Serpentine International Amistad Reservoir, part of the Amistad National Recreation Area, receives water from three meandering rivers—Rio Grande; Pecos, which enters the Rio Grande west of the reservoir; and Devils to the east. Steep canyons have been created by erosion of the Pecos River and Devils River. Along the Rio Grande near Del Rio (not discernible), ground surface is composed of limestone and white beds of caliche. Most of the landscape north of the Rio Grande forms the western edge of the Edwards Plateau, with vegetation consisting primarily of grass prairies and oak, cedar, and mesquite woodlands. Foothills of the Serranias del Burro (a small mountain range in Mexico) are visible (lower left corner).