Two-dimensional assessment of solute transport in shallow waters with thermal imaging and heated water

The two-dimensional distribution of flow velocities in shallow waters is one of the governing factors for solute transport processes. Thus, a direct and simple experimental method to spatially assess mean flow velocity and dispersion could improve the prediction of solute transport. In an experimentally constructed wetland we identified these variables on the basis of highly resolved spatial datasets obtained by a novel tracer approach: we observed slug injections of heated water with hand-held thermographic systems. Adding NaCl to the heated water reduced density differences between the heated and natural water. Determined flow velocities and dispersion changed according to the variation of the wetland shape. The introduced method allows to easily determining basic flow characteristics and when applied to other wetlands or shallow surface waters with complex structures, it may be the first step for a better process understanding.