Modeling ionic solute transport in melting snow

A numerical model that includes the effects of mass transfer between mobile and immobile liquid phases, advection, hydrodynamic dispersion, and melt-freeze episodes was developed to simulate ionic solute transport in melting snow. Model calibration using a tracer-infused laboratory snowpack experiment yielded a dispersivity of 0.05 cm and a mobile-immobile phase mass-transfer coefficient of 4 3 10 s, but these parameter values are tentative because of the artificial nature of the experiment. The modeled concentration of meltwater flowing out the bottom of the snowpack was sensitive to residual water saturation, flow rate, dispersivity, mass-transfer rate, and the initial distribution of solute within the pack, similar to experimental observations. The model was applied to a small watershed, and it was found that the ability of the model to accurately simulate solute movement depends on the validity of the assumption of one-dimensional flow and on the accuracy of modeling the snowpack energy balance.