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Every year, SRP crews clean out Phoenix's canals. This is what they take out — and put back in

It’s first light on a February day when two trucks park by a Salt River Project canal. They’ve come to deliver more than 5,000 white amur from an Arkansas fish farm. The fish are also known as grass carp, and they’re voracious plant eaters, so SRP uses them for weed control. When the time comes, they’re dropped out of metal tubes into the water.

The canals provide water for 2.5 million homes in the Phoenix metropolitan area. They were built on remains of a canal system left by the Hohokam, a tribe that diverted water from the Salt River to irrigate their crops. Laurene Montero, an archeologist with Pueblo Grande Museum, says they cultivated tens of thousands of acres. 

“So basically this is a hot spot, and it’s unrivaled in North America for any prehistoric society,” Montero said.

They lived here for about a thousand years.

“This is really nothing short of remarkable, what they did,” she said.

Even then, the canals had to be maintained. They would fill with silt after floods. So the Hohokam also had to clean them. How did they do it?

“I wish I had an answer for you on that,” she said. “I don’t.”

The best guess is that they did it with hand tools. Sometimes the floods were so bad that new canals were built, the old ones abandoned. Around 1450, they stopped maintaining the canals altogether. Archeologists aren’t sure exactly what happened. There was a long drought. More floods. Social change. When the first white settlers arrived, the Hohokam were gone, but the canals were still in place. The settlers started to use them, but they had the same problems.

“They were at the mercy of the river,” said SRP historian Leah Harrison. “So, there were times of floods, there were times of drought. … There were issues with reliability.”

It was hard to raise crops consistently; even a good canal system was not enough to manage the river.

When the government started funding reclamation projects in the early 1900s, Phoenix was one of the first places selected. In time, lateral canals ran from the main stem to homes and farms. They were cleaned with dredgers, discs and horses.

“The Valley’s canal and lateral system has always been a part of our culture, a part of the visual landscape,” Harrison said.

The canals became gathering places, a point of reference.

“People used to give their lateral number instead of their home address,” Harrison said.

People even swam in them in the days before backyard pools and air conditioning. That’s a bad idea today.

“That water is moving fairly quickly today. The canals are deep, and I think they’re deeper and the water is moving faster than it seems if you just look at the surface.”

Even as the farms give way to subdivisions, the canals still have to move water.

Gary Swinford of Salt River Project says canal maintenance takes place annually.

“You know the water runs from the lakes down the river to Granite Reef Dam, and then comes into this canal so you do get natural sediment deposited,” he said.

Not all the debris is natural.

“You’ll get shopping carts and couches and sofas and chairs and tables and just any odd number of things people throw in there," Swinford said. “Bicycles. You see electric scooters and bicycles that the cities leave out for people, and people throw them in the canals.” 

The shrinking Colorado River keeps making headlines, but Phoenix gets a lot of its water from the Salt and Verde rivers, groundwater and other sources.

Desalination may someday be part of the mix. All of these projects require infrastructure, and infrastructure requires maintenance. Sometimes that means backhoes and heavy equipment. Other times, it means stocking more fish.

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Ron Dungan was a senior field correspondent at KJZZ from 2020 to 2024.