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Modelling the water balance with SWAT as part of the land use impact evaluation in a life cycle study of CO<inf>2</inf> emission reduction scenarios

Abstract:

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. The paper describes the application of the proposed methodology for two locations with different site characteristics and land use patterns. Special attention was paid to aspects of data availability and reliability. Comparison of the simulation results with literature data revealed that SWAT provides reasonable results, which can be used for assessing the land use impact in LCA. The sensitivity analysis indicated low dependency of the model output to minor and moderate changes in model input, with the exception of changes in precipitation and leaf area index (LAI). The study also indicated that the land use library in SWAT needs further development to become universally applicable for LCA purposes. A scenario analysis allowed us to pbkp_redict the impact of land occupation on the hydrology and erosion of both study areas. Finally, the LCA indicators giving the impact on the water balance per functional unit were calculated by expressing the SWAT outputs per kilogram of CO2 emission reduction. Copyright © 2005 John Wiley & Sons, Ltd.