Definition of the river Gacka springs subcatchment areas on the basis of hydrogeological parameters Jasmina

The river Gacka springs catchment area is located in the Dinaric karst, which is globally known as the locus typicus, or classical Karst. It is composed of four major and several minor karst springs of different discharge rates. The river Gacka springs are characterised by great discharge and exceptional quality, so the catchment area of the river is indicated in the Water Management Strategy (OFFICIAL GAZETTE NO. 91/08) as an area with strategically important reserves of drinking water for the Republic of Croatia. To determine the hydrogeological characteristics of the subcatchments of this large and complex aquifer system, hydrological and hydrochemical parameters were measured on the main springs. Data collected on the springs were analysed using the recession analysis by the „matching strip“ method, the statistical analysis of a time series of measured data both by autocorrelation (analysis of individual series) and by cross-correlation methods (analysis of interrelationships between time series), multivariate statistical analysis (Factor Analysis) of hydrochemical parameters using the software package STATISTICA 6.0 (1998), and geochemical modelling of hydrochemical parameters using the NETPATH computer program. Interpretation of lithological, structural and tectonic characteristics of the rocks, together with tracing data and the applied analytical methods, allowed the springs catchment of the river Gacka to be divided into three subcatchments. The results of this study imply the necessity of a multidisciplinary approach to research.