Construction at Grizzly Reservoir Dam causes water discoloration at Roaring Fork River, Lincoln Creek
Regan Mertz/The Aspen Times
The gradual drawdown of water from Grizzly Reservoir, initiated in early July for scheduled dam construction, has led to temporary discoloration in Lincoln Creek and the Roaring Fork River on Tuesday.
According to a Pitkin County alert, this phenomenon is due to an increased release of sediment, which can remain suspended and give the water a muddy appearance for the next few days.
PitCo wants recreational users of the river to exercise additional caution and avoid ingesting the water. Pet owners should also keep their animals away from the river during this period.
“If you were to drink it, it may make you sick to your stomach,” Pitkin County Environmental Health Specialist Bryan Daugherty said. “It may cause skin irritations, so that’s why they’re recommending not having pets in the water.”
The Pitkin County environmental safety team and the Roaring Fork Conservancy had anticipated this sediment release and implemented water quality monitoring in response.
Daugherty, who was out monitoring water quality all day, said that naturally occurring drawdowns happen later into the summer, but coupled with dam drainage, it is roiling up some of the sediment that is at the bottom.
“Those things are just gonna happen anytime you drain the dam,” he said.
Results are not back from the water samples yet.
Typically, as snowpacks recede later on in the summer, the sediment will be stirred up, but there will be much more water that mixes with it than there is now. More water helps to dilute the water, Daugherty said. This is why the Roaring Fork River is so brown. There is less water since it is earlier in the summer.
“This is naturally occurring sediment and metals that come off of the mountain and precipitate into Lincoln Creek and into the reservoir. It happens every single year,” Daugherty said. “Now, we’ve seen this happen more and more often and more intensely, likely due to climate change of the ice melting underneath those mountains and allowing the rocks to be able to interact with the air and water instead of them being frozen in ice.”
For more information on the Grizzly Dam rehabilitation project, visit Pitkin County Civic Alerts online at https://pitkincounty.com/CivicAlerts.aspx?AID=676.
The Aspen Times reporter Westley Crouch contributed to this story.
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