Abstract
Water repellent soils show a complex flow and transport mechanism. Knowledge of the underlying principles is essential for instance to simulate soil and water erosion, water availability for crops and leaching potentials of agrichemicals. The present study aimed to investigate water flow and solute transport processes in a water repellent sandy soil and to introduce and apply a new modeling approach that can be applied for ordinary field conditions. Automated TDR measurements revealed that preferential pathways develop rapidly during severe rainstorms, causing infiltrating water to be preferentially transported to the deeper subsoil. These preferred pathways recurred at the same sites during all rain events. The cross-sectional area can be related to the soil water flux. The process of preferential flow and transport has been incorporated in the well-known SWAP model, and will be compared to traditional preferential flow approaches as the mobile/immobile concept. Flow concept and model structure of the adapted SWAP will be outlined. The improved SWAP model is capable to dynamically switch from uniform to preferential flow conditions and vice versa, in case soils become hydrophobic or hydrophillic, respectively. Field observations of tracer transport at a water repellent sandy soil in the Netherlands clearly show the occurrence of preferential pathways. Observed bromide profiles will be compared with simulated results obtained with the conventional and the adapted SWAP model. The model adaptation allows to investigate the sensitivity of the water and solute balance towards water repellency under all kind of weather, crop, soil and drainage conditions. Preliminary results regarding the implications for ordinary vadose zone flow and transport simulation will be discussed
| Original language | English |
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| Title of host publication | Water and organic matter in anthropogenic soils: dynamics and processes, Berlin, Germany, 2-4 April 2003 |
| Pages | 35 |
| Publication status | Published - 2003 |