The Dos Ríos Pilot Area includes more than 9 million acres split between Texas and Chihuahua. The area is the heart of the Chihuahuan Desert and the core area for decades of bi-national conservation efforts. The Chihuahuan’s highly diverse landscape, composed of desert grasslands and sky islands, streams and riparian corridors, and springs, is noted as having one of the highest levels of biodiversity and endemic species among the world’s arid and semiarid ecosystems. The Río Grande/Bravo’s most important tributary – the Río Conchos of northern Chihuahua, Mexico – is born in the mountains of the Sierra Madres and travels to its confluence with the Río Grande/Bravo. In the headwaters live the indigenous Tarahumara people. Further downstream, irrigation dominates water use before the river travels 120 miles of the amazing, arid environment of northern México to the confluence of the Río Grande/Bravo.