Radio-indicator methods enable the water flow parameters in soils or disturbed rocks to be determined on the basis of observation of the dilution process, or vertical displacement of solution in boreholes. In the hydrogeological investigation of water reserves they make it possible to limit expensive pumping tests, and to give data for location and projection of the optimum depth of boreholes. In the control of the efficiency of sealing elements in deep foundation pits they give information about leakage localities that need to be repaired. Investigation of water flow in landslide slopes proved that the sliding surfaces are apparent in their dilatation sections by intense drainage effects that can be used to determine their location.