The impact of projected climate change on the water balance and the water supply of the vegetation of two cover systems for landfills was investigated in a simulation study with the water balance model for landfills HELP 3.95 D. Selected parameters of the study were (1) climate scenarios RCP2.6 and RCP8.5; (2) three 30-years periods: recent past (1971–2000), near future (2021–2050), and far future (2071– 2100), respectively; (3) four combinations of two global (GCM) and three regional climate models (RCM/ESD), supplying weather data for all three periods; (4) two landfill covers according to the German landfill ordinance, the standard cover for landfill category I (LC I) and the so-called water balance layer (WBL) with a forest vegetation; (5) four German locations (Halle, Dresden, Hamburg, Karlsruhe), where measured weather data from the German Weather Service were available for the recent past. Only results of the combination ECEarth+ EPISODES2018 (GCM+ESD) with a statistical regional model are presented because the precipitation bias of this combination lies between -6.0% (Karlsruhe) and +6.0% (Halle). The average annual actual evapotranspiration of the standard cover for LC I remains approximately constant in RCP2.6; in RCP 8.5 it is increasing by 10% to 13% except for Karlsruhe where it remains approximately constant. The changes of the lateral drainage are heterogeneous; in RCP8.5 in Hamburg, it is increasing by 24% to the far future. Overall, the water supply of the forest vegetation on a WBL deteriorates for all locations and both climate scenarios in the future periods and drought stress is increasing. This is discussed in detail for Dresden. Depending on the location and the climate scenario different impacts such as drought stress or desiccation of mineral barriers should be checked for the future.