Revisiting the simplified evaporation method: Identification of hydraulic functions considering vapor, film and corner flow

Peters, André; Iden, Sascha C.; Durner, Wolfgang

doi:10.1016/j.jhydrol.2015.05.020

Cited by 120 publications

(107 citation statements)

References 20 publications

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“…The data are subsequently analyzed from the average water content, the pressure head readings of the two tensiometers, and the mean total head gradients between the two tensiometers. We refer to Schindler et al (2010a, b) and Peters et al (2015) for detailed descriptions of the setup and the data analysis. The data in our study were generated by running HYDRUS-1D simulations, very similar as done by Peters and Durner (2008) and Peters et al (2015).…”

Section: The Hyprop Measurement System (Hms)mentioning

confidence: 99%

“…We refer to Schindler et al (2010a, b) and Peters et al (2015) for detailed descriptions of the setup and the data analysis. The data in our study were generated by running HYDRUS-1D simulations, very similar as done by Peters and Durner (2008) and Peters et al (2015). For most of the simulations we used a spatial discretization involving 61 nodes, with mesh refinement near the sample upper surface to accommodate higher local pressure head gradients during the simulations.…”

Section: The Hyprop Measurement System (Hms)mentioning

confidence: 99%

“…Peters and Durner (2008) and Peters et al (2015) tested the HMS approach assuming synthetic (virtual) data for the two pressure heads within the sample, as well as for the evaporation rate (and hence the sample weight), as a function of time as generated with numerical solutions of the Richards equation. Peters and Durner (2008) used for this purpose the hydraulic functions of van Genuchten-Mualem (1980), while Peters et al (2015) used the equations of Kosugi (1996) as well as the PDI model of Peters and colleagues (Iden and Durner, 2014;Peters, 2013Peters, , 2014 to account for the effects of film, corner and isothermal vapor flow in very dry soils.…”

Section: Introductionmentioning

confidence: 99%

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Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

Bezerra-Coelho

Zhuang

Barbosa

et al. 2018

Journal of Hydrology and Hydromechanics

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Many soil, hydrologic and environmental applications require information about the unsaturated soil hydraulic properties. The evaporation method has long been used for estimating the drying branches of the soil hydraulic functions. An increasingly popular version of the evaporation method is the semi-automated HYPROP © measurement system (HMS) commercialized by Decagon Devices (Pullman, WA) and UMS AG (München, Germany). Several studies were previously carried out to test the HMS methodology by using the Richards equation and the van-Genuchten-Mualem (VG) or Kosugi-Mualem soil hydraulic functions to obtain synthetic data for use in the HMS analysis, and then to compare results against the original hydraulic properties. Using HYDRUS-1D, we carried out independent tests of the HYPROP system as applied to the VG functions for a broad range of soil textures. Our results closely agreed with previous findings. Accurate estimates were especially obtained for the soil water retention curve and its parameters, at least over the range of available retention measurements. We also successfully tested a dual-porosity soil, as well as an extremely coarse medium with a very high van Genuchten n value. The latter case gave excellent results for water retention, but failed for the hydraulic conductivity. In many cases, especially for soils with intermediate and high n values, an independent estimate of the saturated hydraulic conductivity should be obtained. Overall, the HMS methodology performed extremely well and as such constitutes a much-needed addition to current soil hydraulic measurement techniques.

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Section: The Hyprop Measurement System (Hms)mentioning

confidence: 99%

Section: The Hyprop Measurement System (Hms)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

Bezerra-Coelho

Zhuang

Barbosa

et al. 2018

Journal of Hydrology and Hydromechanics

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“…To determine the peat soil hydraulic properties, we conducted transient evaporation experiments (Schindler, 1980;Peters et al, 2015;Weber et al, 2017a, b) for the retention properties, supplemented with tension disk experiments (Klute and Dirksen, 1986;McCarter et al, 2017). Tension disk experiments are considered to be a more reliable method to determine the unsaturated hydraulic conductivity in the wet range, because transient evaporation experiments contain limited information at pressure heads between 0 and −60 cm for the unsaturated hydraulic conductivity curve (Peters and Durner, 2008).…”

Section: Soil Hydraulic Propertiesmentioning

confidence: 99%

Saturated and unsaturated salt transport in peat from a constructed fen

Simhayov¹,

Weber²,

Price³

2017

Preprint

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Abstract. The underlying processes governing solute transport in peat from an experimentally constructed fen peatland were analyzed by performing saturated and unsaturated solute breakthrough experiments using Na + and Cl − as reactive and non-reactive solutes, respectively. We tested the performance of three solute transport models, including the classical equilibrium convection-dispersion equation (CDE), a chemical non-equilibrium one-site adsorption model (OSA) and a model to account for physical non-equilibrium, the mobile-immobile (MIM) phases. The selection was motivated by the fact that the applicability of the MIM in peat soils finds a wide consensus. However, results from inverse modeling and a robust statistical evaluation of this peat provide evidence that the measured breakthrough of the conservative tracer, Cl − , could be simulated well using the CDE. Furthermore, the very high Damköhler number (which approaches infinity) suggests instantaneous equilibration between the mobile and immobile phases underscoring the redundancy of the MIM approach for this particular peat. Scanning electron microscope images of the peat show the typical multi-pore size distribution structures have been homogenized sufficiently by decomposition, such that physical non-equilibrium solute transport no longer governs the transport process. This result is corroborated by the fact the soil hydraulic properties were adequately described using a unimodal van Genuchten-Mualem model between saturation and a pressure head of ∼ −1000 cm of water. Hence, MIM was not the most suitable choice, and the long tailing of the Na + breakthrough curve was caused by chemical non-equilibrium. Successful description was possible using the OSA model. To test our results for the unsaturated case, we conducted an unsaturated steady-state evaporation experiment to drive Na + and Cl − transport. Using the parameterized transport models from the saturated experiments, we could numerically simulate the unsaturated transport using Hydrus-1-D. The simulation showed a good prediction of observed values, confirming the suitability of the parameters for use in a slightly unsaturated transport simulation. The findings improve the understanding of solute redistribution in the constructed fen and imply that MIM should not be automatically assumed for solute transport in peat but rather should be evidence based.

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“…Cubic Hermitian splines are frequently used in soil hydrology, e.g. for the description of hydraulic functions (Iden and Durner, 2007) or for temporal interpolation of measured values in evaporation experiments (Peters and Durner, 2008;Peters et al, 2015). In contrast to the linear interpolation scheme, the spline interpolation yields a smooth curve at the anchor points and is thus even continuously differentiable.…”

Section: Linear and Spline Interpolation Schemesmentioning

confidence: 99%

Technical note: Improving the AWAT filter with interpolation schemes for advanced processing of high resolution data

Peters

Nehls

Wessolek

2016

Hydrol. Earth Syst. Sci.

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Abstract. Weighing lysimeters with appropriate data filtering yield the most precise and unbiased information for precipitation (P ) and evapotranspiration (ET). A recently introduced filter scheme for such data is the AWAT (Adaptive Window and Adaptive Threshold) filter (Peters et al., 2014). The filter applies an adaptive threshold to separate significant from insignificant mass changes, guaranteeing that P and ET are not overestimated, and uses a step interpolation between the significant mass changes. In this contribution we show that the step interpolation scheme, which reflects the resolution of the measuring system, can lead to unrealistic prediction of P and ET, especially if they are required in high temporal resolution. We introduce linear and spline interpolation schemes to overcome these problems. To guarantee that medium to strong precipitation events abruptly following low or zero fluxes are not smoothed in an unfavourable way, a simple heuristic selection criterion is used, which attributes such precipitations to the step interpolation. The three interpolation schemes (step, linear and spline) are tested and compared using a data set from a grass-reference lysimeter with 1 min resolution, ranging from 1 January to 5 August 2014. The selected output resolutions for P and ET prediction are 1 day, 1 h and 10 min. As expected, the step scheme yielded reasonable flux rates only for a resolution of 1 day, whereas the other two schemes are well able to yield reasonable results for any resolution. The spline scheme returned slightly better results than the linear scheme concerning the differences between filtered values and raw data. Moreover, this scheme allows continuous differentiability of filtered data so that any output resolution for the fluxes is sound. Since computational burden is not problematic for any of the interpolation schemes, we suggest always using the spline scheme.

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Revisiting the simplified evaporation method: Identification of hydraulic functions considering vapor, film and corner flow

Cited by 120 publications

References 20 publications

Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

Further tests of the HYPROP evaporation method for estimating the unsaturated soil hydraulic properties

Saturated and unsaturated salt transport in peat from a constructed fen

Technical note: Improving the AWAT filter with interpolation schemes for advanced processing of high resolution data

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