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San Juan Water Supply Outlook, January 1, 2010

Prepared by Tracy Cox
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah


San Juan Summary

*Median of forecasts within each basin.

San Juan Basin Conditions

The following conditions influenced this month's forecasts:

Seasonal October through December precipitation amounts rose from last month to near average, 105%, due to the wet December.
December precipitation was much above average with 155%.

Current snow water equivalent for the entire basin is 95%, which is near average. Both the Animas and above Navajo basin snow water equivalents were similar with 95% percent of average.
--- Animas River Basin Snow Plot.
--- Above Navajo Basin Snow Plot.

Streamflow for the entire San Juan Basin was much below average in December. Seasonal streamflow since October was also much below average due to the much below average summer through fall precipitation.

Soil Moisture:
Modeled soil moisture as of November 1st, 2009 was below to much below average.

Climate Forecasts:
The correlation of El Nino and April through July water volumes in the San Juan basin is so small that it did not influence the January forecast process.

Forecast Summary:
Even though seasonal precipitation and current snowpack are near average, soil moisture conditions before the winter season were below to much below average in the upper basin. This helped drive the San Juan Water Supply April-July forecast down to 85% of average.

* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

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).

Reservoir Monthly Inflow Forecasts

Monthly Streamflows

Precipitation Maps

Hydrologist: Tracy Cox