Abstract
Metamorphic, igneous and sedimentary rocks, with low to no primary porosity, outcrop in the La Moza micro-basin stream (headwater of the Rio de Oro). In this high mountain system, water isotopic composition of rainwater, water isotopes and geochemistry of groundwater (springs) and surface water were determined. Groundwater flows are associated to phreatic aquifers in relationship with secondary porosity generated by fracturing, which is increased by dissolution processes in case of carbonate formation producing karstic systems and by the weathering phenomenon mainly affecting granodioritic rocks. Water geochemistry shows low to medium electrical conductivity (EC) depending on the geological formation, but a unique calcium bicarbonate facies. Spring water EC shows limited temporal variations. The isotopic composition of spring indicates a meteoric origin, local infiltration and groundwater flows with low residence time. A conceptual model of the recharge zone is proposed that crosses the surface watershed and covers part of the adjacent Rio Jordán basin, where the Berlin Paramo is located.