Results of hydrogeological exploration carried out in the High Karst of western Herzegovina are reported. The hydrogeological map shows the hydrogeological function of the strata, together with full and partial barriers, and terrains of low and high permeability. The exploration indicates an increase in discharge rates from ascending springs after construction of the Salakovac and Tribistovo reservoirs in their hinterland. Areas promising for groundwater exploration occur far from the zones of discharge. The chemical composition of groundwater in the upper part of the Tihaljina river indicates circulation of deep groundwater and an associated increase in sulphate content. The results of observations and measurements of many springs and groundwater tracing experiments are presented. This study has enabled the discovery of potable groundwater in karst areas previously considered as dry.