Upper Colorado 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 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-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

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 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

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