Hydrodynamic mechanisms underlying periodic algal blooms in the tributary bay of a subtropical reservoir

• Published in: Ecological engineering Vol. 120; pp. 6 - 13
• Main Authors: Yang, Zhengjian, Xu, Piao, Liu, Defu, Ma, Jun, Ji, Daobin, Cui, Yujie
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2018; Elsevier BV
• Subjects: Algae; Algal blooms; Bays; Canyons; Chlorophyll; Chlorophyll a; Critical depth; Critical Depth Hypothesis; Critical path; Density currents; Density stratification; Eutrophication; Fluid dynamics; Fluid flow; Fluid mechanics; Hydrodynamics; Layered bidirectional density currents; Mineral nutrients; Nutrient transportation; Nutrients; Observational studies; Reservoirs; Stratification; Stratigraphy; Thermal stratification; Three Gorges Reservoir; Tributaries; Water level fluctuations; Water levels; Water velocity; PAR; Critical Depth Hypothesis; ρ; XXB; CDH; Cl; EEFO; Zeu; Three Gorges Reservoir; Csed; LBDCs; Algal blooms; XXR; T; SLIC; BLDC; YR; Z; Chl.a; MLIC; N2; CJ; g; XX00-XX10; Zmix; Layered bidirectional density currents; Thermal stratification; TGD; Si; v; Nutrient transportation; Kd; Na+; TN; BLIC; Inflow; TP; TGR
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2018.05.003

White vector groups represent currents flowing toward the end direction of XXB, and the black vector groups represent currents flowing toward the estuary. [Display omitted] Periodic algal blooms in certain tributary bays of the Three Gorges Reservoir (TGR) have become a serious environmental problem. A three-year observational study of the water velocity, temperature, nutrients and chlorophyll a (Chl.a) in Xiangxi Bay (XXB), a which is tributary of the TGR, was undertaken to identify the mechanisms underlying algal blooms. The results showed that, in the Xiangxi Bay, bottom-layer intrusive current (BLIC) happened in winter, middle-layer intrusive current (MLIC) occurred in spring and summer, and surface-layer intrusive current (SLIC) happened in autumn. The MLIC could cause a extraordinary thermal stratification. In addition, these density currents carried large amounts of nutrients into XXB, thus inducing eutrophication. The Critical Depth Hypothesis (CDH) implied that algal blooms in XXB would occur continuously when the MLIC happened. As the hydrodynamics in the TGR could be affected singnificantly by the change of the water level, water level operations may represent a method to control algal blooms.