Seven stations were selected as shown in Fig. 1 to investigate the whole area of the River Akagawa. Station 1 is located in the most upstream area and is surrounded with natural large rocks whose color is brown with iron. Station 2 receives the effluent from the mine drainage treatment plant. The areas from St. 3 to St. 7 receive several tributaries and are surrounded with green and agricultural spaces and private houses, although no surface water in the River Akagawa is irrigated to the agricultural lands.