Hydraulic conductivity of saturated bed silts in Chotárny channel, ŽO area, Slovakia

Abstract

This paper deals with the comparison of two different ways used for determination of saturated hydraulic conductivity values of bed silts located along the Chotárny channel, obtained from field measurements in 2018. The Chotárny channel is one of three selected monitored channels at the ŽO area – the flat lowland with channel network. The permeability of bed silts impacts water flow between surface water in the channel and surrounding groundwater in the scope of their interaction at this area. It is expressed by its value of saturated hydraulic conductivity. The bed silts along Chotárny channel were extracted and obtained by two ways, as disturbed samples and as undisturbed samples. The selection of sampling place was made by thickness of bed silt in the measured profiles. The samples were extracted in three different vertical parts of bed silt – from top, middle and bottom part of bed silt layer. In case of the disturbed samples the empirical formulas based on the grain size analysis were used for determination of saturated hydraulic conductivity value. In case of undisturbed samples was used the falling head method for determination of saturated hydraulic conductivity value. The values of saturated hydraulic conductivity obtained from disturbed samples of bed silts K d were calculated by using of several empirical formulas: 1. Bayer – Schweiger; 2. Špaček I.; 3. Špaček II.; 4. Hazen I.; 5. Bayer; 6. USBR and 7. Orechova. The results in Table 1 show that the valid values K d for Chotárny channel in 2018 were from 1.00x10 -10 to 1.19x10 -04 m s -1 . The recommended formula for calculation of K d of bed silts by empirical formulas in Chotárny channel, based on criterium of the largest number of valid obtained results, is Hazen I. formula. The values of saturated hydraulic conductivity obtained from undisturbed samples of bed silts K u were determined according the relation for calculation of average value of saturated hydraulic conductivity (by falling head method in laboratory). These values are illustrated in Table 2. The values K u for Chotárny channel in 2018 reached values from 7.68x10 -08 – 4.53x10 -05 m s -1 . All the results from both methods of determination of saturated hydraulic conductivity were compared.