Lake Powell Water Supply Outlook, April 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-July280 295 325 133 350 375
Pine Ck
Fremont Lk, Abv April-July83 95 101 103 110 117
New Fork
Big Piney, Nr April-July285 325 370 104 420 465
Green
Fontenelle Res, Fontenelle Nr April-July720 780 900 124 1010 1080
Big Sandy
Farson, Nr April-July40 47 52 100 60 68
Green
Green River, Wy, Nr April-July720 790 905 124 1010 1100
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July26 28 33 61 40 49
Viva Naughton Res April-July33 36 43 58 52 65
Blacks Fork
Robertson, Nr April-July51 59 65 73 74 90
Ef Smiths Fork
Stateline Res, Robertson,nr April-July15.7 18.7 21 81 22 26
Green
Flaming Gorge Res, Flaming Gorge Dam, At April-July790 875 1000 102 1130 1300


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-July11 12.7 14.5 63 15.2 17.2
Steamboat Springs April-July124 146 167 64 196 235
Elk
Milner, Nr April-July178 215 240 75 275 315
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July20 29 33 45 41 55
Yampa
Maybell, Nr April-July410 500 575 61 670 790
Little Snake
Slater, Nr April-July58 82 93 60 106 142
Dixon, Nr April-July107 152 175 51 210 285
Lily, Nr April-July98 155 180 52 210 300
Yampa
Deerlodge Park April-July490 645 750 60 865 1060
White
Meeker, Nr April-July118 131 148 53 162 200
Watson, Nr April-July121 136 151 54 166 205


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-July8.9 10.9 12.9 61 14.5 20
Ashley Ck
Vernal, Nr April-July18 23 27 54 30 45
West Fork Duchesne
Vat Diversion, Blo April-July6 7.2 8.5 46 9.9 12.9
Duchesne
Tabiona, Nr April-July50 57 64 59 70 84
Rock Ck
Upper Stillwater Res April-July37 45 50 68 56 66
South Fork Rock Ck
Docs Div, Blo April-July2.5 3.2 3.6 49 4.1 5.4
Rock Ck
Mountain Home, Nr April-July43 53 58 66 65 77
Currant Ck
Currant Ck Res April-July5.8 7.2 8 40 8.7 13.3
Strawberry
Solider Springs,nr April-July15 18 21 30 27 34
Starvation Res, Duchesne, Nr April-July28 34 38 34 43 54
Duchesne
Duchesne, Nr, Knight Div, Abv April-July95 110 120 62 132 160
Lake Fork
Moon Lake Res, Mtn Home, Nr April-July27 35 40 61 47 56
Yellowstone
Altonah, Nr April-July30 39 44 72 49 59
Whiterocks
Whiterocks, Nr April-July22 26 30 56 35 52
Uinta
Neola, Nr April-July32 44 49 66 56 75
Duchesne
Myton April-July88 121 143 43 168 225
Randlett, Nr April-July93 124 145 38 169 235


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-July2.1 2.9 3.9 25 4.8 6.7
Fish Ck
Scofield, Nr, Reservoir, Abv April-July9.6 11.1 13.5 45 16 19.2
Price
Scofield Res, Scofield, Nr April-July12.9 14.8 18 44 21 26
Green
Green River, Ut April-July1500 1760 1920 65 2280 2700
Huntington Ck
Electric Lake April-July3.8 4.3 5.2 39 5.7 8.1
Power Plant, Blo April-July17.7 18.8 20 50 21 28
Seeley Ck
Joes Vly Res, Orangeville, Nr April-July16.4 22 24 43 27 37
Ferron Ck
Ferron, Nr April-July10 13.5 16.5 43 18.8 27
Muddy Ck
Emery, Nr April-July4.4 5.8 6.5 33 7.8 10


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-July140 160 185 84 210 255
Willow Ck
Willow Ck Res, Granby, Nr April-July25 32 40 85 48 56
Fraser
Winter Park April-July15 16.5 18 93 19.5 22
Williams Fork
Williams Fork Res, Parshall, Nr April-July62 72 78 81 86 100
Muddy Ck
Wolford Mountain Reservoir April-July20 26 33 61 40 46
Blue
Dillon Res April-July105 125 140 86 155 175
Green Mtn Res April-July165 200 225 82 250 280
Colorado
Kremmling, Nr April-July530 610 690 80 780 920
Eagle
Gypsum, Blo April-July150 185 210 63 230 290
Colorado
Dotsero, Nr April-July750 880 1020 73 1150 1390
Frying Pan
Ruedi Res, Basalt, Nr April-July62 76 86 62 98 125
Roaring Fork
Glenwood Springs April-July310 380 430 62 460 560
Colorado
Glenwood Springs, Blo April-July1080 1280 1470 70 1600 2020
Cameo, Nr April-July1200 1380 1570 67 1730 2150
Plateau Ck
Cameo, Nr April-July20 30 42 34 52 70
Colorado
Cisco, Nr April-July1700 2000 2300 52 2700 3400
Lake Powell, Glen Cyn Dam, At April-July1900 2700 3100 43 3790 4900


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-July52 56 62 63 67 80
Almont April-July79 86 94 61 105 124
East
Almont April-July83 95 108 59 120 143
Gunnison
Gunnison, Nr April-July170 182 210 57 235 290
Tomichi Ck
Gunnison April-July17 22 26 35 36 48
Lake Fork
Gateview April-July43 58 68 55 83 104
Gunnison
Blue Mesa Res April-July260 310 345 51 400 500
Morrow Point Res April-July290 340 375 51 430 530
Crystal Res April-July330 375 415 50 465 570
Muddy Ck
Paonia Res, Bardine, Nr March-June20 27 32 33 41 50
April-June18 25 30 33 39 48
April-July20 27 32 33 41 50
Nf Gunnison
Somerset, Nr April-July90 115 136 46 158 200
Surface Ck
Cedaredge April-July2.5 3.1 3.8 23 5 7
Uncompahgre
Ridgway Res April-July35 41 47 47 56 70
Colona April-July36 46 55 40 65 89
Delta April-July18 23 30 27 39 61
Gunnison
Grand Junction, Nr April-July480 585 650 44 780 950


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-July55 70 83 34 95 115
Mcphee Res April-July60 75 89 30 106 125
San Miguel
Placerville, Nr April-July35 42 50 39 57 65
Dolores
Cisco, Nr April-July110 130 160 28 190 235


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-July80 92 105 49 120 145
Carracas, Nr April-July120 138 160 42 185 220
Navajo Res, Archuleta, Nr April-July168 197 235 32 265 350
Farmington April-July215 265 310 28 385 485
Bluff, Nr April-July195 240 300 27 370 475
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July19 22 26 48 30 37
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July22 26 32 49 37 43
Piedra
Arboles, Nr April-July43 52 60 29 73 93
Los Pinos
Vallecito Res, Bayfield, Nr April-July38 47 60 31 71 96
Animas
Durango April-July90 111 132 32 160 205
Florida
Lemon Res, Durango, Nr April-July6 9 12 22 16 22
La Plata
Hesperus April-July3 4 5 22 7 9
Mancos
Mancos, Nr April-July4 6 8 26 10 13

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 117.4 96 34 206.8 170 121.7 344.8
untitled Big Sandy
Big Sandy Res, Farson, Nr 33.4 170 87 30.5 156 19.6 38.3
Blacks Fork
Meeks Cabin 12.2 92 41 15.8 118 13.4 29.9
untitled Ef Smiths Fork
Stateline Res, Robertson,nr 6.3 115 46 7.4 135 5.5 13.9
untitled Green
Flaming Gorge Res, Flaming Gorge Dam, At 3184.3 105 85 3169.4 105 3021.3 3749.0
untitled Strawberry
Solider Springs,nr 935.8 141 85 806.8 122 663.7 1105.9
Starvation Res, Duchesne, Nr 164.9 110 100 117.9 79 149.7 165.3
untitled Rock Ck
Upper Stillwater Res 9.0 201 29 2.3 51 4.5 31.4
untitled Lake Fork
Moon Lake Res, Mtn Home, Nr 26.8 98 73 30.0 110 27.3 36.5
untitled Big Brush Ck
Red Fleet Res, Vernal, Nr 21.1 111 82 20.2 106 19.0 25.7
untitled Price
Scofield Res, Scofield, Nr 53.7 174 82 21.7 70 30.9 65.8
untitled Seeley Ck
Joes Vly Res, Orangeville, Nr 45.9 115 73 32.7 82 40.0 62.5
untitled Huntington Ck
Electric Lake 23.3 127 74 16.5 90 18.3 31.5
untitled
TOTAL 4634.1 112 81 4478.1 108 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 431.8 137 88 381.2 121 314.3 490.3
untitled Willow Ck
Willow Ck Res, Granby, Nr 8.8 107 97 7.5 91 8.2 9.1
untitled Williams Fork
Williams Fork Res, Parshall, Nr 66.9 110 69 73.2 120 60.8 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 54.0 124 82 52.0 119 43.7 66.0
untitled Blue
Dillon Res 236.1 110 93 214.0 99 215.5 254.0
Green Mtn Res 65.8 100 45 64.0 97 65.9 146.9
untitled Homestake Ck
Homestake Res -9999.0 -99 -99 32.1 128 25.1 43.0
untitled Frying Pan
Ruedi Res, Basalt, Nr 64.8 103 64 66.2 105 63.2 102.0
untitled Plateau Ck
Vega Res, Collbran, Nr 12.4 87 38 14.5 102 14.2 32.9
untitled Taylor
Taylor Park Res 70.7 113 67 68.7 110 62.4 106.2
untitled Gunnison
Blue Mesa Res 533.5 117 64 571.4 126 454.9 829.5
Morrow Point Res 103.7 93 89 108.3 97 111.7 117.0
Crystal Res 15.5 96 88 16.7 103 16.2 17.5
untitled Muddy Ck
Paonia Res, Bardine, Nr 5.7 186 34 2.8 89 3.1 16.7
untitled Uncompahgre
Ridgway Res 62.4 89 75 65.6 94 70.0 83.0
untitled Dolores
Mcphee Res 277.4 97 73 347.1 122 285.4 381.1
untitled
TOTAL 2009.4 112 73 2085.0 115 1789.4 2749.1
Colorado
Lake Powell 12956.1 76 53 11364.0 67 16941.7 24322.0
untitled
TOTAL 12956.1 76 53 11364.0 67 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 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