The water regime of a landscape commutes more and more between the extremes drought or flooding. The type of vegetation and land use plays an important role in water retention and runoff. Together with scientists from the UK and the US, researchers from the Leibniz- Institute of Freshwater Ecology and Inland Fisheries (IGB) have developed a mathematical model that can reflect the complex interplays between vegetation, soil and water regimes. They show, for example, that in beech forests water is increasingly cycled between soil and vegetation to increase evaporation to the atmosphere, while grass cover promotes groundwater recharge.