Discriminant model and hydrogeochemical processes for characterizing preferential flow paths in four interconnected volcanic aquifers in Costa Rica

Abstract The volcanic Barva and Colima multiaquifer system is crucial for the drinking water supply of about 1.7 million people, 30% population in Costa Rica. complexity this simultaneous occurrence anthropogenic natural processes complicate understanding hydrochemical hydrogeological dynamics, both essential groundwater protection. This research aimed to develop a model discrimination groundwaters according main withdrawn aquifer flow path, assess interaquifer connections, evaluate governing quality. Samples (571) from 38 sampling sites, collected quarterly 2016 2020, were analyzed nitrate, major ions, silica. Principal component analysis discriminant exhibited validated sample grouping primary captured, i.e., Upper Barva, Lower Colima, two paths within aquifers. Hydrochemical statistical analyses showed resilience seasonal chemical variation deeper aquifers also three mixing processes. enriches bicarbonate, magnesium, calcium, sodium, silica, mainly due weathering mafic andesitic-basaltic lavas. higher silica ion content, except indicating longer residence times, dissolution felsic andesitic minerals, calcium adsorption by normal exchange. Weathering aluminosilicates process quality four studied aquifers, whereas cation exchange, leakage, might modify chemistry.