Monitoring glaciers by size and its impact on water reserves in the Peruvian Andes

In almost 58 years analyzed, the behavior of the amount of population using the water resource coming from the tropical glacier presents an inverse relationship, causing an increase of the water deficit in the glacier basins. Therefore, a recent comprehensive analysis of tropical glaciers is necessary. The study was carried out for the Peruvian Andes mountain ranges of the year (1962 and 2020) to know the conservation status of glaciers (surface and volume), distribution (5 sizes of glaciers and 3 zones of the Andes) and ice water reserve per capita per inhabitant. The methodology was to use aerial photographs and images (Sentinel and Spot) to identify glaciers and validate it with GPS points on some glaciers, DEM for the GlabTop model that calculates the volume of glaciers and population censuses in the demarcation of the districts with presence of glaciers. The results show that the surface and volume in 1962 (2,349.20 km² and 69,564 hm³) and in 2020 (1,049 km² and 31,686 hm³), occupying more glacier mass in the Central Andes and Northern Andes. At the same time, there is evidence of a significant decrease in surface area (55 %) and volume (54 %) by 2020, with a concentration of 86 % in the number of glaciers of size < 1.0 km². Regarding population and ice water reserve per capita, it increased from over 650,000 inhabitants to 1,200,000 inhabitants, and decreased from 106,660 m³/inhabitant to 24,858 m³/inhabitant, respectively. The decreasing changes in the sizes of glaciers located in the Peruvian Andes require the importance of continuous monitoring and the need to adequately manage these vulnerable resources in a continuously growing population.