The glacierized areas of Peru are found in 20 distinct mountain ranges (cordilleras) extending from central northern Peru to its southern border, and they include two major glacier systems. The largest system, which is in the central northern part of Peru in the Cordillera Blanca, extends along a distance of 200 kilometers; it has a total glacierized area of 723.4 square kilometers. The second largest system has a glacierized area of 539 square kilometers and is in the southeastern part of Peru in the Cordillera de Vilcanota. The estimated total ice-covered area within Peru is about 2,600 square kilometers.
The glacierized areas are very important because runoff (meltwater) from glaciers is used for agricultural, industrial, and domestic purposes. Runoff from glaciers is particularly important in the hyperarid coastal areas. On the other hand, some glacierized cordilleras have historically been the sites of catastrophes such as ice avalanches, floods, and the like. In the RÝo Santa valley, adjacent to the Cordillera Blanca, for example, 22 such catastrophes of glaciological origin have taken place since 1702 and have caused the destruction of towns, villages, and croplands and have killed tens of thousands of inhabitants.
In this century, studies were begun in 1927 for agricultural, industrial, and scientific purposes, and since 1941, studies and construction projects have been undertaken to prevent damage from glacier hazards. The Government of Peru has completed many successful engineering projects that drain glacier lakes in order to reduce the danger of failure and catastrophic flooding. From 1974 to 1984, the Quelccaya ice cap in the Cordillera de Vilcanota, southern Per˙, has been intensively studied by Ohio State University, in cooperation with Peruvian institutions, in order to determine paleoclimatic conditions. In addition, a national inventory of the glaciers of Peru was finished in 1988 by the Department of Glaciology and Hydrology of Hidrandina S.A.