Fig. 7. Spatial correlations of (a) concentrations, _CC, and (b) stream tube velocities, _vsvs, in the direction perpendicular to the mean flow direction in a layered soil profile (see Fig. 6). Symbols refer to correlations derived from numerical simulations and lines from first-order predictions. Correlations of concentrations were derived at 30 cm below the injection (top layer; solid circles, dashed lines) and at 70 cm below the injection (bottom layer; open circles, solid lines) when the center of mass of the plume is at the boundary of the two layers. Correlations of stream tube velocities were derived at the 40-cm depth (top layer; solid circles, dashed lines) and at the 80-cm depth (bottom layer; open circles, solid lines).