Life cycle assessment (LCA) is an ISO standardized method designed to evaluate the impact of human activities on the environment using objective and measurable indicators. To be effective an LCA analysis should be cost-efficient in data gathering and the methods used for calculating the impact categories ought to be universally applicable. The land use impact category of an LCA deals with impacts of land occupation and land use change on water balance, soil and vegetation. This paper proposes to use a modelling approach to generate indicators for the land use impact Of CO2 emission reduction projects on the ecosystem water balance. The rate variables of the water balance selected to describe the land use impacts are evapotranspiration, surface runoff, discharge, groundwater recharge and soil loss through water erosion. They are simulated making use of the SWAT model.