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Abstract:

Article presents a study on the permeability of weathering covers formed on crystalline rocks, which was conducted in south-western Poland (Sudety Mountains). Evaluation of the infiltration capacity was performed based on field measurements of the vertical hydraulic conductivity carried out by using the Porschet method and the ETC Pask Constant Head Permeameter. During the field investigations conducted in sixteen sites, 28 determinations of the hydraulic conductivity k were made, 16 by the Porschet method and 12 using the ETC Pask Permeameter. Ten sites represent weathering covers of metamorphic rocks (amphibolites, eclogites, mica-schists, crystalline limestones, gneisses) and the next six sites represent covers of igneous rocks (granites). The values of the vertical hydraulic conductivity k determined by the Porschet method ranged between 0.053 and 2.19 m/d, while those obtained using the ETC Pask Permeamet erranged between 0.012 and 0.76 m/d. In the first place, it should be noticed that the results determined during the field investigations conducted according to the Porschet method are generally 3-4 times higher than those obtained using the ETC Pask Permeameter. The results for the vertical hydraulic conductivity allow us to classify weathering sediments of metamorphic and igneous rocks, as semi-permeable to medium permeable rocks. Weathered gneisses were distinctly characterized by the worst capacity to conduct water (semi-permeable) among all types of weathering covers of crystalline rocks. Higher values (0,08-0,8 m/d) of the vertical hydraulic conductivity were found for the weathering covers of the other metamorphic rocks (low permeable). The best conditions to conduct water were found in the weathering covers of granite rocks, which in most cases are classified as medium permeable rocks (more than 0.8 m/d) and exhibit distinctly better permeability coefficients.