Ancient Irrigation Canals Discovered in Marana 10 Years Ago

Happy anniversary, Marana. It’s been a decade since the announced discovery of the Las Capas irrigation canals, the uncovering of what would prove to be the oldest documented irrigation system in North America—and an answer to how ancient farmers grew corn in an arid and cactus-filled Sonoran Desert.

It was 10 years ago that Desert Archaeology began major excavations along the east bank of the Santa Cruz River, downstream of the confluence of the Rillito and Cañada del Oro tributaries as part of an expansion of Pima County’s water reclamation facilities when they found evidence of earlier waterways.

By earlier, according to excavation archaeologist James Vint, we’re speaking of dates from the Early Agricultural period (between 1200 and 800 B.C.) through the Hohokam and Protohistoric eras.

What they found was a network of canals and fields stretching over 100 acres.  According to the Society for American Archaeology: “There were more than 250 well-preserved canals of various sizes and over a thousand bordered fields in multiple stratigraphic levels occupied over a period of 800 years.”

Each of the fields measured 250 square feet, according to Tucson archaeologist Vint, who told the Archaeological Institute of America that the “latticework design of the Las Capas waterworks was located in an ideal place for canal irrigation and, in terms of moving water, the builders had it figured out really well.”

In a report the title of which is almost as long as the report itself (The Anthropogenic Landscape of Las Capas, an Early Agricultural irrigation Community in Southern Arizona), researchers reported that data recovery identified over 5,500 prehistoric features “including pithouses, roasting pits, and pits of other functions that resulted in the recovery of over 113,000 artifacts.”  

The report writers called it “the best example of Early Agricultural period farming technology known to date with fields that could have been irrigated with ease based on the exposed portions of the system,” noting further that: “With the discoveries at Las Capas, it is now evident that this small, local scale of water management represented the beginning of a long trajectory of development in the Sonoran Desert.  The management structures of the later, larger and more complex, Hohokam irrigation systems likely grew out of this early form.”

Writing about another excavation in the same area prior to a Department of Transportation project for Interstate 10, City of Tucson historian Jonathan Mabry noted finds that went back even further to 2800 B.C. involving foraging groups and agriculturalists as early as 2100 B.C.  

“A total of 468 cultural features over 123-acres in three major strata were excavated and 107,000 artifacts recovered,” he wrote in Early Irrigation and Sedentism in a Southwestern Floodplain. “Radiocarbon dates from nearly 50 samples of maize (corn) and other plant remains indicate the site areas were occupied by early agriculturalists almost continuously for five centuries (where) long-term occupation could be supported based on irrigated agriculture.”

In a fact that might prove valuable in a party trivia game, the corn grown at Las Capas by the forerunners of the Hohokam, described as the most accomplished farmers of the Southwest, was similar to the popcorn of today.  Archaeologist speculate the kernels were popped and then ground into meal to make early-day forms of tortillas.

The whole aspect of floodplain cultivation of traditional foods is acknowledged in a couple of Marana adventure opportunities combining Native American history with foods produced in the area.

Billing itself as “The Town of Gastronomy,” Marana offers Gastronomy Tours, the first of its kind approved by UNESCO’s Creative Cities Network.  The monthly 6-hour treks offer ‘an epicurean journey illuminated by 4,000 years of agriculture’ built around the concepts of ancient wild foods, farms foods, and food brought by Europeans.

The 2019 tours will be lead by preservation archaeologist Allen Denoyer of Archeology Southwest and Native American guide Felipe Molina, a Yaqui/Yoem linguist and cultural interpreter focusing on wild foods. 

Interesting fact about Molina is his family has been part of farming and ranching the Marana area since the early 1900s.  

“The first village, name Ili Hu-upa, was settled in 1910 and relied on canal water east of the then-Casa Grande Highway (now Interstate 10),” he said.  

Contemporary villages were built on top of the old ancient farm areas.

“The initial village was between two Hohokam canals that were part of the canal system running west toward the Platform Mound north of I-10,” Molina said. “My grandfather worked a farm there and the Yoeme men helped build the canal that runs from Ina Road to near Sandario Road.”

More information about the gastronomy tours can be found at

Allen, Lee, Tucson Local Media, January 16, 2019