Aerating Circulation as Measures for Blue-Green Algae in Dam Reservoirs

In recent years, phytoplankton increases extraordinarily almost every year, caused by eutrophication in dam reservoirs which are managed by Japan Water Agency (JWA). In particular, blue-green algae are causing serious problems including deterioration of landscape, deterioration of drinking water quality due to foul smell and taste, interference of water purification plants and disorder of agricultural water service system. JWA has been carrying out measures to tackle with these problems. As one of measures, JWA installed aerating circulation facilities and is operating them in dam reservoirs to restrain the outbreak of blue-green algae. The effectiveness is observed to a certain degree. This report outlines the mechanism of restraining the blue-green algae growth by aerating circulation facilities, and describes the interim research findings of water quality improvement by showing data of the vertical distribution of water temperature in the reservoirs and downward trend of the cell count in species of algae.