The effect of salinity-dependent hydraulic conductivity on saltwater intrusion episodes

The ionic strength of percolating water can greatly alter a soil's hydraulic conductivity. This appears to be the result of dispersion and/or swelling of clay particles, and can alter hydraulic conductivity by several orders of magnitude. In this paper, the potential effects of salinity-dependent changes in hydraulic conductivity during saltwater intrusions are analyzed. Results are presented to show that this can increase the degree to which brackish water will penetrate a coastal aquifer. This can also increase the width of the dispersed salt front, and can lead to a much greater circulation of saltwater within the intruding saltwater toe. These results may help to explain field observations that have previously been attributed to “scale-dependent” dispersivity and domain heterogeneity.