Application of data assimilation method on quantification of pollutant load from watershed in SWAT model
In schemes for nutrient reduction from watershed such as Japanese total volume control framework on nutrient or master plan for sewerage system propagation, pollutant load unit method has been used for quantifying pollutant load from watershed, which means that quantification of pollutant load is deterministic. However, this approach is criticised because pollutant load from pollutant sources is not unique in practice, which causes inaccuracy of nutrient behavior in water body like concenration of nutrient observed at environmental standard points. In addition, water quality which is target of such scheme on nutrient reduction is observed in public water quality observation, only about once a month, which means that there is not so adequate data that representativeness of observation data should be watched carefully. In order to resolve these problems, this study applied EnKF, one of data assimilation method, to SWAT(Soil and Water Assessment Tools) model, which can simulate nutrient cycle in watershed and dealt with pollutant load unit of pollutant sources in watershed as objectives of data assimilation process, and concentration of nutrient in river as observation data.
Dr. Yosuke Horie Nippon Koei Co., Ltd