Session3: Environmental Hydraulics
Title: Water Environment Improvement in an Organically Polluted Closed Water Body by Artificial Water Surface Cooling
Masayoshi Harada, Kosuke Hayami, Kazuaki Hiramatsu and Toshinori Tabata
This study focused on water-surface cooling and cool-water-mass downwelling processes to restore the aquatic environment in an organically polluted reservoir. This study was aimed at acquiring fundamental knowledge concerning the improvement of the aquatic environment using two experimental scenarios. First, we measured the impacts of cold-water supply on the physical and biochemical dynamics of water quality in the thermally stratified water column; algae growth was suppressed through limited photosynthesis induced by a low water temperature and poor oxygenation at the lowest depth with high nutrients. Second, the effectiveness of the proposed technique to improve the actual reservoir was estimated via scenario analyses using a vertical onedimensional water-quality-dynamics model that considered thermal convection stemming from water-surface cooling, resulting in the suppression of both algae overgrowth in the hypolimnion as well as long-term anoxification of the epilimnion. The findings of this study indicate that artificial water-surface cooling for conservation and restoration in an organically polluted closed water body was effective.