Lake Powell Water Supply Outlook, May 1, 2018

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by CBRFC
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-July300 320 340 139 360 385
May-July275 295 315 140 335 360
Pine Ck
Fremont Lk, Abv April-July80 93 101 103 108 119
May-July76 89 97 101 104 115
New Fork
Big Piney, Nr April-July265 325 360 101 390 455
May-July240 300 335 102 365 430
Green
Fontenelle Res, Fontenelle Nr April-July745 835 900 124 975 1060
May-July645 735 800 125 875 955
Big Sandy
Farson, Nr April-July38 46 51 98 55 67
May-July35 43 48 100 52 64
Green
Green River, Wy, Nr April-July760 840 910 125 990 1060
May-July655 735 805 126 885 960
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July32 36 41 76 47 55
May-July22 26 31 65 37 45
Viva Naughton Res April-July42 47 53 72 61 71
May-July26 31 37 60 45 55
Blacks Fork
Robertson, Nr April-July50 56 62 70 72 83
May-July44 50 56 66 66 77
Ef Smiths Fork
Stateline Res, Robertson,nr April-July16.1 17.8 20 77 22 26
May-July14.8 16.5 19 73 21 25
Green
Flaming Gorge Res, Flaming Gorge Dam, At April-July820 910 1000 102 1120 1210
May-July700 790 880 104 1000 1090


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-July14.1 15.8 16.6 72 17.2 20
May-July7.5 9.2 10 63 10.6 13.5
Steamboat Springs April-July159 180 196 75 215 250
May-July125 146 162 74 179 215
Elk
Milner, Nr April-July225 255 275 86 295 340
May-July175 205 225 78 245 290
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July35 39 42 58 46 53
May-July17 21 24 48 28 35
Yampa
Maybell, Nr April-July535 590 665 71 710 825
May-July400 455 530 68 575 690
Little Snake
Slater, Nr April-July66 80 93 60 102 123
May-July48 62 75 54 84 105
Dixon, Nr April-July117 150 175 51 192 230
May-July85 118 143 48 160 200
Lily, Nr April-July116 150 176 51 191 230
May-July85 119 145 50 160 200
Yampa
Deerlodge Park April-July635 750 815 66 880 1050
May-July480 595 660 65 725 900
White
Meeker, Nr April-July118 138 148 53 163 198
May-July90 110 120 49 135 170
Watson, Nr April-July119 140 151 54 169 205
May-July90 111 122 52 140 178


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-July7.5 8.9 10.5 50 11.6 16
May-July5.5 6.9 8.5 46 9.6 14
Ashley Ck
Vernal, Nr April-July17.2 18.4 21 42 23 31
May-July14.8 16 19 40 21 29
West Fork Duchesne
Vat Diversion, Blo April-July6.2 7.1 7.8 42 8.7 10
May-July4.9 5.8 6.5 38 7.4 8.7
Duchesne
Tabiona, Nr April-July47 53 60 56 65 73
May-July39 45 52 53 57 65
Rock Ck
Upper Stillwater Res April-July33 38 46 62 50 61
May-July30 35 43 61 47 58
South Fork Rock Ck
Docs Div, Blo April-July2.2 2.8 3.1 42 3.7 4.2
May-July1.8 2.4 2.7 39 3.3 3.8
Rock Ck
Mountain Home, Nr April-July38 44 52 59 56 68
May-July34 40 48 57 52 64
Currant Ck
Currant Ck Res April-July3.9 4.2 5 25 5.7 7.6
May-July2.8 3.1 3.9 23 4.6 6.5
Strawberry
Solider Springs,nr April-July15.5 16.5 19 27 21 24
May-July8.5 9.5 12 21 14 17.3
Starvation Res, Duchesne, Nr April-July21 23 26 23 29 34
May-July12 14.2 17 18.7 20 25
Duchesne
Duchesne, Nr, Knight Div, Abv April-July85 97 110 57 120 138
May-July72 84 97 54 107 125
Lake Fork
Moon Lake Res, Mtn Home, Nr April-July26 29 32 48 38 46
May-July24 27 30 48 36 44
Yellowstone
Altonah, Nr April-July28 32 35 57 40 51
May-July25 29 32 56 37 48
Whiterocks
Whiterocks, Nr April-July20 22 26 48 29 39
May-July17.7 19.4 24 47 27 37
Uinta
Neola, Nr April-July28 34 40 54 44 60
May-July25 31 37 52 41 57
Duchesne
Myton April-July73 88 103 31 126 163
May-July50 65 80 27 103 140
Randlett, Nr April-July75 84 94 24 115 150
May-July50 59 69 20 90 125


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-July1.6 1.6 1.8 11.8 2 2.1
May-July0.75 0.76 1 8.4 1.1 1.3
Fish Ck
Scofield, Nr, Reservoir, Abv April-July10.2 11.6 12.8 43 14.3 17.3
May-July7.9 9.3 10.5 40 12 15
Price
Scofield Res, Scofield, Nr April-July12.9 14.4 16 39 17.6 21
May-July9.5 11 12.6 36 14.2 18
Green
Green River, Ut April-July1610 1870 2060 70 2320 2660
May-July1250 1510 1700 67 1960 2300
Huntington Ck
Electric Lake April-July3.3 4 4.4 33 5.5 6.4
May-July2.4 3.1 3.5 30 4.6 5.5
Power Plant, Blo April-July17.5 19.1 20 50 23 26
May-July14.5 16.1 17 46 19.6 23
Seeley Ck
Joes Vly Res, Orangeville, Nr April-July19.3 22 24 43 26 33
May-July16.2 19.2 21 40 23 30
Ferron Ck
Ferron, Nr April-July11.9 15.2 16.5 43 18.8 23
May-July10 13.3 14.6 42 16.9 21
Muddy Ck
Emery, Nr April-July4.6 5.6 6.5 33 7.1 8.3
May-July3.7 4.7 5.6 31 6.2 7.4


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-July150 165 185 84 205 240
May-July137 152 172 84 192 225
Willow Ck
Willow Ck Res, Granby, Nr April-July28 34 40 85 45 52
May-July23 29 35 81 40 47
Fraser
Winter Park April-July16 17.5 18.5 95 19.5 22
May-July14.8 16.3 17.3 93 18.3 21
Williams Fork
Williams Fork Res, Parshall, Nr April-July65 73 78 81 84 96
May-July59 67 72 80 78 90
Muddy Ck
Wolford Mountain Reservoir April-July24 29 33 61 39 47
May-July18.5 24 28 61 34 42
Blue
Dillon Res April-July115 130 140 86 150 175
May-July104 119 129 84 139 164
Green Mtn Res April-July180 205 225 82 245 275
May-July160 185 205 80 225 255
Colorado
Kremmling, Nr April-July550 620 700 81 770 900
May-July480 550 630 80 700 830
Eagle
Gypsum, Blo April-July160 190 210 63 225 280
May-July138 168 187 59 205 260
Colorado
Dotsero, Nr April-July800 910 1040 74 1150 1340
May-July680 790 920 72 1030 1220
Frying Pan
Ruedi Res, Basalt, Nr April-July66 78 88 63 98 120
May-July58 70 80 62 90 112
Roaring Fork
Glenwood Springs April-July340 390 420 61 460 550
May-July300 350 380 59 420 510
Colorado
Glenwood Springs, Blo April-July1150 1320 1480 70 1600 1950
May-July995 1160 1320 68 1440 1790
Cameo, Nr April-July1250 1400 1570 67 1720 2100
May-July1090 1240 1410 66 1560 1940
Plateau Ck
Cameo, Nr April-July15 30 38 31 50 60
May-July5.7 21 29 28 41 51
Colorado
Cisco, Nr April-July1650 1900 2250 51 2600 3200
May-July1420 1670 1970 51 2370 2970
Lake Powell, Glen Cyn Dam, At April-July2080 2610 3000 42 3300 4180
May-July1700 2230 2620 43 2920 3800


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 Res April-July53 60 66 67 69 81
May-July45 52 58 64 61 73
Almont April-July77 88 94 61 102 122
May-July65 76 82 58 90 110
East
Almont April-July86 98 107 59 113 131
May-July75 87 96 58 102 120
Gunnison
Gunnison, Nr April-July173 193 210 57 225 265
May-July150 170 187 56 200 240
Tomichi Ck
Gunnison April-July14.5 17.5 19.5 26 25 36
May-July9 12 14 23 19 30
Lake Fork
Gateview April-July42 53 61 50 68 82
May-July35 46 54 47 61 75
Gunnison
Blue Mesa Res April-July280 310 350 52 400 460
May-July230 260 300 50 350 410
Morrow Point Res April-July305 335 375 51 425 485
May-July250 280 320 49 370 430
Crystal Res April-July345 375 415 50 465 525
May-July285 315 355 48 405 465
Muddy Ck
Paonia Res, Bardine, Nr March-June23 26 30 31 34 40
April-July22 25 29 30 33 39
May-June15 18 22 32 26 32
May-July16 19 23 31 27 33
Nf Gunnison
Somerset, Nr April-July105 118 128 43 138 165
May-July85 98 108 45 118 145
Surface Ck
Cedaredge April-July3 3.3 3.8 23 4.3 5.5
May-July2 2.3 2.8 19.9 3.3 4.5
Uncompahgre
Ridgway Res April-July30 35 40 40 44 50
May-July25 30 35 38 39 45
Colona April-July34 40 48 35 54 65
May-July29 35 43 36 49 60
Delta April-July17.2 20 26 23 32 42
May-July9 12 18 19.1 24 34
Gunnison
Grand Junction, Nr April-July435 515 555 38 620 735
May-July340 420 460 37 525 640


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-July50 55 62 25 69 79
May-July38 43 50 25 57 67
Mcphee Res April-July50 55 62 21 69 79
May-July38 43 50 23 57 67
San Miguel
Placerville, Nr April-July35 42 46 36 52 61
May-July29 36 40 35 46 55
Dolores
Cisco, Nr April-July79 95 109 19.3 124 149
May-July65 81 95 23 110 135


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-July63 76 83 39 90 103
May-July40 53 60 33 67 80
Carracas, Nr April-July121 138 146 38 156 181
May-July80 97 105 35 115 140
Navajo Res, Archuleta, Nr April-July147 185 200 27 225 280
May-July77 115 130 23 155 210
Farmington April-July183 245 270 25 295 385
May-July110 170 197 22 220 310
Bluff, Nr April-July193 225 250 23 280 370
May-July130 160 186 22 215 305
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July16.7 19.7 23 43 26 29
May-July9 12 15 33 18 21
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July22 25 28 43 31 37
May-July14 17 20 37 23 29
Piedra
Arboles, Nr April-July42 52 57 27 64 77
May-July25 35 40 26 47 60
Los Pinos
Vallecito Res, Bayfield, Nr April-July46 53 60 31 69 85
May-July31 38 45 26 54 70
Animas
Durango April-July83 98 115 28 128 180
May-July67 82 99 27 112 164
Florida
Lemon Res, Durango, Nr April-July8.1 10.6 12.1 22 14.1 17.1
May-July5 7.5 9 18.4 11 14
La Plata
Hesperus April-July3 3.5 4 17.4 5 7
May-July2 2.5 3 16.5 4 6
Mancos
Mancos, Nr April-July4.6 5.6 6.6 21 7.6 9.6
May-July3 4 5 21 6 8

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 Res, Fontenelle Nr 130.4 104 38 127.8 102 125.0 344.8
untitled Big Sandy
Big Sandy Res, Farson, Nr 35.8 168 93 28.7 135 21.3 38.3
Blacks Fork
Meeks Cabin 18.4 112 62 24.7 150 16.5 29.9
untitled Ef Smiths Fork
Stateline Res, Robertson,nr 7.6 117 55 9.6 148 6.5 13.9
untitled Green
Flaming Gorge Res, Flaming Gorge Dam, At 3185.8 105 85 3084.4 101 3040.4 3749.0
untitled Strawberry
Solider Springs,nr 940.9 139 85 850.4 126 676.1 1105.9
Starvation Res, Duchesne, Nr 164.9 109 100 132.4 87 151.9 165.3
untitled Rock Ck
Upper Stillwater Res 8.2 282 26 2.4 85 2.9 31.4
untitled Lake Fork
Moon Lake Res, Mtn Home, Nr 28.8 104 79 29.2 106 27.6 36.5
untitled Big Brush Ck
Red Fleet Res, Vernal, Nr 20.8 104 81 20.1 100 20.1 25.7
untitled Price
Scofield Res, Scofield, Nr 53.8 163 82 34.3 104 33.0 65.8
untitled Seeley Ck
Joes Vly Res, Orangeville, Nr 46.1 116 74 31.6 80 39.6 62.5
untitled Huntington Ck
Electric Lake 23.3 124 74 19.5 104 18.7 31.5
untitled
TOTAL 4664.6 112 82 4395.1 105 4179.6 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 420.5 135 86 392.3 126 311.8 490.3
untitled Willow Ck
Willow Ck Res, Granby, Nr 7.9 102 86 8.0 104 7.7 9.1
untitled Williams Fork
Williams Fork Res, Parshall, Nr 69.9 115 72 74.8 123 60.9 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 55.0 115 83 60.5 127 47.7 66.0
untitled Blue
Dillon Res 233.4 109 92 215.5 101 213.6 254.0
Green Mtn Res 63.0 99 43 69.5 109 63.9 146.9
untitled Homestake Ck
Homestake Res 35.9 191 83 23.7 126 18.8 43.0
untitled Frying Pan
Ruedi Res, Basalt, Nr 67.4 108 66 68.8 110 62.6 102.0
untitled Plateau Ck
Vega Res, Collbran, Nr 16.1 88 49 20.2 110 18.3 32.9
untitled Taylor
Taylor Park Res 71.8 117 68 73.2 120 61.2 106.2
untitled Gunnison
Blue Mesa Res 498.3 109 60 657.6 144 457.1 829.5
Morrow Point Res 112.5 101 96 108.8 97 111.8 117.0
Crystal Res 15.9 95 91 16.6 99 16.7 17.5
untitled Muddy Ck
Paonia Res, Bardine, Nr 11.9 185 71 2.3 36 6.4 16.7
untitled Uncompahgre
Ridgway Res 64.2 96 77 62.9 94 66.6 83.0
untitled Dolores
Mcphee Res 274.7 85 72 353.2 109 323.0 381.1
untitled
TOTAL 2018.3 109 72 2208.0 119 1848.0 2792.1
Colorado
Lake Powell 12669.0 74 52 12149.5 71 17122.8 24322.0
untitled
TOTAL 12669.0 74 52 12149.5 71 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 Res, Bayfield, Nr 73.3 116 58 77.0 122 63.2 125.4
untitled San Juan
Navajo Res, Archuleta, Nr 1236.4 94 73 1460.5 111 1310.4 1696.0
untitled Florida
Lemon Res, Durango, Nr 18.9 87 47 24.5 113 21.7 39.8
untitled
TOTAL 1328.6 95 71 1562.0 112 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