Here’s an in-depth look at the sedimentation problem at Paonia Reservoir from Emily Benson writing for The High Country News. Here’s an excerpt:
The root cause of the problem at the reservoir had been building since the dam was finished in 1962. Year by year, sediment quietly collected on the reservoir bottom, gradually raising its floor. Once the sediment was level with the dam outlet, where water is released downstream, any debris that washed into the reservoir threatened to clog the opening and make the dam inoperable. In the fall of 2014, personnel worked 10-hour days for two weeks to clear logs, branches and dirt from the outlet, by hand and with an excavator. Some of the workers stood directly on waterlogged sand, digging out the grates with pitchforks. When the dam was newly built, they would’ve needed a crane 70 feet tall to reach the same spot.
Silt, sand, gravel and clay are accumulating in nearly all reservoirs in the West, leaving less room to capture water for storage or for flood prevention. Behind many dams, space is starting to run out. Ignoring the problem could jeopardize the West’s water supply in the coming years. To avoid that, water managers are dredging behind dams, retrofitting outlet works and looking for ways to safely pass sediment downstream. “It’s not an immediate crisis,” Randle says. “But it is sort of a ticking time bomb.”