ABSTRACT: The assessment of the exploitable grou nd water amount should distinguish and separately express different levels of these amounts: Qp - maximum ("natural") exploitable amount de termin ed only by natural conditions and ecological requirements, QETK - really exploitable amount in actual economic, qualitative and technical conditions, and QDOK - the part of the QETK sufficient1y evidenced by documentation corresponding to the valid regulations. The assessment of these different amount lev els encounters some particular methodological problems (the relation to natural resources, ecological limits, inclusion of small springs, imaginary wells, potential discharge of wells, exploitation strategy with regard to spatial concentration of sources) discussed in the paper.