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Salinity Transport Mechanisms in a Small Multi-Channel Estuary

Author(s): Mohammad Soltaniasl; Kiyosi Kwanisi; Mahdi Razaz

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Keywords: Salt intrusion; Discharge measurement; FATS; Flushing time; Salt decomposition; Salt fluxes

Abstract: The salt transport mechanism in an estuary is strongly controlled by the advection and dispersive components. In the present study, the long-term salinity and discharge variations in a multi-channel estuary are investigated using the results of an innovative measuring system which is called Fluvial Acoustic Tomography System (FATS). For this purpose, the flushing time of the estuary was estimated based on the freshwater fraction method which is applicable for effective estimations of estuarine flushing time in response to freshwater inputs. The largest and lowest flushing time occurred during the September and July 2009, respectively. However the average flushing time was estimated about 1.8 days under mean flow conditions. Also, the salt fluxes were calculated based on the cross-sectional averaged salinity and velocity into relative physical processes. The magnitude of salinity varied over the spring-neap cycles, with maximum values during the neap tides and minimum values during the spring tides. The comparing of flushing time and salt fluxes variations in the estuary indicated, during the highest level of the flushing time in the estuary, balance of the advection and dispersive fluxes directed landward. It seems, the correlation between these components significantly influence the flushing time fluctuations. To quantify the main forcing on the salt mechanisms a multiple regression was employed. The results showed the freshwater discharge and tidal range fluctuations significantly moderate salt transportation mechanisms during different time scales. But the mean sea level variation was important on seasonal variations of the salt fluxes.


Year: 2012

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