The Foundation of the American Institute of Professional Geologists needs your support. We are looking forward to better times for all. This year we need to rely even more on the financial commitment from AIPG members and others who are able and interested in contributing to the Foundation. As you review your dues statement for 2021, please consider a donation to the Foundation of the American Institute of Professional Geologists. If you have already paid your dues, please consider additional support for the Foundation. Every donation helps the Foundation to provide support toward building the future of geology. The Foundation supports a variety of programs of the AIPG: student scholarships, student and early career professional workshops, educational programs aimed at practitioners, the public, and policy makers, and some special needs that may be requested by AIPG or other professional or educational organizations. The Foundation is proud to be able to serve AIPG and the geosciences by providing financial support for these programs. If you have any questions or comments about the Foundation, please contact me or any of the other Trustees of the Foundation for additional information.
Donations may be made by check payable to the Foundation of the AIPG and mailed to 1333 W. 120th Ave., Suite 211, Westminster, CO 80234-2710 or pay by credit card on the AIPG web site.
Be sure to check the Foundation web page on the AIPG web site
https://aipg.org/page/Foundation for infor- mation on awarded student scholarships and the list of donors. Your continued support is greatly appreci- ated. Thank you.
Barbara H. Murphy, RG, CPG Chairperson, Foundation of the AIPG 480-659-7131 office phone;
bmurphy@geo-logic.com
The Foundation of the American Institute of Professional Geologists is a 501(c)(3) organization. Contributions are tax deductible. EIN 45-2870397
Some say the Tohono O’odham “desert people” of Southern Arizona are their descendants.
Repeated and long-lasting drought most likely lies at the root of the collapse of their society: studies of tree-rings car- ried out at the University of Arizona suggest that there were “mega-droughts” in the southwestern USA from 0-400 AD and from 1000-1400 AD (Routson (2014) and Figure 6)
Historically, until about the late 1700s, the O’odham who lived along the Santa Cruz were known as Sobaípuri (‘fierce’) and identified themselves as Akimel O’odham (River People) rather than Tohono O’odham (Desert People). Tohono O’odham from the desert areas farther west didn’t begin moving into the Santa Cruz Valley till late 1700s to early 1800s after the Sobaípuri had been decimated by European diseases and war- fare with Apache, Janos, Jocome, and Manso groups.
Today, one can visit the Casa Grande Ruins National Monument, in Coolidge, Arizona, just northeast of the city of Casa Grande. This Monument preserves a group of Ancestral Puebloan Hohokam structures of the Pueblo III and Pueblo IV Eras. They have a marvelous gift shop. The best evidence for the canals is now preserved in old photographs in Arizona museums, publications, online websites, and occasional archaeological dig sites. Modern Phoenix farmers once readily
8 TPG •
Jan.Feb.Mar 2021
identified Hohokam canals and often mimicked their loca- tions for their modern irrigation canal alignments. After the centuries of use by the Hohokam they could be recognized because they retained water and the surface soils over them were darker than the natural alluvial soils because they were more silty, clayey and organic-rich. Aerial photographs, land use maps, plot plans, and environmental assessments indicate that urbanization, energy and water utility networks, trans- portation corridors, and modern farming have erased much of the Hohokam irrigation systems from the Salt, Gila, and Santa Cruz River Basins.
Another noticeable thing is the way that the largest group of canals fans out from the area of the outcrops that constrict the river, forming a natural weir at high stages, just west of Tempe.
Furthermore, the Sonoran Desert in Southern Arizona is relatively lush because it has both winter and summer rainy seasons, with about 10 to 13 inches of annual rainfall in its southern alluvial valleys, and 4 to 10 inches in its northern valleys. The surrounding uplifted mountains receive nearly twice that amount. This means that the major rivers are perennial or almost so, as was the case of the Santa Cruz River below Centennial Peak (‘A’ Mountain) in Tucson before
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