Changes of streamflow regulation in an Andean watershed with shrinking glaciers: implications for water security

Glaciated Andean mountains have experienced several decades of shrinkage in their transition to non-glaciated regimes. This study analyses the period of hydrologic transition from 1956 to 2020 in a watershed of the Sierra Nevada del Cocuy (SNC), which is the most extensive remaining tropical glacier in Colombia. Using ground hydrometeorological data, remote sensing products, a metric of extreme flow regulation, and decadal flow duration curves, the study shows how the combined effect of continuous glacier shrinkage, highly variable precipitation regimes and increasing human extractions have altered the hydrological capacity of the watershed to regulate high, low, and mean flows. The alteration is noticeable since the 2000s, when communities have effectively benefited from the surplus of baseflow provided by the shrinking glacier to the limit, creating an unsustainable dependency with potential restrictions of use in the short run and major implications for water security of humans and the environment in the forthcoming decades.

Automated summary

This study analyzes the period of hydrologic transition in the Sierra Nevada del Cocuy watershed in Colombia from 1956 to 2020. The research shows that continuous glacier shrinkage, highly variable precipitation regimes, and increasing human activities have altered the watershed's capacity to regulate high, low, and mean flows. This alteration has become noticeable since the 2000s, with local communities depending unsustainably on the shrinking glacier for water resources, potentially leading to usage restrictions and major implications for water security in the future.