Upper Colorado Water Supply Outlook, May 1, 2019

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-July200 225 250 114 270 295
May-July182 205 230 112 250 275
Willow Ck
Willow Ck Reservoir, Granby, Nr April-July55 62 68 145 76 85
May-July48 55 61 142 69 78
Fraser
Winter Park April-July16.7 18.2 19.5 101 21 24
May-July15.7 17.2 18.5 99 20 23
Williams Fork
Williams Fork Reservoir, Parshall April-July85 92 100 104 110 120
May-July77 84 92 102 102 112
Muddy Ck
Wolford Mountain Reservoir April-July50 56 62 115 71 80
May-July41 47 53 115 62 71
Blue
Dillon Reservoir April-July175 190 205 126 220 240
May-July162 177 192 125 205 225
Green Mtn Reservoir April-July275 300 325 118 350 385
May-July250 275 300 118 325 360
Colorado
Kremmling, Nr April-July850 925 1000 116 1080 1200
May-July750 825 900 115 980 1100
Eagle
Gypsum, Blo April-July320 350 375 112 415 460
May-July290 320 345 110 385 430
Colorado
Dotsero, Nr April-July1380 1500 1610 115 1780 2000
May-July1220 1340 1450 113 1620 1840
Frying Pan
Ruedi Reservoir, Basalt, Nr April-July138 155 170 122 185 200
May-July127 144 159 122 174 189
Roaring Fork
Glenwood Springs April-July700 760 825 120 880 980
May-July630 690 755 118 810 910
Colorado
Glenwood Springs, Blo April-July2100 2300 2500 118 2750 3000
May-July1870 2070 2270 118 2520 2770
Cameo, Nr April-July2400 2610 2800 119 3080 3500
May-July2150 2360 2550 119 2830 3250
Plateau Ck
Cameo, Nr April-July150 167 185 149 200 225
May-July126 143 161 155 176 200
Colorado
Cisco, Nr April-July5000 5450 5850 132 6350 6900
May-July4270 4720 5120 133 5620 6170
Lake Powell, Glen Cyn Dam, At April-July7640 8740 9200 128 9770 11240
May-July6400 7500 7960 130 8530 10000


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 Reservoir April-July116 123 130 131 139 156
May-July105 112 119 132 128 145
Almont April-July185 197 210 135 230 260
May-July168 180 194 138 215 245
East
Almont April-July225 230 245 135 260 290
May-July205 210 225 136 240 270
Gunnison
Gunnison, Nr April-July465 485 510 138 540 625
May-July420 440 465 139 495 580
Tomichi Ck
Gunnison April-July92 102 112 151 127 148
May-July70 80 90 145 105 126
Lake Fork
Gateview April-July140 157 169 137 182 220
May-July129 146 158 136 171 210
Gunnison
Blue Mesa Reservoir April-July870 945 970 144 1040 1200
May-July750 825 850 142 915 1080
Morrow Point Reservoir April-July960 1040 1060 143 1130 1290
May-July825 900 925 142 990 1150
Crystal Reservoir April-July1090 1160 1180 141 1250 1410
May-July935 1010 1030 140 1100 1260
Muddy Ck
Paonia Reservoir, Bardine, Nr March-June131 138 143 149 151 163
April-July135 142 147 152 155 167
May-June100 107 112 162 120 132
May-July107 114 119 159 127 157
Nf Gunnison
Somerset, Nr April-July360 375 395 134 420 465
May-July300 315 335 140 360 405
Surface Ck
Cedaredge April-July26 28 30 179 32 35
May-July22 24 26 184 28 31
Uncompahgre
Ridgway Reservoir April-July101 110 118 117 126 143
May-July90 99 107 118 115 132
Colona April-July129 143 156 114 169 195
May-July115 129 142 118 155 181
Delta April-July113 124 139 123 151 178
May-July87 98 113 120 125 152
Gunnison
Grand Junction, Nr April-July1850 2030 2100 142 2250 2500
May-July1550 1730 1800 145 1950 2200


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-July295 310 325 133 345 375
May-July245 260 275 138 295 325
Mcphee Reservoir April-July365 390 420 142 445 485
May-July260 285 315 143 340 380
San Miguel
Placerville, Nr April-July138 150 158 123 168 183
May-July120 132 140 124 150 165
Dolores
Cisco, Nr April-July770 825 860 152 895 990
May-July550 605 640 154 675 770

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 343.0 110 70 420.5 135 311.8 490.3
untitled Willow Ck
Willow Ck Reservoir, Granby, Nr 8.3 108 91 7.9 102 7.7 9.1
untitled Williams Fork
Williams Fork Reservoir, Parshall 67.6 111 70 70.2 115 60.9 96.9
untitled Muddy Ck
Wolford Mountain Reservoir 38.0 80 58 55.9 117 47.7 66.0
untitled Blue
Dillon Reservoir 185.1 87 73 233.7 109 213.6 254.0
Green Mtn Reservoir 57.3 90 39 63.0 99 63.9 146.9
untitled Homestake Ck
Homestake Reservoir 9.7 52 23 35.6 189 18.8 43.0
untitled Frying Pan
Ruedi Reservoir, Basalt, Nr 60.3 96 59 67.4 108 62.6 102.0
untitled Plateau Ck
Vega Reservoir, Collbran, Nr 15.7 86 48 15.7 86 18.3 32.9
untitled Taylor
Taylor Park Reservoir 63.9 105 60 71.8 117 61.2 106.2
untitled Gunnison
Blue Mesa Reservoir 334.8 73 40 498.3 109 457.1 829.5
Morrow Point Reservoir 113.1 101 97 112.5 101 111.8 117.0
Crystal Reservoir 17.0 102 97 15.9 95 16.7 17.5
untitled Muddy Ck
Paonia Reservoir, Bardine, Nr 6.2 97 37 11.9 185 6.4 16.7
untitled Uncompahgre
Ridgway Reservoir 56.0 84 67 64.2 96 66.6 83.0
untitled Dolores
Mcphee Reservoir 258.4 80 68 274.7 85 323.0 381.1
untitled
TOTAL 1634.7 88 59 2019.1 109 1848.0 2792.1
Colorado
Lake Powell 9197.9 54 38 12669.0 74 17122.8 24322.0
untitled
TOTAL 9197.9 54 38 12669.0 74 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