Abstract
The model of water quality and hydrology of the Ito-numa oxbow lake is proposed by integrating Tank Model of runoff, denitrification and snow melting . Nitrogen flows into the oxbow lake was simulated. The following results were obtained. Inflow of water during irrigation period account for 80% of total amount, but inflow of nitrogen load account for only 30% of annual loading, And 50% of the total amount of nitrogen load flows into the lake during snow melting period. In addition, it's expected that landuse exchange from paddy field to upland field causes eutrophication of the oxbow lake.
