On the errors associated with two-dimensional stochastic solute transport models

Many subsurface solute transport studies employ numerical modeling techniqu es to estimate solute arrival times. Simplifying assumptions must be made t o define the modeling domain within a mathematical framework. One common as sumption is that the vertical flow is negligible such that the flow field c an be simulated with a two-dimensional model. Reducing the vertical dimensi on reduces the number of flow paths that a solute can take. In a heterogeno us medium, artificially removing the 3rd dimension may lead to erroneous re sults. We investigate the error in the simulated solute breakthrough associ ated with a two-dimensional model. We also use a stochastic solution of sol ute arrival time to derive a transform of a two-dimensional ln (k) field so that solute transport more closely resembles three-dimensional transport b ehavior. The moment equations for two- and three-dimensional domains were s olved simultaneously to calculate this transform. The results indicate that the removal of the vertical variability (3D --> 2D) introduces a 5-10% err or in the predicted solute breakthrough. The error tends to increase with i ncreased hydraulic conductivity variance. Numerical experiments confirm tha t the transform developed herein decreases the relative error of particle b reakthrough curves.