The present study is a contribution to a regional-scale analysis of the C and water cycles on managed grasslands. A common set of eco-physiological parameters was identified for pasture simulation model (PaSim). C and water fluxes estimated with the parameter set are in good agreement with observations. The model with the new parameters estimated that European grasslands uptake - 213 g C yr-1, which is close to the observed NEE flux of the studied sites (-185 g C yr-1 on average). The estimated yearly average GPP and RECO for all of the study sites are 1220 and 1006 g C yr-1, respectively, in agreement with observed average GPP (1230 g C yr-1) and RECO (1046 g C yr-1). For evapotranspiration (ET), the average value of simulated ET (415 mm yr-1) for all sites and years is close to the average value of the observed ET (451 mm yr-1) by flux towers.