The researchers studied water quality in the Han River basin in South Korea by looking at how different landscape features affect it. They found that water quality varies depending on where you are in the basin, with higher pollution levels in urban areas and lower levels in forested areas. They also discovered that nitrogen levels are higher in winter, while suspended solids are higher in summer. By using spatial models, they were able to better understand how different factors influence water quality in the river. Overall, considering the spatial aspects of sampling sites is crucial for accurately modeling water quality in the Han River basin.