The spatial and temporal patterns of surface water (SW) - groundwater (GW) exchange are significantly affected by riverbed silting, clogging or erosion processes, by altering the thickness and hydraulic conductivity of riverbed sediments. The duration of SW-GW exchange is controlled by the drainage and infiltration resistance of river bottom sediments (e.g. Andrássy et al., 2012). Generally, these two parameters primarily depend on the hydraulic conductivity and on the thickness of clogged layer. In this study the flow processes between GW and SW were modeled by model TRIWACO for different infiltration resistance and drainage resistance of riverbed sediments. The model area is situated on the Rye Island, which is a lowland area with very low slope. In this area a channel network was built up, where the flow conditions are controlled by water-gates. Because of the low slope and the system of water gates built on the channels, the riverbeds are influenced by intensive clogging processes. First, the applicability of model TRIWACO in the study area was tested by modelling the response of GW on SW level fluctuation. It was simulated, how the regulation of water level and flow direction in the channels influence the GW level, especially in extreme hydrological conditions (drought/flood), and if the GW flow direction and GW level change as it was expected. Next, the influence of channel network silting up on GW-SW interaction was modeled. The thickness of riverbed sediments was measured and their hydraulic conductivity from disturbed sediment samples was evaluated. The assessed hydraulic conductivity was used to calculate the infiltration resistance and the drainage resistance of riverbed sediments in the study area. Then, the GW level and flow direction was simulated for different infiltration resistance and drainage resistance of sediments.

The testing of a model performance is important and is also a challenging part of scientific work. In this paper, the results of the physically-based EROSION-3D (Jürgen Schmidt, Berlin, Germany) model were compared with trapped sediments in a small reservoir. The model was applied to simulate runoff-erosion processes in the Svacenický Creek catchment in the western part of the Slovak Republic. The model is sufficient to identify the areas vulnerable to erosion and deposition within the catchment. The volume of sediments was measured by a bathymetric field survey during three terrain journeys (in 2015, 2016, and 2017). The results of the model point to an underestimation of the actual processes by 30% to 80%. The initial soil moisture played an important role, and the results also revealed that rainfall events are able to erode and contribute to a significant part of sediments.

The objective of this paper is to investigate and analyze the silting and subsequent aggradation of the irrigation canals in Žitný Ostrov (Rye Island). The irrigation canal network, located in Southern Slovakia, was built to provide for irrigation water and drainage in the region. The water level in the irrigation canals and groundwater level in Žitný Ostrov area affect each other. Because of this mutual interaction, it has been necessary to evaluate the impact of silting in the canal network due to the presence of the alluvials. Water surface elevations in Danube River affect groundwater infiltration from the Žitný Ostrov aquifer, in and out of the canals, and causes fluctuation of the flow in the canals. The amount of groundwater infiltration is a function of the silt hydraulic conductivity. Tests were done in 1993 and 2004 to measure the silt thickness and granularity at 166 measurement points along approximately 77 km of the canal network. This paper discusses the change in silt thicknesses and silt v...