Effects Of Hydrodynamic Condition On The Growth Of Algae At Secondary Tributary In The Three Gorges Reservoir

After the formation of Three Gorges Reservoir(TGR),subject to the influence of flow backward and backwater by the main stream, the hydrological environment conditions have significantly changed at the secondary tributary in the TGR area.The flow velocity slows down, water update cycle becomes longer, disturbance becomes smaller,the capacity of self-purification declines, algae bloom explodes frequently in spring and summer.Therefore hydrodynamic conditions closely relate to the algae bloom. As the characteristic hydrological parameters in secondary tributary of TGR, flow velocity and turbulent dissipation have effects on algal growth. Study these effects on the growth of algae, provide a theoretical basis for the governance of the bloom.Through self-designed velocity annular flume experiment device and turbulent dissipation vertically oscillating grid experiment device, the experiments are carried out to research the effects of the flow velocity and turbulence dissipation on the growth of algae and water environment at the secondary tributary. Based on the collecting data that algae growth-related in the TGR area, researching algae growth under different flow velocity and turbulent dissipation at the secondary tributary in the TGR area with adequate nutrients and temperature.To explore the relationship between impact factors and establish the dominant species growing hydrodynamic growth models related items.Through the simulation experiments and analysis,the following conclusions were shown as following:① Flow velocity(0.00~0.12m/s) can promote algae growth at the secondary tributary in the TGR area. High strength flow velocity(0.12~0.60 m /s) will inhibit the growth of algae at the secondary tributary in the TGR area. Critical flow velocity is in the range of 0.08m/s~0.12m/s.② Smaller turbulent dissipation rate(0.00~0.62m2/s3×10-4) can promote algae at the secondary tributary in the TGR area. High intensity turbulent dissipation(0.62~4.98m2/s3×10-4) will inhibit the growth of algae. Critical turbulent dissipation in the range of 0.08 ~1.62 m2/s3×10-4.③ Influence of hydrodynamic conditions on algae growth is mainly manifested in: the light intensity, the length of the cell and the transport of nutrients.④ Under hydrodynamic conditions in the test, diatoms become the dominant species at the secondary tributary in the TGR area. Green algae become the dominant⑤ Through the grey relational analysis about diatom growth-related impact factor,the result shows that hydrodynamic impact on the growth of diatoms is indirect effects. By changing the interaction that nutrients, dissolved oxygen and p H interaction with the diatom, hydrodynamic impact affect the growth of diatoms.⑥ Establishing diatom growth hydrodynamic model.