San Juan Water Supply Outlook, February 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-July95 115 135 63 160 230
Carracas, Nr April-July170 200 240 63 295 400
Navajo Res, Archuleta, Nr April-July275 350 430 59 505 750
Farmington April-July415 530 640 58 745 1080
Bluff, Nr April-July400 510 640 58 750 1050
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July27 31 38 70 45 60
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July31 36 45 69 56 70
Piedra
Arboles, Nr April-July80 102 120 57 152 225
Los Pinos
Vallecito Res, Bayfield, Nr April-July92 119 135 70 165 210
Animas
Durango April-July200 265 290 70 355 425
Florida
Lemon Res, Durango, Nr April-July22 29 35 64 44 58
La Plata
Hesperus April-July10 13.5 16.5 72 21 25
Mancos
Mancos, Nr April-July10 14 17 55 23 33

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 Res, Bayfield, Nr 37.2 59 30 67.3 106 63.5 125.4
untitled San Juan
Navajo Res, Archuleta, Nr 869.1 66 51 1254.9 96 1310.4 1696.0
untitled Florida
Lemon Res, Durango, Nr 6.9 33 17 18.6 89 20.9 39.8
untitled
TOTAL 913.2 65 49 1340.8 96 1394.7 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