Journal of Environmental Conservation Engineering

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To ensure dam capacity, DASHIDAIRA dam at KUROBE river in TOYAMA prefecture is equipped with two flushing gates. Sediment in DASHIDAIRA dam lake should be flushed out thorough these gates at appropriate intervals. In the past sediment flushing from the dam had caused serious problems for many industries of the area, such as agriculture and fishery, because of anaerobic sediment from DASHIDAIRA dam lake. The purposes of this study are to evaluate the temperature dependency of anaerobic decomposition of the sediment and to recommend a policy of the flushing timing and interval. Column and batch experiments were conducted with the sediment taken at the DASHIDAIRA dam lake. From the column experiments, the anaerobic decomposition rate at 15°C was found to be one quarter of that at 25°C. From the batch experiments at 25°C, the induction period for the initiation of anaerobic decomposition was found to be 30 days. These experimental results show that the flushing should be conducted every year before increment (the increase) of the lake water temperature during the summer season.

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