THE SAN PEDRO RIVER DRAINAGE
Below: The San pedro River viewed from lower Soza Mesa; cottonwoods/willows just leafing out, in early March:
The San Pedro River begins in Mexico (not far from the city of Cananea in northern Sonora) and ends at its confluence with the Gila River near Winkelman, Arizona. Its southerly, upstream portion is by far the best known to outsiders, by virtue of its proximity to the burgeoning city of Sierra Vista, Arizona and the major military complex at Fort Huachuca, and the recent designation of a large strip of the watershed there as the San Pedro Riparian National Conservation Area by the U.S. Congress in 1988. Our area, near Cascabel, Arizona, is well downstream from this complex, but The U.S.D.A. (Department of Agriculture) and E.P.A. (Environmental Protection Agency) are including part of our area in what they call the "Upper San Pedro Watershed" (click on this link for more information), a designation suggesting our interconnectedness. In the following account we will try to place our area in the wider ecological and historical contexts of this major Watershed. (For map references, see the previous link, or our own San Pedro River Maps.)
Below: a view of the valley in February, from Soza Mesa looking toward El Potrero.
Below: the valley in July from one of the lower fingers of Soza Mesa; terraces and foothills of the Catalinas rise beyond.
For a land-and-water image tour along the San Pedro, including views of tributary washes, see
See the following website for an excellent introduction to the various dimensions of our major river system:
http://www.lastgreatplaces.org/SanPedro/Index.htm
Ecoregions or Biomes distinguished by the World Wildlife Fund (see this link) for our area include the Sonoran Desert (our area and toward the north and west), the Chihuahuan Desert (our area and toward the south and east), and the Arizona Mountains Forests. All three of these zones are characterized by very high degrees of biodiversity, and our Saguaro Juniper lands stand at a crossroads of the three. Indeed, our situation is more complex than this -- our status as a crossroads is reflected in the fact that definitions, interpretations, and boundaries of these ecoregions, and their subdivisions for our area, remain at issue. The Nature Conservancy, for example, distinguishes the Apache Highlands rather than the Chihuahuan Desert as an eastern/southern boundary to the Sonoran Desert -- see that link. And several major authorities disagree about the classification of these biomes. Here we consider some of these problems in relation to our area in the materials indicated below:
- For more detailed accounts of our area's relationship to "Ecoregions" or "Biomes" (and the differences between authorities), see the following link:
- For an introduction to the major vegetation forms of The San Pedro Valley, both now and in deep time perspective, see
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For a summary of changes in our area's vegetation from the mid-19th century to 1960, see
- For a bibliography of San Pedro River history, see the following link (and search for "San Pedro"):
- For information about conservation proposals for the Hot Springs Canyon corridor of the San Pedro River Drainage, see
Hot Springs Canyon Tributary Drainage
The Udall Center at the University of Arizona provides a series of website pages relating to the San Pedro River Basin, called San Pedro River Basin Projects -- which includes materials from a number of news sources on both sides of the border and covering the following range of topics: water, land use and growth, U.S.-Mexico border issues, science research, and weather and climate change. Click on the link to access this resource.
We will present further description and illustration of the region as time permits.
