Archeologists have uncovered a sophisticated system of irrigation canals dating back to 1,200 BC in Tucson, according to a story in The (Marana) Explorer. There are photos at the newspaper's site and at Desert Archeology, Inc, one of the contractors working on the project.
The site is named Las Capas, or The Layers, at the confluence of the Canada del Oro, Rillito Creek and Santa Cruz River. It appears the area was buried in a flood around 800 BC and never fully restored. The site is on the grounds of Pima County's Ina Road waste water treatment facility. [right, Las Capas site with "the oldest known north of central Mexico. One canal runs diagonally through the middle of this excavation area." Photo copyright Adriel Heisey. Credit, Desert Archeology, Inc.]
The story says, "archaeologists have unearthed the remains of an ancient farming community that could potentially rewrite the history of human settlement in the Southwest."
[thanks to the local blog Southwest Archeology Today for spotting this]