FGUS65 KSTR 051613
ESGNM 
TTAA00 KSLR DDHHMM
NATIONAL WEATHER SERVICE
COLORADO BASIN RIVER FORECAST CENTER
SALT LAKE CITY UT
Mar 5, 2019

 SAN JUAN RIVER BASIN SPRING FLOOD POTENTIAL OUTLOOK


Peak flows due to snowmelt are expected to be near or above average
this spring. The latest hydrologic model guidance does not indicate
flood levels being reached even at the 10% exceedance probability
level. Highest annual peaks tend to occur during the summer monsoon
period and not the snowmelt runoff period.

Due to recent significant increase in snowpack conditions streams 
are expected to run much higher than they did in spring of 2018. Heavy
rainfall during peak runoff can cause flood related issues in any
year and would have a larger impact this spring as the snowpack
continues to increase.

Peak flow procedures do not exist for all streams. Those areas that
typically experience high water issued in normal or above normal
snow years will again be susceptible to similar issues during peak
runoff this year.

Precipitation in February and into early March has been significant 
in the San Juan Basin. Over 10 inches of precipitation was received
in February at some higher elevation headwater locations. In the first
5 days of March an additional 5 inches of precipitation has occurred.

Snowpack conditions have improved dramatically over the past several
weeks and ranges from near 125 to 155 percent of normal for early March. 
Several SNOTEL sites have met or exceeded the annual peak snow that 
typically occurs in April.

Early March runoff volume forecasts for the April-July period range
from near 90 to 105 percent of the 1981-2010 average. 
 
With an active weather pattern expected through at least mid March
additional increase in the snowpack is anticipated. The spring runoff peak
flow outlook will continue to evolve with a possible further increase 
in forecasts.

Further assessment will be made regarding any snow melt flood 
threat as the season progresses. Specific peak flow forecasts will
be issued by the second week of March. The latest April-July runoff
volumes are included below:

San Juan River Basin
                           Period     50%  %AVG    10%    30%    70%    90%    AVG
                           ------    ----  ----   ----   ----   ----   ----    ---
San Juan River
  Pagosa Springs           Apr-Jul    205    95    280    220    178    148    215
  Carracas, nr             Apr-Jul    360    95    500    400    300    250    380
Rio Blanco River
  Pagosa Springs, nr, Bla  Apr-Jul     55   102     70     61     45     39     54
Navajo River
  Chromo, nr, Oso Div Dam  Apr-Jul     62    95     81     69     52     44     65
Piedra River
  Arboles, nr              Apr-Jul    195    93    285    225    162    130    210
Los Pinos River
  Vallecito Res, Bayfield  Apr-Jul    205   106    270    220    183    150    194
San Juan River
  Navajo Res, Archuleta,   Apr-Jul    690    94   1010    790    570    455    735
Florida River
  Lemon Res, Durango, nr   Apr-Jul     56   102     77     63     47     39     55
Animas River
  Durango                  Apr-Jul    425   102    550    460    370    290    415
San Juan River
  Farmington               Apr-Jul   1060    96   1530   1180    860    680   1100
La Plata River
  Hesperus                 Apr-Jul     25   109     32     27   20.0   17.0     23
San Juan River
  Bluff, nr                Apr-Jul   1060    96   1560   1180    880    660   1100
Mancos River
  Mancos, nr               Apr-Jul     30    97     44     36   24.0   18.0     31

50% Most probable volume in 1000 acre-feet.
%AVG  Most probable volume in percent of the 1981-2010 average.
10% Volume that has a 10 percent chance of being exceeded.
30% Volume that has a 30 percent chance of being exceeded.
90% Volume that has a 90 percent chance of being exceeded.
70% Volume that has a 70 percent chance of being exceeded.
AVG   average volume for the 1981-2010 period.

All forecast volumes reflect natural flow.  Actual observed flow may
be affected by upstream water management.

G. Smith/ CBRFC

NNNN
$$