Tracer Test on the Mala Gora Landfill near Ribnica in South-Eastern Slovenia

The Mala gora landfill near Ribnica is one of the nine still active landfills on Slovene karst. According to our legislation the monitoring of its impact on groundwater have to be performed, but this can only be effective when the characteristics of the underground water flow in the area of the landfill are well known. Therefore a tracer test was carried out on the Mala gora landfill and the main underground water connections towards the Tominčev studenec, Javornikov izvir, Debeljakov izvir and Šica springs near the settlement Dvor in the Krka valley were proved. In lower concentrations the uranine was detected in the Podpeška jama and Kompoljska jama Caves, as well as in the Šica near Mala Račna spring and both springs of the Krka river. At high waters the flow from the landfill towards the Globočec spring was proved also, but this important source of water supply is primary recharged from other parts of the karst aquifer. The appearance of tracer is forwarded by favourable hydrological conditions and increased concentrations of uranine were measured at all springs after more intensive precipitation events even one year after the injection. Obtained results were considered in the preparation of the monitoring plan.