a river in northern Mexico, a right-bank tributary of the Rio Bravo del Norte (American name, Rio Grande), which flows along the border with the United States. Length, about 700 km. Basin area, about 77,000 sq km. Rising in the Sierra Madre Occidental, it flows across the Meseta Central, passing through canyons in some places. It is low in the summer but at flood stage in the winter and spring. The average rate of flow is 70 cu m per sec. In its middle course the Boquilla Dam, the site of a hydroelectric power plant, forms the large Toronto Reservoir. The waters of the Conchos are used for irrigation.