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Hydrogeological responses in tropical mountainous springs

Abstract:

This study presents a hydrogeochemical analysis of spring responses (2013–2017) in the tropical mountainous region of the Central Valley of Costa Rica. The isotopic distribution of δ 18 O and δ 2 H in rainfall resulted in a highly significant meteoric water line: δ 2 H = 7.93·δ 18 O + 10.37 (r 2 = 0.97). Rainfall isotopic composition exhibited a strong amount-dependent seasonality. The isotopic variation (δ 18 O) of two springs within the Barva aquifer was simulated using the FlowPC program to determine mean transit times (MTTs). Exponential-piston and dispersion distribution functions provided the best-fit to the observed isotopic composition at Flores and Sacramento springs, respectively. MTTs corresponded to 1.23 ± 0.03 (Sacramento) and 1.42 ± 0.04 (Flores) years. The greater MTT was represented by a homogeneous geochemical composition at Flores, whereas the smaller MTT at Sacramento is reflected in a more variable geochemical response. The results may be used to enhance modelling efforts in central Costa Rica, whereby scarcity of long-term data limits water resources management plans.