Abstract
One of countermeasures of reducing loads from non-point source is the use of water purifi. cation functions of a lagoon. In this study, a water quality model was developed for the lagoon around Lake Biwa in order to estimate its water quality and examine its management to enhance purification efficiency.
This model amsists of two sub models. One of them consists of a tank model and L-Q formula, and it estimates discharge and load flowing into a lagoon. Another sub model consists of a water quantity balance model and an ecosystem model, and it evaluates water quality of the lagoon. In addition, Noda Lagoon is divided into two boxes to estimate water quality, since it is divided into two portions of short-circuit and retention.
The simulation is carried out using this water quality model to control the primary production in the case of extending the operation term of a facility of circular irrigation. As a result of extending an operation term for 20 days, it can be said that the rise of the COD concentration by primary production may be controlled.
