SANTA FE, N.M. — Thirty years ago, biologist David Propst was fresh out of graduate school when he started working on the Gila River. Tucked into the southwestern corner of New Mexico, the Gila’s headwaters run out of the Mogollon Mountains and flow through southern Arizona and into the Colorado River. Small farms along the way divert irrigation water. But there are no large dams.
At 649 miles, the Gila remains one of the last of the West’s free-flowing major rivers. The Yellowstone River, also undammed, is 692 miles long.
“If I were to get up on a hill overlooking the Cliff-Gila Valley,” said Propst, referring to where the Gila bursts from the canyon-constricted wilderness and opens to a wide valley, “and contrast that today with what it looked like in 1983, you would be hard pressed to see any differences.”