On November 11, officials from the U.S. Department of Interior started a “high-flow experimental release” from Glen Canyon Dam in northern Arizona. Instead of the dam’s normal flow rate of 5,000 to 8,000 cubic feet per second (cfs) downstream, the dam released about 34,100 cfs for 96 hours.
This was the second high release on the Colorado River at Glen Canyon Dam under a protocol adopted in May 2012 that called for better science-based management of water flows.
According to the Department of the Interior:
Dam managers and resource specialists have determined that the right conditions exist to trigger a high flow that will mobilize the tremendous amount of sediment deposited by the Paria River since late July—nearly 1.5 million metric tons. Using dam operations to create a flood that mimics pre-dam natural flooding in the watershed, the sediment carried and deposited downstream in Grand Canyon National Park will build sandbars that provide key wildlife habitat for animals and fish, create recreational opportunities for the public, and protect archaeological resources. The high flows will not change the total annual delivery of water from Lake Powell to Lake Mead; they will simply slightly modify the timing of delivery. The available sediment volume is approximately three times greater than it was in the fall of 2012.
The agency added:
High-flow experimental releases are designed to mimic the natural flooding of the Colorado River through Glen and Grand canyons that occurred prior to the construction and operation of Glen Canyon Dam. Nearly all the natural sediment load once transported by these floods is now trapped behind the dam resulting in the loss of downstream sandbars, beaches, and associated resources critical to the ecosystem health along the Colorado River corridor in Grand Canyon National Park and Glen Canyon National Recreation Area. Episodic floods from tributaries downstream from the dam, such as the Paria River, are critical sources of sand input and the Department of the Interior anticipates that high-flow experimental releases will benefit downstream resources when conducted under sediment rich conditions.
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