The study presents results of basic physical and chemical properties of hydrogenic soils occurring in the central part of the Grójec Valley as well as its lateral branches. Water holding capacity of organic levels as well as their retention capabilities were determined. It was found that considerable quantities of bound water found in those soils can prolong significantly the period of evapotranspiration. This, on the one hand, limits possibilities of the decline in the concentration of organic matter but, on the other hand � from agricultural point of view � it restricts water availability for plants, which makes intensive irrigation of these soils necessary. The planned "Drzewce" opencast brown coal mine will cause drainage degradation of these soils, although the extent of this degradation may vary considerably depending on the depth of organic layers, degree of humification of organic matter, soil genesis and texture composition of the mineral substrate.