Lake Powell Water Supply Outlook, April 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-July185 200 225 92 250 270
Pine Ck
Fremont Lk, Abv April-July60 70 82 84 90 96
New Fork
Big Piney, Nr April-July165 205 260 73 300 350
Green
Fontenelle Reservoir, Fontenelle, Nr April-July500 550 650 90 770 850
Big Sandy
Farson, Nr April-July21 27 32 62 40 48
Green
Green River, Wy, Nr April-July490 550 650 89 780 880
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30 34 45 83 55 68
Viva Naughton Reservoir April-July42 48 60 81 78 102
Blacks Fork
Robertson, Nr April-July67 73 85 96 100 118
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July22 25 28 108 31 35
Green
Flaming Gorge Reservoir April-July680 750 880 90 1100 1400


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-July17 19 21 91 25 33
Steamboat Springs April-July215 240 275 106 305 350
Elk
Milner, Nr April-July285 330 360 113 405 440
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July50 65 75 103 86 105
Yampa
Maybell, Nr April-July780 920 1010 108 1130 1290
Little Snake
Slater, Nr April-July110 145 162 104 175 215
Dixon, Nr April-July220 300 345 100 390 500
Lily, Nr April-July220 300 360 104 410 550
Yampa
Deerlodge Park April-July990 1210 1360 110 1500 1770
White
Meeker, Nr April-July200 225 250 89 265 310
Watson, Nr April-July210 235 260 93 285 335


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-July14 17 20 95 22 29
Ashley Ck
Vernal, Nr April-July30 35 45 90 50 70
West Fork Duchesne
Vat Diversion, Blo April-July11 13 15 81 17 22
Duchesne
Tabiona, Nr April-July79 87 95 88 102 120
Rock Ck
Upper Stillwater Reservoir April-July55 64 70 95 79 95
South Fork Rock Ck
Docs Div, Blo April-July4.5 5 6 82 7 8.5
Rock Ck
Mountain Home, Nr April-July66 75 83 94 93 112
Currant Ck
Currant Ck Reservoir April-July13.5 15 17 85 19 24
Strawberry
Strawberry Reservoir, Soldier Springs April-July30 33 45 63 53 70
Starvation Reservoir, Duchesne, Nr April-July73 81 90 80 100 130
Duchesne
Duchesne, Nr, Knight Div, Abv April-July145 165 175 90 195 230
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July43 50 57 86 63 74
Yellowstone
Altonah, Nr April-July45 55 62 102 67 84
Whiterocks
Whiterocks, Nr April-July34 40 45 83 53 71
Uinta
Neola, Nr April-July50 60 70 95 78 100
Duchesne
Myton April-July185 230 255 77 310 400
Randlett, Nr April-July195 245 280 73 330 450


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-July9 11.5 13 84 16 21
Fish Ck
Scofield, Nr, Reservoir, Abv April-July20 22 25 83 28 34
Price
Scofield Reservoir, Scofield, Nr April-July27 30 34 83 38 47
Green
Green River, Ut April-July2200 2500 2750 93 3300 4000
Huntington Ck
Electric Lake April-July7 8 9.7 73 12 15
Power Plant, Blo April-July26 32 37 93 44 54
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July33 41 47 84 52 65
Ferron Ck
Ferron, Nr April-July25 30 34 89 37 48
Muddy Ck
Emery, Nr April-July10 12 13.7 69 17 21


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-July170 195 220 100 255 290
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July28 36 45 96 55 66
Fraser
Winter Park April-July16 18 20 103 22 25
Williams Fork
Williams Fork Reservoir, Parshall April-July70 80 92 96 105 120
Muddy Ck
Wolford Mountain Reservoir April-July48 57 66 122 76 86
Blue
Dillon Reservoir April-July145 160 180 110 200 220
Green Mtn Reservoir April-July230 255 280 102 315 350
Colorado
Kremmling, Nr April-July710 800 890 103 1020 1150
Eagle
Gypsum, Blo April-July250 280 315 94 365 415
Colorado
Dotsero, Nr April-July1100 1230 1370 98 1600 1850
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July105 120 135 97 150 175
Roaring Fork
Glenwood Springs April-July485 545 605 88 685 765
Colorado
Glenwood Springs, Blo April-July1620 1800 2000 95 2330 2660
Cameo, Nr April-July1750 1980 2200 93 2550 2900
Plateau Ck
Cameo, Nr April-July45 58 70 56 90 115
Colorado
Cisco, Nr April-July2700 3100 3500 79 4100 4850
Lake Powell, Glen Cyn Dam, At April-July4100 5000 5600 78 6500 8100


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-July67 74 78 79 86 106
Almont April-July102 115 121 78 134 164
East
Almont April-July99 114 130 71 144 178
Gunnison
Gunnison, Nr April-July225 245 275 74 305 385
Tomichi Ck
Gunnison April-July43 48 59 80 75 94
Lake Fork
Gateview April-July66 85 96 78 118 146
Gunnison
Blue Mesa Reservoir April-July410 480 525 78 575 750
Morrow Point Reservoir April-July445 515 570 77 625 820
Crystal Reservoir April-July500 580 640 77 710 920
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June42 52 63 66 72 87
April-June39 49 60 66 69 84
April-July43 54 64 66 77 89
Nf Gunnison
Somerset, Nr April-July150 183 210 71 240 290
Surface Ck
Cedaredge April-July5.8 7 9 54 10.1 13.5
Uncompahgre
Ridgway Reservoir April-July55 67 75 74 87 114
Colona April-July64 80 91 66 106 145
Delta April-July37 49 63 56 81 121
Gunnison
Grand Junction, Nr April-July785 950 1070 72 1210 1580


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-July116 149 173 71 210 250
Mcphee Reservoir April-July132 166 200 68 245 290
San Miguel
Placerville, Nr April-July61 79 92 72 106 128
Dolores
Cisco, Nr April-July220 285 350 62 415 505


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-July100 118 132 61 159 197
Carracas, Nr April-July170 197 230 61 270 330
Navajo Reservoir, Archuleta, Nr April-July300 370 440 60 530 645
Farmington April-July460 545 675 61 845 1020
Bluff, Nr April-July455 535 680 62 865 1050
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July25 29 35 65 40 48
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July28 33 40 62 46 54
Little Navajo
Oso Div Dam,bl,chromo,nr April-July3 3.9 4.6 61 5.5 7
Piedra
Arboles, Nr April-July97 115 135 64 164 205
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July108 126 151 78 169 205
Animas
Durango April-July210 255 310 75 370 425
Florida
Lemon Reservoir, Durango, Nr April-July29 34 41 75 48 58
La Plata
Hesperus April-July12.1 14.5 18 78 22 27
Mancos
Mancos, Nr April-July10.6 13.2 18 58 22 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 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 397.3 126 81 343.2 109 314.3 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 9.6 117 105 9.0 109 8.2 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 74.4 122 77 64.2 105 60.8 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 50.8 116 77 33.6 77 43.7 66.0
untitled Blue
Dillon Reservoir 228.1 106 90 179.0 83 215.5 254.0
Green Mtn Reservoir 69.2 105 47 49.4 75 65.9 146.9
untitled Homestake Ck
Homestake Reservoir 41.0 163 95 18.3 73 25.1 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 68.2 108 67 55.9 88 63.2 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 7.8 55 24 7.8 55 14.2 32.9
untitled Taylor
Taylor Park Reservoir 71.4 114 67 60.4 97 62.4 106.2
untitled Gunnison
Blue Mesa Reservoir 534.4 117 64 249.7 55 454.9 829.5
Morrow Point Reservoir 105.9 95 90 106.7 95 111.7 117.0
Crystal Reservoir 17.4 107 99 16.9 104 16.2 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 7.8 252 46 4.0 129 3.1 16.7
untitled Uncompahgre
Ridgway Reservoir 67.0 96 81 50.0 71 70.0 83.0
untitled Dolores
Mcphee Reservoir 280.3 98 74 168.2 59 285.4 381.1
untitled
TOTAL 2030.3 112 73 1416.2 78 1814.5 2792.1
Colorado
Lake Powell 11822.0 70 49 9049.0 53 16941.7 24322.0
untitled
TOTAL 11822.0 70 49 9049.0 53 16941.7 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 83.5 132 67 40.3 64 63.2 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1292.5 99 76 955.5 73 1310.4 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 17.7 82 45 7.3 34 21.7 39.8
untitled
TOTAL 1393.7 100 75 1003.1 72 1395.3 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