nSan Juan Water Supply Outlook, May 1, 2017

San Juan Water Supply Outlook, May 1, 2017

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-July200 215 225 105 235 255
May-July137 152 161 89 172 192
Carracas, Nr April-July350 370 395 104 415 450
May-July225 245 270 90 290 325
Navajo Res, Archuleta, Nr April-July585 660 695 95 725 820
May-July350 425 460 81 490 585
Farmington April-July965 1040 1100 100 1160 1330
May-July630 705 770 88 825 995
Bluff, Nr April-July950 1020 1100 100 1170 1380
May-July620 695 770 90 840 1050
Rio Blanco
Pagosa Springs, Nr, Blanco Dam, Blo April-July47 53 56 104 58 65
May-July32 38 41 91 43 50
Navajo
Chromo, Nr, Oso Div Dam, Blo April-July57 65 69 106 73 81
May-July38 46 50 93 54 62
Piedra
Arboles, Nr April-July184 197 210 100 220 245
May-July110 123 136 89 145 171
Los Pinos
Vallecito Res, Bayfield, Nr April-July170 193 205 106 210 250
May-July125 148 160 94 165 205
Animas
Durango April-July365 410 440 106 475 555
May-July285 330 360 99 395 475
Florida
Lemon Res, Durango, Nr April-July40 48 53 96 56 68
May-July30 38 43 88 46 58
La Plata
Hesperus April-July23 25 27 117 29 32
May-July16 18 20 110 22 25
Mancos
Mancos, Nr April-July33 36 39 126 42 45
May-July23 26 29 121 32 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).

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 86.5 117 69 104.9 142 74.0 125.4
untitled San Juan
Navajo Res, Archuleta, Nr 1597.7 117 94 1491.0 110 1361.0 1696.0
untitled Florida
Lemon Res, Durango, Nr 26.5 110 67 27.5 114 24.1 39.8
untitled
TOTAL 1710.7 117 92 1623.4 111 1459.0 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