Salt intrusion in multi-channel estuaries: a case study in the Mekong Delta, Vietnam

A. D. Nguyen (1, 2) , H. H. G. Savenije (1, 2)

1 Department of Management and Institutions
2 Department of Water Management

There is a well-tested theory for the computation of salt intrusion in alluvial estuaries that is fully analytical and predictable, in the sense that it has well-tested analytical equations to predict the mixing behaviour of the estuary based on measurable quantities, such as channel topography, river discharge and tidal characteristics. This theory has been described in a range of publications (Savenije, 1986, 1989, 1993) and a recent book (Savenije, 2005). This theory applies to single-channel topographies and estuaries that demonstrate moderate tidal damping. The Mekong delta is a multi-channel estuary where the tide is damped due to a relatively strong river discharge (in the order of 2000m/s), even during the dry season. As a result the Mekong is a strongly riverine estuary. This paper aims to test if the theory can be applied to such a riverine multi-channel estuary, and to see if possible adjustments or generalisations need to be made. The paper presents salt intrusion measurements that were done by moving boat in 2005, to which the salt intrusion model was calibrated. The theory was expanded to cater for tidal damping. Subsequently the model was validated with observations made at fixed locations over the years 1998 and 1999. Finally it was tested whether the Mekong calibration fits the overall predictive equations derived in other estuaries. The test was successful and led to a slight adjustment of the predictive equation to cater for estuaries that experience a sloping bottom.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

A. D. Nguyen, H. H. G. Savenije. Salt intrusion in multi-channel estuaries: a case study in the Mekong Delta, Vietnam. Hydrology and Earth System Sciences Discussions, 2006, 3 (2), pp.499-527. ⟨hal-00298673⟩