OVERVIEW

There are different types of salt intrusion, depending on topography, hydrology, and tide. A classification is presented with the related characteristics and conditions for occurrence.

The salt intrusion in alluvial estuaries is generally of the well-mixed or partially mixed type, particularly in the period when it matters: the dry season. This salt intrusion can be adequately described by the one-dimensional dispersion equation. When this equation is combined with equations describing topography and dispersion, it yields a predictive equation that can be used for both unsteady and steady state, particularly for the tidal average situation, high water slack, and low water slack. The influence of rainfall and evaporation on salt intrusion is also taken into account, which sometimes is crucial to understand the salinity distribution. Under extreme circumstances hypersalinity can occur, which is illustrated with case material.