the actual phosphorus and nitrogen emissions reached their limit values in most of the zones over the planning horizon (i.e., phosphorus and nitrogen emissions reaching 969 tonnes and 3814 tonnes under k = 1.00,respectively; phosphorus and nitrogen emissions reaching 972 tonnes and 3891 tonnes under k = 0.70,respectively). When the credibility level reduces from 1.00 to 0.70, system benefit would rise by 32.60% and groundwater consumption would be reduced by 79.51%. However, the pollutant discharge would not increase as expected, which would be reduced by 40.14% on the contrary. If system benefit is not of major concern, an aggressive strategy is suggested by selecting a rather low credibility level (say, 0.70). This strategy is suggested for guaranteeing protection of local groundwater resources and mitigation of local environmental deterioration by sacrificing part of system benefit.