The Dynamics of Dissolved Organic Carbon Concentration at the Mountainous River in Japan

Dissolved Organic Carbon, DOC, is the role in providing the energy for organisms supporting the base of the ecosystem in the mountainous river. Estimating the accurate annual flux of DOC due to clarify the impact of the ecosystem needs to apply the physical-based model that reflects the hydrological processes and DOC source. In our research, we reveal factors controlled DOC concentration in the mountain river as the first step of building the DOC model. The investigation was carried out at Miuchi experimental catchment in Aichi, Japan where the needle forest was planted 30 years ago. The water depth to calculate the discharge was measured every 10 minutes continuously, and river water was collected once a day automatically. The investigation was conducted from 1st of May in 2015 to 30th of April in 2016. The average DOC concentration is 0.8 (mg/L) and the maximum recorded 3.0 (mg/L). The increasing DOC concentrations were observed in the rain event when the rain caused the increasing discharge. And DOC concentrations decreased with the decreasing discharge on a rainy day. The flow pass, especially surface flow overflows the DOC source adjacent to the main river, caused by the precipitation would be one of the factors to change the DOC concentrations in a rainy day. These considerations that the hydrological process during a rainy day and DOC amount in the source are the keys to the physical process of the formation of DOC in the mountain river.