The Rio Grande River originates in the San Juan Mountains of in southwestern Colorado and follows 1,885-mile course before it empties into the Gulf of Mexico between Brownsville, Texas and Matamoros, Mexico. After Mexican independence from Spain in 1821, numerous American colonies were established in Texas. There was dispute over the Texas-Mexican border which was one of the main causes of the Texas Revolution in 1835-1836. The Rio Grande, or the Rio Bravo as known in Mexico, forms the international border between the two countries for the 2,053 kilometers of river boundary.
The Rio Grande is an important natural resource for industry, agriculture, domestic water supply, recreation, wildlife and aquatic habitat. The two main tributaries are the Rio Conchos and the Pecos River. Substantial agricultural areas where river water is diverted for irrigation include the El Paso/Ciudad Juarez area, Eagle Pass/Piedras Negras area, and Rio Grande/Rio Bravo valley downstream from International Falcon Dam. the river constitutes the primary drinking water source for up to 98% of the population on both sides of the border.