Prediction of Nitrogenous Pollutant Runoff due to Rainfall from the Watershed

Sea-dyke is sometimes constructed, so one part of bay has been enclosed. This kind of situation is also observed at Isahaya of Nagasaki in Japan, that is a big project of construction of sea-dyke and reclamation, In order to make clean the enclosed water bodies, it becomes necessary to reduce the untreated pollutant runoff from the watershed as well as to remove the pollutants loaded in the receiving water or to suppress their desorption. Among all, it cannot be avoided to exactly predict and treat the pollutants from the non-point sources, attaining the desirable water environment. In this paper, pollutant runoff mechanism from the non-point sources has been investigated through a field observation. At the same time, a method of exactly predicting the pollutant runoff rates has been discussed for establishing the effective water management.