<p>Tailing dams store substantial amounts of chemically soluble contaminants, which increase the risk of leakage from the body and foundation of the dam. The presence of highly concentrated pore fluid contaminants can significantly affect soil hydraulic properties, influencing flow and contaminant transport regimes. Despite existing hydraulic models, none have considered the influence of dissolved salts in flow modeling. Therefore, this study aims to enhance fluid flow predictions in a tailings dam through embedding osmotic-dependent fluid-retention and unsaturated hydraulic conductivity models. The numerical model is based on realistic parameters and the geometry of Sarcheshmeh tailings dam, located in southeastern Iran, downstream of one of the world's largest copper mines. The results for several serviceability scenarios are compared against the conventional two-phase flow model using pure water as permeating fluid. The results reveal that dissolved ions in pore water cause higher contaminant transport rate compared to pure water. For example, contaminant transport rates increase by 17% through the foundation and 30% through the dam due to differences in material properties. The observed increase in transport rate due to higher solute concentration results from enhanced hydraulic conductivity caused by a flocculent structure of salt-amended soils. Additionally, transient conditions like rainfall and evaporation increase contaminant transport due to a more suppressed retention capacity of soil exposed to impure pore fluid. Lastly, embedding a geosynthetic clay liner (GCL) as a barrier at the reservoir floor reduces contaminant transport by 22% compared to the uninsulated condition.</p>