The State of Texas, stretching from the Southern Plains and the Desert Southwest to the Gulf of Mexico, is drained by numerous streams and rivers which comprise thirteen major watersheds. The Canadian River flows across the north section of the Northern Panhandle (eventually merging with the Arkansas River in Oklahoma) while the Red River watershed drains the Panhandle's southern section and a narrow strip along the border with Oklahoma and Arkansas.
South of the Red River watershed, a series of parallel watersheds are aligned from northeastern to southwestern Texas, all flowing southeastward toward the Gulf of Mexico. From northeast to southwest, the primary watersheds are the Sabine, the Trinity (including Metro Dallas), the Brazos (including Lubbock), the Colorado (including Austin) and the Pecos-Rio Grande Rivers. Close to the Gulf are shorter watersheds, also flowing southeastward to the sea; the Nueces, San Antonio, Guadelupe and Lavaca watersheds are aligned southwest to northeast between the Rio Grande and Colorado Rivers, the San Jacinto watershed (including Houston and Galveston) lies between the Brazos and Trinity Rivers and the Naches watershed lies between the Trinity and Sabine Rivers.
In effect, the landscape of Texas, a vast mosaic of plains, plateaus, mountain ranges, canyonlands, hill country and coastal wetlands, tilts downward from northwest to southeast, yielding the parallel watersheds described above. As expected, the highest elevations lie in the Northern and Western Panhandles; Amarillo has an elevation of 3600 feet and Lubbock sits at 3256 feet while Guadelupe Peak (8751 feet), the crest of the Guadelupe Mountains in extreme West Texas, is the highest point in the State.
