At this time there are less scientific analysis about the use and impact of grove plantations on the stability of flood protection dams. In the course of this thesis, the influence of two different plant cover variants on the water supply of dams has been investigated, in the form of Lysimeterexperiments on the test plant in Deutsch Wagram (Niederösterreich). Reducing the soil water content increases soil stability and consequently the shear strength. Therefore it was determined how quickly and well plantations with willow shrubs or grasses and herbs are and how they develop in serious conditions that prevail on a dam and how much they will be to lower the soil moisture and subsequently, to increase the dam stability. The results of the second growing season were compared with those of the first. The willow shrubs develop in the first year better than in the second. Their leaf area index decreases from the first to the second growing season by more than half. The grasses and herbs grow in both growing seasons, however, very good. Both growth forms are already in the first year after a strong root growth. At the willow shrubs the underground biomass after 15 months makes up more than half of the total biomass. After two growing seasons, the root volume of grasses and herbs in the first 10 cm soil depth is greater than that of the willow shrubs. The woods dominate on the other hand in the deeper layers of under 10 cm at its root-mass. Below 60 cm the root volume of grasses and herbs is very low compared to the shrubs. The amount of leachate of both plantings is while the entire study period, from March to October 2010, very low. The soil water content is significantly lower than in the non-planted surface. This is caused by the strong evapotranspiration, which is higher after 15 months by a multiple, than the evaporation of the unvegetated area. The soil water tension in turn is higher among the planting so many times, resulting in improved soil stability.