Impacts of a capillary barrier on infiltration and subsurface stormflow in layered slope deposits monitored with 3-D ERT and hydrometric measurements
Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models. Hillslopes are the essential interface for water movement in catchments. The shallow subsurface on slopes typically consists of different layers with varying characteristic...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
|
| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/21/5181/2017/hess-21-5181-2017.pdf |
| Summary: | Identifying principles of water movement in the shallow subsurface is crucial for adequate process-based hydrological models.
Hillslopes are the essential interface for water movement in catchments.
The shallow subsurface on slopes typically consists of different layers with varying characteristics.
The aim of this study was to draw conclusions about the infiltration behaviour, to identify water flow
pathways and derive some general interpretations for the validity of the water movement on a hillslope
with periglacial slope deposits (cover beds), where the layers differ in their sedimentological and hydrological properties.
Especially the described varying influence of the basal layer (LB) as an impeding layer on the one hand and as
a remarkable pathway for rapid subsurface stormflow on the other.
We used a time lapse 3-D electrical resistivity tomography (ERT) approach combined with punctual hydrometric data to trace the spreading and the
progression of an irrigation plume in layered slope deposits during two irrigation experiments.
This multi-technical approach enables us to connect the high spatial resolution of the 3-D ERT with the high
temporal resolution of the hydrometric devices.
Infiltration through the uppermost layer was dominated by preferential flow, whereas the water flow in the
deeper layers was mainly matrix flow.
Subsurface stormflow due to impeding characteristic of the underlying layer occurs in form of <q>organic layer
interflow</q> and at the interface to the first basal layer (LB1).
However, the main driving factor for subsurface stormflow is the formation of a capillary barrier at the
interface to the second basal layer (LB2).
The capillary barrier prevents water from entering the deeper layer under unsaturated conditions and diverts
the seepage water according to the slope inclination.
With higher saturation, the capillary barrier breaks down and water reaches the highly conductive deeper layer.
This highlights the importance of the capillary barrier effect for the prevention or activation of different
flow pathways under variable hydrological conditions. |
|---|---|
| ISSN: | 1027-5606 1607-7938 |