Agriculture in the prehistoric Southwest
After the Hohokam disappeared, Spanish explorers of the 16th century noted the use of canal irrigation in only two areas of the Southwest: eastern Sonora, primarily practiced by the Opata and Lower Pima, and among the Pueblos of northern New Mexico. Irrigation by the Opata and Pueblos had different objectives. In Sonora, with a long growing season, two crops of maize a year were grown in river valleys. The spring crop during the dry season was dependent upon irrigation; the summer and fall crop during the rainy season utilized irrigation to supplement rainfall. The necessity of irrigation probably required a high level of social organization. In New Mexico, with only one crop of maize per year possible, irrigation was supplemental and the lesser dependence on irrigation implies less social organization than in Sonora.
Havasupai
Prior to modern times agriculture was the essential means of progress and survival for the Havasupai. While in the winter the tribe members stationed themselves on the plateau of the canyon, in the summer irrigation gardening of the crop fields brought the members back inside the canyon walls. As vast and uneven as the Grand Canyon is, it is somewhat of an anomaly that the Havasupai were able to agriculturally sustain and thrive in such a voluminous landscape. Because of a lack of available soil rich in nutrients, it has been suggested that the tribe cultivated only of land on the canyon floor. Although lacking space, the tribe's irrigation technology was far more advanced than others in the Southwest which allowed them to be agriculturally intensive. However, being located at the bottom of a canyon left the fields vulnerable to flooding as a result of rain and the overflowing of Cataract Creek, as was the case in 1911 when almost an entire crop field was destroyed. In 1920 to combat the issue the federal government assisted the tribe in constructing a new irrigation system which was generally effective in ceasing soil erosion from water overflows.