Field Observation on Water Quality Changes at Northern Area of Isahaya Flood Regulation Pond

In closed water area, the adequate methods on water quality management are required for the prevention of eutrophication. It is essential to understand the temporal and spatial changes of organic matters and nutrimental ones in water area. In this study, the field observation was carried out to grasp the water quality condition at the northern area of Isahaya flood regulation pond. According to the obtained results, although the vertical variations of observed water quality indices were not large, turbidity and concentration of suspended sollids took large value near the water bottom. Water temperature and concentration of chlorophyll-a had diurnal variation. The attenuation coefficient of light quantum was estimated as 6.0m-1, approximately. Absorption rate of right quantum at water surface was about 50% in this pond