Photograph by Jack W. Dykinga, National Geographic
Algae colors the confluence of the Rio Grande and Arroyo San Carlos.
The population in the Lower Rio Grande Valley is exploding in both the United States and Mexico, driven by NAFTA-era factories and agricultural productivity. But by the time it reaches Matamoros, the river's level is so low that it often falls below the Mexican city's intake pipes. Farmers in Texas say they lose $400 million annually due to lack of irrigation water.
The region's wetlands, once critical stopover points for migrating birds, are getting choked off. All these problems are made worse by the decades-long drought gripping the region.
