The river begins at
Lake Chapala, running through
Ocotlán and continuing roughly north-west through the
Sierra Madre Occidental range, receiving the
Verde,
Juchipila,
Bolaños,
Huaynamota,
Mololoa, and other tributaries. The Río Grande de Santiago then descends over 1700 meters as it heads towards the sea. Downstream from Lake Chapala, the river and its major tributaries have carved deep narrow canyons, or
barrancas, which can be 600 meters lower than the surrounding plateau. The lower elevation and year-round moisture in the canyon bottoms sustain forests, which include many coastal tropical species not found on the plateaus. The
Barranca de Oblatos or Barranca de Huentitán is a scenic and protected area popular with residents of the city of
Guadalajara, which lies on the plateau immediately south of the barranca. At
La Yesca, the
La Yesca Dam was completed in 2012 and the
El Cajón Dam was completed downstream in 2007. Below El Cajón, the
Aguamilpa Dam was completed in 1993, creating a reservoir covering a large part of the territory of the municipality of
El Nayar in
Nayarit. From Aguamilpa, the river descends to the coastal lowlands, passing by
Santiago Ixcuintla and empties into the Pacific Ocean, northwest of
San Blas, in Nayarit. The Santiago River alone is reported to be 269 miles long. It is viewed by some sources as a continuation of the
Lerma River, which flows into Lake Chapala and at 466 miles long is one of Mexico's longest rivers. Together the Lerma–Santiago river system is a little over 600 miles long. ==Fauna==