Abstract
Appearance of blue-green-algae blooms in summer is still one of the serious water quality problems in Sagami Lake, Kanagawa, Japan, although several countermeasures have been implemented to mitigate it. Since the control of water discharge for hydropower generation is now considered as one of the possible measures, we tried to understand the difference in circulation patterns in the lake during both durations of operating and non-operating water discharge. Field data for currents and water temperature were collected in August, 2012. From the results, we found that during the period operating discharge, water flows into the lower layer following the meandering bathymetry. On the other hand, during the non-operation period, though overall currents become weak, adverse currents are observed in the upper layer of the upstream part of the lake.
