|M.Sc Student||Reut Glassman|
|Subject||Investigation of the Relationship between Soil Heterogeneity|
and Flow Processes in the Vadose Zone
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Furman Alex|
|Full Professor Noam Veisbrod|
Flow processes occurring near the surface in the unsaturated zone, have great importance for agriculture and the environment. This research focuses on understanding the physical heterogeneity of the subsurface soil and the relationships between soil heterogeneity and flow processes in the unsaturated (vadose) zone.
For this purpose, we placed various sensors in a two-dimensional soil section in an orchard in the southern Carmel coastal area, Israel. By collecting data in high temporal and spatial resolution over one year, and analyzing soil samples in the laboratory, we tried to learn about the nature of the flow in the soil and its hydraulic properties. Simultaneously we built models that simulate the flow of water. The characteristics of the flow were examined and we tried to find an effective way to characterize the flow system in the vadose zone.
The results indicated that mostly wetting fronts did not move downwards uniformly, and in most cases the flow was in specific paths (preferential flow paths). The flow near major tree roots often differed from the flow in areas without roots, and a clear difference in flow was observed between the near-surface (upper few cm) and deeper areas. We found that preferential flow paths were similar in various flow regimes, including high (soil flooding) and moderate (gentle sprinkling) flow rates. The results of the models have shown that it is possible to describe the water flow in the soil by dividing it to three distinct sub-regions. It is important to refer to the soil as heterogeneous due to the existence of roots.
In summary, the clear difference in the nature of the water flow near the roots, as compared to surrounding areas, emphasizes the need to consider this sub-region as a separate flow region and to hydraulically treat the root zone differently than deeper parts of the vadose zone.