Zastosowanie metod geofizycznych do rozpoznania warunków hydrogeologicznych w osadach czwartorzędowych na przykładzie Wrocławia

In order to better constrain the hydrogeological conditions to the depth of 50 m in the area of water extraction for Wroclaw city, a multi-faceted geophysical survey has been applied. We have combined electrical resistivity tomography (ERT), ground penetrating radar (GPR) and magnetic resonance sounding (MRS) techniques. The results of geophysical investigations indicate the presence of three rock layers with different permeability. The first layer, up to 2 m below ground surface, represents a discontinuous horizon composed of impermeable rocks. The next one, a porous and permeable stratum (aquifer) with a thickness of approx. 5-10 m, comprises saturated sands and gravels. The observed aquifer is characterized by good hydrogeological parameters, wherein hydraulic conductivity (k) equals 5 X 10-4 m/s and porosity reaches 23%. The third layer, below 10 m, is composed of loamy impermeable sediments intercalated with moraine till. At greater depths (>20 m) they are still loamy rocks, but occurring with interbeds of sands (sandy loam). This is confirmed by the hydraulic conductivity in the order of 10-6 m/s, which is typicalfor semi-permeable rocks. Noteworthy, no additional aquifers have been observed to the depth of 50 m.