Optimal decision schemes for agricultural water quality management planning with imprecise objective

Agricultural activities are the main sources of water pollution to surface water and groundwater in rural areas. Extensive soil disturbance and application of fertilizer and manure in agriculture cause nonpoint source losses of soil and nutrients such as nitrogen and phosphorus. How to generate preferred decision schemes for agricultural activities that cause such nonpoint source water pollution is a critical issue for the decision makers. In this study, an inexact agricultural water quality management (IAWQM) model is developed and applied to a case study to generate optimal decision schemes for integrated water quality management within an agricultural system. The model is based on a hybrid fuzzy possibilistic robust programming approach, which improves upon the existing fuzzy possibilistic programming and fuzzy robust programming methods by allowing fuzzy information in the model's objective and constraints to be directly communicated into the optimization processes and resulting solutions. Optimal decision schemes for agricultural activities can be generated, including cropping area, manure/fertilizer applied, and livestock husbandry size, where implications of water quality/quantity restrictions for achieving regional economic development objectives are studied. The results of the case study indicate that useful information can be obtained through the proposed IAWQM model for providing feasible decision schemes, which reflect tradeoffs between economic and environmental considerations. The decision variables are useful for the decision makers to justify and/or adjust the decision schemes for agricultural activities through incorporation of their implicit knowledge on water quality management.