Grand Canyon flooded in giant eco-experiment

Floodgates have been opened on a dam upstream of the Grand Canyon in an effort to improve biodiversity in the Colorado River and allow scientists to gauge the impact of a good soaking on the ecosystem.

The jet tubes of the Glen Canyon Dam were opened last Wednesday and allow a flow of a huge 41,500 cubic feet per second into the Grand Canyon below.

Like that other 'natural disaster' of the American south, the wildfire, flooding is a major inconvenience to mankind but vital to the overall health of the ecosystem.

Successive damming of the Colorado River has led to silt which would have been washed along its entire length building up in a series of reservoirs, reducing their capacity while at the same time starving riverine plants and animals of vital nutrients.

Silt which has made it past the dams has also been allowed to settle earlier than might otherwise have been the case, due to slower water flow.

Secretary of the Interior, Dirk Kempthorne, opened the jet tubes for a 60-hour high-flow test which will allow scientists to learn more about improving the river for wildlife.

The flow increase is expected to push silt and sand onto the banks of the river and create new sandbars.

"This experiment has been timed to take advantage of the highest sediment deposits in a decade and designed to better assess the ability of these releases to rebuild beaches that provide habitat for endangered wildlife and campsites for thousands of Grand Canyon National Park tourists," said Secretary Kempthorne.

"The water will be released at a rate that would fill the Empire State Building within twenty minutes. It will transport enough sediment to cover a football field 100 feet deep with silt and sand."

Evaluation of the results of the release will be part of an effort to fashion a long-term, science-based river management process.

Scientists hope to gain a better understanding about whether higher flows created by releasing water from the dam can be used to rebuild eroded beaches downstream.

These Colorado River sandbars within Grand Canyon not only provide habitat for wildlife and camping beaches for tourists, but also supply sand needed to protect archaeological sites.

High flows also create slow-flowing backwaters, used by young native fishes, particularly endangered humpback chub.

Most sediment entering Grand Canyon National Park now arrives from the Paria River and upper Marble Canyon tributaries below the dam.

Sam Bond



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