Hydrogeological responses in tropical mountainous springs

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 <i>δ</i>¹⁸O and <i>δ</i>²H in rainfall resulted in a highly significant meteoric water line: <i>δ</i>²H = 7.93·<i>δ</i>¹⁸O + 10.37 (<i>r² </i>= 0.97). Rainfall isotopic composition exhibited a strong amount-dependent seasonality. The isotopic variation (<i>δ</i>¹⁸O) 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.