ABSTRACT
Different tracer methods were used to investigate the generation of runoff components in the Loechernbach catchment (1.7 km2) in the Southwest of Germany. This paper describes a tracer experiment in the unsaturated zone, using the artificial tracers uranine and bromide. It was carried out on a crop field, which is drained by an artificial drainage system. The flow through the macro- and micropore systems was evaluated quantitatively by using a non-destructive method.
For a simulated heavy rainstorm the mean residence time of water in the unsaturated zone (depth 1.2 m) was 2.5 hours. Different tracer transport models (deterministic and probabilistic models) were compared. These models take only one flow system in the unsaturated zone into consideration. In a second step, a new method was generated for the simulation of the tracer transport in the unsaturated zone. The method distinguishes between the macro- and micropore system. Very good results were obtained when modeling the flow in the macropores with the Single Fissure Dispersion Model (SFDM) and modeling the flow in the matrix of the soil with the Convection Dispersion Model (CDM). The SFDM was developed to describe the flow through fissures of saturated hard rock aquifers. This inverse validation of the SFDM for the macropore flow in the unsaturated zone shows its further potential.
