Analysis of the Mechanism of Musty-odor Occurrence in a Dam Reservoir

Abstract

There have been reports of abnormal odor and taste of water from dams throughout Japan. To investigate this phenomenon, we conducted observations and two-dimensional vertical model simulations at Takisato Dam on the Sorachi River in Takisato Town for three purposes: (1) to examine flow regime, water temperature, water quality components, and behavior of the blue-green algae that cause mustiness; (2) to understand how the odoriferous material 2-methyl-isobomeol (2-MIB) is formed and released; and (3) to propose and evaluate water quality improvement measures. It was shown that stagnation develops where the reservoir widens and where it narrows and curves at the middle. This stagnation causes water temperature increases, which in turn cause blue-green algae proliferation and 2-MIB generation. The simulation indicates that algae proliferation can be controlled by blocking sunlight. Flood-time calculations suggest that floods suppress algae proliferation.