A NEW TECHNIQUE FOR CONTROLLING ALGAL BLOOMS IN THE WITHDRAWAL ZONE OF RESERVOIRS USING VERTICAL CURTAINS

Terauchi Dam Reservoir in Kyushu, Japan has supplied water for paddy f ield irrigation and domestic consumption. During recent years it has s hown serious deterioration of water quality, especially in summer, The rmocline destruction is prohibited to maintain desirable temperature d ownstream of the reservoir for paddy field irrigation; thus, most of t he existing control devices cannot be applied to the reservoir. Algal blooms in the reservoir, two vertical curtains, having depths to cover the epilimnion thickness, were installed across the reservoir to curt ail the nutrient supply from the nutrient-rich inflow to the downstrea m epilimnion of the reservoir. Withdrawal level was also regulated to keep the downstream epilimnion off the nutrient supply. The results of this study illustrate the consequences of curtains on algal blooms in the reservoir. This method can mostly be applied for a reservoir or l ake having an elongated shape.