Presa Álvaro Obregón (El Oviáchic)

El Oviáchic, as everyone in southern Sonora calls the Álvaro Obregón Dam, holds back the Yaqui River at the point where it leaves the foothills of the Sierra Madre Occidental and widens toward the coastal plain. The name is Yaqui for "the difficult one." Built between 1947 and 1952 under President Miguel Alemán and inaugurated on August 28, 1957, it is an embankment dam 1,457 meters long and 360 meters wide at the base, wedged between the Oviáchic and La Cantera hills. Its hydroelectric plant started running in April 1958.

At full capacity the reservoir stores 2,989 million cubic meters over roughly 205 square kilometers, about 21 km long and up to 6.75 km wide, which makes it the largest reservoir in the state. Working with La Angostura and El Novillo dams upstream, it evens out the river's flow, prevents floods, generates power and above all irrigates the Yaqui Valley farms around Ciudad Obregón. The original village of Buena Vista was flooded when the lake filled, after its people were moved; in dry years the cross of its old church shows above the water. Today's Buenavista, on the shore, depends heavily on fishing, with around a hundred families living from it.

Water levels swing hard with drought, so set your expectations. In April 2024 the dam was at 12 percent and local fishermen stopped going out because their boats grounded; a year later it stood near 15 percent. When the lake is low you get bare shorelines and dry hills rather than a brimming reservoir, though the view from above is still wide.

A day trip here is simple. Stop at the scenic lookout at the entrance for the view of the dam wall and the water between the hills, look at the spillway, then head down to the shore. Anglers come for black bass, with tournaments through the year, plus catfish and tilapia; there is boating, kayaking and water skiing, and people camp along the banks. The hills are made of Precambrian metamorphic rock, Mesozoic marine sediments and volcanic agglomerates.