EXAMINATION OF RELATIONSHIPS BETWEEN THE INCREASE RATE OF RIVER WATER TEMPERATURE AND WATERSHED CHARACTERISTICS IN THE FIRST-CLASS RIVERS IN THE CHUGOKU DISTRICT

Abstract

 It is expected that not only air temperature but also watershed characteristics could affect the river water temperature increase rate. In this study, we examined the relationships between the river water temperature and watershed characteristics in the 10 first-class rivers in the Chugoku District and calculated the increase rate of the water temperature relative to the air temperature increase. We also examined how land use ratio in the watersheds could affect the river temperature increase rate in the study sites. Our results indicated that the river water increase rate could significantly increase as farmland and paddy filed ratios and building ratio increased and forest ratio decreased in our study system. These results suggest that the land development could strongly affect the river water increase rate in the study region.