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Upper Colorado Water Supply Outlook, February 1, 2009


Prepared by Brenda Alcorn, Tracy Cox
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Upper Colorado Summary

There was a large discrepancy in the January precipitation between the northern half of the Colorado River Basin and the southern half. The Upper Colorado Basin had 120% of average precipitation during the month, while the Gunnison Basin had 80% and the Dolores Basin had just 55% of average. The February 1st snow water equivalent percent of average decreased from January 1st in the Gunnison and Dolores basins but is still above average, as it is in the Upper Colorado.



*Median of forecasts within each basin.


Upper Colorado Mainstem Basin Conditions

-Model Soil Moisture/Observed Streamflow... Soil moisture was near to above normal in the Upper Colorado heading into the winter. January streamflow was near normal.

-Snowpack/Precipitation... January precipitation was 120% of average in the Upper Colorado River Basin keeping the water year precipitation at 110% of average. The basin wide February 1st snow water equivalent percent of average also held steady, as compared to January 1st, at 125% although some individual sub-basins did see changes. The Muddy Creek basin, which includes Wolford Mountain Reservoir, had the greatest gain in the snowpack and is now over 110% of average, compared to less than 90% of average at the beginning of January. On the flip side, the Mill Creek basin in Utah near the Colorado border had a decrease of over 30% of average in its snowpack from last month. The Roaring Fork basin snow water equivalent percent of average decreased by about 10% from last month, but is still the highest in the Upper Colorado Basin at over 130% of average.

-General Discussion... Changes to the April through July streamflow volume forecasts from last month generally corresponded to the changes in the snowpack. Muddy Creek had the biggest increase going from 92% to 103% of average and Mill Creek had the biggest decrease going from 106% to 96%. The rest of the forecast volumes remained the same or were increased up to 5% over last month's forecasts reflecting changes in snow water equivalent. The April through July streamflow volume forecasts now range between 96% and 116% of average, with a median value of 110%.



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

Gunnison Basin Conditions

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the Gunnison was near to slightly below average in the fall. Observed streamflow for the month of January was average for the Gunnison.

-Snowpack/Precipitation...Precipitation over the Gunnison Basin as a whole for January was below average at 80 percent. However, the northern portions of the basin were near average while the southern portions were much below average. As a result, the February 1st snow water equivalent percent of averages changed very little from the January 1st values in the East River and North Fork Gunnison drainages, and dropped 5-10 percent in the Tomichi and Lake Fork drainages. Seasonal precipitation for the Gunnison is 110 percent of average and overall snow water equivalent remains above average at 115% of average.

-Short Term Precipitation Forecast...The forecast models through the first week of February keep the Gunnison Basin relatively dry with slighly above average temperatures.

-General Discussion...The CPC guidance shows the possibility of above average precipitation and below normal temperatures for the secound week of February. However, for February through April, CPC suggests a chance for above average temperatures and below average preciptation. Due to the average soil moiture in the upper basin this fall and the combination of current snowpack conditions and the CPC forecast, the median April-July forecast for the Gunnison Basin is 110 percent of average. This is up 5 percent from last month's forecast due to the average January precipitation and steady snowpack across the northern portions of the Gunnison.



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

Dolores Basin Conditions

-Model Soil Moisture/Observed Streamflow...Soil moisture for most of the upper basins in the Dolores was below average in the fall. This was most likely due to limited monsoonal precipitation during the summer months. Observed streamflow for the month of January was mostly below average for the Dolores.

-Snowpack/Precipitation...As of February 1st, snow water equivalents across the Dolores were currently 120 percent of average. Precipitation over the Dolores Basin for January was much below average with 55 percent. Seasonal average precipitation for the Dolores Basin is average with 100 percent.

-Short Term Precipitation Forecast...The forecast models through the first week of February keep the Dolores Basin relatively dry with above average temperatures.

-General Discussion...The CPC guidance shows the possibility of above average precipitation and below normal temperatures for the secound week of February. However, for February through April, CPC suggests a chance for above average temperatures and below average preciptation for the Dolores Basin. Due to the below average soil moiture in the upper basin this fall and the combination of current snowpack conditions and the CPC forecast, the median April-July forecast for the Dolores Basin is 105 percent 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: Brenda Alcorn, Tracy Cox