Discharge recession patterns of karstic springs as observed in Triassic carbonate aquifers of Slovakia

Master recession curves of 117 karstic springs from Middle and Upper Triassic carbonate aquifers in the Slovakian territory of the mountainous Western Carpathians were assembled from gauged discharge data. Identified slow-flow and fast-flow components were very diversely represented. Fast-flow components were missing in 47% of springs. In another 20% of springs, only fast-flow components were recognized, while slow-flow components were absent. Simultaneous discharge of both slow-flow and fast-flow components was found at 39 springs (33%). Known geology of recharge areas enabled examination of the impact that outcropping dolomites and/or limestones may pose to the discharge recession. It was found that dolomites in springsheds significantly affect slow-flow components, but do not influence the occurrence of the fast-flow ones. The purely fast-flow-driven recession was present both in limestone and dolomitic springsheds, but merely one fast-flow component was typical for the dolomitic ones. Two or three fast-flow components may appear in “purely limestone” springsheds. Recession coefficients of slow-flow components were within the interval of 0.0004–0.18 days⁻¹ and those of fast-flow within 0.0017–0.31 days⁻¹. The duration of the fast-flow components is mostly several days or several tens of days, while the theoretical duration of slow-flow may last for decades. Storage in matrix, fractures or conduits of the saturated zone cannot be separately estimated because, in discharged volumes, water from unsaturated and epikarst zones is included. Variable shapes of assembled master recession curves point to the important influence of unsaturated and epikarst zones on the discharge recessional patterns of karst springs.