Four arcs of water unleashed from a dam coursed through the Grand Canyon in a flood meant to mimic the natural ones that used to nourish the ecosystem by spreading sediment.

More than 300,000 gallons (more than a million liters) of water per second were released from Lake Powell above the dam near the Arizona-Utah border.

That’s enough water to fill the Empire State Building in 20 minutes, said Interior Secretary Dirk Kempthorne.

“This gives you a glimpse of what nature has been doing for millions of years, cutting through and creating this magnificent canyon,” Kempthorne said after he pulled the lever Wednesday, releasing the water from Glen Canyon Dam, upstream from Grand Canyon National Park.

The water gushed from two of four giant steel tubes in parallel arcs into the Colorado River. By afternoon, water poured from all four tubes, creating a churning pool beneath the sheer, sandstone canyon walls rising hundreds of feet.

The water level in the Grand Canyon rose 15 feet (4.6 meters) in some places.

Officials hope water from the three-day, controlled flood will leave behind sediment and restore sandbars as it goes back to normal levels.

Officials have flooded the canyon twice before, in 1996 and 2004.

“Clear” Science for Muddy Water

Before the dam was built in 1963, the river was warm and muddy, and natural flooding built up sandbars that are essential to native plant and fish species. The river is now cool and clear, its sediment blocked by the dam.

The change helped speed the extinction of four fish species and push two others, including the endangered humpback chub, near the edge.

Shrinking beaches have led to the loss of half the camping sites in the canyon in the past decade.

Since Glen Canyon Dam was built, 98 percent of the sediment carried by the Colorado River has been lost, Grand Canyon National Park Superintendent Steve Martin said.

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