The Rio Bavispe encompasses a large part of the northern part of the Rio Yaqui watershed (Sonora's largest). The main stem of the Bavispe starts in the Sierra Madre right on the border of Chihuahua, southeast of Huachinera, flowing northwest through mountainous country until the upper end of the wide Bavispe Valley. This valley trends northward until making a 180 degree curve around the Sierra El Tigre. From here it flows southward for around 80 miles before meeting the larger Rio Aros to form the Yaqui. Presa La Angostura interrupts this stretch forming a large reservoir.
The Rio Bavispe valley holds quite a bit of history having been the center of many Apache raids and Mexican military attacks. Missionaries first settled this area in the early 1600's.
The Rio Agua Prieta begins in the southeastern corner of Arizona around Douglas and the surrounding country and meets up with the Rio Fronteras which flows north from near Nacozari de Garcia. The Fronteras flows perennially in areas and has some nice cottonwood/willow riparian forest. Sonoran Mud Turtles and native fish can be found there.
The Cajón Bonito joins the system near here and drains the Sierra San Luis and northern end of the Sierra Madre. The upper part of the Cajón Bonito is an amazing example of an extraordinarily healthy riparian ecosystem. From here the Rio San Bernardino flows south to meet the Bavispe proper at Morelos at the Northern end of the Sierra El Tigre.