Portrait of a runoff, through a tunnel

Picture 4

The screenshot above is an indication that the natural flow of snowmelt water in the upper Roaring Fork River drainage dropped off on Tuesday, July 12, marking a downward shift in what has been a unusually prolonged runoff season.

The gauge above is from the Twin Lakes tunnel at Grizzly Reservoir. The tunnel diverts almost all of the water from Lost Man Creek, the main stem of the upper Roaring Fork River, and from Lincoln Creek to the eastern side of the Continental Divide.

The tunnel is a good indicator of the runoff levels in the upper Roaring Fork River drainage, and a true indicator of how much water is being sent to Twin Lakes Reservoir, Colorado Springs, Aurora, Pueblo, Pueblo West and fields north of the Arkansas River in Crowley and Antero counties.

The operators of the tunnel, the Twin Lakes Reservoir and Canal Co., have been diverting water through the tunnel at the maximum rate of about 625 cubic feet of water for about six weeks, save for two days on June 21 and 22. If the operators of the private company could keep diverting water through the tunnel at the maximum level of about 625 cfs, they would, as it is consistent with the company's mission to serve its shareholders by delivering water to them.

But on Tuesday, the outflow through the tunnel dropped, and did so in a manner that presumably corresponds to the drop in the natural runoff in the headwaters of the Roaring Fork River above the diversion dams, although other factors could be involved, such as downstream storage capacity.

By Saturday morning, the flow to the east through the tunnel was almost down to 275 cfs. The great runoff 2011, at least in the upper Roaring Fork River watershed, appears to be on the decline.

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