San Juan Water Supply Outlook, June 1, 2019

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

Contents

San Juan Summary






*Median of forecasts within each basin.


San Juan Basin Conditions




Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.


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-July280 290 295 137 305 315
June-July145 155 160 167 170 180
Carracas, Nr April-July465 480 490 129 500 530
June-July225 240 250 158 260 290
Navajo Reservoir, Archuleta, Nr April-July950 985 1000 136 1040 1110
June-July450 485 500 172 540 610
Farmington April-July1520 1550 1570 143 1640 1700
June-July830 855 875 186 950 1010
Bluff, Nr April-July1550 1580 1600 145 1680 1730
June-July820 845 870 193 950 1000
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July66 68 71 131 74 77
June-July37 39 42 183 45 48
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July73 77 80 123 83 88
June-July40 44 47 157 50 55
Piedra
Arboles, Nr April-July280 290 295 140 305 320
June-July115 125 130 176 140 155
Los Pinos
Vallecito Reservoir, Bayfield, Nr April-July260 270 275 142 290 310
June-July169 179 184 186 197 220
Animas
Durango April-July555 590 605 146 625 660
June-July355 390 405 184 425 460
Florida
Lemon Reservoir, Durango, Nr April-July64 67 70 127 74 78
June-July46 49 52 193 56 60
La Plata
Hesperus April-July30 32 33 143 35 37
June-July17 19 20 235 22 24
Mancos
Mancos, Nr April-July34 36 38 123 39 42
June-July12 14 16 154 17 20

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).

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 Reservoir, Bayfield, Nr 64.5 64 51 84.4 84 100.5 125.4
untitled San Juan
Navajo Reservoir, Archuleta, Nr 1278.8 89 75 1223.2 86 1429.7 1696.0
untitled Florida
Lemon Reservoir, Durango, Nr 18.9 59 47 18.5 58 32.1 39.8
untitled
TOTAL 1362.1 87 73 1326.1 85 1562.3 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


Hydrologist: Greg Smith