Colorado River Basin snowpack at about 77 percent of average as of early February
By Summit Voice
SUMMIT COUNTY — Low season flows into Lake Powell have been near normal in recent weeks, with the Colorado River delivering about 356,000 acre feet (99 percent of average) during January, leaving the reservoir about 63 feet below full pool.
With the overall snowpack in the Upper Colorado Basin at about 77 percent of average and the long-term weather outlook uncertain, water managers aren’t sure how the runoff season will go.
For now, the U.S. Bureau of Reclamation’s water supply forecast for April through July is predicting an inflow of about 5 million acre feet, which is about 71 percent of average — but that outlook comes with a caveat: “At this time of year however, there is a high level of uncertainty in hydrologic forecasts and the annual release volume from Glen Canyon Dam in WY2012 will ultimately be based on the actual inflows that occur during 2012 rather than this Water Supply forecast,” the USBR wrote in the monthly update.
Looking ahead month by month, the forecasted unregulated inflow to Lake Powell is projected at 390,000 acre feet in February (99 percent of average), 550,000 AF in March (83 percent of average) and 800,000 AF in April (78 percent of average), based on a comparison with the 1981-2010 period.
The best-guess forecast for the 2012 water year is for a total of about 8.5 million AF (78 percent of average), but the forecasters tried to cover all the possible weather bases by saying the total could be as low as 5.5 million AF (51 percent of average) to as high as 12.65 million AF (117 percent of average) “depending on the range of precipitation patterns that could occur over the next several months.”
Upper Colorado flows have been near normal since 2005, with big year-to-year variations, averaging about 11 million AF during that span and raning from a low of 8.62 million AF in 2006 (80 percent of average) to a high of almost 16 million AF in 2011, which brought near-record snowfall to much of the Colorado River Basin.
Storage in the Colorado River Basin has increased by nearly 10 million AF since the beginning of water year 2005 — a significant improvement over drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 million AF (50.2 percent of capacity). As of Jan. 30, 2012 the total reservoir storage in the Colorado River Basin was 38.35 million AF. (64.3 percent of capacity).