Upper Colorado Water Supply Outlook, June 1, 2018

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

Contents

Upper Colorado Summary




*Median of forecasts within each basin.


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.


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-July155 170 180 82 190 210
June-July65 80 90 62 100 120
Willow Ck
Willow Ck Res, Granby, Nr April-July29 32 35 74 38 42
June-July3.4 6.4 9.4 45 12.4 16.4
Fraser
Winter Park April-July16.5 18 19 98 20 21
June-July8.5 10 11 77 12 13.5
Williams Fork
Williams Fork Res, Parshall, Nr April-July68 73 78 81 84 92
June-July37 42 47 72 53 61
Muddy Ck
Wolford Mountain Reservoir April-July30 32 34 63 37 42
June-July1.9 3.9 5.9 31 8.9 13.9
Blue
Dillon Res April-July110 120 130 80 140 150
June-July50 60 70 64 80 90
Green Mtn Res April-July185 200 215 78 230 250
June-July86 101 116 63 131 151
Colorado
Kremmling, Nr April-July570 620 670 78 720 790
June-July220 270 320 61 370 440
Eagle
Gypsum, Blo April-July170 190 210 63 230 250
June-July51 71 91 42 111 131
Colorado
Dotsero, Nr April-July850 930 1000 71 1070 1150
June-July305 385 455 54 525 605
Frying Pan
Ruedi Res, Basalt, Nr April-July70 78 87 63 93 100
June-July23 31 40 45 46 53
Roaring Fork
Glenwood Springs April-July340 370 400 58 440 480
June-July146 176 205 45 245 285
Colorado
Glenwood Springs, Blo April-July1180 1300 1430 68 1600 1800
June-July425 545 675 52 845 1050
Cameo, Nr April-July1250 1360 1460 62 1600 1800
June-July475 585 685 48 825 1030
Plateau Ck
Cameo, Nr April-July26 28 31 25 35 40
June-July1.8 3.8 6.8 13.9 10.8 15.8
Colorado
Cisco, Nr April-July1750 1950 2150 48 2350 2600
June-July420 620 820 35 1020 1270
Lake Powell, Glen Cyn Dam, At April-July2340 2540 2800 39 2990 3370
June-July750 950 1210 32 1400 1780


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-July54 56 58 59 61 63
June-July21 23 25 40 28 30
Almont April-July76 78 81 52 86 88
June-July33 35 38 40 43 45
East
Almont April-July89 92 95 52 99 101
May-July0 0 0 0 0 0
June-July40 43 46 43 50 52
Gunnison
Gunnison, Nr April-July167 171 174 47 178 184
June-July75 79 82 38 86 92
Tomichi Ck
Gunnison April-July13.4 13.9 14.4 19.5 15.4 15.9
June-July2.5 3 3.5 9.5 4.5 5
Lake Fork
Gateview April-July54 56 58 47 63 68
June-July20 22 24 30 29 34
Gunnison
Blue Mesa Res April-July255 260 270 40 280 290
June-July95 100 110 29 120 130
Morrow Point Res April-July275 280 290 39 300 310
June-July100 105 115 28 125 135
Crystal Res April-July295 300 310 37 320 330
June-July106 111 121 27 131 141
Muddy Ck
Paonia Res, Bardine, Nr March-June18.7 18.9 19.2 20 19.5 19.7
April-July21 21 21 22 21 22
June-June1.5 1.7 2 8.7 2.3 2.5
June-July2 2.2 2.5 8.6 2.8 3
Nf Gunnison
Somerset, Nr April-July99 101 103 35 106 108
June-July26 28 30 26 33 35
Surface Ck
Cedaredge April-July4.7 4.8 5 30 5.5 5.2
June-July1.5 1.6 1.8 24 2.3 2
Uncompahgre
Ridgway Res April-July32 34 35 35 37 39
June-July14 15.5 17 26 18.5 21
Colona April-July34 36 37 27 40 44
June-July13 15 16 19.8 19 23
Delta April-July20 21 21 18.6 23 24
June-July3 3.5 4 7 5.5 7
Gunnison
Grand Junction, Nr April-July435 440 450 30 460 475
June-July145 150 158 23 168 185


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-July43 43 44 18 46 48
June-July9 9.5 10 10.9 12 14
Mcphee Res April-July45 46 46 15.6 49 51
June-July9.5 10.5 11 11.3 14 16
San Miguel
Placerville, Nr April-July32 33 34 27 36 38
June-July12 13 14 18.7 16 18
Dolores
Cisco, Nr April-July68 69 71 12.6 77 81
June-July22 23 25 13.6 31 35

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).

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 489.9 135 100 451.6 124 363.6 490.3
untitled Willow Ck
Willow Ck Res, Granby, Nr 9.5 106 104 9.4 106 8.9 9.1
untitled Williams Fork
Williams Fork Res, Parshall, Nr 86.6 119 89 82.5 113 73.0 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 67.0 112 102 67.2 112 59.9 66.0
untitled Blue
Dillon Res 257.1 110 101 232.6 100 232.7 254.0
Green Mtn Res 95.9 107 65 90.8 101 89.8 146.9
untitled Homestake Ck
Homestake Res 35.3 142 82 29.7 120 24.8 43.0
untitled Frying Pan
Ruedi Res, Basalt, Nr 81.2 104 80 78.2 100 78.0 102.0
untitled Plateau Ck
Vega Res, Collbran, Nr 24.9 81 76 33.5 109 30.8 32.9
untitled Taylor
Taylor Park Res 83.9 112 79 84.3 113 74.7 106.2
untitled Gunnison
Blue Mesa Res 512.6 89 62 596.8 104 575.3 829.5
Morrow Point Res 112.0 99 96 108.8 96 113.2 117.0
Crystal Res 15.9 95 91 19.0 114 16.7 17.5
untitled Muddy Ck
Paonia Res, Bardine, Nr 15.6 100 93 12.0 77 15.7 16.7
untitled Uncompahgre
Ridgway Res 64.4 91 78 64.8 92 70.7 83.0
untitled Dolores
Mcphee Res 258.1 74 68 367.1 106 347.8 381.1
untitled
TOTAL 2210.0 102 79 2328.3 107 2175.6 2792.1
Colorado
Lake Powell 12885.9 71 53 13667.1 75 18186.3 24322.0
untitled
TOTAL 12885.9 71 53 13667.1 75 18186.3 24322.0

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: Cody Moser, Greg Smith