Technical Note: Enhancement of SWAT-REMM to Simulate Reduction of Total Nitrogen with Riparian Buffer

Abstract

In recent years, riparian buffers have become known as one of the most effective best management practices for nonpoint-source pollution. However, establishment of riparian buffer systems with respect to plant species and their position in the buffer zone has not been investigated due to lack of efficient evaluation methods for the analysis of water quality improvement with established riparian buffers. To solve this problem, the SWAT-REMM prototype version was developed by researchers in Canada. In the SWAT-REMM prototype version, many riparian-related input parameters are not directly read from the local input data. Thus, a SWAT-REMM enhancement was developed by improving three major limitations of the prototype version of SWAT-REMM: (1) riparian buffers at designated reaches in the watersheds, (2) riparian buffers using local soil properties at the riparian buffer zone along reaches, and (3) multiple weather stations in a larger-scale watershed. The enhanced SWAT-REMM version was applied to the Bonggok watershed in Korea. This study investigated riparian buffers with different widths (10 m, 5 m, and 1 m) along the slope. Total nitrogen reduction ranged from 14.8% to 54.0% in each catchment for 10 m widths. Total nitrogen reduction ranged from 6.9% to 31.6% in each catchment for 1 m widths. The reduction efficiency was not simply proportional to the width of buffers. This study evaluated the enhanced SWAT-REMM simulation of water quality improvement. Based on this research, the enhanced SWAT-REMM can be used to evaluate water quality improvement by riparian buffers at various watersheds worldwide using local data. In particular, simulation of riparian buffers at user-designated reaches in a watershed enables simulation of riparian buffers in watersheds experiencing frequent flooding where no riparian buffers can be established. It is expected that the enhanced SWAT-REMM can be used to determine economical and environmentally optimum riparian buffer scenarios.