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San Juan Water Supply Outlook, April 1, 2009

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


San Juan Summary

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the San Juan were below average last fall. This was most likely due to limited monsoonal precipitation over the summer months. Observed streamflow for the month of March was mostly below average for the lower San Juan while the upper portions saw above to much above average flows due to above normal temperatures in early March.

-Snowpack/Precipitation...Snow water equivalent for the entire San Juan Basin on April 1st was 90 percent of average. Precipitation over the San Juan Basin for March was a dismal 45% of average. Because of this, seasonal precipitation for the San Juan Basin dropped to 95 percent of average.

-Short Term Precipitation Forecast...The forecast models through the middle of April suggest a slight probability of above average precipitation for the San Juan Basin.

-General Discussion...Due to the below average soil moiture in the upper basin this fall and the combination of current snowpack conditions and low March monthly precipitation, the median April-July forecast for the San Juan Basin is 85 percent of average. This is a 15 percent drop from last month's forecast.

*Median of forecasts within each basin.

San Juan Basin Conditions

* 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