Abstract
In order to preserve water environment of lakes and lagoons, sustainable management of water cycle and elucidation of water quality formation are needed. In this study, we made a tank model for water quality estimation of lakes. This model consists of complex tank model that adopting the coefficients of concentration and simple lake model using retention time, and identified water quality of Toyano Lagoo in Kamedagou basin. We took into consideration about the influence of water management of agricultural use. We simulated effects on a water quality of the lagoon by this model for 2 cases. First, increase of delusion water to the lagoon is effective to decrease COD value in April. Second, decrease of irrigation water by decrease of paddy field area will cause use of COD value in mid-summer drainage season In case of lake in urbanizing watershed that has paddy field, this model can predict effects on water quality changes.
