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A Modelling Study of Water Age in a Tide-Dominated Estuary

Author(s): Yuheng Ren; Binliang Lin; Jian Sun

Linked Author(s): Binliang Lin

Keywords: No Keywords

Abstract: The main aim of this study was to determine the age of water (AW) in a tide-dominated large estuary, i. e. the Pearl River Estuary (PRE), China, using a passive conservative tracer as a surrogate. With multiple river discharges, four in the east side and four in the west side of the estuary, the seasonal variation of flow current is significant. Based on the age concentration method developed by Delhez et al. (1999), the AW distribution of the whole PRE estuary was predicted by considering tracer released from the eight tributaries. The AW distribution due to tracer release from each tributary was also predicted. The influences of the freshwater inflow rate, salinity stratification and variations of tide at the offshore on AW have been investigated. It has been shown that these factors play an important role in the transport mechanism for the pollutant. The model predictions indicated that an increase in river discharges resulted in larger residual currents, especially in the middle deep channel, which caused a decrease of AW in the whole area and an increase in gravitational circulation. The tracer discharged into the PRE was transported out more quickly. The gravitational circulation enhanced the salinity stratification and thus raised the AW difference between the surface and bottom layers in the inner estuary. However, it caused a decrease in the AW difference between the upper and lower parts of the estuary. When constant mean river discharges were applied, the results showed a seasonal variability of the AW, which could be attributed to the variations of tide at the offshore region.


Year: 2012

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