| Sumario: |
The linkage between precipitation and recharge is still poorlyunderstood in the Central America region. This study focuses onstable isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa
Rica. During the dry season, rainfall samples corresponded to enriched events with high deuterium excess. By mid-May, the Intertropical Convergence Zone poses over Costa Rica resulting in a depletion of 18O/16O and 2 H/H ratios. A parsimonious four variable regression model (r2= 0.52) was able to predict daily δ18Oin precipitation. Air mass back trajectories indicated a combination of Caribbean Sea and Pacific Ocean sources, which is clearly depicted in groundwater isoscape. Aquifers relying on Pacific-originated recharge exhibited a more depleted pattern, whereas recharge areas relying on Caribbean parental moisture showed an enrichment trend. These results can be used to enhance modelling efforts in Central America where scarcity of
long-term data limits water resources management plans.
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