The Rio Grande is a river of immense geographic and political significance. First, it serves as a natural international border for approximately 1,250 miles between the United States (Texas) and Mexico, making it one of the most monitored river borders in the world. Second, despite its name meaning "Big River," it frequently suffers from severe water depletion; in many years, the river is so heavily tapped for irrigation and municipal use that it fails to reach the Gulf of Mexico, disappearing into the sand before the coast. Third, it is one of the few rivers that flows through three distinct North American eco-regions: the high alpine tundra of the San Juan Mountains in Colorado, the arid Chihuahuan Desert, and the subtropical Rio Grande Valley. Fourth, the river is surprisingly shallow for much of its length, which is why it earned the nickname "El Río Bravo del Norte" in Mexico, referring to its "fierce" or turbulent nature during floods despite its low average depth. Fifth, it is an essential "avian highway," serving as a critical migratory corridor for hundreds of species of birds traveling between North and South America, supporting some of the best birdwatching spots in the Western Hemisphere.