The Sonoran Desert Environment

The Hohokam successfully faced the challenges of a low, hot, desert environment. Their geographic extent to the north and east coincided closely with the vegetational boundaries of the Sonoran Desert. Unlike Southwestern deserts to the east and west, the Sonoran Desert experiences both summer and winter rains. This bi-seasonal distribution of rainfall supports an array of large desert plant forms. Relatively large cacti such as saguaro and cholla, and desert trees such as mesquite, paloverde, and ironwood offer a unique bounty in food resources.

Figure 1.3.5  Pima woman collecting saguaro fruit.

Figure 1.3.6  Woman making mesquite flour.

Although yearly precipitation in the area inhabited by the Hohokam rarely surpasses 15 inches, local averages vary by a factor of two. Annual precipitation below 9 inches correspondes with greater yearly variation and higher summer temperatures in the middle of the Hohokam domain near the modern city of Phoenix and in a swath to the southwest. Phoenix temperatures reach 100° F about 90 days per year. To the north, east, and south, there is somewhat more rainfall, especially in the summer, and somewhat moderated temperatures.

Hohokam Core and Periphery

Lower rainfall and higher temperature in the Phoenix Basin at the center of the Hohokam world were countered by the most favorable water supplies for agriculturalists. The confluence of the Salt and Gila rivers lies just southwest of Phoenix. The two conjoined valley segments upstream from the confluence form the Phoenix Basin, which contains the broadest expanse of flat, irrigable Hohokam land. In this core area, two cropping seasons were possible for irrigators along largest scale canal networks north of Peru. Archaeologists have mapped more than 300 miles of main trunk lines. The densest Hohokam population, perhaps as high as 100,000, and largest settlements were in the Phoenix Basin. Regional sectors of settlement surrounding the Phoenix Basin are termed the Hohokam “periphery.”

The core-periphery dichotomy has been considered a distinction between riverine and nonriverine desert regions, based on the implications of differential opportunities for large-scale irrigation. In spite of higher rainfall north, east, and south of the Phoenix core, rivers lack sizable upland watersheds and are intermittently flowing rather than perennial. Basin and floodplain topography restricts irrigable land. Peak flows in summer rather than spring and greater frost hazards limit early crops. Settlement was more dispersed in these areas, and until recently, it was generally assumed that populations lacked the productive base for equally elaborated cultural developments.

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