Green Water Supply Outlook, April 1, 2021

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.
Prepared by Ashley Nielson,Patrick Kormos
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Green Summary




*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 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-July125 150 175 71 198 225
Pine Ck
Fremont Lk, Abv April-July45 57 67 68 75 82
New Fork
Big Piney, Nr April-July95 131 170 48 220 265
Green
Fontenelle Reservoir, Fontenelle, Nr April-July240 320 430 59 505 580
Big Sandy
Farson, Nr April-July16 22 27 52 35 43
Green
Green River, Wy, Nr April-July235 310 420 58 500 605
Hams Fork
Frontier, Nr, Pole Ck, Blo April-July22 27 31 57 40 50
Viva Naughton Reservoir April-July28 34 40 54 52 70
Blacks Fork
Robertson, Nr April-July36 44 50 56 61 78
Ef Smiths Fork
Stateline Reservoir, Robertson,nr April-July13 16 19 73 21 25
Green
Flaming Gorge Reservoir April-July330 410 530 54 680 910


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-July9 11 13.5 59 16 19
Steamboat Springs April-July97 119 143 55 173 215
Elk
Milner, Nr April-July154 187 215 67 250 295
Elkhead Ck
Long Gulch, Abv, Hayden, Nr April-July18 28 34 47 44 55
Yampa
Maybell, Nr April-July365 470 550 59 650 765
Little Snake
Slater, Nr April-July69 91 110 71 128 150
Dixon, Nr April-July130 170 205 59 260 325
Lily, Nr April-July120 168 205 59 260 340
Yampa
Deerlodge Park April-July475 650 775 63 920 1120
White
Meeker, Nr April-July126 145 160 57 183 225
Watson, Nr April-July130 148 161 58 188 235


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-July7.6 9.2 11.9 57 12.7 19.1
Ashley Ck
Vernal, Nr April-July15.6 19.3 23 46 25 40
West Fork Duchesne
Vat Diversion, Blo April-July4.6 5.9 7.4 40 7.9 10.9
Duchesne
Tabiona, Nr April-July42 49 57 53 62 73
Rock Ck
Upper Stillwater Reservoir April-July27 35 40 54 45 56
South Fork Rock Ck
Docs Div, Blo April-July1.9 2.8 3.3 45 3.8 4.9
Rock Ck
Mountain Home, Nr April-July33 42 49 56 53 66
Currant Ck
Currant Ck Reservoir April-July4.3 5.5 6.7 34 9.9 12
Strawberry
Strawberry Reservoir, Soldier Springs April-July10 14.6 18.8 26 21 31
Starvation Reservoir, Duchesne, Nr April-July29 37 40 36 49 58
Duchesne
Duchesne, Nr, Knight Div, Abv April-July76 92 104 54 114 137
Lake Fork
Moon Lake Reservoir, Mtn Home, Nr April-July19 29 33 50 36 47
Yellowstone
Altonah, Nr April-July21 28 33 54 36 47
Whiterocks
Whiterocks, Nr April-July14 21 25 46 27 37
Uinta
Neola, Nr April-July18.5 28 35 47 39 56
Duchesne
Myton April-July55 84 110 33 122 174
Randlett, Nr April-July65 94 116 30 132 186


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-July1.7 3.1 4.3 28 4.8 6.9
Fish Ck
Scofield, Nr, Reservoir, Abv April-July9.3 11.6 13.9 46 15 19.9
Price
Scofield Reservoir, Scofield, Nr April-July11.9 14.7 17.6 43 18.9 26
Green
Green River, Ut April-July970 1250 1500 51 1890 2450
Huntington Ck
Electric Lake April-July4 4.5 5.1 38 5.7 7.9
Power Plant, Blo April-July18 19.1 20 50 21 28
Seeley Ck
Joes Vly Reservoir, Orangeville, Nr April-July16.8 19.6 24 43 27 38
Ferron Ck
Ferron, Nr April-July9.7 13.6 18.1 48 21 29
Muddy Ck
Emery, Nr April-July5.1 6.1 7.4 37 8.2 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 Reservoir, Fontenelle, Nr 120.9 99 36 135.8 112 121.7 334.0
untitled Big Sandy
Big Sandy Reservoir, Nr Farson 9.2 47 24 24.5 125 19.6 38.3
Blacks Fork
Meeks Cabin 6.0 44 20 12.1 90 13.4 29.9
untitled Ef Smiths Fork
Stateline Reservoir, Robertson,nr 4.0 72 29 5.8 106 5.5 13.9
untitled Green
Flaming Gorge Reservoir 3168.0 105 85 3220.1 107 3021.3 3749.0
untitled Strawberry
Strawberry Reservoir, Soldier Springs 927.6 140 84 978.4 147 663.7 1105.9
Starvation Reservoir, Duchesne, Nr 161.3 108 98 164.7 110 149.7 165.3
untitled Rock Ck
Upper Stillwater Reservoir 2.0 45 6 6.7 150 4.5 31.4
untitled Lake Fork
Moon Lake Reservoir, Mtn Home, Nr 14.2 52 39 29.5 108 27.3 36.5
untitled Big Brush Ck
Red Fleet Reservoir, Vernal, Nr 16.6 87 65 22.0 115 19.0 25.7
untitled Price
Scofield Reservoir, Scofield, Nr 36.1 117 55 52.2 169 30.9 65.8
untitled Seeley Ck
Joes Vly Reservoir, Orangeville, Nr 38.5 96 62 48.5 121 40.0 62.5
untitled Huntington Ck
Electric Lake 18.6 102 59 22.7 124 18.3 31.5
untitled
TOTAL 4522.9 109 79 4723.1 114 4134.9 5689.6

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


Hydrologist: Ashley Nielson,Patrick Kormos