abv April-July150 158 165 85 177 190
June-July60 68 75 65 87 100
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July54 56 60 91 64 69
June-July25 27 31 72 35 40
Yellowstone
Altonah, Nr April-July52 56 60 98 62 68
June-July27 31 35 85 37 43
Whiterocks
Whiterocks, Nr April-July32 36 40 74 42 46
June-July13 17.6 21 62 23 27
Uinta
Neola, Nr April-July56 61 65 88 69 76
June-July27 32 36 72 40 47
Duchesne
Myton April-July188 196 210 64 230 260
June-July60 68 82 47 100 132
Randlett, Nr April-July193 205 220 57 240 275
June-July60 70 87 41 106 140


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-July4.3 4.4 4.5 29 5 5.5
June-July0.67 0.77 0.9 26 1.4 1.9
Fish Ck
Scofield, Nr, Reservoir, Abv April-July14.3 14.8 15.1 50 15.9 16.8
June-July2.5 3 3.3 34 4.1 5
Price
Scofield Reservoir, Scofield, Nr April-July17.8 18.4 19.1 47 20 21
June-July2.7 3.3 4 30 5.2 6.2
Green
Green River, Ut April-July1940 2070 2220 75 2390 2640
June-July750 880 1030 66 1200 1450
Huntington Ck
Electric Lake April-July7.1 7.4 7.9 59 8.6 9.5
June-July1.2 1.5 2 42 2.7 3.6
Power Plant, Blo April-July24 25 26 65 28 29
June-July10.3 11.2 12 61 13.9 15.1
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July37 40 42 75 46 49
June-July14.7 17.1 20 63 24 27
Ferron Ck
Ferron, Nr April-July26 28 29 76 31 33
June-July9.7 11.3 12.7 60 14.5 16.3
Muddy Ck
Emery, Nr April-July10.5 11.3 12 60 13 14.2
June-July4.6 5.4 6.1 52 7.1 8.3


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-July190 205 220 100 235 250
June-July97 112 127 88 142 157
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July34 37 40 85 44 48
June-July7 10 13 62 17 21
Fraser
Winter Park April-July16 17.2 18.4 95 20 22
June-July10 11.2 12.4 87 14 16
Williams Fork
Williams Fork Reservoir, Parshall April-July75 80 86 90 93 100
June-July40 45 51 78 58 65
Muddy Ck
Wolford Mountain Reservoir April-July58 62 66 122 71 75
June-July8.1 12.1 16.1 83 21 25
Blue
Dillon Reservoir April-July135 145 155 95 165 175
June-July78 88 98 89 108 118
Green Mtn Reservoir April-July225 240 255 93 275 290
June-July125 140 155 84 175 190
Colorado
Kremmling, Nr April-July720 770 825 96 880 930
June-July335 385 440 84 495 545
Eagle
Gypsum, Blo April-July235 255 275 82 295 315
June-July117 137 157 73 177 197
Colorado
Dotsero, Nr April-July1080 1150 1220 87 1300 1380
June-July510 580 650 77 730 810
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July100 110 120 86 130 140
June-July53 63 73 82 83 93
Roaring Fork
Glenwood Springs April-July440 475 510 74 550 590
June-July255 290 325 71 365 405
Colorado
Glenwood Springs, Blo April-July1500 1640 1780 84 1940 2100
June-July715 855 995 77 1160 1320
Cameo, Nr April-July1600 1720 1850 78 2000 2150
June-July790 910 1040 73 1190 1340
Plateau Ck
Cameo, Nr April-July32 36 40 32 50 60
June-July2.1 6.1 10.1 21 20 30
Colorado
Cisco, Nr April-July2250 2500 2700 61 2900 3150
June-July960 1210 1410 60 1610 1860
Lake Powell, Glen Cyn Dam, At April-July3520 3760 4100 57 4430 4720
June-July1500 1740 2080 55 2410 2700


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-July61 65 69 70 73 79
June-July30 34 38 61 42 48
Almont April-July88 96 103 66 109 118
June-July43 51 58 62 64 73
East
Almont April-July103 110 116 64 125 137
June-July45 52 58 55 67 79
Gunnison
Gunnison, Nr April-July200 215 235 64 250 275
June-July90 106 122 57 140 165
Tomichi Ck
Gunnison April-July36 41 44 59 48 52
June-July12 16.9 20 54 24 28
Lake Fork
Gateview April-July67 74 79 64 86 95
June-July31 38 43 53 50 59
Gunnison
Blue Mesa Reservoir April-July350 375 395 59 425 470
June-July145 174 193 51 220 265
Morrow Point Reservoir April-July370 405 425 57 450 495
June-July155 189 210 52 235 280
Crystal Reservoir April-July405 440 465 56 500 540
June-July170 205 230 51 265 305
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June29 30 31 32 32 35
April-July28 29 30 31 32 35
June-June3.5 4.4 5.5 24 6.5 9.5
June-July4.9 5.9 6.9 24 8.9 11.9
Nf Gunnison
Somerset, Nr April-July134 139 148 50 159 177
June-July32 37 46 40 57 75
Surface Ck
Cedaredge April-July5.4 6 6.4 38 6.6 7.5
June-July1 1.6 2 26 2.2 3.1
Uncompahgre
Ridgway Reservoir April-July48 52 55 54 59 64
June-July27 31 34 52 38 43
Colona April-July47 50 54 39 61 69
June-July24 27 31 38 38 46
Delta April-July25 30 33 29 37 42
June-July7 12.7 15.5 27 18.9 24
Gunnison
Grand Junction, Nr April-July600 640 685 46 750 850
June-July210 250 295 42 360 460


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-July87 92 96 39 102 114
June-July19 24 28 30 34 46
Mcphee Reservoir April-July86 91 95 32 102 115
June-July19 24 28 29 35 48
San Miguel
Placerville, Nr April-July53 58 64 50 70 76
June-July24 29 35 47 41 47
Dolores
Cisco, Nr April-July142 148 155 27 171 205
June-July39 45 52 28 68 100


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-July117 120 127 59 132 145
June-July19 22 29 30 34 47
Carracas, Nr April-July182 187 200 53 210 225
June-July39 44 57 36 65 82
Navajo Reservoir, Archuleta, Nr April-July320 335 365 50 385 410
June-July41 55 86 30 108 130
Farmington April-July510 540 570 52 620 680
June-July127 155 186 40 235 295
Bluff, Nr April-July475 510 545 50 595 655
June-July100 134 168 37 220 280
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July28 29 31 57 33 35
June-July6 7.2 9 39 10.5 13
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July30 31 33 51 35 39
June-July7 8.1 10 33 12.4 16
Little Navajo
Oso Div Dam,bl,chromo,nr April-July2.5 2.6 2.9 38 3 3.1
June-July0.2 0.25 0.6 30 0.69 0.8
Piedra
Arboles, Nr April-July101 104 112 53 116 125
June-July18 21 29 39 33 42
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July114 121 130 67 138 150
June-July32 39 48 48 56 68
Animas
Durango April-July230 245 260 63 275 305
June-July82 96 113 51 130 160
Florida
Lemon Reservoir, Durango, Nr April-July29 32 34 62 36 39
June-July7.5 11 13 48 15 18
La Plata
Hesperus April-July10.1 11.1 11.9 52 12.8 14.1
June-July2 3 3.8 45 4.7 6
Mancos
Mancos, Nr April-July10.1 10.2 10.7 35 11 12.7
June-July1.7 1.8 2.3 22 2.6 4.3

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 135.8 112 39 95.1 78 121.7 344.8
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 24.5 125 64 17.6 90 19.6 38.3
Blacks Fork
Meeks Cabin 12.1 90 40 6.8 51 13.4 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 5.8 106 42 4.2 76 5.5 13.9
untitled Green
Flaming Gorge Reservoir 3220.1 107 86 3185.0 105 3021.3 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 978.8 147 89 860.5 130 663.7 1105.9
Starvation Reservoir, Duchesne, Nr 164.7 110 100 142.6 95 149.7 165.3
untitled Rock Ck
Upper Stillwater Reservoir 6.6 149 21 2.1 48 4.5 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 29.7 109 81 15.5 57 27.3 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 22.0 115 85 13.3 70 19.0 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 52.2 169 79 28.6 93 30.9 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 48.5 121 78 30.0 75 40.0 62.5
untitled Huntington Ck
Electric Lake 22.7 124 72 16.2 89 18.3 31.5
untitled
TOTAL 4723.6 114 83 4417.5 107 4134.9 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 483.3 133 99 375.7 103 363.6 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 8.9 100 98 8.1 91 8.9 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 88.3 121 91 80.3 110 73.0 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 66.0 110 100 57.2 95 59.9 66.0
untitled Blue
Dillon Reservoir 245.6 106 97 186.6 80 232.7 254.0
Green Mtn Reservoir 108.5 121 74 85.4 95 89.8 146.9
untitled Homestake Ck
Homestake Reservoir 29.2 118 68 13.2 53 24.8 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 79.4 102 78 66.1 85 78.0 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 25.9 84 79 24.1 78 30.8 32.9
untitled Taylor
Taylor Park Reservoir 86.0 115 81 58.8 79 74.7 106.2
untitled Gunnison
Blue Mesa Reservoir 549.7 96 66 447.2 78 575.3 829.5
Morrow Point Reservoir 106.5 94 91 112.8 100 113.2 117.0
Crystal Reservoir 17.4 104 99 18.9 113 16.7 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 15.7 100 94 6.8 43 15.7 16.7
untitled Uncompahgre
Ridgway Reservoir 67.9 96 82 59.1 84 70.7 83.0
untitled Dolores
Mcphee Reservoir 283.4 81 74 333.7 96 347.8 381.1
untitled
TOTAL 2261.8 104 81 1934.1 89 2175.6 2792.1
Colorado
Lake Powell 12238.5 67 50 10343.1 57 18186.3 24322.0
untitled
TOTAL 12238.5 67 50 10343.1 57 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 123.7 123 99 64.5 64 100.5 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1366.7 96 81 1278.8 89 1429.7 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 28.9 90 73 18.9 59 32.1 39.8
untitled
TOTAL 1519.3 97 82 1362.1 87 1562.3 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