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.
Pueblo I Period
The most advanced communities in the Chaco Canyon region had "great houses", roads and elaborate kivas.By the Pueblo I period, the Ancient Pueblo people were reliant upon agriculture and they faced periods of lower rates of precipitation, like the major drought from 850-900 in the Petrified Forest National Park. It is likely that people also settled on the mesas and ridges to benefit from heavier winter snowfall and summer precipitation. Water management and conservation techniques, including the use of reservoirs and silt-retaining dams also emerged during this period to efficiently utilize their water supply. Large earthenware vessels, sealed with stone lids, were used to store harvested corn and protect it from rodents and rotting.