ABSTRACT: Hydrograph analyses of groundwater depletion process in the spring were used for estimation of karstification degree and groundwater sensitivity to pollution in the whole catchmenťs area. The depletion groundwater hydrograph reflects not only the overall regime, but also the individual laminar and turbulent sub-regimes, that are linked with the open micro- to macrofissures and karst channels (conduits). Differences in character of individual depletion hydrographs enable assessment of the anticipated extent of absorption, atlenuation and selfpurification processes during the groundwater penetration through the rock environment, between its infiltration and its outflow in the spring (exploited source). The method, described by Kullman (2000) was applied in the SW part of the Velka Fatra Mts. (Slovakia), "Tlstá" hydrogeological structure. In total, 209 individual recession curves from 20 gauged springs were analysed. Depending on characteristic groundwater depletion hydrograph with independent sub-regimes, 10 original categories of depletion equations describing individual hydrographs categories were extended - the evaluation scale was refined. The different categories of sensitivity to pollution were spread to the whole structure according to the spatial distribution of different litostratigraphical units.