Optimization of Best Management Practices to Reduce Phosphorus Runoff in the Grand River Watershed Using a Multi-Objective Optimization Algorithm

Abstract

As water quality issues become an increasingly global concern, public administrators are looking for new ways to reduce water pollution from different sources, including agricultural runoff. Best management practices are agri-environmental activities, which aim to decrease the impact of agricultural activities on the environment as compared to conventional management practices. However, the selection of best management practices distribution is not without challenges and therefore an optimization model is introduced here to support policy and decision-making and minimize nutrients load with the limited available resources. Therefore, this research sets out a multi-objective optimization model to optimize phosphorus reductions in the Grand River watershed and conduct an economic analysis of best management practices and assess their cost-effectiveness. A set of optimal solutions is generated from the Pareto-optimal front within the constraints of two objective functions designed to achieve a reduction in total phosphorus load at minimal costs to support decision making and watershed management. With maximum retention of total phosphorus, the optimization results show that nutrient management plan is the most cost-effective best management practice, while manure storage is the least cost-effective best management practice. Regarding the minimization of total phosphorus load, none of the single best management practices for cover crops, nutrient management plan, and buffer strips could achieve a total phosphorus reduction of greater than 20%. According to the optimization of best management practices combinations, up to 32% of the total phosphorus load can be reduced at a minimum unit cost of $1,328 per hectare per year. The combination of cover crops and nutrient management plan is the most recommended best management practices for the entire Grand River watershed. In order to improve water quality based on existing best management practices, implementing a combination of best management practices is a good option for the Grand River Conservation Authority.