Unraveling the Role of Groundwater in the Andean Páramo

The Andean páramo is a critical ecosystem for regional downstream water supply. However, understanding the often neglected role of groundwater in the páramo is challenging due to measurement constraints at depth in the rock. Drilling monitoring wells, collecting samples, and analyzing water and rock samples often require substantial economic resources. This study examines the connectivity between groundwater and surface water by integrating hydrometric and hydrochemical measurements from measured sources into a Bayesian mixing model. Results reveal that groundwater flows through bedrock fractures, contributing up to 12% of the total annual streamflow. Additionally, in terms of the contribution of groundwater to other hydrological units, groundwater makes 16–41% of the water in springs and 37–62% in Histosols during our study period. We also found that Histosols can be differentiated into groundwater-fed, receiving water from below 20 meters, and rainfall-fed, receiving contributions from hillslope flow. Groundwater is crucial in regulating baseflow in the study catchment, accounting for up to 12.3% of streamflow at the catchment outlet via direct contribution during dry periods. Groundwater also sustains groundwater-fed Histosols and springs during dry periods, accounting for up to 62% and 41% of their total water mixture. Considering the contribution of groundwater-fed Histosols and springs to streamflow during dry periods, the total contribution of groundwater to streamflow results in 49.8%. Due to critically sustained baseflow during dry periods, a holistic understanding of the hydrological system, which includes both deep and shallow groundwater, is necessary to address the increasing water scarcity, prolonged droughts, and changing precipitation patterns.