The results of simulation modelling carried out with GLEAMS on hypothetical scenarios driven by the Reform of Common Agricultural Policy are presented. The model was set up with data collected in recent research projects to simulate a typical cultivated environment of the Venetian Plain (north east Italy) where field experiments are in progress. Agro-environmental simulations were conducted over a long period using a 30-year whether record. First single crops, then entire rotations and finally the whole farm production patterns were simulated, based on the present standard agrotechnologies of the study area and on proposed low input systems. The alternative farm scenarios were taken from those hypthesised by economists on the basis of the recent Common Agricultural Policy (CAP) Reform with multi-objective modelling. Environmental evaluation of alternative scenarios was carried out with 6 proposed indexes quantifying water pollution due to nutrient and pesticide releases associated with leaching and runoff phenomena. The environmental indexes focus on the efficiency of applied agrochemicals, regulatory and toxicity limits for drinkable water and risks for aquatic ecosystems (fish toxicity and eutrophication). The results confirmed the potential risks of intensive cultivation systems, in particular when livestock wastes are distributed, and the various levels of efficacy of proposed eco-compatible systems to mitigate water pollution phenomena.