It is formed by the confluence of the Salado and Grande rivers, which drain the dry Tehuacán and Cuicatlán valleys west of the Sierra Madre de Oaxaca.

It joins with the Valle Nacional River above San Juan Bautista Tuxtepec to form the Papaloapan.

[1] To alleviate these problems, the Cerro de Oro Dam was constructed on the river just above the junction with the Valle Nacional, completed in 1989.

The reservoir behind the dam is connected by a channel to Lake Miguel Alemán, the reservoir formed by the Miguel Alemán Dam on the Tonto River.

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