Groundwater and surface water sourced from the high Andes of Argentina are highly important for societal, agricultural, and domestic usage in the foothills and valleys, less than hundred kilometers away from the headwaters. Despite their importance, efforts to provide estimates and predictions of surface water and especially groundwater sources and sinks have been limited. During most of the year, precipitation in the high Andes falls primarily as snow, with minimal rainfall over the summer. A widespread lack of measurements and statistical analysis in the region makes it difficult to understand groundwater storage and flow patterns in the Andean watersheds. The contribution of mountain snowmelt to groundwater is a key component of recharge to this area. While this study is limited to a small watershed in the Altar valley of the Central Andes of Argentina, it is representative of most of the Dry Andes region, which runs from Bolivia south to a latitude of 35S between Argentina and Chile. This region is characterized by steep and abrupt topography, highly fractured bedrock, and large fault systems. Here, we investigate the groundwater flow system through observations from pressure transducers and weather stations installed by a mining company exploring the area. We use this data to create a MODFLOW groundwater model of the watershed and develop then a sensitivity analysis to gain insight into the hydrologic system. We explore changes in hydraulic conductivity with depth and reduction in recharge due to uncertainties in sublimation and evaporation and potential future trends. We then analyze heads, surface outflows to assess the impact of these changes within the hydrologic system. In addition, ages distribution in particles from the one well and the river are analyzed. ? This research contributes to the understanding of groundwater recharge and discharge estimates and the hydraulic behavior of upland mountainous watersheds toward better water management in the area.