NUTRIENT RUNOFF IN THE KAMAFUSA CATCHMENT

Abstract

In the Kamafusa Lake catchment, we measured water discharge and water samples once a month at twelve points and once an hour at one point. The samples were analyzed for total-phosphrus, souble-P, total-N, nitrate-nitrogen, and ammonium-nitrogen. In a flood, the increasin g of total-N is similar to water discharge, and the increasing of total-P is earlier than the increasing of water discharge. Inorganic nitrogen is almost covered with nitrate-nitrogen in this catchment. The upper-course in forest, nitrogen runoff is larger but middle-course is smaller, and downstream is large. The reason is why upper-course covered with forest land, in middle-course has smaller forest is decreasing, and downstream has urban field usually. Nitrogen flow out from urban area in this area. On the other hand, Nitrogen flow out from urban area, barron land and paddy field in flood period.