Dillon Reservoir to fill early, may drop fast in late summer

There probably won't be much excess water spilling down the glory hole and into the Lower Blue this year.

Denver Water diverting majority of Blue River flows through Roberts Tunnel to the Front Range

By Bob Berwyn

SUMMIT COUNTY — Denver Water officials said this week they expect Dillon Reservoir to fill, or come very close to filling sometime in early June, depending on the timing of the spring runoff, but water levels could drop rapidly in late summer, and there won’t be much water released to the Lower Blue.

Currently, the reservoir is only about four feet below capacity. Last summer the reservoir filled July 27, one of the latest dates on record, as Denver Water made way for abundant runoff required by drawing the water level way down in spring and early summer.

Some other fill-and-spill dates:

2001 – June 17
2002 – did not fill, highest elevation was 8,993.17 feet on June 12
2003 – did not fill, but got within about 1.5 inches of the lip of the glory hole
2004 – did not spill, highest elevation was 9,010.38 on August 10
2005 – June 19
2006 – June 4
2007 – June 5
2008 – June 27
2009 – May 25
2010 – May 24

Read more about Dillon Reservoir fill and spill operations in this Summit Voice story.

Denver Water is releasing about 53 cubic feet per second to the Lower Blue, just a shade more than the required mininum flows of 50 cfs set to protect the fishery. More than three times that amount of water is going through the Roberts Tunnel to the Front Range. Tunnel diversions have been averaging about 150 to 225 cfs in recent weeks, according to Bob Steger, manager of raw water supplies for Denver Water.

The inflow from the Blue River, Snake River, Tenmile Creek and other minor tributaries combined has been averaging between 150 and 200 cfs, Steger said.

“I’d say people might want to think about doing their boating in May and June,” Steger said, adding that he doesn’t expect much of a boating season below the reservoir this year.





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