The paper presents the results of water permeability tests of soils forming north abrasive slopes of the Czorsztyn-Niedzica reservoir from the side of the Pieniny National Park. The basic geotechnical characteristics of the tested soils were determined basing on the results of the tests carried out according to standard procedures. The tests of water permeability of the soils were carried out using methods: in situ according to Giryński – in open pits, in laboratory – in a medium size apparatus, and analytic method using empirical formulas basing on the grain size distribution and porosity of soils. the analysis of the tests results was conducted in terms of possibility of determination of the optimum method of testing the permeability of soils forming abrasion slops of the tested reservoir and maximum safe velocity of lowering the water level in the reservoir. It was found that the most appropriate method for determination of the water permeability of the tested soils was a Giryński’s method. The maximum allowable speed of lowering the water in the reservoir should be 0.103 m ⋅ h–1.