One of these cultures, the Hohokam, practiced irrigation-based agriculture. Knowledge of Hohokam irrigation systems is based on archaeological remains found in southern Arizona as well as on extrapolation from technologies currently in use. Because the land was desert with less than 10 inches of rainfall a year, agriculture required catchment dams, irrigation canals, and water conservation. Between A.D. 300 and 900, the Hohokam manipulated the arid environment by building large canals, some as wide as 30 feet across, 7 feet deep, and 8 miles long, that could fertilize as many as 8,000 acres at a time with water from the Salt and Gila river systems. The Hohokam could grow crops and store them throughout the year, producing a continual supply of food. An environmental consequence of irrigated agriculture, however, is that water from the rivers leaches out salts, drawing them up from the subsoil and leaving salinated (salty) topsoils. Just as the Mesopotamian settlements of the Near East were abandoned owing to salinization of the land, the Hohokam may have been forced to abandon their villages. Alternatively, they may have remained, evolving and adapting to changed conditions. By the time the Spanish arrived in the region in the sixteenth century, they met Amerindians called Akimel O’odham, who were still practicing a form of irrigation, but not on the enormous scale developed by the Hohokam. Other explanations for the disappearance of Hohokam culture include flooding, drought, earthquakes, and deforestation.
