The Geodynamic Observatory Moxa is located around 4 km to the north of the Hohenwarte reservoir, a medium-sized artificial reserv oir, holding on average 182 Mill. m3 of water. The data of the installed seismometers and strainmeters at Moxa are successfully used for studies of the Earth's inte rior structure and properties. It is possible to observe tilt changes in the ran ge of 10 9 rad and displacement changes of 10 9 strain. We explore the possibility that registrations of the seismo meters and strain- meters are influenced by deformation changes induced by lake -level fluctuations of the Hohenwarte reservoir, both on a short-term seasonal time scale and a long- term decadal time scale. We use the Finite Element method to calculate defor- mations in vicinity of the Hohenwarte reservoir. We show that the influence of lake-level fluctuations of up to 30% to tilt and strain regist rations at the observa- tory is larger than the resolution of the instruments, with d ifferences of at most 48 nrad for the tilt and 6 nstrain for the strain. Thus, at the l ocation of Moxa, the influence of lake-level changes on the registrations is sign ificant.