Application of Grain Size Analysis for Saturated Hydraulic Conductivity Assessment of Bed Silts along Komárňanský Channel – Žitný Ostrov

Abstract

The objective of this study is the evaluation of permeability of the bed silts located along the Komárňanský channel of the Žitný ostrov, Slovakia. Komárňanský channel is the largest one from three main channels at the Žitný ostrov area – the flat lowland with channel network. The bed silt permeability is expressed by value of saturated hydraulic conductivity. This parameter is one of the key inputs for estimating solute and water movement between surface water channel and surrounding groundwater in the scope of their interaction at this area. The bed silts were obtained by two ways, as disturbed samples and as undisturbed samples. In this study we deal with disturbed samples extracted from the Komárňanský channel and for that reason only the empirical formulas based on the grain size analysis could be used for saturated hydraulic conductivity assessment. The disturbed samples were extracted in three levels of silt - top, middle and bottom part of silt layer and subsequently as mixed samples in each selected profile of the Komárňanský channel. The selection of sampling place was made by thickness of bed silt in the measured profiles. The values of saturated hydraulic conductivity obtained from disturbed samples of bed silt - Kd were calculated according to three empirical formulas: 1. Bayer – Schweiger formula; 2. Špacek I formula and 3. Špacek II formula, firstly for samples from the top, middle and bottom part of the silt layer and then for mixed samples. The valid values Kd from single parts of the silt layers reached from 1.44 x 10−07 to 1.74 x 10−05 m s−1, the valid values Kd from mixed samples reached from 2.96 x 10−07 to 2.05 x 10−05 m s−1. According to results of comparison of Kd from single parts of silt layers and Kd from mixed samples it is not possible to assess explicitly the reliability of saturated hydraulic conductivity value set by that way. Therefore, in the next step, it will be necessary to compare these results with the values of saturated hydraulic conductivity from undisturbed samples of bed silt determined by the laboratory falling head method.