2007 Volume 51 Pages 1219-1224
The maintenance flow discharge of the Ohyama River (upper Chikugo River) had been restricted to 1.5m3/s by a hydroelectric dam. To improve the river environment, the river administrator has changed it to 4.5m3/s in summer and to 1.8m3/s in winter. In this study, we aim at investigating the effects of discharge increase on epilithic biofilms composed of algae. We conducted sampling of attached algae every two weeks from March to July, 2006, at an impact reach increasing the disharge, at a control reach maintained a constant discharge, and at two reference reaches in upstream of the hydroelectric dam. Results of the field surveys show that chlorophyll-a at the impact reach is higher than one at the control reach. However, in case of controling flood disturbance by a dam, there is no difference in chlorophyll-a between the impact reach and the control reach, because attached algae is regulated by heterotrophic process.
