Lake Powell Water Supply Outlook, May 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 220 235 96 260 275
May-July188 210 225 100 250 265
Pine Ck
Fremont Lk, Abv April-July62 71 80 82 87 100
May-July61 70 79 82 86 99
New Fork
Big Piney, Nr April-July175 220 250 70 280 345
May-July153 198 230 70 260 325
Green
Fontenelle Reservoir, Fontenelle, Nr April-July530 610 670 92 755 830
May-July445 525 585 91 670 745
Big Sandy
Farson, Nr April-July23 27 32 62 38 49
May-July20 24 29 60 35 46
Green
Green River, Wy, Nr April-July520 605 670 92 755 830
May-July440 525 590 92 675 750
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30 36 45 83 53 62
May-July25 31 40 83 48 57
Viva Naughton Reservoir April-July45 52 60 81 71 84
May-July37 44 52 84 63 76
Blacks Fork
Robertson, Nr April-July62 69 75 84 83 93
May-July58 65 71 84 79 89
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July21 23 26 100 28 32
May-July20 22 25 96 27 31
Green
Flaming Gorge Reservoir April-July670 765 880 90 1030 1100
May-July555 650 765 91 915 985


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 28
May-July10.2 12.2 14 88 18 21
Steamboat Springs April-July225 240 260 100 280 320
May-July187 200 220 100 240 280
Elk
Milner, Nr April-July290 320 340 106 365 405
May-July250 280 300 103 325 365
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July62 70 78 107 87 95
May-July40 48 56 112 65 73
Yampa
Maybell, Nr April-July800 860 935 100 1000 1100
May-July655 715 790 102 855 950
Little Snake
Slater, Nr April-July120 133 147 94 158 176
May-July104 117 131 95 142 160
Dixon, Nr April-July230 255 295 86 320 370
May-July189 215 255 86 280 330
Lily, Nr April-July230 255 300 87 335 385
May-July192 215 260 90 295 345
Yampa
Deerlodge Park April-July1010 1100 1220 98 1310 1470
May-July835 925 1040 102 1130 1290
White
Meeker, Nr April-July190 205 220 79 240 270
May-July163 178 195 80 215 245
Watson, Nr April-July180 205 225 80 255 285
May-July154 179 200 85 230 260


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-July14 15.5 17 81 19 23
May-July12.9 14.4 15.9 86 17.9 22
Ashley Ck
Vernal, Nr April-July27 32 40 80 45 55
May-July25 30 38 81 43 53
West Fork Duchesne
Vat Diversion, Blo April-July9.5 10.5 12 65 13.5 15
May-July8.5 9.5 11 64 12.5 14
Duchesne
Tabiona, Nr April-July70 76 87 81 95 105
May-July62 68 79 81 87 97
Rock Ck
Upper Stillwater Reservoir April-July51 57 64 86 70 80
May-July48 54 61 86 67 77
South Fork Rock Ck
Docs Div, Blo April-July4 4.5 5.5 75 6.2 7
May-July3.6 4.1 5.1 74 5.8 6.6
Rock Ck
Mountain Home, Nr April-July60 67 75 85 82 92
May-July56 63 71 85 78 88
Currant Ck
Currant Ck Reservoir April-July11.5 12.5 15 75 16.5 19
May-July8.9 9.9 12.4 73 13.9 16.4
Strawberry
Strawberry Reservoir, Soldier Springs April-July20 23 30 42 37 42
May-July15 17.6 25 43 32 37
Starvation Reservoir, Duchesne, Nr April-July50 55 65 58 75 84
May-July40 45 55 60 65 74
Duchesne
Duchesne, Nr, Knight Div, Abv April-July130 145 160 82 180 195
May-July118 133 148 83 168 183
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July40 44 50 76 55 66
May-July37 41 47 75 52 63
Yellowstone
Altonah, Nr April-July42 49 55 90 60 71
May-July38 45 51 89 56 67
Whiterocks
Whiterocks, Nr April-July29 33 40 74 45 57
May-July27 31 38 75 43 55
Uinta
Neola, Nr April-July43 50 60 81 66 82
May-July40 47 57 80 63 79
Duchesne
Myton April-July150 175 210 64 250 290
May-July129 154 189 64 230 270
Randlett, Nr April-July165 190 220 57 260 310
May-July141 166 196 57 235 285


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-July5.6 6.7 7.5 48 8.6 9.8
May-July4.1 5.2 6 50 7.1 8.3
Fish Ck
Scofield, Nr, Reservoir, Abv April-July19.3 22 24 80 27 31
May-July17.3 19.5 22 85 25 29
Price
Scofield Reservoir, Scofield, Nr April-July26 29 32 78 36 41
May-July22 25 28 80 32 37
Green
Green River, Ut April-July2070 2350 2540 86 2780 3220
May-July1750 2030 2220 87 2460 2900
Huntington Ck
Electric Lake April-July6.1 7.9 9.3 70 10.7 12.3
May-July5.1 6.9 8.3 70 9.7 11.3
Power Plant, Blo April-July25 29 33 83 38 44
May-July22 26 30 81 35 41
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July32 37 42 75 47 53
May-July30 35 40 77 45 51
Ferron Ck
Ferron, Nr April-July24 28 33 87 37 41
May-July22 26 31 89 35 39
Muddy Ck
Emery, Nr April-July9.5 11.3 12.9 65 15.1 17.5
May-July8.3 10.1 11.7 65 13.9 16.3


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-July180 200 220 100 245 270
May-July167 187 205 100 230 255
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July32 38 45 96 52 60
May-July28 34 41 95 48 56
Fraser
Winter Park April-July16.5 18.5 20 103 22 24
May-July15.6 17.6 19.1 103 21 23
Williams Fork
Williams Fork Reservoir, Parshall April-July74 82 90 94 100 110
May-July68 76 84 93 94 104
Muddy Ck
Wolford Mountain Reservoir April-July52 59 66 122 74 82
May-July44 51 58 126 66 74
Blue
Dillon Reservoir April-July140 155 170 104 185 205
May-July131 146 161 105 176 196
Green Mtn Reservoir April-July220 245 270 98 300 330
May-July200 225 250 98 280 310
Colorado
Kremmling, Nr April-July720 790 860 100 960 1070
May-July650 720 790 101 890 1000
Eagle
Gypsum, Blo April-July230 260 290 87 330 370
May-July215 245 275 87 315 355
Colorado
Dotsero, Nr April-July1100 1200 1330 95 1500 1700
May-July995 1100 1230 96 1400 1600
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July100 110 125 90 140 160
May-July93 103 118 91 133 153
Roaring Fork
Glenwood Springs April-July440 480 530 77 600 680
May-July405 445 495 77 565 645
Colorado
Glenwood Springs, Blo April-July1550 1700 1900 90 2100 2350
May-July1410 1560 1760 91 1960 2210
Cameo, Nr April-July1650 1820 2000 85 2300 2550
May-July1500 1670 1850 86 2150 2400
Plateau Ck
Cameo, Nr April-July25 35 50 40 65 85
May-July17.1 27 42 40 57 77
Colorado
Cisco, Nr April-July2300 2600 2950 66 3450 4000
May-July2030 2330 2680 69 3180 3730
Lake Powell, Glen Cyn Dam, At April-July3170 3920 4650 65 5270 6370
May-July2700 3450 4180 69 4800 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-July64 68 73 74 81 100
May-July57 61 66 73 74 93
Almont April-July97 105 113 73 125 153
May-July86 94 102 72 114 142
East
Almont April-July102 110 120 66 138 168
May-July92 100 110 66 128 158
Gunnison
Gunnison, Nr April-July205 220 250 68 285 350
May-July178 197 225 67 260 325
Tomichi Ck
Gunnison April-July35 41 50 68 57 76
May-July26 32 41 66 48 67
Lake Fork
Gateview April-July60 73 83 67 95 125
May-July55 68 78 67 90 120
Gunnison
Blue Mesa Reservoir April-July360 410 450 67 510 650
May-July310 360 400 67 460 600
Morrow Point Reservoir April-July395 445 485 66 545 695
May-July340 390 430 66 490 640
Crystal Reservoir April-July435 495 535 64 610 770
May-July375 435 475 65 550 710
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June36 44 51 53 56 67
April-July33 41 51 53 53 64
May-June26 34 41 59 46 57
May-July26 34 42 56 46 57
Nf Gunnison
Somerset, Nr April-July140 156 171 58 193 235
May-July119 135 150 63 172 215
Surface Ck
Cedaredge April-July4.7 5.9 7.2 43 8.4 10.2
May-July3.5 4.7 6 43 7.2 9
Uncompahgre
Ridgway Reservoir April-July51 58 65 64 71 87
May-July46 53 60 66 66 82
Colona April-July51 61 71 52 80 101
May-July47 57 67 56 76 97
Delta April-July25 36 46 41 54 74
May-July19 30 40 43 48 68
Gunnison
Grand Junction, Nr April-July680 770 855 58 1020 1260
May-July570 660 745 60 910 1150


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-July84 104 127 52 145 175
May-July72 92 115 58 133 163
Mcphee Reservoir April-July84 106 130 44 150 189
May-July73 95 119 54 139 178
San Miguel
Placerville, Nr April-July51 60 71 55 81 96
May-July45 54 65 58 75 90
Dolores
Cisco, Nr April-July140 165 205 36 250 325
May-July115 140 180 43 225 300


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-July98 115 127 59 140 165
May-July68 85 97 54 110 135
Carracas, Nr April-July150 179 200 53 220 260
May-July110 139 162 54 178 220
Navajo Reservoir, Archuleta, Nr April-July270 325 365 50 395 475
May-July190 245 285 50 315 395
Farmington April-July430 495 570 52 630 765
May-July340 405 480 55 540 675
Bluff, Nr April-July385 470 550 50 615 770
May-July290 375 455 53 520 675
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July24 28 31 57 34 40
May-July18 22 25 56 28 34
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July25 29 33 51 37 44
May-July19 23 27 50 31 38
Little Navajo
Oso Div Dam,bl,chromo,nr April-July2.5 3.2 3.7 49 4.2 4.7
May-July1.8 2.5 3 56 3.5 4
Piedra
Arboles, Nr April-July88 105 117 56 127 146
May-July61 78 90 59 100 119
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July101 114 126 65 138 158
May-July85 98 110 64 122 142
Animas
Durango April-July197 230 260 63 290 340
May-July170 205 235 64 265 315
Florida
Lemon Reservoir, Durango, Nr April-July25 30 34 62 38 44
May-July22 27 31 63 35 41
La Plata
Hesperus April-July10.1 12.2 14.1 61 16.1 18.1
May-July8 10.1 12 66 14 16
Mancos
Mancos, Nr April-July7.6 10.1 13 42 15 18
May-July5.6 8.1 11 46 13 16

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 405.7 130 83 343.0 110 311.8 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 8.9 116 98 8.3 108 7.7 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 75.6 124 78 67.6 111 60.9 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 54.5 114 83 38.7 81 47.7 66.0
untitled Blue
Dillon Reservoir 231.4 108 91 185.1 87 213.6 254.0
Green Mtn Reservoir 67.5 106 46 57.3 90 63.9 146.9
untitled Homestake Ck
Homestake Reservoir 24.0 128 56 9.7 52 18.8 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 65.3 104 64 60.3 96 62.6 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 17.8 97 54 12.3 67 18.3 32.9
untitled Taylor
Taylor Park Reservoir 72.6 119 68 63.9 105 61.2 106.2
untitled Gunnison
Blue Mesa Reservoir 509.6 111 61 334.8 73 457.1 829.5
Morrow Point Reservoir 106.8 96 91 113.1 101 111.8 117.0
Crystal Reservoir 17.4 104 99 17.0 102 16.7 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 10.8 168 65 6.2 97 6.4 16.7
untitled Uncompahgre
Ridgway Reservoir 66.1 99 80 56.0 84 66.6 83.0
untitled Dolores
Mcphee Reservoir 276.0 85 72 258.4 80 323.0 381.1
untitled
TOTAL 2010.0 109 72 1631.8 88 1848.0 2792.1
Colorado
Lake Powell 11685.3 68 48 9197.9 54 17122.8 24322.0
untitled
TOTAL 11685.3 68 48 9197.9 54 17122.8 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 95.1 128 76 47.1 64 74.0 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1296.8 95 76 1116.7 82 1361.0 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 19.8 82 50 12.5 52 24.1 39.8
untitled
TOTAL 1411.7 97 76 1176.4 81 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