The most popular backpackers’ route — though far bumpier, dustier, and longer than the Casma route [1] — is the Cañon de Pato route, which begins in Santa, just north of Chimbote. This 10-hour journey follows the old highway, built by a mining company in the 1930s, along the Río Santa from the dry desert near its mouth up into the sheer walls of Cañon de Pato.
Dozens of tunnels were drilled through the canyon walls to make this route along the river, which has been reduced to a trickle because of the hydroelectric dam operated by Duke Energy, the Charlotte, North Carolina–based energy company.
Because it is mostly gravel, this road can be taken during the rainy season, and it becomes fully paved at Huancacalle, at the northern end of the Callejón de Huaylas [2], where there is simple lodging.
Links:
[1] http://www.moon.com/destinations/peru/huaraz-and-the-cordillera-blanca/huaraz/adventure-routes-huaraz/the-casma-route
[2] http://www.moon.com/destinations/peru/huaraz-and-the-cordillera-blanca/callejon-de-huaylas