River, west-central Peru.
Rising in the Cordillera Blanca branch of the Andes Mountains, it descends to the northwest to form the Huaylas Valley, a densely populated agricultural region. Below Huallanca, it veers west and plunges through a spectacular gorge, the Pato Canyon, to enter the Pacific Ocean after a course of 200 mi (300 km). It is harnessed by hydroelectric stations to provide power.