RELATIONSHIP BETWEEN RIVER BASIN CONDITIONS AND HYDRAULIC PARAMERERS AND WATER QUALITY COMPONENTS IN A RIVER IN A COLD, SNOWY REGION

Almost half of Japan is classified as cold and snowy in winter, and snowfall is thought to greatly affect the dynamics of water runoff and water quality. Although many researchers have clarified the relationships between such dynamics and physical conditions of a specific river basin, few studies have clarified the dynamics of water runoff and water quality and the physical conditions that basins in cold, snowy regions share with each other. This study uses quantification theory I and a multiple regression analysis to analyze the relationship between basin conditions (e.g., vegetation, geology, winter precipitation, as a share of annual precipitation) and water runoff, and that between basin conditions and water quality. The focus of this study is Hokkaido, typifies which one of the cold, snowy regions of Japan, where snowfall accounts for nearly 20 to 40% of annual precipitation. The results show that the relationship between basin conditions and water runoff is consistent with past studies, and that snow accumulation contributes to flow regime stability to some extent. The relationship between basin conditions and water quality also shows that basin geology influences most of the water quality categories examined