Coupled application of single-storm events and tracer analyses to characterize the flow and transport features of a karst aquifer

Karst aquifers play a very important role in supplying a large part of the world's population with drinking water. The recharge conditions, together with the internal characteristics of the karst aquifer, are the most important factors determining its function. The water that infiltrates into the aquifer may originate from precipitation (rain and snow) falling on the karst area (autogenous recharge), or it may collect in neighbouring areas of relatively insoluble rock and flow into the karst as allogenic recharge. Therefore, understanding these processes is essential for planning appropriate utilisation and protection of karst water resources.

The proposed project focuses on the functioning of the karst aquifer on the southern edge of Planinsko polje in south-west Slovenia and on the Malenščica spring, a regional water source that is potentially threatened and needs to be better understood to ensure water quality in the future. The main objective is to investigate the impact of individual precipitation events on the response of the karst aquifer using multidisciplinary analyses, to determine the role of recharge processes under different hydrological conditions and to investigate how water quantity and quality changes at different observation points during a single precipitation event.

Extensive hydrological and meteorological measurements will be carried out as part of the project, including continuous measurements of selected physical and chemical water properties, water sampling for quality analyses, flow measurements and precipitation measurements. These measurements will be complemented by frequent water sampling for major ions and microbiological indicators during two precipitation events under significantly different hydrological conditions. A combined tracing experiment will also be conducted under hydrological conditions that allow for rapid pollutant transfer, where two injection points will be allogenic and autogenic recharge sources in the immediate hinterland of the Malenščica spring. A time series analysis of several individual precipitation events will be performed to extract a range of hydrological and hydrochemical parameters that can be further used for multivariate analysis. The results will contribute to a better understanding of the characteristics of flow and material transport in the hinterland of the karst aquifer. A conceptual model will be used to further analyse the results. The comprehensive study could be used in the future to prepare risk analyses as part of the planning for the protection of the Malenščica water source.