Analysis of the DO Distribution and the Influencing Factors at the Downstream of Large Dam

Abstract

During the discharge of high dam, strong collision occurred along with the energy dissipation of the high velocity aerated flow. A great deal of air incorporated into the water and formed bubbles for the water was tumbling and gyration tempestuously. A large amount of air was released from the bubbles under the action of the hydrostatic pressure, and dissolved in the water, as a result, total dissolved gas (TDG) supersaturation was caused in the water. However, the supersaturation of the TDG has some important adverse effects on the surivival and reproduction of the aquatic, eapecially the fish. This paper analysised the longitudinal distribution and vertical distribution of the total dissolved oxygen (DO) saturation and the possible causing factors through using the measured data on the discharge in the Three - Gorge cascade hydropower station, combine with the theory of the water TDG supersaturation caused by the outflow from dam. The result shows that, the construction and operation of the cascade hydropower station can lead to the higher concentration of the total dissolved oxygen in the water,and even the supersaturation. Besides, total oxygen saturation decresde with the increasing of the water depth. Furthermore, the water level in front of the dam and the energy dissipating mode have some important effect on the total dissolved oxygen supersaturation.