Abstract: The construction of a river-type reservoir will normally cause a change of hydrodynamic condition and a decrease of flow velocity in branch bays, leading to the formation of algae bloom when appropriate environmental conditions and sufficient nutrient supply are encountered, and thereby, causing the deterioration of fluvial ecosystem therein. To investigate the effects of hydrodynamic conditions on algae bloom, flow velocity was taken as the characteristic parameter, and controlled differently in the closed and recurrent models under identical environmental and nutrient conditions. The results showed that the increase of the flow velocity in a range of <0.4 m·s^-1 would accelerate the growth of algae and the occurrence of bloom. Under the conditions of different flow velocity, the growth of algae was similar to the common process of other microorganisms, namely, lag phase firstly,exponential phase secondly, stationary phase thirdly, and decline phase lastly. Accordingly, the outbreak peak and regression floor of the algae bloom would occur. Therefore, the increase of flow velocity in a range of <0.4 m·s^-1 would not inhibit the growth of algae and the occurrence of bloom. The effective characteristic parameter of the hydrodynamic conditions would be studied in depth in future.

Key words: polyacrylamide (PAM), compost, urban green soil, biochar, pollution reduction, soil permeability improvement