The Mezquital Valley is a series of small valleys and flat areas located in central Mexico in the western part of the state of Hidalgo. It is part of the Trans-Mexico Volcanic Belt, with elevations ranging between 1,700 meters (5,600 ft) and 2,100 meters (6,900 ft) above sea level. The valley region is one of the main semi-arid regions of Mexico, where its native vegetation is dominated by cacti, mesquite trees and magoi with pines and oaks in the higher elevations. The valley was a sparsely populated area and a very poor area, but by the 20th century, irrigation works were established to tap the water in the Tula River, along with sewage discharged from the Valley of Mexico for agriculture. Today, the valley produces many grains and products, including a quarter of the green chilies grown in Mexico.