Application of tritium in precipitation and in groundwater of the Kouris catchment (Cyprus) for description of the regional groundwater flow

The Kouris catchment is located in the south of the Troodos massif in Cyprus. It constitutes one of the biggest catchments of the island with important freshwater resources. Geologically, the catchment includes an ophiolitic complex outcropping in the north which is overlaid by sedimentary rocks in the south. The hydrology is driven by a Mediterranean climate, a mountainous topography, and a complex distribution of the hydrogeological properties resulting from the complex geology. To improve the understanding of groundwater hydrology of the Kouris catchment, 176 groundwater and precipitation samples were collected and their 3H contents were analyzed. The three-dimensional 3H transport in the groundwater was simulated by the PMPATH code. For numerical modelling, a regional input function of 3H in precipitation was constructed from a linear regression between data for Cyprus and for neighboring meteorological stations. The calculated residence times for the groundwaters in the sedimentary aquifer and Pillow Lavas were greater than 48 a and were considerably greater than those of the ophiolitic complex (14–30 a). The calibrated aquifer porosities were in a range of 0.05–0.06. The PMPATH model was applied for delineation of spring catchments that were represented by quite narrow zones of lengths up to 5 km. Another contribution resulting from the 3H analysis was a better understanding of the river–aquifer interactions. In most of the southern part, the lithified sediments received only negligible amounts of water from the rivers, while the alluvial aquifer contained mostly water infiltrated from rivers. The largest springs in the southern part, associated with the alluvial aquifer, also discharged water identical to that in the rivers.