Lake Powell Water Supply Outlook, May 1, 2019

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-July160 191 205 84 225 245
May-July143 174 188 84 210 230
Pine Ck
Fremont Lk, Abv April-July78 89 95 97 99 110
May-July75 86 92 96 96 107
New Fork
Big Piney, Nr April-July275 335 360 101 380 460
May-July245 305 330 100 350 430
Green
Fontenelle Reservoir, Fontenelle, Nr April-July565 680 740 102 810 915
May-July450 565 625 98 695 800
Big Sandy
Farson, Nr April-July41 49 55 106 60 70
May-July36 44 50 104 55 65
Green
Green River, Wy, Nr April-July550 690 740 101 815 935
May-July440 580 630 98 705 825
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30 33 38 70 47 55
May-July24 27 32 67 41 49
Viva Naughton Reservoir April-July41 43 50 68 59 72
May-July31 33 40 65 49 62
Blacks Fork
Robertson, Nr April-July73 85 94 106 99 114
May-July69 81 90 106 95 110
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July25 27 30 115 32 37
May-July23 25 28 108 30 35
Green
Flaming Gorge Reservoir April-July790 970 1050 107 1190 1340
May-July550 730 815 96 955 1100


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-July19.1 21 23 100 24 32
May-July11.5 13.2 15 94 16.3 24
Steamboat Springs April-July230 250 275 106 290 335
May-July185 205 230 105 245 290
Elk
Milner, Nr April-July340 375 405 127 430 475
May-July265 300 330 114 355 400
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July67 76 81 111 87 99
May-July39 48 53 106 59 71
Yampa
Maybell, Nr April-July860 935 1030 110 1120 1250
May-July660 735 835 108 920 1050
Little Snake
Slater, Nr April-July131 149 164 105 175 205
May-July107 125 140 101 151 182
Dixon, Nr April-July285 320 365 106 390 465
May-July220 255 300 102 325 400
Lily, Nr April-July310 350 395 114 420 495
May-July240 280 325 112 350 425
Yampa
Deerlodge Park April-July1160 1300 1450 117 1550 1740
May-July900 1040 1190 117 1290 1480
White
Meeker, Nr April-July230 265 285 102 295 345
May-July194 225 245 100 255 305
Watson, Nr April-July250 280 310 111 320 390
May-July210 240 270 115 280 350


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-July15.4 17.3 20 95 22 27
May-July13.5 15.4 18.1 98 19.9 25
Ashley Ck
Vernal, Nr April-July39 47 50 100 54 66
May-July37 45 48 102 52 64
West Fork Duchesne
Vat Diversion, Blo April-July22 24 26 140 30 31
May-July21 23 25 145 29 30
Duchesne
Tabiona, Nr April-July116 122 136 126 149 158
May-July103 109 123 126 136 145
Rock Ck
Upper Stillwater Reservoir April-July80 86 95 128 101 113
May-July76 82 91 128 97 109
South Fork Rock Ck
Docs Div, Blo April-July7.8 8.7 9.2 126 9.9 11
May-July7.5 8.4 8.9 129 9.6 10.7
Rock Ck
Mountain Home, Nr April-July95 102 112 127 118 132
May-July89 96 106 126 112 126
Currant Ck
Currant Ck Reservoir April-July25 27 31 155 34 37
May-July22 24 28 164 31 34
Strawberry
Strawberry Reservoir, Soldier Springs April-July88 95 105 148 118 125
May-July68 75 85 147 98 105
Starvation Reservoir, Duchesne, Nr April-July158 177 193 172 215 230
May-July125 144 160 176 180 197
Duchesne
Duchesne, Nr, Knight Div, Abv April-July205 220 240 124 265 285
May-July192 205 225 126 250 270
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July70 74 83 126 90 100
May-July66 70 79 125 86 96
Yellowstone
Altonah, Nr April-July61 68 75 123 80 95
May-July57 64 71 125 76 91
Whiterocks
Whiterocks, Nr April-July41 46 55 102 58 74
May-July38 43 52 102 55 71
Uinta
Neola, Nr April-July71 80 94 127 99 120
May-July67 76 90 127 95 116
Duchesne
Myton April-July380 420 470 142 520 570
May-July330 370 420 142 470 520
Randlett, Nr April-July415 455 530 138 585 670
May-July365 405 480 139 535 620


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-July19.9 24 26 168 29 32
May-July14 18.3 20 168 23 26
Fish Ck
Scofield, Nr, Reservoir, Abv April-July42 46 50 167 56 59
May-July38 42 46 177 52 55
Price
Scofield Reservoir, Scofield, Nr April-July62 69 74 180 83 88
May-July54 61 66 189 75 80
Green
Green River, Ut April-July3000 3250 3450 117 3670 4240
May-July2460 2710 2910 115 3130 3700
Huntington Ck
Electric Lake April-July20 22 24 180 27 29
May-July19 21 23 195 26 28
Power Plant, Blo April-July60 67 72 180 81 88
May-July56 63 68 184 77 84
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July66 75 79 141 84 96
May-July61 70 74 142 79 91
Ferron Ck
Ferron, Nr April-July52 57 61 161 64 73
May-July47 52 56 160 59 68
Muddy Ck
Emery, Nr April-July21 25 27 136 29 34
May-July19 23 25 138 27 32


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-July200 225 250 114 270 295
May-July182 205 230 112 250 275
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July55 62 68 145 76 85
May-July48 55 61 142 69 78
Fraser
Winter Park April-July16.7 18.2 19.5 101 21 24
May-July15.7 17.2 18.5 99 20 23
Williams Fork
Williams Fork Reservoir, Parshall April-July85 92 100 104 110 120
May-July77 84 92 102 102 112
Muddy Ck
Wolford Mountain Reservoir April-July50 56 62 115 71 80
May-July41 47 53 115 62 71
Blue
Dillon Reservoir April-July175 190 205 126 220 240
May-July162 177 192 125 205 225
Green Mtn Reservoir April-July275 300 325 118 350 385
May-July250 275 300 118 325 360
Colorado
Kremmling, Nr April-July850 925 1000 116 1080 1200
May-July750 825 900 115 980 1100
Eagle
Gypsum, Blo April-July320 350 375 112 415 460
May-July290 320 345 110 385 430
Colorado
Dotsero, Nr April-July1380 1500 1610 115 1780 2000
May-July1220 1340 1450 113 1620 1840
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July138 155 170 122 185 200
May-July127 144 159 122 174 189
Roaring Fork
Glenwood Springs April-July700 760 825 120 880 980
May-July630 690 755 118 810 910
Colorado
Glenwood Springs, Blo April-July2100 2300 2500 118 2750 3000
May-July1870 2070 2270 118 2520 2770
Cameo, Nr April-July2400 2610 2800 119 3080 3500
May-July2150 2360 2550 119 2830 3250
Plateau Ck
Cameo, Nr April-July150 167 185 149 200 225
May-July126 143 161 155 176 200
Colorado
Cisco, Nr April-July5000 5450 5850 132 6350 6900
May-July4270 4720 5120 133 5620 6170
Lake Powell, Glen Cyn Dam, At April-July7640 8740 9200 128 9770 11240
May-July6400 7500 7960 130 8530 10000


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-July116 123 130 131 139 156
May-July105 112 119 132 128 145
Almont April-July185 197 210 135 230 260
May-July168 180 194 138 215 245
East
Almont April-July225 230 245 135 260 290
May-July205 210 225 136 240 270
Gunnison
Gunnison, Nr April-July465 485 510 138 540 625
May-July420 440 465 139 495 580
Tomichi Ck
Gunnison April-July92 102 112 151 127 148
May-July70 80 90 145 105 126
Lake Fork
Gateview April-July140 157 169 137 182 220
May-July129 146 158 136 171 210
Gunnison
Blue Mesa Reservoir April-July870 945 970 144 1040 1200
May-July750 825 850 142 915 1080
Morrow Point Reservoir April-July960 1040 1060 143 1130 1290
May-July825 900 925 142 990 1150
Crystal Reservoir April-July1090 1160 1180 141 1250 1410
May-July935 1010 1030 140 1100 1260
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June131 138 143 149 151 163
April-July135 142 147 152 155 167
May-June100 107 112 162 120 132
May-July107 114 119 159 127 157
Nf Gunnison
Somerset, Nr April-July360 375 395 134 420 465
May-July300 315 335 140 360 405
Surface Ck
Cedaredge April-July26 28 30 179 32 35
May-July22 24 26 184 28 31
Uncompahgre
Ridgway Reservoir April-July101 110 118 117 126 143
May-July90 99 107 118 115 132
Colona April-July129 143 156 114 169 195
May-July115 129 142 118 155 181
Delta April-July113 124 139 123 151 178
May-July87 98 113 120 125 152
Gunnison
Grand Junction, Nr April-July1850 2030 2100 142 2250 2500
May-July1550 1730 1800 145 1950 2200


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-July295 310 325 133 345 375
May-July245 260 275 138 295 325
Mcphee Reservoir April-July365 390 420 142 445 485
May-July260 285 315 143 340 380
San Miguel
Placerville, Nr April-July138 150 158 123 168 183
May-July120 132 140 124 150 165
Dolores
Cisco, Nr April-July770 825 860 152 895 990
May-July550 605 640 154 675 770


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-July250 260 270 126 285 305
May-July198 210 220 122 235 255
Carracas, Nr April-July420 445 460 121 480 515
May-July315 340 355 118 375 410
Navajo Reservoir, Archuleta, Nr April-July810 870 930 127 970 1060
May-July580 640 700 124 740 830
Farmington April-July1280 1350 1420 129 1500 1650
May-July975 1050 1120 127 1200 1350
Bluff, Nr April-July1270 1350 1420 129 1500 1660
May-July950 1030 1100 129 1180 1340
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July58 63 67 124 71 76
May-July47 52 56 124 60 65
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July66 71 75 115 80 86
May-July53 58 62 115 67 73
Piedra
Arboles, Nr April-July265 280 295 140 310 330
May-July184 199 215 141 230 250
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July215 235 255 131 270 305
May-July180 200 220 129 235 270
Animas
Durango April-July460 500 535 129 555 685
May-July380 420 455 125 475 605
Florida
Lemon Reservoir, Durango, Nr April-July53 59 65 118 71 80
May-July47 53 59 120 65 74
La Plata
Hesperus April-July27 29 31 135 34 37
May-July22 24 26 143 29 32
Mancos
Mancos, Nr April-July29 31 34 110 38 41
May-July21 23 26 108 30 33

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 204.1 124 59 260.4 159 164.0 344.8
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 29.2 99 76 38.5 131 29.4 38.3
Blacks Fork
Meeks Cabin 22.5 90 75 30.2 121 24.9 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 9.4 83 68 14.0 124 11.3 13.9
untitled Green
Flaming Gorge Reservoir 3376.5 110 90 3294.2 107 3071.5 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 966.2 135 87 949.2 133 716.0 1105.9
Starvation Reservoir, Duchesne, Nr 154.7 100 94 155.2 100 154.8 165.3
untitled Rock Ck
Upper Stillwater Reservoir 6.3 40 20 19.0 121 15.7 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 13.7 48 37 36.0 126 28.6 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 19.9 85 77 19.9 85 23.4 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 44.3 91 67 51.4 106 48.5 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 27.6 53 44 51.6 100 51.6 62.5
untitled Huntington Ck
Electric Lake 20.1 84 64 23.5 99 23.8 31.5
untitled
TOTAL 4894.4 112 86 4943.0 113 4363.6 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 343.0 110 70 420.5 135 311.8 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 8.3 108 91 7.9 102 7.7 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 67.6 111 70 70.2 115 60.9 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 38.0 80 58 55.9 117 47.7 66.0
untitled Blue
Dillon Reservoir 185.1 87 73 233.7 109 213.6 254.0
Green Mtn Reservoir 57.3 90 39 63.0 99 63.9 146.9
untitled Homestake Ck
Homestake Reservoir 9.7 52 23 35.6 189 18.8 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 60.3 96 59 67.4 108 62.6 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 15.7 86 48 15.7 86 18.3 32.9
untitled Taylor
Taylor Park Reservoir 63.9 105 60 71.8 117 61.2 106.2
untitled Gunnison
Blue Mesa Reservoir 334.8 73 40 498.3 109 457.1 829.5
Morrow Point Reservoir 113.1 101 97 112.5 101 111.8 117.0
Crystal Reservoir 17.0 102 97 15.9 95 16.7 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 6.2 97 37 11.9 185 6.4 16.7
untitled Uncompahgre
Ridgway Reservoir 56.0 84 67 64.2 96 66.6 83.0
untitled Dolores
Mcphee Reservoir 258.4 80 68 274.7 85 323.0 381.1
untitled
TOTAL 1634.7 88 59 2019.1 109 1848.0 2792.1
Colorado
Lake Powell 9197.9 54 38 12669.0 74 17122.8 24322.0
untitled
TOTAL 9197.9 54 38 12669.0 74 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 47.1 64 38 85.3 115 74.0 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1116.7 82 66 1222.4 90 1361.0 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 12.5 52 32 21.5 89 24.1 39.8
untitled
TOTAL 1176.4 81 63 1329.2 91 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