A controlled flood to restock the Grand Canyon’s snaking beaches has been called off this year, as officials contend with the effects of a two-decade drought on the Colorado River.
Persistent dry and hot weather in the American west has left Arizona’s Glen Canyon Dam, which forms Lake Powell, one of the country’s largest reservoirs, at an all-time low.
Eight times since 1996, the US Bureau of Reclamation, which handles water distribution, has released a torrent of water from the dam to break up sand in the river below and redistribute it to beaches downstream. They pull the trigger when hundreds of thousands of tonnes of sediment has built up in the Colorado River. The last flow occurred in 2018.
The process is vital to repair and expand the Grand Canyon’s withering beaches, which erode over time and are damaged by rain, and preserve the national park’s ecology, campsites and archaeological places.
This year, despite a million tonnes of sediment having accumulated in the river, the government has decided to withhold the flow amid perilously low water levels.
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Lee Traynham, a programme manager, said the bureau carefully considered whether unacceptable negative effects would come from a flood experiment. “And in this case, this year, we determined that there would be,” she said, despite “perhaps the second-largest sediment contribution that we’ve seen.”
Officials say they take into account not just sediment build-up and the needs of the Grand Canyon’s beaches, but also water quality, Native American tribes, fish stocks and, crucially, power generation. In 2015 officials called off the flood to stop the spread of a non-native fish.
The bureau has cited underwhelming hydropower production as a reason to cancel the flood. The Glen Canyon Dam must maintain an elevation of 3,525ft to generate power, but drought and heatwaves have pushed it to the brink. Its water level sits at 3,544ft, down from 3,628ft at the same point in 2017.
A 192-hour flood would drop the lake’s elevation by 5ft while a 60-hour flow would reduce it by 2ft.
Already the Western Area Power Administration, a government agency that transmits power, is unable to keep up with demand.
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River guides and academics insist the flow should proceed anyway. “This is the first time that a flood has been cancelled because of politics and revenue and economics and it’s a dangerous precedent,” Jack Schmidt of Utah State University told the Las Vegas Review-Journal.
“Here’s what it means,” John Weisheit, a Colorado River guide, said. “Our bottom line budget is more important than the Grand Canyon.”
The Bureau of Reclamation said its officials used the best available scientific information.
The Colorado River, which meanders through the Rocky Mountains to the Gulf of California, has declined by about 20 per cent over the past century, according to the US Geological Survey.
Persistent drought, extreme heatwaves and wildfires across the American west have been tied to climate change.
