Abstract
We have been studying runoff by applying a water quality tank model. Runoff water quality has been surveyed at a agricultural watershed for seven years. In this research, we propose the necessity to consider transformation within the runoff process, accumulation in the soil, denitrification in a paddy field, and the land use patterns of a watershed concerning nitrogen runoff. We made a water quality tank model which included all these items, and we compared the simulated results with observed data. The results established that it satisfied two of the values between calculated and observed which did not coincide well. Therefore, this model verified that we can efficiently use it to predict nitrogen runoff loads from a watershed. Moreover, we show that nitrogen runoff loads can be calculated from rainfall data and fertilizer amounts with this model. Hence, it is verified that this newly developed model can be used efficiently as an essential tool to manage the water quality at various watershed levels.
