Estimation of the catchment area of a karst spring is not possible in all areas for various reasons. The Slovak Karst is protected by the highest degree of protection and karst springs are used as a source of drinking water for the second largest city in Slovakia, Košice. From this reason, no results on ionic runoff or chemical denudation have been published from this area and the most appropriate way to obtain information about the denudation rate is to determine the ionic runoff. This paper provides an overview of ionic runoff results based on sampling and analysis of karst water from six springs in the period November 2013–October 2016 (three hydrological years) and periodic measurements. Springs have significantly fluctuated flow rates from 0 L/s in summer and autumn up to 192 L/s, and episodic events during the snow melting and heavy rain in the spring of 2013 are also known (more than 380 L/s). The total value of ionic runoff for the area of 40,847 m3/y.km2 is comparable with the Vracanska Plateau in Bulgaria, which lies at a similar altitude and with a similar amount of precipitation.

Our study presents the hydrochemical data obtained from seven perennial springs located on the Jasov Plateau -Slovak Karst. It is part of the most heavily karstified area in Slovakia extending into northern Hungary. Monthly observations of discharge, temperature and the calcium content have been carried out on perennial springs for 19 months. Since November 2013 the seasonal changes of the basic hydrochemical parameters (water temperature, electric conductivity, pH and major ions), the stable isotope composition and tritium content have been measured on a regular basis. Except for water temperature, no other parameter showed a clear seasonal signal. Statistically significant relationships were discovered between some springs concerning the fluctuation of the various parameters. The stable isotope analyses of the water samples showed that the springs are of meteoric origin, their stable isotope composition varied between -74.9‰ to -62.1‰ and from -10.5‰ to -9.5‰ for δD and δ 18 O, respectively. The mean residence time of the water varies between 3.5 and 6 years (tritium concentration).