Natural water resources are in continuous dynamic interaction with each other. Hydrodynamic processes between surface water and groundwater are very complex, and they are influenced by many factors and conditions (topography, climatic conditions, hydrogeology, stream hydrology and morphology, etc.). Groundwater – surface water interactions are also influenced by riverbed sedimentation and clogging processes. The thickness and hydraulic conductivity of bed sediments can significantly affect the temporal and spatial patterns of hyporheic exchange. The aim of this study was to investigate the influence of riverbed clogging on groundwater – surface water interaction in a lowland area with intensive agricultural production (Rye Island, Slovakia). In this locality, a canal network was constructed for draining the excessive GW from the adjacent farmlands. Due to the topography, land use and climatic conditions the canals are exposed to intensive aggradation, what may negatively affect their draining function. Therefore, regular field monitoring of the canal bottom sediments should be performed. In this study, the sediment deposits in the Gabcikovo – Topolniky canal were investigated. The thickness of sediments was measured along the canal by 1 km step, and undisturbed sediment samples were taken in selected cross sections. From the samples the saturated hydraulic conductivity of bottom sediments was assessed by laboratory methods. The collected data were used for numerical modelling. The impact of canal sediments on the groundwater – surface water interaction was simulated by the TRIWACO model. Several model scenarios were considered for different sediment thicknesses. The results of the numerical simulations confirmed the influence of canal bottom sediments on groundwater – surface water interaction along the Gabcikovo – Topolniky canal. It was shown, that thicker sediment deposits (>0.5 m) would obstruct the canals drainage function in a great extent, possibly even cut off the communication between the canal and the aquifer. The results suggest that bottom sediments should be regularly removed to ensure the hydraulic connection between the canals and the surrounding aquifer, and hence guarantee the canals proper draining ability and the protection of adjacent agricultural areas from flood hazard.

Groundwater (GW) – surface water (SW) interaction, riverbed sediments, model TRIWACO