Lake Powell Water Supply Outlook, May 1, 2015

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Alcorn
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		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Green
Daniel, Nr, Warren Bridge, At April-July146 182 74 215
May-July125 161 72 195
Pine Ck
Fremont Lk, Abv April-July54 73 74 92
May-July50 69 72 88
New Fork
Big Piney, Nr April-July137 205 58 300
May-July117 185 56 280
Green
Fontenelle Res, Fontenelle Nr April-July360 495 68 630
May-July275 410 64 545
Big Sandy
Farson, Nr April-July22 32 62 45
May-July18.3 28 58 41
Green
Green River, Wy, Nr April-July340 475 65 620
May-July260 395 62 540
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July30 38 70 48
May-July17 25 52 35
Viva Naughton Res April-July36 44 59 57
May-July21 29 47 42
Blacks Fork
Robertson, Nr April-July40 50 56 65
May-July32 42 49 57
Ef Smiths Fork
Stateline Res, Robertson,nr April-July12.8 16 62 19.8
May-July11 14.2 55 18
Green
Flaming Gorge Res, Flaming Gorge Dam, At April-July430 570 58 740
May-July320 460 54 630


Yampa/White Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Yampa
Stagecoach Rsvr, Abv April-July14.6 16.3 71 18.5
May-July8 9.7 61 11.9
Steamboat Springs April-July128 156 60 196
May-July92 120 55 160
Elk
Milner, Nr April-July169 199 62 245
May-July130 160 55 205
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July26 31 42 40
May-July9.8 14.8 30 23
Yampa
Maybell, Nr April-July405 480 51 605
May-July280 355 46 480
Little Snake
Slater, Nr April-July71 86 55 109
May-July52 67 49 90
Dixon, Nr April-July107 134 39 182
May-July75 102 35 150
Lily, Nr April-July99 134 39 183
May-July67 102 35 151
Yampa
Deerlodge Park April-July510 620 50 785
May-July350 460 45 625
White
Meeker, Nr April-July155 180 64 230
May-July110 135 55 184
Watson, Nr April-July151 177 63 225
May-July110 136 58 184


Duchesne Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Big Brush Ck
Vernal, Nr, Red Fleet Res, Abv April-July5.6 7.5 36 10.7
May-July4.1 6 33 9.2
Ashley Ck
Vernal, Nr April-July13.7 17.3 35 24
May-July11.3 14.9 32 22
West Fork Duchesne
Vat Diversion, Blo April-July5.4 7.2 39 9.9
May-July4 5.8 34 8.5
Duchesne
Tabiona, Nr April-July47 58 54 69
May-July37 48 49 59
Rock Ck
Upper Stillwater Res April-July35 45 61 53
May-July28 38 54 46
South Fork Rock Ck
Docs Div, Blo April-July2.3 2.9 40 3.6
May-July1.8 2.4 35 3.1
Rock Ck
Mountain Home, Nr April-July38 49 56 62
May-July32 43 51 56
Currant Ck
Currant Ck Res April-July3.6 5 25 6.4
May-July1.7 3.1 18.1 4.5
Strawberry
Solider Springs,nr April-July11.2 13.5 19 19.4
May-July7.8 10.1 17.4 16
Starvation Res, Duchesne, Nr April-July17.6 23 21 30
May-July11.3 16.5 18.1 24
Duchesne
Duchesne, Nr, Knight Div, Abv April-July89 106 55 125
May-July72 89 50 108
Lake Fork
Moon Lake Res, Mtn Home, Nr April-July24 30 45 40
May-July21 27 43 37
Yellowstone
Altonah, Nr April-July26 32 52 42
May-July23 29 51 39
Whiterocks
Whiterocks, Nr April-July19.2 25 46 34
May-July17 23 45 32
Uinta
Neola, Nr April-July24 33 45 48
May-July21 30 42 45
Duchesne
Myton April-July70 92 28 130
May-July45 67 23 105
Randlett, Nr April-July72 95 25 135
May-July47 70 20 110


Lower Green Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
White
Blo Tabbyune Ck, Soldier Summit, Nr April-July0.94 1.2 7.8 1.7
May-July0.35 0.62 5.2 1.1
Fish Ck
Scofield, Nr, Reservoir, Abv April-July7.1 9.1 30 13
May-July4.5 6.5 25 10.4
Price
Scofield Res, Scofield, Nr April-July8.1 11.1 27 15.9
May-July4.5 7.5 21 12.3
Green
Green River, Ut April-July1150 1430 48 1830
May-July825 1100 43 1500
Huntington Ck
Electric Lake April-July2.6 3.6 27 5.1
May-July1.5 2.5 21 4
Power Plant, Blo April-July15.7 17.2 43 21
May-July13 14.5 39 18
Seeley Ck
Joes Vly Res, Orangeville, Nr April-July18 23 41 29
May-July15.1 20 38 26
Ferron Ck
Ferron, Nr April-July15 18.8 49 25
May-July12.9 16.7 48 23
Muddy Ck
Emery, Nr April-July7.3 9.1 46 11.8
May-July6 7.8 43 10.5


Upper Colorado Mainstem Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Colorado
Lake Granby, Granby, Nr April-July175 200 91 240
May-July155 180 88 220
Willow Ck
Willow Ck Res, Granby, Nr April-July28 35 74 42
May-July21 28 65 35
Fraser
Winter Park April-July15.1 17.1 88 21
May-July14 16 86 20
Williams Fork
Williams Fork Res, Parshall, Nr April-July73 82 85 102
May-July65 74 82 94
Muddy Ck
Wolford Mountain Reservoir April-July28 34 63 44
May-July19 25 54 35
Blue
Dillon Res April-July148 170 104 200
May-July135 157 103 187
Green Mtn Res April-July235 265 96 320
May-July210 240 94 295
Colorado
Kremmling, Nr April-July640 730 85 890
May-July550 640 82 800
Eagle
Gypsum, Blo April-July200 245 73 320
May-July175 220 70 295
Colorado
Dotsero, Nr April-July930 1080 77 1340
May-July790 940 73 1200
Frying Pan
Ruedi Res, Basalt, Nr April-July86 100 72 141
May-July77 91 70 132
Roaring Fork
Glenwood Springs April-July420 470 68 605
May-July370 420 66 555
Colorado
Glenwood Springs, Blo April-July1360 1570 74 1970
May-July1160 1370 71 1770
Cameo, Nr April-July1380 1600 68 2050
May-July1180 1400 65 1850
Plateau Ck
Cameo, Nr April-July31 40 32 51
May-July22 31 30 42
Colorado
Cisco, Nr April-July2270 2580 58 3300
May-July1860 2170 56 2890
Lake Powell, Glen Cyn Dam, At April-July2250 3000 42 4220
May-July1610 2360 39 3580


Gunnison Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Taylor
Taylor Park Res April-July49 62 63 79
May-July40 53 59 70
Almont April-July76 96 62 121
May-July63 83 59 108
East
Almont April-July79 104 57 129
May-July60 85 51 110
Gunnison
Gunnison, Nr April-July172 197 53 245
May-July135 160 48 210
Tomichi Ck
Gunnison April-July38 50 68 69
May-July29 41 66 60
Lake Fork
Gateview April-July74 94 76 114
May-July65 85 73 105
Gunnison
Blue Mesa Res April-July370 440 65 540
May-July300 365 61 470
Morrow Point Res April-July405 470 64 575
May-July330 395 61 500
Crystal Res April-July450 510 61 620
May-July370 430 59 540
Muddy Ck
Paonia Res, Bardine, Nr March-June29 34 35 49
April-July25 30 31 45
May-June15 20 29 35
May-July16 21 28 36
Nf Gunnison
Somerset, Nr April-July102 127 43 172
May-July75 100 42 145
Surface Ck
Cedaredge April-July3.5 5 30 8
May-July1.5 3 21 6
Uncompahgre
Ridgway Res April-July50 60 59 78
May-July44 54 59 72
Colona April-July47 65 47 87
May-July40 58 48 80
Delta April-July25 36 32 55
May-July20 31 33 50
Gunnison
Grand Junction, Nr April-July590 765 52 955
May-July450 625 50 815


Dolores Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
Dolores
Dolores April-July88 111 45 137
May-July66 89 45 115
Mcphee Res April-July86 108 37 131
May-July65 87 40 110
San Miguel
Placerville, Nr April-July60 78 61 100
May-July50 68 60 90
Dolores
Cisco, Nr April-July150 152 27 235
May-July115 117 28 200


San Juan Specific Site Forecasts (kaf)

Click site name for graph.
Forecast
Period		90%
Exceedance
Volume		50%
Exceedance
Volume		Percent
Average		10%
Exceedance
Volume
San Juan
Pagosa Springs April-July53 68 32 85
May-July30 45 25 62
Carracas, Nr April-July96 122 32 151
May-July60 86 29 115
Navajo Res, Archuleta, Nr April-July170 230 31 300
May-July90 150 27 220
Farmington April-July255 320 29 455
May-July160 225 26 360
Bluff, Nr April-July250 300 27 430
May-July150 200 23 330
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July14.2 20 37 26
May-July9 14.8 33 21
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July15.6 23 35 31
May-July10 17 31 25
Piedra
Arboles, Nr April-July72 84 40 105
May-July43 55 36 76
Los Pinos
Vallecito Res, Bayfield, Nr April-July74 94 48 116
May-July55 75 44 97
Animas
Durango April-July154 205 49 270
May-July120 171 47 235
Florida
Lemon Res, Durango, Nr April-July15.4 22 40 30
May-July10.5 17.1 35 25
La Plata
Hesperus April-July4.5 7.9 34 10.9
May-July2.6 6 33 9
Mancos
Mancos, Nr April-July5 9.5 31 12
May-July4 8.5 35 11

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 185.1 148 54 137.7 110 125.0 344.8
untitled Big Sandy
Big Sandy Res, Farson, Nr 26.5 124 69 14.7 69 21.3 38.3
Blacks Fork
Meeks Cabin 30.5 185 102 22.2 135 16.5 29.9
untitled Ef Smiths Fork
Stateline Res, Robertson,nr 11.8 182 85 9.0 139 6.5 13.9
untitled Green
Flaming Gorge Res, Flaming Gorge Dam, At 3212.6 106 86 2970.8 98 3040.4 3749.0
untitled Strawberry
Solider Springs,nr 846.0 125 76 851.0 126 676.1 1105.9
Starvation Res, Duchesne, Nr 164.2 108 99 164.5 108 151.9 165.3
untitled Rock Ck
Upper Stillwater Res 6.6 228 21 2.4 84 2.9 31.4
untitled Lake Fork
Moon Lake Res, Mtn Home, Nr 36.2 131 99 26.1 94 27.6 36.5
untitled Big Brush Ck
Red Fleet Res, Vernal, Nr 12.4 62 48 12.5 62 20.1 25.7
untitled Price
Scofield Res, Scofield, Nr 16.7 51 25 20.5 62 33.0 65.8
untitled Seeley Ck
Joes Vly Res, Orangeville, Nr 42.0 106 67 34.4 87 39.6 62.5
untitled Huntington Ck
Electric Lake 18.2 98 58 17.9 96 18.7 31.5
untitled
TOTAL 4608.9 110 81 4283.6 102 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 491.3 158 100 295.7 95 311.8 490.3
untitled Willow Ck
Willow Ck Res, Granby, Nr 7.5 97 82 8.1 106 7.7 9.1
untitled Williams Fork
Williams Fork Res, Parshall, Nr 83.7 137 86 75.2 123 60.9 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 49.7 104 75 46.3 97 47.7 66.0
untitled Blue
Dillon Res 247.1 116 97 206.4 97 213.6 254.0
Green Mtn Res 72.1 113 49 68.9 108 63.9 146.9
untitled Homestake Ck
Homestake Res 20.8 111 48 0.1 0 18.8 43.0
untitled Frying Pan
Ruedi Res, Basalt, Nr 75.9 121 74 64.9 104 62.6 102.0
untitled Plateau Ck
Vega Res, Collbran, Nr 19.7 107 60 23.8 130 18.3 32.9
untitled Taylor
Taylor Park Res 82.1 134 77 70.3 115 61.2 106.2
untitled Gunnison
Blue Mesa Res 597.3 131 72 509.1 111 457.1 829.5
Morrow Point Res 109.5 98 94 106.1 95 111.8 117.0
Crystal Res 16.6 99 94 14.2 85 16.7 17.5
untitled Muddy Ck
Paonia Res, Bardine, Nr 14.0 218 84 0.7 11 6.4 16.7
untitled Uncompahgre
Ridgway Res 71.6 108 86 67.3 101 66.6 83.0
untitled Dolores
Mcphee Res 208.6 65 55 223.3 69 323.0 381.1
untitled
TOTAL 2167.7 117 78 1780.3 96 1848.0 2792.1
Colorado
Lake Powell 10836.8 63 45 9731.9 57 17122.8 24322.0
untitled
TOTAL 10836.8 63 45 9731.9 57 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 108.3 146 86 105.8 143 74.0 125.4
untitled San Juan
Navajo Res, Archuleta, Nr 1170.5 86 69 1052.7 77 1361.0 1696.0
untitled Florida
Lemon Res, Durango, Nr 28.1 117 70 24.7 103 24.1 39.8
untitled
TOTAL 1306.8 90 70 1183.2 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