Assessing the Effects of Land Use Changes on Non-Point Source Pollution Reduction for the Three Gorges Watershed Using the SWAT Model

Abstract

This study presents a new attempt of applying the hydrological model SWAT to the Three Gorges watershed in China for addressing its non-point source (NPS) pollution control issues. The model was calibrated and validated using the monitoring data collected during 2002-2008, and satisfactory values of R^2 and ENS (Nash-Suttclife Efficiency) were obtained. The calibrated SWAT model was then used to simulate 6 different land use scenarios for investigating the effects of each scenario on the non-point source (NPS) pollution control in the watershed. Six scenarios were designed with distinct land use focuses and include five newly-designed scenarios (Q1-Q5) representing 5 different land use alternatives and a baseline scenario (Q6) representing the land use pattern the watershed had in 2005. It was identified that the farmland is the dominant contributor to the NPS pollution in the watershed in terms of yields of sediment, TN and TP. If the farmland is changed to the woodland, grassland or shrubland, a better control and reduction over the NPS pollution could be achieved. This study provides a good understanding of the interactions between different land use patterns and the NPS pollution control for decision-makers to make sound decisions. Changing the land use pattern and implementing alternative management practices could help reduce the non-point source pollution effectively and thus play a significant role in improving reservoir water quality of the watershed.

Keywords: land use, management, non-point source, SWAT, Three Gorges watershed