Impacts of water level rise on algal bloom prevention in the tributary of Three Gorges Reservoir, China

• Published in: Ecological engineering Vol. 98; pp. 70 - 81
• Main Authors: Ji, Daobin, Wells, Scott A., Yang, Zhengjian, Liu, Defu, Huang, Yuling, Ma, Jun, Berger, Chris J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2017; Elsevier BV
• Subjects: Algae; Algal bloom; Algal blooms; Brunt-vaisala frequency; Buoyancy; Canyons; CE-QUAL-W2; Duration; Eddy viscosity; Eutrophication; Flow velocity; Fluid dynamics; Hydrodynamics; Inflow; Intrusion; Mixed layer; Mixed layer depth; Overflow; Prevention; Reservoirs; Sea level; Thermal structure; Three Gorges Reservoir; Tributaries; Turbulence; Underflow; Viscosity; Vortices; Water circulation; Water circulation patterns; Water depth; Water inflow; Water level fluctuations; Water level rise; Water levels; China, People's Rep., Sichuan Prov., Changjiang R., Three Gorges Dam; China, People's Rep; Algal bloom; Water circulation patterns; Water level rise; CE-QUAL-W2; Three Gorges Reservoir
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2016.10.019

Water level fluctuation plays an important role in algal blooms within the side arms. Field observations of the impacts of fluctuations of water level in Xiangxi Bay (XXB), one of the tributaries of the TGR, were analyzed from 2008 to 2010. Water level rise can result in increases as well as decreases in Chl. a, which depends on the water circulation patterns in the XXB. Those effective/ineffective water circulation patterns in preventing algal blooms in the XXB were based on the tributary inflow but also from the intrusion flow from the TGR. Flow velocity, thermal structure, hydrodynamic characteristics including water age, the turbulent eddy viscosity, the buoyancy frequency, the mixing depth, and the ratio of the euphotic depth and the mixed layer depth were evaluated for these scenarios. It is showed that the effective water circulation patterns in the XXB occurred when there was a converging of the inflow from the upstream with an intrusive overflow, lower-interflow, underflow or the combination from the TGR mainstream. Larger daily WL fluctuation and a longer duration of WL rise would enhance algal bloom prevention in the XXB. These results can provide assistance in managing the operation of water levels in TGR.