Geoscience Reference
In-Depth Information
were forced to develop ways to divert water from rivers and even devise ways
of storing it for future use. h e residents of Chaco Canyon built an extensive
system of diversion dams and canals, directing rainwater from the mesa tops
to i elds on the canyon l oor, allowing them to expand the area of arable land.
With the help of this early water development, Chaco Canyon grew into
a complex center of Ancestral Pueblo culture during the tenth and eleventh
centuries. Water diversion features found in Chaco Canyon include terraced
clif s, ditches, overl ow ponds, and masonry irrigation canals and dams. h e
Ancestral Pueblo were primarily agricultural, depending on their primary
crops of corn, beans, and squash, which were supplemented with occasional
hunting and the gathering of wild plants.
For centuries, the Ancestral Pueblo society thrived, closely connected to
the natural climatic rhythms of the region. h e summer monsoons provided
sui cient water during the growing season, and, in the occasional years
when the monsoons failed, residents relied on food reserves kept in large
storage rooms in the great houses. h e population in the Four Corners region
swelled throughout the eleventh and twelt h centuries—until things began
to go wrong.
Farther to the west in southern central Arizona, the Hohokam people
settled near the conl uence of Arizona's only three rivers—Gila, Verde, and
Salt. h is culture initially practiced l oodwater farming on the Gila and
Salt rivers. Each year, they planted crops in the wet l oodplain soils at er the
spring l oods overtopped the riverbanks and spread water and nutrient-rich
silts and clays in a manner analogous to ancient farmers thousands of miles
away along the River Nile.
Within i t y years or so, the Hohokam had developed a new technology,
canal irrigation, which began with the construction of small canals close to the
rivers for transporting water to the i elds. h e Hohokam civilization thrived
in central Arizona for a thousand years, building an extensive network of
integrated canal systems that were capable of transporting large volumes of
water long distances. h e largest canals were twenty-four feet wide, nineteen
feet deep, and twenty miles long—capable of irrigating over 10,000 acres of
land. h e engineering of these complex canal networks is considered to be the
Hohokam's greatest achievement, and the irrigation systems of the Hohokam
are considered the best in prehistoric North America. h eir success allowed
them to expand across a large region of Arizona, from modern-day Tucson to
Flagstaf , a distance of 260 miles. At the peak, an estimated 40,000 Hohokam
lived in Arizona, but they suddenly vanished in the mid-i t eenth century.
