As people walk the streets in the Valley, how many realize the unique history that is buried just below their feet?

The work of ancient engineers reflects monumental efforts in the familiar, modern-day topics of sustainable agriculture and the organization of people to construct enormous infrastructure.

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Archaeologists are aware of an ancient group of people who began farming along the desert rivers at least as early as 1200 B.C. They were part of a worldwide movement that began at the end of the last ice age. This trend, known as the Neolithic Revolution, represented our greatest change in human lifestyles. Moving from roaming groups of hunters and gatherers living off what nature provided, people began to produce food through farming.

By A.D. 1, this early group became the culture we know as the Hohokams.

Farming, growing crops of corn, beans and squash in the arid Sonoran Desert was not a simple mater. The limited rainfall was insufficient to water crops. If you waited for the rains to come, your crops would wither and die.

To provide water to their crops, these early farmers began to construct well-engineered networks of irrigation canals across the Valley. Unprecedented in size, Hohokam canals often extended to 16 miles or more in length. One prehistoric canal investigated in Mesa measured 15 feet deep and 45 feet wide and was rebuilt at least 13 times.

The engineering of the irrigation systems was amazingly advanced. The main canals were precisely mapped onto the landscape to achieve a gradient, or drop, of only a few feet per mile. The canals were engineered to keep water flowing through the canals at a constant rate. This avoided problems of channel erosion from fast-moving water and the depositing of silts that occurs when the water slows down and drops the particles of soil it carries.

Canals today still follow the same routes, and many were built by simply cleaning out the original Hohokam channels.

By the Classic Period, 1150 to 1450, the Hohokam irrigation systems could deliver water to over 110,000 acres and support the largest population in the Southwest at that time. It was the largest canal irrigation system ever developed in the prehistoric New World.

The Hohokams were also the only prehistoric culture in North America to rely on irrigation networks to raise crops. They transformed their environment, creating a cultural landscape with agricultural fields that stretched as far as the eye could see.

Although some have suggested that they caused environmental catastrophes, such as salt buildups on the fields that would destroy the crops, more recent research dismisses this notion. In fact, the Hohokams created a system of sustainable agriculture that survived for at least 1,500 years.

The Hohokams were a unique culture whose descendants, the O'odham people along the Salt and Gila rivers, continue as a living and vibrant culture today.

The legacy of the Hohokams is a lasting one. They laid out a template or design followed by our modern canal system. They transformed the earth of the Valley, creating some of the finest agricultural soils in the world. At a time when we are looking for sustainable agricultural systems, the Hohokams have much to teach us.

Studying the past can also give us hope for the future. If the Hohokams, without modern machinery and technology, can create monumental irrigation systems and thrive in this arid desert environment, what is it we cannot do if we put our minds to it?

Jerry Howard is curator of anthropology at the Arizona Museum of Natural History.

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