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| Home > Publications database > Analysis of spatial soil moisture dynamics using wireless sensor networks |
| Dissertation / PhD Thesis/Book | PreJuSER-17114 |
2011
Forschungszentrum Jülich Gmbh Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-710
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Abstract: To understand short-term and long-term dynamics in spatial soil moisture patterns at the small catchment scale, appropriate measurement techniques are needed. Recently developed wireless sensor networks help to bridge the gap between local (e.g. hydrogeophysical methods) and regional soil moisture measurement techniques (e.g. satellite borne remote sensing). Wireless sensor networks like SoilNet routinely provide continuous soil moisture data with both high temporal and spatial resolution, also spatial coverage of a given test site. An essential requirement for the development of a wireless sensor network is the selection of appropriate soil water content sensors. Low-cost sensors are often criticized concerning their measurement accuracy in terms of considerable variation between individual sensors, temperature-dependency and spurious effects of electrical conductivity on the sensor response. In this thesis, by means of laboratory experiments using dielectric reference liquids soil moisture sensors ECH$_{2}$O (Decagon Devices, Inc., Pullman, WA) were evaluated regarding their measuring accuracy, i.e. sensor-to-sensor variability and temperature as well as electric conductivity effects. Consideration of sensor-to-sensor variability by means of a sensorspecific calibration significantly improves the apparent dielectric permittivity estimate, in particular in the high permittivity range (i.e. high soil water content range). Temperature effects on the apparent dielectric permittivity measurement, which could be related to the sensor circuitry, were successfully quantified in dielectric reference liquids, furthermore corrected and also validated for selected soil samples of different texture classes. The assessment of electrical conductivity effects on apparent dielectric permittivity estimation was limited to the high permittivity range (ε > ~26) due to method constrains. However,[...]
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