Life cycle assessment (LCA) calculates the environmental impact of a production process by evaluating all fluxes of energy and materials during the whole life cycle. The use of LCA in forestry and agriculture asks for a new impact category: land use. The study is restricted to the water aspect within the land use impact category. Our goal is to define a set of indicators that describe the impact of land use on the water balance and to develop a methodology to quantify these indicators. Therefore different hydrological models, of avrying complexity, are compared. The main criteria used for evaluting the suitability of a model for LCA are universal applicability and cost efficiency.