Simulation of soil erosion and nutrient impact using an integrated system dynamics model in a watershed in Taiwan

In recent years, erosion, sediment, and nutrient pollution have become issues of major concern in Taiwan. Keelung River, as it flows across the Taipei metropolitan area, is one of the most important rivers with regard to these issues. This research aims to compute and simulate erosion, sediment yield, and resulting nutrient pollution, together with related economic factors. Related physical models were programmed using a system dynamics software package Vensim®, for convenience in scenario designs and simulations. GIS software ArcView® was employed to integrate digitized themes that contain data necessary for further computation and applications. EXCEL® was also used to link ArcView and Vensim and made an interactive computational model. Five submodels, i.e., the soil erosion model, the sediment transportation model, the runoff model, the nutrient model, and the economic model, were included in this integrated model. Through this model, it was estimated that, according to the hydrological and geographical data from last five years, the total annual amounts of soil erosion, sediment yield, and nutrient load are 292,327 tons, 101,661 tons, and 1428 tons, respectively. These results can be compared with those derived from models in other researches. As the model in this research was driven by a system dynamics core, scenario simulations can be carried out based on various combinations of system parameters. This offers the model additional flexibility and applicability.