Combined Transient Method for Determining Soil Hydraulic Properties in a Wide Pressure Head Range

2011 ◽  
Vol 75 (5) ◽  
pp. 1681-1693 ◽  
Author(s):  
H. Schelle ◽  
S. C. Iden ◽  
W. Durner
Keyword(s):  
Hydraulic Properties ◽  
Pressure Head ◽  
Transient Method ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic ◽  
Wide Pressure

scholarly journals Bayesian Inversion of Soil Hydraulic Properties from Simplified Evaporation Experiments: Use of DREAM(ZS) Algorithm

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2614
Author(s):  
Xinghui Wang ◽  
Xu-sheng Wang ◽  
Na Li ◽  
Li Wan
Keyword(s):  
Inverse Modeling ◽  
Hydraulic Properties ◽  
Evaporation Rate ◽  
Likelihood Function ◽  
Pressure Head ◽  
Soil Hydraulic Properties ◽  
Parameter Uncertainties ◽  
Soil Hydraulic ◽  
Stage 1 ◽  
Better Than

There is an increasing interest in identifying soil hydraulic properties from simplified evaporation experiments. However, the conventional simplified evaporation method includes a deficit due to using the linear assumption and not accounting for uncertainty in parameters. A suggested alternative method is assessing the parameter uncertainties through inverse modeling. We examined the combination of a Bayesian inverse method, namely, DREAM(ZS), and a numerical simulation model, namely, HYDRUS-1D, for parameter inversion with data in simplified evaporation experiments. The likelihood function could be conditioned only on pressure head observations (single-objective (SO)), or on both pressure head and evaporation rate observations (multi-objective (MO)), with different treatments on the top boundary condition. Three synthetic numerical experiments were generated in terms of the soil types of sand, loam and clay to verify the inverse modeling method. The MO approach performed better than the SO approach and linear assumption when the stage 1 evaporation rate was kept constant. However, the SO inversion was more robust when oscillations existed in the potential evaporation rate. Then, the SO inverse modeling was adopted to investigate two real experiments on loamy-sand soils and compared with the linear assumption. The linear assumption could be reliable for wet conditions with stage 1 evaporation but was not always useable for a relatively dry condition, such as that with stage 2 evaporation. The inverse modeling could be more successful in capturing the whole evaporation process of soils when both stage 1 and stage 2 were involved.

scholarly journals Conditions of Hydraulic Heterogeneity under Which Bayesian Estimation is More Reliable

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 160 ◽  
Author(s):  
Hao-Qing Yang ◽  
Xiangyu Chen ◽  
Lulu Zhang ◽  
Jie Zhang ◽  
Xiao Wei ◽  
...  
Keyword(s):  
Bayesian Estimation ◽  
Unsaturated Zone ◽  
Hydraulic Properties ◽  
Back Analysis ◽  
Ground Surface ◽  
Pressure Head ◽  
Monitoring Data ◽  
Percentage Error ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic

Natural heterogeneity of soil hydraulic properties is significant for the design and construction of geotechnical structures, and should be adequately characterized. Accurate measurements of hydraulic properties remain a difficult job and do not always work well for further design and analysis. Field hydraulic monitoring data reflects the overall slope performance and provide a more representative estimation of in-situ soil hydraulic properties for back analysis. The objective of this study is to explore the conditions under which monitoring data can provide reliable estimates of hydraulic parameters. Different distributions of soil heterogeneity generate a total number of 500 sets of synesthetic monitoring data. Bayesian inversion with the integration of Karhunen-Loève (K-L) and polynomial chaos expansion (PCE) is chosen to estimate the spatially varied saturated coefficient of permeability ks. The results show that the method is accurate and reliable, with less than 3% percentage error and 0.08 coefficient of variation (COV) around the monitoring points. There are two characteristics of the best-estimated fields. First, the ranges of ks for best-estimated fields are much narrower than the worst estimated fields. Second, when the larger ks values are distributed in the unsaturated zone of slope crest, it will lead to the best estimation. It is suggested that monitoring data can provide a reliable estimation of heterogeneous ks when the ratio of ground surface flux to ks in the unsaturated zone of slope crest is less than 1/150. Small values of ks in the slope crest result in the response of pressure head far from the responses of homogenous ks in the unsaturated zone. This complex response of the pressure head further causes the ill identification of ks by Bayesian estimation.

The impact of the permanent grass cover or conventional tillage on hydraulic properties of Haplic Cambisol developed on paragneiss substrate

Biologia ◽  
2016 ◽  
Vol 71 (10) ◽  
Author(s):  
Miroslav Fér ◽  
Radka Kodešová ◽  
Antonín Nikodem ◽  
Veronika Jirků ◽  
Ondřej Jakšík ◽  
...  
Keyword(s):  
Hydraulic Properties ◽  
Arable Land ◽  
Applied Pressure ◽  
Pressure Head ◽  
Conventional Tillage ◽  
Grass Cover ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic ◽  
Multistep Outflow ◽  
The Impact

AbstractThis study is focused on the comparison of soil structure and soil hydraulic properties of a Haplic Cambisol on paragneiss under two different land managements. Soil samples were taken from all diagnostic horizons (A, Bw and C) of the soil profile under the permanent grass cover (grassland) and under the conventional tillage (arable land). Basic soil properties were measured. Aggregate stability was assessed using the WSA index. Soil composition was evaluated using micromorphological images. Tension disk infiltrometers with two diameters of 2.22 and 10.25 cm (and applied pressure head of −2 cm) and Guelph permeameter were used to measure unsaturated and saturated hydraulic conductivities, respectively. Soil hydraulic properties were measured in the laboratory using the multistep outflow experiment, which was performed on the undisturbed 100 cm

Comparison of the Instantaneous Profile Method and inverse modelling for the prediction of effective soil hydraulic properties

Soil Research ◽  
2005 ◽  
Vol 43 (5) ◽  
pp. 599 ◽  
Author(s):  
Oagile Dikinya
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Sandy Soil ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Pressure Head ◽  
Inverse Modelling ◽  
Soil Hydraulic Properties ◽  
Loamy Soil ◽  
Soil Hydraulic

Soil hydraulic conductivity K(θ) and soil water retention θ(h) have been determined from a drainage experiment. Two lysimeters, one filled with a sandy soil and the other with a loamy soil, were set up for a 1-dimensional transient flow experiment. The data were collected after flooding the lysimeters with water. Soil water contents were measured by time domain reflectrometry (TDR) and pressure heads were measured by tensiometers with mercury manometers. The experimental data determined by the instantaneous profile method (IPM) were compared with the results obtained by inverse modelling. The inverse modelling proved to be superior to the IPM methodology in effective prediction of hydraulic properties. The measurable properties water content and pressure head were optimised for the following datasets: water content (WC), pressure head (P-h), and a combination of WC and P-h. For both soils the optimisation of the dataset with both WC and P-h resulted in parameters that corresponded closely to the soil hydraulic data generated by the IPM method. The correspondence for the water retention data was better than for the hydraulic conductivity data. The datasets with WC only or P-h only did not contain enough information to accurately estimate the soil hydraulic properties. In most cases the results indicated that the sandy soil gave better agreement than the loamy soil. This was attributed to the faster drainage of the sandy than the loamy soil.

A modified upward infiltration method for characterizing soil hydraulic properties

2002 ◽  
Vol 66 (1) ◽  
pp. 57 ◽  
Author(s):  
M. H. Young ◽  
A. Karagunduz ◽  
J. Šimůnek ◽  
K. D. Pennell
Keyword(s):  
Hydraulic Properties ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic ◽  
Infiltration Method

scholarly journals Pinhole Multistep Centrifuge Outflow Method for Estimating Unsaturated Hydraulic Properties with Small Volume Soil Samples

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1169
Author(s):  
Long Thanh Bui ◽  
Yasushi Mori
Keyword(s):  
Hydraulic Properties ◽  
Volcanic Ash ◽  
Small Volume ◽  
Clayey Soil ◽  
Soil Hydraulic Properties ◽  
Retention Curve ◽  
Volcanic Ash Soil ◽  
Equilibrium Data ◽  
Soil Hydraulic ◽  
Water Holding

If soil hydraulic conductivity or water holding capacity could be measured with a small volume of samples, it would benefit international fields where researchers can only carry a limited amount of soils out of particular regions. We performed a pinhole multistep centrifuge outflow method on three types of soil, which included granite decomposed soil (Masa soil), volcanic ash soil (Andisol soil), and alluvial clayey soil (paddy soil). The experiment was conducted using 2 mL and 15 mL centrifuge tubes in which pinholes were created on the top and bottom for air intrusion and outflow, respectively. Water content was measured at 5, 15, and 30 min after applying the centrifuge to examine the equilibrium time. The results showed that pinhole drainage worked well for outflow, and 15 or 30 min was sufficient to obtain data for each step. Compared with equilibrium data, the retention curve was successfully optimized. Although the curve shape was similar, unsaturated hydraulic conductivities deviated largely, which implied that Ks caused convergence issues. When Ks was set as a measured constant, the unsaturated hydraulic properties converged well and gave excellent results. This method can provide soil hydraulic properties of regions where soil sampling is limited and lacks soil data.

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