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| Titel |
Effect of sediments generated by rill erosion on soil hydrology at small spatial scale |
| VerfasserIn |
R. Giménez, J. Casalí, J. Díez |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024474
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| Zusammenfassung |
| After formation, a rill may remain in the field for weeks or months contributing to a
large percentage of the sediment production downstream. Recent findings show
that the rill flow transport capacity of soil clods can be much different from that in
overland flow depending on the prevailing discharges. It is then hypothesized that
within the sedimentation area of a rill network, rill erosion is able to generate a
layer of sediments whose granulometric characteristic should be different than that
produced by interill erosion (i.e., by overland flow). To what extent these granulometric
differences also lead to local disparities in the hydrological behaviour of the soil (e.g.,
infiltration rate), is uncertain. The aim of this work is (i) to determine the incidence
of the sediments generated by rill erosion on the hydrological properties of the
sedimentation area, and (ii) to evaluate the granulometric characteristic of these
sediments.
In a region strongly affected by rill erosion, a 25 m x 15 m plot containing
well-defined eroded and sedimentation areas was selected to carry out experiments. Rills
were obliterated by tillage and the plot was then protected by a fence during ca.
one year until a noticeable rill network was again clearly developed within the
experimental site. Detailed topographic surveys were made at different stages of rill system
formation using a robotic-surveying, no-prism total station. In addition, rainfall and
soil moisture content at different depths were monitored using a pluviograph and
TDR probes, respectively. Four contrasting treatments were defined within the rill
network: (i) A the top of the plot only affected by splash erosion; (ii) in the eroding
area affected mainly by interrill erosion, (iii) in the sedimentation area of rills, and
(iv) in the same location of (i) but removing the soil crust. In each of these sites,
in-situ hydraulic conductivities, K, made at several tension, (Φ = 2, 5, 12 17 cm of
water) were determined using a disk infiltrometer. In addition, soil samples for
granulometric and sediment size analysis were also taken at the depths of 0-1, 0-5 and 0-10
cm.
For all the experimental treatments and for Φ >12 cm, K values converge to a steady
value of ca. 0.08 mm/h. Instead, from Φ 10 mm) soil clods, while only 25% of
those clods are present in the soil mass of treatments (ii) and (iii). Therefore, the
minimal infiltration rate under the sediments from rill erosion is mainly a matter of
continuity of soil porosity rather than a limiting amount of macro aggregates in the soil
material.
Rill erosion and deposition processes can dramatically affect the hydrological behaviour
of soils due to the local granulometric characteristics of the depositional materials. This
occurs mainly in a range of tension whose active porous and soil moisture content are
critical for direct penetration of raindrops and for irrigation planning, respectively. |
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