HomeBBC NEWSTravelThe watery secret of ancient North America

    The watery secret of ancient North America


    The 180 miles of canals that criss-cross Phoenix, Arizona, allow millions of people to live in the sun-drenched desert. But most people don’t know the story of their mysterious origins.

    Criss-crossed Phoenix, Arizona has 180 miles of canals – more than twice as many as Venice and Amsterdam combined. As a native Phoenician, I spent a lot of time biking along their banks, next to joggers and fishermen casting for carp. On a summer evening, I strolled with wildlife watchers on Arizona’s main canal to watch Mexican tailless bats fluttering in large numbers from their roosts. I have talked with long-time residents who fondly recall making water skis out of plywood, attaching tow ropes to pickup trucks, and walking through their neighborhoods in a spray of water and dust.

    The canals carry irrigation and drinking water throughout the metropolitan area, enabling millions of people to live in this sun-drenched desert. They are a major reason for Phoenix’s existence, and the city’s name hints at their mysterious origins.

    In 1867, the city’s founding father, Jack Swilling – a prospector who fought on both sides of the Civil War – stood above the Salt River Valley and saw the remnants of the irrigation canal snaking through the landscape like stretch marks twisting and turning. He realized that some society had farmed this desert centuries ago. Soon after, Swilling began clearing the debris-clogged ditches to bring agriculture back to the area.

    I prophesy that a new city will spring, phoenix-like, from the ruins and ashes of the old

    Three years later, Swilling met with other Anglo pioneers to consider names for their settlements. The biggest contenders were Pumpkinville and Stonewall. Fortunately, the eccentric English adventurer “Lord” Darrell Duppa came up with a name inspired by the resurrection of the canal. “A great race once lived here, and another great race will live here in the future,” he mused. “I prophesy that a new city will be born like a phoenix out of the ruins and ashes of the old.”

    The canals that criss-cross Phoenix allow millions of people to live in the sun-baked desert (Credit: Art Wager/Getty Images)

    That great society was the Hohokam, and between 100 and 1450 A.D., they built 1,000 miles of canals – the largest waterway system in the Americas in northern Peru. This complex irrigation system harnessed the river’s water and annual rainfall of only 7 inches and delivered it to more than 100,000 acres of farmland. They dug it all by hand with rocks and sticks.

    “The engineering was outstanding,” says Kathy Henderson, principal investigator for Desert Archeology, a cultural resource management and research firm based in Arizona. “We didn’t see them in a sequence that started small. As early as 500 or 600 [CE] canals were built to scale. They must have been very familiar with how to transport water over long distances.”

    The engineering is phenomenal… They must have been very attuned to how to transport water a long distance

    For Gary Huckleberry, a geologist and adjunct researcher at the University of Arizona, the water-wise Hohokam and its ancestors are still important today. “In the Southwest, we have some serious issues to deal with in terms of water resources,” he says. “The Colorado River is a major water source in the Southwest and is over-allocated. Population growth and climate change. How are we going to deal with that? I think something can be learned by looking back at societies who have managed water for thousands of years.”

    Many of the city’s modern canals were constructed by retracing the Hohokam’s handiwork (Credit: Salt River Project)

    Native Americans have been building canals in Arizona for at least 3,500 years. The oldest waterway archaeologists have found dates back to 1500 B.C. and diverts water from the Santa Cruz River in Tucson, Huckleberry notes, adding that through repeated experimentation, these ancient river people accumulated knowledge passed down from generation to generation. “So, by the time you get to Hohokam, they were already skilled hydraulic engineers.”

    Today, the Salt River, which was dammed, is dry most of the time in Phoenix. But visit the city’s northeastern suburbs – where kayakers paddle salt past ochre mountains, clover poplars and wild horses splashing along the coast – and you can get a sense of the possibilities the Hohokam encountered when they migrated here from southern Arizona. The Sonoran Desert is the most biodiverse desert in the world. In addition to Hohokam’s staple crops of corn, squash, beans and cotton, it offers an abundance of plants and animals.

    Since Hohokam has no livestock, they carve canals by hand with stone hoes with handles. Using these simple tools, they created precise downhill slopes of 0.3 to 0.5 meters per 1.6 kilometers. At the center of the system, the Salt River, the channels start out large – more than 25m wide in some places. Then, as they branch into laterals and ditches, they become slender and as large as watery arteries and capillaries. These design features help keep flow consistent while minimizing siltation and erosion.

    As Hohokam expanded their network, they had to deal with the complex topography of the area. With multiple mountain ranges towering around Phoenix and through the metro, it is, in my opinion, the most hike-friendly large city in the world. But it’s a challenge for hydraulic engineers, especially because of the epic summer monsoon downpours that wash along the hard surfaces. Floodwaters regularly break through the locks and fill the channels with sediment, meaning that Hohokam is constantly repairing, cleaning and rerouting the canals. This requires a highly coordinated community.

    The Hohokam were desert farmers, whose sophisticated irrigation system harnessed river water to bring agriculture to the region (Credit: Benedek/Getty Images)

    “It requires cooperation because all users who draw water from that canal must agree to not only build it, but also maintain it,” Henderson said. “The coalition of users has to agree to certain conditions to keep the whole system running.”

    For example, she explains, not all farmers can open the gates to their fields at the same time, because some won’t get any water further away. As a result, Hohokam is committed to sharing water sources and putting itself on a schedule. “This led to the development of water rights,” she adds.

    By the 13th century, as many as 50,000 Hohokam lived in villages that were regularly distributed along the canal system. This suggests to archaeologists that water and irrigation land were fairly equitably distributed among the communities.

    Over the centuries, the canal system was reorganized several times, but its basic structure remained the same. After 1300, however, the community and the canals began to diminish, and by 1450 the population had declined sharply. No one knows why. Climate may have played a role, but there is no evidence of a particularly strong climatic event at that time. Although some irrigation-based cultures faced soil salinization, there is evidence that Hohokam did a good job of controlling salt accumulation. Although archaeologists once believed that the Hohokam population collapsed after a catastrophe, improved techniques now suggest that a complex combination of community consolidation, flooding, siltation, diminished wild food resources, and conflict led to a gradual decline in population.

    The Grand Canal is getting spruced up as part of a project to connect Phoenix’s east and west suburbs in a continuous multi-use trail (Credit: BCFC/Getty Images)

    Huckleberry says there is still much to learn from Hohokam and its ancestors, who used the canals to irrigate for 3,000 years. “To me, that’s the definition of sustainable,” he said. “They learned how to farm sustainably, manage water resources, and not damage their soil in a commendable way, which may give us insight into how to deal with the current dilemma. I think one of the key lessons is you don’t want to put all your eggs in one basket; you want to prepare for the worst and diversify your strategy.”

    The Hohokam may have stopped managing their canal system, but they haven’t disappeared. Their story continues with their descendants Akimel O’odham (“River People”) and Tohono O’odham (“Desert People”), who live today in central and southern Arizona.

    Their legacy is also present in the city’s modern canals, many of which were built by hand by tracing the Hohokam. The Grand Canal is now being refurbished as part of a project to connect Phoenix’s eastern and western suburbs with a continuous multi-use trail. Phoenix Mayor Kate Gallego announced in 2020, “Today, we are integrating the canals into our neighborhoods to improve neighborhood access, add new public art spaces, and contribute to the health of Phoenix by bringing them in as recreational amenities.”

    Hohokam’s legacy is also preserved in their village, Pueblo Grande, a museum and archaeological park where visitors can see ballfields, platform mounds (ceremonial houses) and reconstructed adobe houses. Hikers can follow the trails of South Mountain Preserve and Deer Valley Petroglyph Preserve in search of coyotes, goats and the spiraling Hohokam petroglyphs. Travelers can use the A Deeper Map app to swipe right on a modern map of Phoenix to reveal the Hohokam innovations hidden beneath their feet.

    But perhaps one of Hohokam’s most important legacies is less obvious: that living sustainably in this sun-drenched desert is possible through collaboration, commitment and shared knowledge.

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