The Rio Grande forms much of the border between the United States and Mexico before reaching the Gulf of Mexico.
Known in Mexico as the Río Bravo del Norte, the river rises in Colorado’s San Juan Mountains. It flows through New Mexico and Texas before entering the Gulf of Mexico. Its total length is about 3,034 kilometres, although measurements vary with the chosen source and river channel.
The international boundary follows portions of the river from El Paso, Texas, and Ciudad Juárez southward to the Gulf. The river’s course has shifted in places, creating complicated legal and water-management issues between the two countries.
The Rio Grande is also an important water source for agriculture and cities in an arid region. Dams, irrigation withdrawals, drought, and climate variability can leave some lower sections with greatly reduced flow. The river is therefore both a geographic boundary and a heavily managed environmental system.