Hohokam

The only way to grow crops in central Arizona is with irrigation. The Hohokam culture lasted from 300 AD to 1500 AD. They occupied an area from Flagstaff to the Mexican border. They extracted water from the Salt River and constructed hundreds of miles of irrigation canals and irrigated an area from east Phoenix to Casa Grande, approximately 40 miles south of Phoenix.

The earliest known irrigation system in the Americas was in Tucson, Arizona. Native Americans developed a network of irrigation channels along the Santa Cruz River to irrigate corn in 2000 BC. They laid out channels and watered 100 square plots surrounded by small ridges. This early irrigation system included small dams and structures that diverted water from the river to channels and from channels to individual plots.

Figure 15‑38. Artist’s conception of Hohokam irrigation system. Credit USBR. Artist Peter Hurd.

The largest Native American irrigation system was the Hohokam irrigation network. The Hohokam occupied central and southern Arizona from the first to the 15^th century AD. They began irrigation in 800 AD and developed hundreds of miles of irrigation canals along with many diversion structures along the Salt and Gila rivers. Their irrigation canal networks were as extensive as the Mesopotamian systems. The diversion structures consisted of a wier placed across part of the river in order to raise the elevation of the river. They learned to increase or decrease the size of channels in order to maintain flow velocity above the sedimentation velocity but below the critical velocity at which the water would erode the canal. They developed many type of water control structures in order to divert water from main canals into distribution canals and from distribution canals into fields (Figure 15‑38).

Archaeologists estimate that the Hohokam moved over a million cubic meters of soil with stone tools in order to construct canals (Figure 15‑39). In addition, flooding and other factors degraded canals and led to canal maintenance requirements. In order to organize such massive undertakings, there must have been a strong organizational structure in the Hohokam community. Archeologists have found several large Hohokam platform mounds that had external walls, a large public plaza and a series of buildings that were unlike the typical Hohokam residential communities. These platform mounds might have been administrative centers or they might have had a religious function. Archaeologists are not sure. The Hohokam civilization vanished in the 15^th century. Although a drought was certainly a factor in the demise of the Hohokam, archaologists have determined that it was a combination of drought, administrative failures, and the fact that the huge irrigation network was no longer sustainable with a lower population base. Instead of vanishing, it is possible that the Gila River and the Tohono O’Odham Indian communities are the descendants of the Hohokam.

Figure 15-39. Hohokam canal. Credit. State Museum.arizona.edu. Accessed at https://www.inmaricopa.com/hohokam-canals-maricopa/

The Owens Valley Paiute in California had the most extensive Native American irrigation system in the historical period (period with writing since the European settlers), but it was nothing compared to the Hohokam system. They had a main canal that was several miles long and many small branch canals. Each year, they built a new dam in the Owens River with boulders, sticks, and mud in order to divert water into their canals. They controlled water flow into branch canals with small mud and stick dams. As with the Iraqis, they rotated plots and let the land lie fallow in alternate years. [1] The Owens River became the focus of one of the most famous battles in water history as Director Mulholland of the the Metropolitan Water District in Los Angeles bought out the water rights of Owens Valley farmers (not the original Native American farmers) and ended agriculture in the Owens Valley. Water was moved to LA in the Los Angeles Aqueduct. The book Water and Power describes the dispute between Mulholland and the Owens Valley farmers.

References

[1] JRP Historical Consulting Services and California Department of Transportation, Water conveyance systems in California, Report prepared in December, 2000.

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Salt River in Phoenix, Arizona. Credit: Aznaturalist. Used here per CC BY-SA 3.0.

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