Comparison of unconfined and confined unsaturated hydraulic conductivity |
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| Institution: | 1. College of Life Sciences, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing 210095, China;2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;1. Cell-Mineral Research Centre, Kroto Research Institute, University of Sheffield, Broad Lane, Sheffield S3 7HQ, United Kingdom;2. University of Limerick, Department of Life Sciences, Limerick, Ireland;3. University of Applied Science and Arts, Department of Bioanalytics, Friedrich-Streib-Str. 2, 96450 Coburg, Germany;1. Dipartimento dei Sistemi Agro-Ambientali, Università degli Studi di Palermo, Viale delle Scienze, Palermo 90128 (Italy);2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China);1. Department of Physics, University of Petroleum and Energy Studies, Bidholi, Dehradun, India;2. Department of Computer Science & Engineering Uttaranchal University, Dehradun, India;3. Department of Chemistry, Maharishi Markandeshwar University, Ambala, Haryana, India;4. Department of Environmental System Science, ETH Zurich, Tannenstrasse, Switzerland;5. University School of Environment Management, Guru Gobind Singh Indraprastha University, Delhi, India |
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| Abstract: | The field tension infiltrometer (TI) and the laboratory unit hydraulic gradient (UHG) methods are widely applied to determine the near-saturated soil hydraulic conductivity, K. Comparison between the two methods is relevant given that they differ in the explored soil volume (undetached or detached) and in the flow process (unconfined or confined). The objective of this investigation was to compare unconfined and confined measurements of unsaturated hydraulic conductivity. Twenty TI experiments were conducted in a relatively coarse-textured soil having an appreciable hysteretic behavior by using two different dry-to-wet-to-dry (DTWTD) sequences of pressure head, h0, values that differed by the highest h0 value imposed within the sequence (i.e. h0 = − 150, − 75, − 30, + 5, − 30, − 75, − 150 in site A or h0 = − 150, − 75, − 30, − 10, − 30, − 75, − 150 in site B). The same pressure head sequences were applied on twenty undisturbed soil cores, collected at the exact location of the TI measurements, to perform the laboratory UHG measurements. Regardless of the type of experiment (i.e. unconfined or confined) and the applied pressure head sequence (i.e. site A or B), higher K0 values were obtained with a drying sequence of h0 values (K0,d) than with a wetting one (K0,w)and the discrepancies between K0,w and K0,d decreased as the imposed h0 value increased, as it was expected due to hysteresis. A tendency of the UHG method to overestimate the K0 values was detected (ratios of mean K0,1D to mean K0,3D values ranging from 0.93 to 4.35), but the statistical significance of the observed differences varied with the considered sequence of pressure head values. It was concluded that both the TI and the UHG methods were effective in detecting hysteresis effects on K0, but the laboratory method resulted in K0 values that were higher and more variable probably as a consequence of a more substantial effect of macropore flow on the measured flow rates. |
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