A novel methodology of determination of the mean translational velocity of groundwater flow and its application in the karst.

The paper deals with a novel methodology for determining the mean translational velocity of groundwater flow and application in the Dinaric karst of Croatia. Until now, it has only been possible to calculate the apparent velocity of groundwater flow in the karst system after obtaining experimental field investigation to verify e.g. the movement of pollution through the underground karst system, by applying the dye-tracing test technique using a dye tracer. The methodology for calculation of the apparent velocity of groundwater flow takes into account the measured "actual or real" travel time and shortest (air) distance (path) between sites of dye insertion and dye appearance which means that it does not include the "actual or real" distance with multidimensionality and extremely nonlinear behavior of karst system. In contrast with this methodology, the calculation of mean translational velocity is based on "actual or real" data of measured travel time and distance required that dye appears on springs from the moment when the dye was inserted in the sinkhole, and the minor and major semi-axes of the boundary ellipse. This mathematically presented novel methodology takes into account information such as measured travel time and environmental characteristics (aquifer boundaries) which makes novel methodology innovative and sustainable. Since it would be good to know the velocity as close as possible to the "actual or real" groundwater flow velocity, the paper discusses the possibility of obtaining the mean translational velocity based on theoretical calculations and improving the existing calculation of the apparent velocity of groundwater flow. Additionally, the value of this paper is a quantification of the relationships between the qualitative features of the karst system, i.e. makes them measurable contributing to SDG6.