Spring could see high runoff
April 5, 2008BY TED HOLTEEN | Durango Herald Staff Writer
Despite a surprisingly dry March that caused snowpack levels to drop by almost 30 percent in Southwest Colorado, expect swollen rivers as testament to one of the snowiest winters in recent memory.
After consistently heavy snow in December, January and February, snowpack levels March 1 stood at 155 percent of average in the Animas, Dolores and San Juan river basins. By April 1, the level had dropped 29 percent but was still at 126 percent of average and 217 percent of the level from the same date in 2007.
Colorado's total snowpack was 123 percent of average April 1, its highest measured level since 1993. State hydrologists consider the April 1 readings to be the most important snowpack measurements of the year.
"Fortunately for the state's water supplies, the areas experiencing the driest conditions during March had already accumulated the greatest snowpack totals during the winter months," said Allen Green, state conservationist with the U.S. Department of Agriculture's Natural Resources Conservation Service.
Mike Gillespie, a surveyor with the NRCS, said the accumulated snowpack in the high country will have a profound effect on rivers and streams, which could meet or exceed the highest flows in nearly 40 years.
"I think we'll see a peak around June 1 and by July, it will go back down pretty low," he said. "It's really dependent on spring weather patterns and if we get additional moisture."
Other rivers in Southwest Colorado also should see high spring runoffs.
Inflows from the Pine and Florida rivers into Vallecito and Lemon reservoirs are 124 percent and 121 percent of average, respectively.
Gillespie said the largest increase in flow is expected on the San Juan River near Carracas, in Archuleta County near the Navajo Reservoir, where flows are 153 percent of average. Close behind is the Mancos River at 145 percent of average.
If the Animas River hits 9,000 cfs, it will be the highest on record since September 1970, when the recorded flow was 11,600 cfs.
The highest flow since 1970 occurred in May 2005, when the flow peaked at 8,550 cfs. The all-time high for the Animas River was 25,000 cfs in October 1911.
On Oct. 5, 1911, heavy rains near Durango caused the Animas River to rise to 8 feet above flood stage, according to the National Weather Service.
