Experimental and analytical studies of solute transport during run-off over vegetated surfaces

Solute transport in overland flow is considered as one of the main contributors to water pollution. Although many mechanism models of solute transport from soil to runoff have been proposed, the solute transport mechanism in runoff over vegetated surface still remains unclear. In this study, a series of laboratory experiments were conducted to study the solute transport over vegetated surfaces. Based on the experimental results, the conception of “stationary water layer” in runoff was proposed. Applying the complete mixing layer theory in the stationary water layer, an analytical solute transport model was developed with the assumption that the solute concentration in stationary water layer is equal to that in upper runoff. The results show that the predictions made by the transport model are in good agreement with the measured experimental data. In the vegetated surfaces, the depth of stationary water layer is mostly related to the rainfall intensity, bed slope and vegetation density. The solute transport rate increases from zero to a maximum and then decreases to zero. The analytical solution shows that the maximum solute transport occurs at the time of concentration. This study may advance our understanding of the mechanisms of solute transport in vegetated area, which is particularly useful for the management of water pollution