Click the link to read the article on The Fairplay Flume website (Meryl Phair). Here’s an excerpt:
July 8, 2024
Rainbow and brown trout are free to move as they please through Eleven Mile Canyon once again, following the removal of an unused dam on the stretch of South Platte River near Lake George. The 1952 Colorado Springs Utilities diversion dam was removed last year as part of a $4.8 million project to unite 45 miles of river. The river and its surrounding ecosystems have already seen significant benefits, particularly for fish who make their home in the clear waters of the mountain canyon.
“We have photos of fish attempting to jump the dam when it was in place,” said Charles M. Shobe, a Research Geomorphologist with the Forest Service’s Rocky Mountain Research Station. “Now that they’re able to move upstream, they’re bringing their biomass upstream which provides a better distribution of nutrients throughout the watershed.”
[…]
Scientists from the Rocky Mountain Research Station along with members of the South Park Ranger District conducted river sampling on April 25, mapping the bottom of the riverbed to get information on the shape of the river channel, collecting sediment samples to look at the aquatic habitat of the riverbed and bagging insect larvae to get a measure on who’s there. Measuring in April was essential for the team, Shobe explained, as it was after the dam’s disassembly but before the river that was diverted through a spillway while the dam was taken down, filled the canyon once again. Another sampling will be taken likely in June and then annually through 2027…
Returning the stretch of the South Platte to its pre-dam state will likely first improve habitat for the little insects that live in the stream bed, which in term will revitalize the whole system as fish feed on the insects, and bigger animals like eagles feed on the fish. While the research is still in the works, Shobe said they’ve observed anecdotally a change in the former pond area from finer sediment like mud and sand to coarser, larger sediments like gravel which will be a positive change for the aquatic organisms that swim in the stream as they tend to not do as well in a muddier environment. The buildup of sediment is a unique aspect of the Eleven Mile Canyon dam removal project as unlike other dams where removal of the river obstruction has flushed a wave of collected sediment downstream, a lot of the sediment was able to be dug out from behind the dam before removal. For that reason, downstream impacts aren’t expected, and the scope of the ongoing research will only include a couple 200 feet downstream of the former dam.
