Multi-wire time domain reflectometry (TDR) probe with electrical impedance discontinuities for measuring water content distribution |
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| Institution: | 1. School of Earth Sciences, Zhejiang University, Hangzhou, Zhejiang, People''s Republic of China;2. Academy of Cultural Heritage, Zhejiang University, Hangzhou, Zhejiang, People''s Republic of China;3. Centre for Pure & Applied Geology, University of Sindh, Jamshoro, Pakistan;4. Department of Geography, University of Sindh, Jamshoro, Pakistan;1. School of Marine Sciences, Sun Yat-sen University, Guangzhou 510275, China;2. Guangdong University Key Laboratory of Offshore Oil Exploration and Development/Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510275, China;3. Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation, Ministry of Land and Resources, Chengdu University of Technology, Chengdu, 610059, China;4. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China |
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| Abstract: | The adequate estimation of water content distribution in wetted volume is fundamental in determining the number of drippers per plant and their location below the plant canopy in drip irrigation. Measurements of water content distribution are usually made by opening trenches, which is a time-consuming method and sometimes imprecise. Recent scientific developments have created the possibility of monitoring the soil moisture content using electronic sensors. The objective of this research was to develop and test two multi-wire time domain reflectometry (TDR) probes with electrical impedance discontinuities (referred to as the multi-wire probe) for sensing soil profile water content distribution. The experiment was divided in two parts. In part one, the laboratory performance of two multi-wire probe designs was studied and their reliability to monitor the water content variation in a porous media profile was evaluated. The second part was conducted in a 250 l bucket and the soil water content distribution, for an application depth of 15 mm, was evaluated by monitoring over 6 days at discharge rates of 2 and 4 l h?1. The results demonstrated the viability of using multi-wire probes to estimate soil water content distribution with different probe designs and to consistently obtain water content measurement in water dynamic processes. The following conclusion may drawn from the main results: (1) The measured characteristic impedance of the multi-wire probe for different designs was not the same as that geometrically calculated. This was due to the non-ideal probe geometry which provoked signal loss, thus, hindering peak impedance interpretation, mainly for probe 1 design. (2) The use of multi-wire probes in the TDR equipment showed a speedy determination of soil profile water content distribution using a single measurement. |
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