In this study we investigate numerical simulations of one-dimensional water flow and solute transport in a soil with a nonuniform pore-size distribution. Water transport was modeled by treating the soil as one domain by applying Richards equation, while using alternatively a unimodal and a bimodal model for the hydraulic properties. The retention curves were fitted to a set of measured data; the relative conductivity functions were estimated by Mualem's <1976> model. Contrary to the unimodal case, the bimodal conductivity curve shows a steep decrease in water content &thgr; near saturation. Simulated water regimes under transient boundary conditions differed strongly for the two cases. The use of the bimodal functions yielded a preferential flow characteristic which was not obtained using unimodal functions. For both hydraulic regimes we modeled solute transport comparing four different variants of the convection-dispersion equation. For the classical one-region model we found that the breakthrough curve of an ideal tracer was not affected by the dynamics of the water flow. For the two-region approach, where the water-filled pore domain is divided into a mobile region &thgr;m and an immobile region &thgr;im, three different conceptual treatments of &thgr;m under transient conditions were investigated. For the case where &thgr;im was kept constant, the different hydraulic regimes again caused only minor differences in solute transport. The same was true for the alternative case where the ratio &thgr;m/&thgr; was kept constant. However, for the third case, where &thgr;m was treated as a dynamic variable which changes with the actual water content in a way that depends on the shape of the hydraulic conductivity function, the transport simulation based on the bimodal hydraulic model reflected enhanced preferential transport at high-infiltration rates. ¿ American Geophysical Union 1996