Ap pli ca tion of pol lu tion in di ces for the spatiotemporal as sess ment of neg a tive im pact of a mu nic i pal land fill on ground wa ter (Tychy, south ern Po land). Geo log i cal Quar terly, 62 (3): 496-508, doi: 10.7306/gq.1420 As so ci ate ed i tor: Stanis³aw Wo³kowicz Risk as sess ment plays an es sen tial role in the pro tec tion of ground wa ter re sources, es pe cially in the re gions of po ten tial con tam i na tion sources. The pres ent re search was aimed at as sess ing the risk of ground wa ter con tam i na tion in the vi cin ity of the Tychy-Urbanowice mu nic i pal land fill sys tems (south ern Po land), us ing the con tam i na tion in dex tool. Ground wa ter samples from the Qua ter nary Aqui fer were col lected from 22 piezometers lo cated near the for mer land fill site (cur rently closed) and the new sealed land fill site dur ing a mon i tor ing pe riod from 1995 to 2015. Ex tremely high val ues (1700) of the ground water con tam i na tion in dex were ob served in a piezometer that cap tures wa ter be neath the aban doned land fill. Very high in dex val ues (154 or 216) were also no ticed in piezometers lo cated in the ground wa ter out flow from the land fill site. Re sults of in terpo la tion for in di vid ual piezometers, which cap ture only the up per or lower part of an aqui fer, are un rep re sen ta tive. The in terpo la tion for the mean val ues of the con tam i na tion in dex in creased the ground wa ter risk as sess ment. Key words: hydrogeology, ground wa ter risk as sess ment, con tam i na tion in dex, mu nic i pal land fill site, Tychy-Urbanowice.