scholarly journals A Modified Green-Ampt Model and Parameter Determination for Water Infiltration in Fine-textured Soil with Coarse Interlayer

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 787
Author(s):  
Shuai Chen ◽  
Xiaomin Mao ◽  
Chunying Wang
Keyword(s):  
Water Content ◽  
Soil Column ◽  
Soil Layer ◽  
Water Infiltration ◽  
Richards Equation ◽  
Parameter Determination ◽  
Wetting Front ◽  
Soil Matrix ◽  
Simulation Results ◽  
Two Parameters

A modified Green-Ampt model was developed to simulate water infiltration in fine-textured soil with a coarse interlayer. Because under such a soil structure, the two soils may not be fully saturated during infiltration, the model introduced two parameters—that is, the saturation coefficients a and b, to reflect the incomplete saturation condition and their influence on infiltration processes. In order to analyze the variation pattern of the two parameters in the above proposed model, scenarios were set for soil column infiltration in fine-textured soil with a coarse interlayer under different buried depths. A Richards equation-based model (RE-Model) was built for simulating the above scenarios and to obtain the evolution of soil water content along the soil profiles. Simulation results show that the infiltration rate decreased to a constant value when the wetting front crossed the upper interface between the fine and coarse soil layer. The soil matrix suction (ψ2) at the upper interface remained unchanged after the wetting front advanced into the coarse layer, and the steady value of ψ2 showed a linear relationship with the buried depth of the coarse layer. Based on the simulation results of the RE-Model, a method was proposed to determine the saturation coefficients related to the relative hydraulic conductivity and water content at ψ2 in the modified Green-Ampt model. Then, the modified model was tested under various infiltration conditions with different soil layered structures, and the results showed good agreement with the experimental data.

scholarly journals Numerical investigation of wetting front migration and soil water distribution under vertical line source irrigation with different influencing factors

2021 ◽  
Author(s):  
Yanwei Fan ◽  
Liangjun Ma ◽  
Hujun Wei ◽  
Pengcheng Zhu
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Influencing Factors ◽  
Line Source ◽  
Vertical Line ◽  
Initial Water Content ◽  
Wetting Front ◽  
Simulation Results ◽  
Soil Wetting

Abstract Vertical line source irrigation (VLSI) is an underground irrigation method suitable for deep-rooted plants. Understanding the characteristics of the soil wetting body of the VLSI was the key to designing this irrigation system. On the basis of experimental verification of the reliability of the HYDRUS simulation results of VLSI under the conditions of soil texture (ST), initial water content (θi), line source buried depth (B), line source diameter (D) and line source length (L), numerical studies of the migration law of the wetting front of VLSI and the distribution characteristics of soil moisture were performed. The wetting front migration (WFM) was mainly influenced by ST, θi, D and L (P < 0.05), while B had little effect on WFM (P > 0.05). The shape of the soil wetting body changed little under different influencing factors. The water content contour was approximately ‘ellipsoidal’ around the line source. The soil moisture near the line source was close to the saturated moisture content. The moisture content around the line source gradually decreased outward, and the contour lines gradually became dense. According to the simulation results, a prediction model of multiple factors influencing the migration process of the VLSI wetting front was established. The predicted value was in good agreement with the measured value. The results of this research could provide a theoretical basis for further optimizing the combination of VLSI and irrigation elements.

Surface-positioned double-ring to improve traditional infiltrometer for measuring soil infiltration

Soil Research ◽  
2020 ◽  
Vol 58 (3) ◽  
pp. 314
Author(s):  
Jing Zhang ◽  
Shaopeng Li
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Accuracy ◽  
Soil Column ◽  
Saturated Hydraulic Conductivity ◽  
Experimental Results ◽  
Water Infiltration ◽  
Maximum Relative Error ◽  
Wetting Front ◽  
Double Ring ◽  
Improve Measurement

The installation of a traditional double-ring infiltrometer (DRI) into soil is difficult and time consuming. It results in reduced accuracy because of soil disturbance and water leakage along the gaps between the ring wall and the soil. In this study, a surface-positioned DRI (SPDRI) was suggested to improve measurement accuracy and convenience of the DRI. Laboratory experiments were conducted to evaluate performance of the method in terms of the influence of the lateral flow of water on the accuracy of infiltration rate, average vertical wetting front depth and saturated hydraulic conductivity. A cylindrical soil column was used to simulate the ideal ring infiltrometer (IRI) of the one-dimensional vertical infiltration process for comparison purposes. Experimental results indicated that the infiltration rates measured by the SPDRI and IRI were nearly identical, with maximum relative error (RE) of 18.75%. The vertical wetting front depth of the SPDRI was nearly identical to that of the IRI, with proportional coefficients of 0.97 and R2 > 0.95. Comparison of the soil saturated hydraulic conductivity with those from IRI indicated that the REs were 7.05–10.63% for the SPDRI. Experimental results demonstrated that the SPDRI could improve the measurement accuracy and facilitate the soil water infiltration measurement process.

An assessment of soil moisture in the MARINE flash flood model using in situ measurements, reanalysis and satellite derived estimates

2020 ◽  
Author(s):  
Judith Eeckman ◽  
Hélène Roux ◽  
Bertrand Bonan ◽  
Clément Albergel ◽  
Audrey Douniot
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Model Calibration ◽  
Flash Flood ◽  
Soil Column ◽  
Subsurface Flow ◽  
Soil Layer ◽  
Observation Network

<p>The representation of soil moisture is a key factor for the simulation of flash flood in the Mediterranean region. The MARINE hydrological model is a distributed model dedicaded to flash flood simulation. Recent developments of the MARINE model lead to an improvement of the subsurface flow representation : on the one hand, the transfers through the subsurface take place in a homogeneous soil column based on the volumic soil water content instead of the water height. On the other hand, the soil column is divided into two layers, which represent respectively the upper soil layer and the deep weathered rocks. The aim of this work is to assess the performances of these new representations of the subsurface flow with respect to the soil saturation dynamics during flash flood events. The performances of the model are estimated with respect to three soil moisture products: i) the gridded soil moisture product provided by the LDAS-Monde assimilation chain. LDAS-Monde is based on the ISBA-a-gs land surface model and integrates high resolution spatial remote sensing data from the Copernicus Global Land Service for vegetation through data assimilation; ii) the upper soil moisture measurements taken from the SMOSMANIA observation network ; iii) The satellite derived surface soil moisture data from Sentinel1. The case study is led over two french mediterranean catchments impacted by flash flood events over the 2017-2019 period and where one SMOSMANIA station is available. Additionnal tests for the initialisation of MARINE water content for the two soil layers are assessed. Results show first that the dynamic of the soil moisture both provided by LDAS-Monde and simulated for the upper soil layer in MARINE are locally consistent with the SMOSMANIA observations. Secondly, the use of soil water content instead of water height to describe lateral flows in MARINE is cleary more relevant with respect to both LDAS-Monde simulations and SMOSMANIA stations. The dynamic of the deep layer moisture content also appears to be consistent with the LDAS-Monde product for deeper layers. However, the bias on these values strongly rely on the calibration of the new two-layers model. The opportunity of improving the two-layers model calibration is then discussed. Finally, the impact of the soil water content initialisation is shown to be significant mainly during the flood rising, and also to be dependent on the model calibration. In conclusion, the new developments presented for the representation of subsurface flow in the MARINE model appear to enhance the soil moisture simulation during flash floods, with respect to both the LDAS-Monde product and the SMOSMANIA observation network.</p>

Water flow in unsaturated soils subjected to multiple infiltration events

2020 ◽  
Vol 57 (3) ◽  
pp. 366-376
Author(s):  
Xiaokun Hou ◽  
Sai K. Vanapalli ◽  
Tonglu Li
Keyword(s):  
Water Content ◽  
Water Flow ◽  
Unsaturated Zone ◽  
Unsaturated Soils ◽  
Water Infiltration ◽  
Wetting Front ◽  
Influx Rate ◽  
The Relationship ◽  
Stable Zone

In this paper, water flow in a 4 m height column with an unsaturated soil that is subjected to multiple infiltration events for a 62 day period is investigated. One-dimensional (1D) numerical analysis is also undertaken to analyze the flow, extending the seepage theory for unsaturated soils. Results highlight the formation of two wetting fronts; namely, wetting front I and wetting front II that are induced by the first and subsequent infiltration events, respectively. There is a stable zone where the water content is approximately constant; it forms between the two fronts. A conceptual model of the suction profile is proposed for interpreting in situ water flow by dividing the unsaturated zone into four distinct zones; namely, active, steady, transition, and capillary fringe zones. This division is helpful for providing a rational explanation of water flow in different zones. Novel contributions from this study include a relationship between the hydraulic properties in the steady zone and the flow velocity, which is determined by an average influx rate. In addition, the rate of groundwater recharge can also be estimated using the average influx rate. Results of the present study are useful to understand and interpret the relationship between water infiltration and suction or water content profile in the unsaturated zone as well as variation of groundwater table level.

scholarly journals Feasibility Investigation of Improving the Modified Green–Ampt Model for Treatment of Horizontal Infiltration in Soil

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 645 ◽  
Author(s):  
Ding-feng Cao ◽  
Bin Shi ◽  
Hong-hu Zhu ◽  
Hilary Inyang ◽  
Guang-qing Wei ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Linear Functions ◽  
Moisture Distribution ◽  
Water Infiltration ◽  
Richards Equation ◽  
Accurate Estimation ◽  
Wetting Front ◽  
Size Change ◽  
Moisture Profile ◽  
Horizontal Infiltration

Water infiltration in soil is a complex process that still requires appreciation of interactions among three phases (soil particles, water and air) to enable accurate estimation of water transport rates. To simulate this process, the Green–Ampt (GA) model and the Modified Green-Ampt (MGA) model introduced in the paper “A new method to estimate soil water infiltration based on a modified Green–Ampt model” have been widely used. The GA model is based on the hypothesis that the advance of the wetting front in soil under matric suction can be treated as a rectangular piston flow that is instantaneously transformed after passage of the infiltration front, and the MGA model does not contain the influence of pore size change. This cannot accurately reflect the soil moisture change process from unsaturation to saturation. Due to soil stratification and other inhomogeneity, predictions produced with these models often differ widely from observations. To quickly obtain the soil moisture distribution after passage of the wetting front for horizontal infiltration, an improved modified Green–Ampt (IMGA) model is presented, which estimates the soil moisture profile along a horizontal column in a piecewise manner with three functions. A logarithmic function is used to describe the gradual soil saturation process in the transmission zone, and two linear functions are used to represent the wetting zone. The algorithm of the IMGA model for estimating the water infiltration rate and cumulative infiltration is configured. To verify the effectiveness of IMGA model, a lab model test was performed, and a numerical model was built to solve the horizontal one-dimensional Richards equation using the finite–element method. The results show that the IMGA model is more accurate than the GA and MGA models. The horizontal soil moisture profiles obtained by the IMGA model are closer to the measured data than the numerical simulation results. The relative errors of the MGA and IMGA models decrease with an increase in infiltration time, whereas that of the GA model first decreases and then increases with infiltration time. The primary novelty of this study is nonlinear description of soil moisture content distribution, and derivation of unit transfer coefficient.

scholarly journals Handling the water content discontinuity at the interface between layered soils within a numerical scheme

Soil Research ◽  
2005 ◽  
Vol 43 (8) ◽  
pp. 945 ◽  
Author(s):  
C. J. Matthews ◽  
F. J. Cook ◽  
J. H. Knight ◽  
R. D. Braddock
Keyword(s):  
Numerical Solution ◽  
Water Content ◽  
Numerical Scheme ◽  
Iterative Scheme ◽  
Method Of Lines ◽  
Soil Layer ◽  
Iterative Solution ◽  
Richards Equation ◽  
Layered Soils ◽  
Fine Soil

In general, the water content (θ) form of Richards’ equation is not used when modeling water flow through layered soil since θ is discontinuous across soil layers. Within the literature, there have been some examples of models developed for layered soils using the θ-form of Richards’ equation. However, these models usually rely on an approximation of the discontinuity at the soil layer interface. For the first time, we will develop an iterative scheme based on Newton’s method, to explicitly solve for θ at the interface between 2 soils within a numerical scheme. The numerical scheme used here is the Method of Lines (MoL); however, the principles of the iterative solution could be used in other numerical techniques. It will be shown that the iterative scheme is highly effective, converging within 1 to 2 iterations. To ensure the convergence behaviour holds, the numerical scheme will be tested on a fine-over-coarse and a coarse-over-fine soil with highly contrasting soil properties. For each case, the contrast between the soil types will be controlled artificially to extend and decrease the extent of the θ discontinuity. In addition, the numerical solution will be compared against a steady-state analytical solution and a numerical solution from the literature.

Influence of infiltration on Babaoliao shallow landslide in Taiwan using hydro-mechanical coupled model

2020 ◽  
Author(s):  
Ya-Sin Yang ◽  
Hsin-Fu Yeh
Keyword(s):  
Slope Stability ◽  
Water Content ◽  
Soil Layer ◽  
Coupled Model ◽  
Shallow Landslide ◽  
Residual Soil ◽  
Wetting Front ◽  
Element Analysis ◽  
Unstable Slope ◽  
The Impact

<p>Babaoliao landslide is located in Chiayi County of Taiwan. The geological drilling and core interpretation in previous investigation showed that exist 1 to 2 meter depths of residual soil layer above the bedrock. In this area, shallow landslides frequently occur due to the intense rainfall events. An understanding of the hydro-mechanical change under rainfall infiltration within hillslope is critical to capture the slope stability. This study used hydro-mechanical coupled model and finite element analysis to compute the field water content and stress suction, and then assess the field slope stability based on theory of local of factor. Results showed the response of internal hydraulic behavior distribution is related to terrain and the depths of bedrock. The impact of rainfall on slope stability concentrated in shallow residual soil area, since higher permeability of soil cause rainfall infiltrate into hillslope easily and form lateral flow paths, thus limiting the depths of wetting front. The discontinuity of water content distribution within hillslope may accelerate the change of hydro-mechanical behavior and unstable slope development in the hillslope. This study demonstrated the varied distribution of water content, suction stress and LFS over time and space and got the insight into the relativity unstable range of the shallow slope affected by rainfall event.</p>

scholarly journals Water mass balance in the case of vertical infiltration

2013 ◽  
Vol 7 (3) ◽  
pp. 274-280
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Algebraic Model ◽  
Water Infiltration ◽  
Wetting Front ◽  
Retention Curve ◽  
Soil Water Infiltration ◽  
Cumulative Infiltration ◽  
Richard's Equation ◽  
Water Mass Balance

Water movement in the unsaturated zone is an important hydrological process. Richard’s equation is windily used to describe both soil water infiltration and soil water absorption. Various methods have been developed to solve Richard’s equation. Wang et al. (2003) have developed an algebraic model for the description of soil water infiltration, based on Parlange’s solution of Richard’s equation and on soil retention curve and hydraulic conductivity equation given by Brooks and Corey. Their model utilizes experimental measurements of the cumulative infiltration volume and the wetting front distance as functions of time in order to describe soil water infiltration. The objective of this paper is to test the accuracy of the Wang et al. algebraic model for the one-dimensional (vertical) soil water infiltration. A vertical infiltration experiment was conducted on a sandy soil, for the measurement of the cumulative infiltration volume and the wetting front distance. Soil water content was determined at selected times and positions, using gamma ray absorption. Additionally the hydraulic conductivity K(θ) and the soil retention curve Ψ(θ) were determined. The algebraic model developed by Wang et al., was found simple to use since the required data are the cumulative infiltration (F), the wetting front distance (zf) and the initial and saturated soil water content (θi and θs respectively). The results show a fair agreement between calculated and measured values on soil water content profiles, hydraulic conductivity and on the water mass balance.

Using GPR surveys and infiltration experiments for assessing soil physical quality of an agricultural soil

2021 ◽  
Author(s):  
Simone Di Prima ◽  
Vittoria Giannini ◽  
Ludmila Ribeiro Roder ◽  
Ryan D. Stewart ◽  
Majdi R. Abou Najm ◽  
...  
Keyword(s):  
Soil Layer ◽  
Pore Network ◽  
Water Infiltration ◽  
Soil Matrix ◽  
Physical Quality ◽  
Soil Physical Quality ◽  
Amplitude Fluctuations ◽  
Single Ring ◽  
Infiltration Experiment

<p>Time-lapse ground penetrating radar (GPR) surveys in conjunction with automated single-ring infiltration experiments can be used for non-invasive monitoring of the spatial distribution of infiltrated water and for generating 3D representations of the wetted zone. In this study we developed and tested a protocol to quantify and visualize water distribution fluxes under unsaturated and saturated conditions into layered soils. We carried out a gridded GPR survey on a 0.3-m thick sandy clay loam layer underlain by a restrictive limestone layer at the Ottava experimental station of the University of Sassari (Sardinia, IT). We firstly established a survey grid (1 m × 1 m), consisting of six horizontal and six vertical parallel survey lines with 0.2 m intervals between them. The field survey then consisted of six steps, including <strong>i)</strong> a first GPR survey, <strong>ii)</strong> a tension infiltration experiment conducted within the grid and aimed at activating only the soil matrix, <strong>iii)</strong> a second GPR survey aimed at highlighting the amplitude fluctuations between repeated GPR radargrams of the first and second surveys, due to the infiltrated water moving within the matrix flow region, <strong>iv)</strong> a single-ring infiltration experiment of the Beerkan type carried out within the grid on the same infiltration surface using a solution of brilliant blue dye (E133) and aimed to activate the whole pore network, <strong>v)</strong> a third GPR survey aimed to highlight the amplitude fluctuations between repeated GPR radargrams of the first and third surveys, due to the infiltrated water moving within the whole pore network (both matrix and fast-flow regions), and <strong>vi)</strong> the excavation of the soil to expose the wetted region. The shapes of the 3D diagrams of the wetted zones facilitated the interpretation of the infiltrometer data, allowing us to resolve water infiltration into the layered system. Finally, we used the infiltrometer data in conjunction with the Beerkan estimation of soil transfer parameter (BEST) method to determine the following capacitive indicators of soil physical quality of the upper soil layer: air capacity <em>AC</em> (m<sup>3</sup> m<sup>–3</sup>), plant-available water capacity <em>PAWC</em> (m<sup>3</sup> m<sup>–3</sup>), relative field capacity <em>RFC</em> (–), and soil macroporosity <em>p<sub>MAC</sub></em> (m<sup>3</sup> m<sup>–3</sup>). Results showed that the investigated soil was characterized by high soil aeration and macroporosity (i.e., <em>AC</em> and <em>p<sub>MAC</sub></em>) along with low values for indicators associated with microporosity (i.e., <em>PAWC</em> and <em>RFC</em>). These findings suggest that the upper soil layer facilitates root proliferation and quickly drains excess water towards the underlying limestone layer, and, on the contrary, has limited ability to store and provide water to plant roots. In addition, the 3D diagram allowed the detection of non-uniform downward water movement through the restrictive limestone layer. The detected difference between the two layers in terms of hydraulic conductivity suggests that surface ponding and overland flow generation occurs via a saturation-excess mechanism. Indeed, percolating water may accumulate above the restrictive limestone layer and form a shallow perched water table that, in case of extreme rainfall events, could rise causing the complete saturation of the soil profile.</p>

Drying and wetting characteristics of a two-layer soil column

2007 ◽  
Vol 44 (1) ◽  
pp. 20-32 ◽  
Author(s):  
I Gde Budi Indrawan ◽  
Harianto Rahardjo ◽  
Eng-Choon Leong
Keyword(s):  
Water Flow ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Characteristic Curve ◽  
Soil Column ◽  
Soil Layer ◽  
Time Domain Reflectometry ◽  
Water Infiltration ◽  
Numerical Analyses ◽  
Laboratory Model

The drying and wetting characteristics of a two-layer soil column consisting of a 50 cm thick soil mixture over a 50 cm thick gravelly sand were investigated in this study. A series of infiltration tests were conducted in the laboratory through an infiltration column apparatus equipped with a tensiometer–transducer system, time-domain reflectometry, and water flow measurement system. Numerical analyses were performed using a finite element model to simulate water infiltration into the laboratory model under steady-state and transient conditions. The experimental data and numerical simulation results showed that static nonequilibrium profiles of pore-water pressure head were developed in the gravelly sand shortly after a drying process was started. The low unsaturated permeability of the gravelly sand resulted in a delay in downward water flow into the lower soil layer during a wetting process portion of the rainfall test.Key words: drying and wetting characteristics, soil column, infiltration, numerical analyses, soil-water characteristic curve, permeability function.

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