The Inohana Lake is a branch lake of the Hamana Lake. The Inohana Lake is an estuary rather than a brackish lake, and has suffered environmental problems such as eutrophication and bottom hypoxic water. In this study,...The Inohana Lake is a branch lake of the Hamana Lake. The Inohana Lake is an estuary rather than a brackish lake, and has suffered environmental problems such as eutrophication and bottom hypoxic water. In this study, the coupled hydrodynamic and ecological models （eco-hydrodynamic model） were used to construct the strategy for preventing the bottom hypoxic water and improving or recovering the water quality in the lake. Using the model input obtained from the summertime data over 1998-2002, the summer-average flow field and oxygen concentration and budget of the standard run were calculated. Remedial measures used in this study are divided into two parts： the biogeochemical and physical changes in the present situation. For the remedial measures including the biogeochemical changes in the present situation, the simulations considering the reductions of the nutrient inputs from the river, main lake （land） and bottom sediment, and the sediment oxygen demand （SOD） were carried out. For the remedial measures including the physical changes, the 50 and 100 m extensions of the inlet width were considered in the model runs. These simulated results were compared in terms of changes in the dissolved oxygen （DO） concentration and oxygen budget in the bottom layer in the Inohana Lake. There was no significant change in the DO concentration and oxygen stock in the simulations for the reduction of the nutrient inputs from the land and bottom sediment, however increases in those in the simulations for the reduction of SOD. When SOD was reduced by 50%, the bottom DO concentration increased by approximately 2 mg/L and the oxygen stock in the bottom layer increased by 47% comparing the present situation （the standard run） of the lake. The simulation results for inlet width extension showed that the extension of width makes the DO concentration and oxygen stock lower. The remedial measures for the sediment control were proposed to prevent the bottom hypoxia and manage the water quality.展开更多
文摘The Inohana Lake is a branch lake of the Hamana Lake. The Inohana Lake is an estuary rather than a brackish lake, and has suffered environmental problems such as eutrophication and bottom hypoxic water. In this study, the coupled hydrodynamic and ecological models （eco-hydrodynamic model） were used to construct the strategy for preventing the bottom hypoxic water and improving or recovering the water quality in the lake. Using the model input obtained from the summertime data over 1998-2002, the summer-average flow field and oxygen concentration and budget of the standard run were calculated. Remedial measures used in this study are divided into two parts： the biogeochemical and physical changes in the present situation. For the remedial measures including the biogeochemical changes in the present situation, the simulations considering the reductions of the nutrient inputs from the river, main lake （land） and bottom sediment, and the sediment oxygen demand （SOD） were carried out. For the remedial measures including the physical changes, the 50 and 100 m extensions of the inlet width were considered in the model runs. These simulated results were compared in terms of changes in the dissolved oxygen （DO） concentration and oxygen budget in the bottom layer in the Inohana Lake. There was no significant change in the DO concentration and oxygen stock in the simulations for the reduction of the nutrient inputs from the land and bottom sediment, however increases in those in the simulations for the reduction of SOD. When SOD was reduced by 50%, the bottom DO concentration increased by approximately 2 mg/L and the oxygen stock in the bottom layer increased by 47% comparing the present situation （the standard run） of the lake. The simulation results for inlet width extension showed that the extension of width makes the DO concentration and oxygen stock lower. The remedial measures for the sediment control were proposed to prevent the bottom hypoxia and manage the water quality.
