 The Pico de Orizaba is covered in snow year round; the Cofre de Perote is covered in winter.Major valleys include the Acultzingo, Córdoba, Maltrata, Orizaba and San Andrés.More than 40 rivers and tributaries provide water for irrigation and hydroelectric power; they also carry rich silt down from the eroding highlands, which is deposited in the valleys and coastal areas.