The Colorado River below Glen Canyon Dam is experiencing dangerously low levels of dissolved oxygen (DO), due in part to lower water levels at Lake Powell and rising temperatures in the river, according to the Bureau of Reclamation.
Fish native to the Colorado River, such as humpback chub and razorback sucker, are generally located farther downstream where low DO levels are remedied by riffles and runs that aerate the water. The poor water quality just below the dam and its associated 1,320 MW hydro powerhouse, is adversely impacting local rainbow trout populations. Reduced oxygen in the water causes stress, increases metabolic rates and ultimately can result in fish kills or fish moving downstream to seek refuge in cooler, more oxygen-rich river habitats.
“Reclamation’s water quality forecasts suggested that there was potential for reaching low dissolved oxygen levels below the dam this year, but we didn’t anticipate it happening until early autumn,” said Reclamation fish biologist Clarence Fullard.
Prolonged drought and low runoff conditions accelerated by climate change, including extreme heat and low precipitation, have led to historically low water levels in Lake Powell and have worsened ecosystem disruption in the river downstream of Glen Canyon Dam.
Over the past two decades, Department of Interior leaders have engaged with Colorado River Basin partners on drought response operations. Earlier this month, the 2023 Colorado River water operations were announced, including reduced releases from Lake Powell and additional shortage declarations downriver for Lake Mead, demonstrating the severity of the drought and critically low reservoirs.
Reclamation works with the U.S. Geological Survey to closely monitor water quality conditions and is working with partners and stakeholders to better understand potential effects, according to a release.
