MODELING IONIC SOLUTE TRANSPORT IN MELTING SNOW

A numerical model that includes the effects of mass transfer between m obile and immobile liquid phases, advection, hydrodynamic dispersion, and melt-freeze episodes was developed to simulate ionic solute transp ort in melting snow. Model calibration using a tracer-infused laborato ry snowpack experiment yielded a dispersivity of 0.05 cm and a mobile- immobile phase mass-transfer coefficient of 4 x 10(-6) s(-1), but thes e parameter values are tentative because of the artificial nature of t he experiment. The modeled concentration of meltwater flowing out the bottom of the snowpack was sensitive to residual water saturation, flo w 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 abil ity of the model to accurately simulate solute movement depends on the validity of the assumption of one-dimensional flow and on the accurac y of modeling the snowpack energy balance.