Residual Fluxes in a Cross-section of the Valdivia River Estuary, Chile

The circulation dynamics, the transport of suspended sediment and salt as well as the residual flow of water, salt and particulated matter in suspension during a tidal cycle in the mouth of the Valdivia River Estuary, southern coast of Chile, are analysed. Results show a marked saline and thermic stratification during the low tide with differences of up to 20%, and 7 °C between surface and bottom. Maximum speed of the currents was 0•9 m s-1 on the ebb direction. Concentrations of inorganic suspended and combustible matter (organic carbon) were variable with maxima of up to 7 and 15 mg l-1, respectively. Residual transport computations show that Stokes drift and tidal pumping are important features in the net inward transport of water, salt and suspended matter. In the cases of salt and organic seston, it cannot be compensated by the Lagrangian transport through the section. Also the results confirm the fact that the behaviour of the Valdivia Estuary is of the partially mixed type. Previously, this had been deduced from longitudinal profiles of salinity and temperature.