Modelling the cost-effective solutions of nitrogen reduction in Jiulong River Watershed, China

To inform the decision makers the value of taking a watershed approach to managing land-based sources of pollution, this paper presented a systematic framework and models to estimate the minimum cost solutions of nutrient reduction in watershed. The established models considered the spatial heterogeneity of emissions sources, emission impact on the receiving waters, and the abatement cost. Empirical estimates in Jiulong River Watershed of China indicated that a 30% reduction of the nitrogen load to the receiving waters can be achieved by abating about 29% of total nitrogen emission and at a cost of RMB 263 million per year. Reduced applications of fertilizers and livestock holdings were the main abatement measures, and the urban sub-basins the main abatement regions due to their high abatement capacity. It was necessary to specify a target water body located in the middle or upstream of the watershed to capture the local damage of excessive nitrogen emission although this will generates a high cost and a high reduction. Sensitivity analysis indicated that for the same absolute values of load reductions, the emission reductions are more robust against changes in the retention and leakage parameters than that of the total cost. Additionally, changing the parameter values for abatement functions will only affect the total cost.