Experimental Study of the Flow Patterns in Capillary Zone

Ali Mahdavi Mazdeh1, Stefan Wohnlich2

P 9.11 in Groundwater-surface water-interactions - processes and methods

Infiltrated solutes from agricultural lands during rainfall or irrigation plays an important role in groundwater and surface water pollution in hydraulically connected groundwater and surface waters. Therefore, the characterization water movement pathways and their effects on solute transport have been studied intensively.  However, the complexity of solute movements within the CF not fully elucidated. Some studies, have reported horizontal movement of flow and solutes within the CF. The small scale glass tank in the laboratory of RUB (1.20 m long, 0.62 m high and 0.150 m wide) were used to investigate the flow movement in the capillary fringe. The tank is filled with a real sample of capillary fringe from the study area (Sand and Tongrube Brüggen, Germany). The experiments have done in steady-state water flow conditions and by injecting the fluorescent dye tracer (Uranin) at different depth the flow patterns in the capillary zone where investigated. The results indicate that capillary fringe can be divided into two moving and statutory zones. In the moving zone, 3 flow pattern was observed. An upward horizontal movement and downward horizontal movement were observed near the inflow and outflow boundaries, respectively. However, the flow pattern in the middle part of the capillary fringe is almost parallel to the groundwater table slope. Regarding experimental results, the velocity increases almost linearly towards the groundwater table. Furthermore, in current experimental condition, 30% of the total flow was passed through the capillary fringe. The results of the study confirmed that capillary fringe can play an important role in the transport of infiltrated solutes from agricultural lands.