| Autor: |
Henrik H. Nissen, Ole H. Jacobsen, L. W. de Jonge, Per Moldrup |
| Rok vydání: |
1999 |
| Předmět: |
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| Zdroj: |
Soil Science Society of America Journal. 63:493-500 |
| ISSN: |
0361-5995 |
| DOI: |
10.2136/sssaj1999.03615995006300030011x |
| Popis: |
The study of fingered flow and other unstable flow phenomena in soil requires a nondestructive technique for measuring changes in volumetric water content (θ) with high temporal and spatial resolution. In this study, a small-scale time domain reflectometry (TDR) coil probe is tested and used to measure the spatial and temporal development of stable and unstable wetting fronts in two sandy soils and a 0.0005- to 0.002-m size fraction of a sandy soil. The small outer dimensions of the coil probe (0.015-m length, 0.0036-m diameter) allowed the use of a Hele-Shaw cell in which progressive wetting fronts could be observed both visually and by TDR measurements of θ. The sample volume originates at the outer surface of the coil and extends 0.002 to 0.003 m into the soil. Despite this small sample volume, the accuracy of the coil probe relative to the gravimetric method was ±0.017 m 3 m 3 (across a water content range of 0.01 ≤ θ ≤ 0.135 m 3 m -3 ). Coil probes, which were small enough to be located at different positions in several of the wetting-front fingers, indicated lateral movement of otter from the center of the finger toward the outer fringe surrounding the finger. Profiles of the vertical soil water distribution within a linger measured with the coil probe compared well with a profile from literature measured by the moisture-content-visualization technique. It was concluded that the TDR coil probe is capable of obtaining direct measurements of θ with high spatial and temporal resolution. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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