Saturated Hydraulic Conductivity Values Research Articles

Hydraulic conductivity over a wide suction range of loess with different dry densities

Experimental research into the hydraulic conductivity curve (HCC) of unsaturated soil is limited due to the inherent challenge associated with labor, cost, and time. Typically, the HCC is estimated using the soil water characteristic curve (SWCC) based models and saturated hydraulic conductivity (SHC). However, the efficiency of the SWCC-based model is rarely assessed, and the influence of soil density and pore structure on HCC remains incomplete due to limited experimental data. To address this gap, this study employs an innovative filter-paper-based column method, which can measure the HCC over a wide suction range (e.g. 0−105 kPa), to capture the HCCs of both intact and compacted specimens with varying dry densities. The efficiency of two typical SWCC-based models is assessed using the measured data. Meanwhile, the mercury intrusion porosity (MIP) technique is employed to obtain the pore characteristic (i.e. pore size distribution (PSD)) and a method of predicting the HCC using the PSD data is proposed, emphasizing the dominant role of the pore structure in shaping the HCC. The results reveal that the dry density's influence on the HCC is primarily observed within the low suction range, corresponding to variations in the dominant and large pores. In the high suction range, the HCCs align along a linear trajectory when plotted in a log-log format. A notable finding is the overestimation of the HCC obtained from the SWCC-based models using the measured SHC. When the SHC is regarded as a fitting parameter, good agreement is achieved. The adjusted SHC value is typically 0-1 order of magnitude lower than the measured value, and this discrepancy diminishes as dry density increases. On the other hand, the proposed PSD-based model performs well with the measured SHC data. Caution is exercised when using the SHC to estimate the HCC for modeling water movement in partially saturated soil.

ESTABLISHING THE FIRST DATABASE OF SOIL HYDRAULIC PROPERTIES IN TUNISIA BASED ON PEDOTRANSFER FUNCTIONS

Soil hydraulic properties play a crucial role in the unsaturated soil water supply process. Currently, Tunisia lacks a database containing essential values for soil retention properties and soil saturated hydraulic conductivity. The main objective of this study is to create the inaugural soil hydraulic properties database through the utilization of open-access data and pedotransfer functions (PTFs). To achieve this goal, the harmonized world soil database (FAO) was employed to identify 752 measurement points across Tunisia. Subsequently, the soil texture, organic carbon content, and bulk density were determined at each point. These acquired values were then entered into the CalcPTF software to estimate the van Genuchten soil retention parameters. The calculation of soil saturated hydraulic conductivity was accomplished using two widely recognized pedotransfer functions (Saxton and Rosetta). The outcomes facilitated the creation of a catalog containing soil hydraulic parameter value for each soil texture. Significance of discrepancies between values obtained from the PTFs was assessed using a Tukey test. The spatial variability of each soil hydraulic property was studied using the simple kriging. In conclusion, the establishment of this significant soil hydraulic properties database holds diverse applications in agricultural, hydrological, and environmental studies in Tunisia.

Achieving Real-World Saturated Hydraulic Conductivity: Practical and Theoretical Findings from Using an Exponential One-Phase Decay Model

Obtaining accurate values of saturated hydraulic conductivity (Ksat) is very important for managing all natural or artificial processes involving water flow into soils. Double-ring infiltration (DRI) is one of the easiest-to-work-with techniques commonly used for Ksat determination. Unfortunately, when improperly used, it leads to important variations and inaccurate results. This study was designed to investigate the necessary conditions to reach the true-value or real-world saturated hydraulic conductivity (Ksat-real-world) in the field. For this purpose, the effects of two factors—namely, the measured infiltration data type (cumulative, instant rate, and average rate) and the related non-linear regression equation type—were analyzed. Measurements with DRI were performed with samples from 106 locations in three West African countries, namely, Burkina Faso, Mali, and Cote d’Ivoire. The soils were composed of loam, sandy loam, and sandy clay loam. The results show that when infiltration rates are used rather than cumulative infiltration non-linear regression curves, the variability between the measured Ksat and the real-world saturated hydraulic conductivity (Ksat-real-world) could reach from 2.2% to 58.8%. This variability was caused by the approximate amplification—according to the procedure used—of time-increment measurement errors. Extending the test duration to more than 4 h, especially when clay soils were involved, and using the exponential one-phase decay non-linear regression of the cumulative infiltration data based on a clear measurement protocol provided the Ksat values that were closest to Ksat-real-world.

Approximation of van Genuchten Parameter Ranges from Hydraulic Conductivity Data.

The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem-van Genuchten model which requires the shape parameters and . These, however, are difficult to obtain. When data is scarce, and are often taken from literature and may deviate largely from actual values. The current study presents a novel mathematical model for the approximation of and and for the further estimation of realistic value ranges, which may be used as parameter space, for example, for the calibration of a numerical model. The model was developed for cases where data is scarce and only values of saturated hydraulic conductivity are available. It is based on a large data set from literature and it is demonstrated that the model estimates mean values from that data set with a good accuracy. In order to show the applicability of the model, a second data set has been compiled anew (provided as Supporting Information). The model is incorporated into the current version of the freeware computer program HYPAGS, which enables easy usage.

The Role of Biochar and Perlite in Improving some Physical Properties of Clay Loam and Sandy Loam Soil

A laboratory experiment was carried out in the laboratory of the Department of soil sciences and Water Resources, College of Agriculture – the University of Diyala, where the experimental factors was the soil type factor (clay loam and sandy loam) and the soil conditioners agent by adding biochar at the level of 1 and 2% and symbolized by B1 and B2 and perlite at the level of 1 and 2% and symbol it has P1 and P2, and it was added according to the soil dry weight, with three replications, CRD design, and plastic tubes were used to incubate the treatments for 14 weeks. The results showed an increase in the water infiltration in the clay loam soil by an increase of 23% when using biochar ratios 1 and 2%, while the infiltration decreased in the sandy loam soil by a decrease of 16 and 31% when using biochar 1 and 2%, while the use of perlite in the proportions of 1 and 2% increased the infiltration. In the sandy loam soil. This applies to the saturated hydraulic conductivity values. The Bulk density soil decreased when using biochar ratios 1 and 2% in the clay loam soil with decrease rates of 13 and 26%, and it also decreased when using perlite ratios 1 and 2% with decrease rates of 10 and 13%, and it also decreased when using ratios 1 and 2% biochar with sandy loam soil with decrease rates of 11 and 17%. The soil porosity increased when 1 and 2% biochar was used in the clay loam soil with an increase of 15 and 7%, and it increased when 1 and 2% perlite was added in the same soil with an increase of 5 and 6%.

Study of the effect of the compaction level on the hydrodynamic properties of loamy sand soil in an agricultural context

Agricultural soil compaction adversely affects crop water use and yield performance and should be avoided or remediated through appropriate soil management strategies. The investigation of the impact of different levels of soil compaction on its hydrodynamic properties remains a crucial step in improving water use and crop yields. We examined five compaction levels of silty sand soil sampled from a potato field in the agricultural regions of northern Quebec (Canada). Soil hydraulic characteristics (saturated and unsaturated hydraulic conductivity, soil water retention capacity) were measured using the constant head method, the HYPROP device, and a WP4C dew point potentiometer. The sixteen hydraulic models integrated into the HYPROP software were fitted to the soil water retention curve (SWRC) data for the studied compaction levels. Statistical parameters such as the mean bias error, mean absolute error, correlation coefficient, and root mean square error were used to measure the performance of the models. The results show that saturated and unsaturated conductivity decreases with increasing soil compaction. The lowest saturated hydraulic conductivity (Ks) value is observed for the highest level of soil compaction, reflecting a solid medium with less pore space and connectivity. Among the hydraulic models, the Peters-Durner-Iden (PDI) variant of van Genuchten's unconstrained bimodal model (VGm-b-PDI) outperformed all other models for SWRC simulation of different soil compaction levels and was, accordingly, selected as the optimal model. This model was implemented in HYDRUS-1D to estimate the amount of irrigation for different compaction levels. We simulated irrigation scenarios with the dual-porosity model. The results indicated that soil compaction can strongly influence soil hydraulic properties and water differently. However, the amount of irrigation for the potato crop was optimal at a moderate level of soil compaction. Overall, combined HYPROP and HYDRUS 1D can provide helpful information on the soil hydraulics properties dynamics and a rigorous simulation for irrigation planning and management in potato fields.

Effect of Different Tillage and Residue Management Options on Soil Water Transmission and Mechanical Behavior

Understanding the variability in the mechanical and hydrological soil characteristics resulting from diverse tillage and residue management practices is essential for evaluating the adoption of conservation strategies to preserve soil’s physical well-being. Zero-tillage techniques combined with residue retention or incorporation have gained widespread recognition for their capacity to conserve soil and water resources, reduce energy consumption, and enhance soil quality and environmental sustainability. Nevertheless, the choice of tillage and residue management options may vary depending on the geographical locations and specific soil conditions. To assess the impacts of four distinct tillage and residue management approaches, a two-year experiment (2020–2021 and 2021–2022) was conducted: T1: conventional tillage followed by wheat sowing after the removal of rice straw (CT-RS); T2: zero tillage with wheat sowing using a Happy Seeder while retaining rice straw (ZT+RS); T3: conventional tillage followed by wheat sowing after rice straw incorporation using a reversible mouldboard plough (CT+RS); T4: minimum tillage with wheat sowing using a Super Seeder with rice straw incorporation (MT+RS); the effects were recorded on the physical soil properties. Our findings indicate that zero tillage combined with residue retention (T2) had a positive influence on various physical soil attributes. Notably, significant differences were observed among the tillage and residue management options, particularly in terms of the bulk density with T1 exhibiting the highest values and the lowest being in T2, whereas the soil penetration resistance was lowest in T3 compared to T1. In the case of T3, sandy loam and clay loam soils had the highest measured saturated hydraulic conductivity values, measuring 5.08 and 4.57 cm h−1 and 4.07 and 3.73 cm h−1, respectively. Furthermore, T2 (zero tillage with residue retention) demonstrated the highest mean weight diameter (MWD) and maximum water stable aggregate. These results collectively underscore the positive effects of adopting zero tillage and retaining residue (T2) on soil structure and quality, particularly concerning the mechanical and hydrological soil properties.

Testing CASE: A new event‐based Morgan‐Morgan‐Finney‐type erosion model for different rainfall experimental scenarios

AbstractEvery application of soil erosion models brings the need of proper parameterisation, that is, finding physically or conceptually plausible parameter values that allow a model to reproduce measured values. No universal approach for model parameterisation, calibration and validation exists, as it depends on the model, spatial and temporal resolution and the nature of the datasets used. We explored some existing options for parameterisation, calibration and validation for erosion modelling exemplary with a specific dataset and modelling approach. A new Morgan‐Morgan‐Finney (MMF)‐type model was developed, representing a balanced position between physically‐based and empirical modelling approaches. The resulting model termed ‘calculator for soil erosion’ (CASE), works in a spatially distributed way on the timescale of individual rainfall events. A dataset of 142 high‐intensity rainfall experiments in Central Europe (AT, HU, IT, CZ), covering various slopes, soil types and experimental designs was used for calibration and validation with a modified Monte‐Carlo approach. Subsequently, model parameter values were compared to parameter values obtained by alternative methods (measurements, pedotransfer functions, literature data). The model reproduced runoff and soil loss of the dataset in the validation setting with R2adj of 0.89 and 0.76, respectively. Satisfactory agreement for the water phase was found, with calibrated saturated hydraulic conductivity (ksat) values falling within the interquartile range of ksat predicted with 14 different pedotransfer functions, or being within one order of magnitude. The chosen approach also well reflected specific experimental setups contained in the dataset dealing with the effects of consecutive rainfall and different soil water conditions. For the sediment phase of the tested model agreement between calibrated cohesion, literature values and field measurements were only partially in line. The methods we explored may specifically be interesting for use with other MMF‐type models, or with similar datasets.

Effect of Date Residues and Organic Acids on Some Physical Properties of Gypsiferous Soil

A laboratory experiment was carried out at the College of Agriculture, University of Anbar, located at 43°20‘09.7“E longitude, 33°25‘36.7“N latitude for the period from 1/10/2021 to 1/10/2022, to study the effect of date residues, organic acids, and wetting / drying cycles on some physical properties of gypsiferous soil. The soil was selected from the site of the Fallujah palm station that located at longitude 43º51'. 05. 36 E. and latitude 33º17'. 46. 82‘N., date residues were added in three levels, without addition (comparison treatment), 0.1% and 0.2% mixed with soil. Organic acids was added at 0% and 0.1% and packaged in plastic cylinders and the treatments were exposed for two levels of wetting and drying cycles (6 and 8) cycles. The stability of aggregates, dispersion ratio, saturated hydraulic conductivity, and cumulative infiltration were measured. The results showed that the addition of date residues by 0.2% improved all the physical properties. Aggregates stability values increased by 13.41% and saturated hydraulic conductivity values decreased, which reached 4.33 cm.h-1. Accumulator infiltration up to 24.01cm and the capillary height reached to 40.0 cm, while the dispersion rate decreased to 37. 27%. The aggregates stability increased and the dispersion ratio, water conductivity and infiltration decreased by adding organic acids when their averages reached 12.12%, 40.77%, 5.19 cm-1 and 21.41cm, respectively. Increasing the number of wetting / drying cycles negatively affected most of the studied properties, as the dispersion ratio increased to 42.08%, and the cumulative infiltration decreased to 21.73 cm.

Attenuation of erythromycin-laden waste water using the constructed wetland technique

Erythromycin (ERY) is environmentally resilient because of its aromatic nature, which hinders degradation. In the present study, silty–sandy soil, with a saturated hydraulic conductivity (K) value of 1.66 × 10−7 m/s, was studied for its potential to remove aqueous ERY using a laboratory-scale constructed wetland. With a dose of 10 g/l, a concentration of 25 mg/l and a contact time of 30 min, the maximum adsorption reached 89.79 ± 1.5%, as found from batch experiments. The Freundlich isotherm (R 2 = 0.983, n = 0.575, K f = 0.04 mg/g) was the best fitting among different user models. In the kinetic study, the pseudo-second-order model (q e = 1.297 mg/g, K 2 = 0.182 g/(mg min)) had the best fit with experimental data. A one-dimensional vertical column study exhibited an exhaustion time of 2.7 days for a 40 mm deep soil bed to remove ERY. A laboratory-scale constructed wetland model composed of silty–sandy soil showed a reduction of ERY of 92.44%. Finally, the results were validated with the CW2D wetland model of the Hydrus software, which corroborated the experimental results. The outcome exhorts that constructed wetlands with silty–sandy soil may be an effective technique for the reduction of ERY present in waste water, which has profound importance from a social health perspective.

Hydraulic conductivity assessment of falling head percolation tests used for the design of on-site wastewater treatment systems

The suitability of a location for an on-site wastewater treatment process (for areas which lack access to centralised wastewater treatment systems) requires an assessment of the permeability of the soil into which the effluent will be discharged. In many jurisdictions this is determined using some type of in-situ percolation test. Falling head percolation tests, which give a value of percolation time (PT) that is empirically related to the notion of hydraulic conductivity, are widely used as they are relatively simple to carry out, but the test does not have a sound theoretical framework and test methods are not standardised internationally. In comparison, the saturated hydraulic conductivity of a soil obtained from a constant head well permeameter test is independent of test conditions, and so is a more suitable metric for design. A database of over 900 falling head tests carried out across a range of different subsoil types in Ireland has been collated, all with the inherent limitations of the existing regulative framework regarding the percolation test and soil texture assessment. These tests were then modelled using Hydrus 2-D numerical modelling simulations to determine equivalent field saturated hydraulic conductivity (Kfs) values and thereby provide a correlation with PT values across the range of subsoil conditions. In addition, falling head tests have been carried out in parallel to constant head permeameter tests in the field and compared against the relationship derived from the broad dataset of simulated results. This revealed an optimal solution by which to determine Kfs from the field permeameter test (using parameters recommended for most structured soils from clays to loams). The trendline based on Irish data was also compared against more generic formulations of the relationship between PT, and Kfs and shown to match closely, particularly the Reynolds (2016) ‘unified’ methodology. Finally, the Irish threshold PT limits for on-site wastewater treatment have been converted to Kfs values and compared against other international standards.

ANALISIS KONDUKTIVITAS HIDROLIK JENUH TANAH PADA BERBAGAI JENIS NAUNGAN DI LAHAN KOPI RAKYAT KECAMATAN SUMBERMANJING WETAN

Coffee plants are one of the plantation crops that are widely cultivated by smallholders in Sumbermanjing Wetan District. The problem that is often experienced by coffee farmers is the decline in coffee production due to climate. The adverse effect of climate change can be overcome through mitigation by implementing shade plants. The saturated hydraulic conductivity of the soil is defined as the movement of water in a porous medium in a saturated state. By measuring hydraulic conductivity, it can determine the ability of the soil to conduct water and see the movement of water in the soil. The highest value of saturated hydraulic conductivity at a depth of 0-20 cm was found in coffee plants with sengon shade at 31.02 cm hour-1. The highest value of saturated hydraulic conductivity at a depth of 20-40 cm was found in coffee plants with the shade of Dadap plants, which was 56.67 cm hour-1, included in the fast category. Differences in shade and soil depth in coffee fields affect the value of the saturated hydraulic conductivity. There is a relationship between several physical properties of the soil and the saturated hydraulic conductivity of the soil. The physical properties of the soil affect the saturated hydraulic conductivity of the soil.

EFFECT OF PHOSPHOGYPSUM IN SOME PHYSICAL PROPERTIES OF SOIL

Alaboratory experiment was carried out during 2020 in the laboratories of the College of Agriculture / University of Anbar in order to study the role of phosphogypsum in the values ​​of saturated hydraulic conductivity, capillary height and water holding capacity of soil in clay soil. The phosphogypsum was added mixed with the soil at four levels (without adding, 0.3%, 0.6% and 0.9%) by weight of the soil. The treatments were incubated for 90 days by adding water at the limits of the field capacity and compensation the lost water after deplete 50% of the available water. The amount of available water, the saturated hydraulic conductivity, and the capillary height has been estimated. The soil water holding capacity increased significantly, which was 16.91% at the addition of 0.9% compared to the treatment without addition. While the highest value of the saturated hydraulic conductivity was 0.35 cm per hour -1at the level of 0.9% addition. The capillary height decreased significantly with the increase in the level of phosphogypsum addition, and the lowest value was 52 cm when adding 0.9%.

Inverse estimation of hydraulic parameters of soils with rock fragments

The application of inverse modeling to determine the hydraulic properties of layered soils with rock fragments (RF > 2 mm) is associated with complex challenges such as selecting suitable hydraulic functions and defining a strategy to optimize many parameters. These two issues were addressed in this study by performing field drainage experiments in layered soil profiles (three layers) with different particle size distributions and different percentages of RF. Water contents (θ) and pressure heads (h) were monitored at different soil depths during drainage experiments (h ≥ −200 cm). Data of θ and h for a drier range (h < −5000 cm) were determined with a dew point potentiometer on disturbed soil samples. The unimodal and bimodal van Genuchten-Mualem functions were evaluated, and their parameters were optimized using the Hydrus-1D “Inverse solution”. The RETC curve fitting software was used to estimate the second set of parameters of the bimodal function. The parameters for the uni- and bimodal models (15 and 27 parameters, respectively) were repeatedly optimized by fixing some parameters while estimating others. The unimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements only when either drainage or dew point potentiometer measurements were used. On the other hand, the bimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements when both sets of data (drainage and dew point potentiometer measurements) were used simultaneously. Furthermore, the optimized parameters were physically consistent except for a few high saturated hydraulic conductivity values. Therefore, bimodal functions should be considered to represent the hydraulic properties of soils with RF. The problem of many calibrated parameters when using bimodal functions can be managed using sequential optimization, which allowed us to estimate 27 parameters for layered soils with RF successfully.

Spatial Variability of Saturated Hydraulic Conductivity in a Karstic Environmental Protection Area

Saturated hydraulic conductivity (Ksat) is a fundamental property to understand water and solute dynamics in saturated and unsaturated soils. The objective of this study is to present and assess the results of a statistical analysis of the data obtained from the determination of the permeability of a variety of soils (Argisols, Latosols, Gleysols, and Cambisols) of the Lagoa Santa Karst Environmental Protection Area (State of Minas Gerais, Brazil). Software R version 4.0.4 was used for the statistical analyses. Argisol, Cambisol, and Gleysol samples yielded normal conductivity distributions at depth, with mean values of 1.16 x 10-1 m/d, 6.14 x 10-2 m/d, and 1.95 x 10-3 m/d, respectively. Regarding the log-normal distributed Latosol samples P48 and P52 and Gleysol sample P54sup, it was concluded that probability, respectively of 85.72%, 96.55%, and 47.37%, exists for hydraulic conductivity values between 0.1 x 10-1 m/d and 4 x 10-1 m/d to occur. Studies or criteria to establish Ksat values that should be really representative of the whole study area have not been found. It was preferable to characterize Ksat in terms of levels of probability of occurrence rather than values, such as the mean or median, in order to represent an area that will be subject to the same water flow control operations (irrigation and drainage practices, leaching and erosion control, etc.). Therefore, it is not appropriate to assume a normal distribution of saturated hydraulic conductivity values for areas with the characteristics of Lagoa Santa.

Analytical solution for coupled hydro-mechanical modeling of infiltration in unsaturated soils

• Analytical solution presented for coupled modeling of 1D unsaturated infiltration. • Coupling effect can be significant for depending on soil type and stiffness. • Solution can be used in site-specific or regional analyses of unsaturated soils. Simulating water infiltration in unsaturated soils is an important step in analyzing a wide range of engineering and geosciences applications. The infiltration problem inherently possesses a coupled hydro-mechanical problem in which the unsaturated flow and the soil deformation interact and affect each other. This hydro-mechanical coupling, however, has been ignored in the majority of existing analytical solutions, mainly due to the complexity associated with the mathematical derivation. This paper presents a novel analytical solution for coupled hydro-mechanical modeling of one-dimensional (vertical) infiltration in unsaturated soils. We present an analytical solution for two problems where infiltration is applied at the top boundary as a constant pressure head (first problem) or as a constant flow rate (second problem). A parametric study was performed to examine the effects of hydro-mechanical coupling and various soil parameters on pressure head and strain profiles versus depth. Results reveal that the coupling effect can be pronounced for various values of saturated hydraulic conductivity, Gardner’s α parameter, and Young’s Modulus. The solution can be readily incorporated into site-specific (e.g., groundwater modeling, slope stability) or regional-scale (e.g., landslide mapping) analyses of unsaturated natural and man-made slopes and earthen structures subject to infiltration. Further, the presented analytical framework offers a benchmark for the validation of numerical methods.

Saturated and unsaturated seepage analysis of earth-fill dams using fractal hydraulic conductivity function and its verification

One of the most important factors concerning the design of earth-fill dams is the accurate seepage estimation, which is highly correlated to the permeability and hydraulic conductivity of the core material. With the geographic coordinates of 37°31′35.9,“ North and 46°07′55.6″ East, Gale chay dam is located in the northwest of Iran in East Azerbaijan province. The dam is highly important regarding the provided economic benefits for the region. In this research, the steady-state seepage analysis of the Gale Chay dam was conducted via the finite element model (FEM) using a novel saturated fractal hydraulic conductivity model, and the results were compared with those obtained from the conventional and fractal models in the unsaturated condition. For estimating the saturated hydraulic conductivity of the core material, the fractal theory was employed using the image processing technique, the Scanning Electron Microscope (SEM) images, and a new fractal permeability model. The estimated saturated hydraulic conductivities were in good accordance with the measured values. Furthermore, since the fractal theory considers the distribution of the pores, the estimated upper and lower bounds of the saturated hydraulic conductivity resulted in better seepage estimations. Using the estimated maximum, minimum, and average fractal hydraulic conductivities, the results of the saturated seepage analysis indicated relative errors of 15.6%, 8%, and 10.8% compared to the observed seepage. The results were acceptable in terms of safety and economic aspects. Conducting the unsaturated seepage analysis, it was observed that the estimated seepage was highly influenced by the saturated hydraulic conductivity value. Hence, the estimated average fractal hydraulic conductivity by the image processing technique affected the unsaturated fractal and conventional models in a way that the unsaturated seepage analysis was improved by an average of 80%. Moreover, the unsaturated fractal model revealed reliable estimations compared to the conventional models and was considered a feasible alternative for estimating the unsaturated hydraulic conductivity.

Model for water infiltration in vegetated soil with preferential flow oriented by plant roots

PurposeThere is strong experimental evidence that root systems substantially change the hydraulic properties of soil. However, the mechanisms by which they do this remain largely unknown. In this work, we made the hypothesis that a preferential flow of soil moisture occurs in directions which follow the orientation and distribution of roots within the soil, and that this phenomenon alters soil moisture flow patterns.MethodsWe modified Richards’ equation to incorporate root-oriented preferential flow of soil moisture. Using the finite element method and Bayesian optimisation, we developed a pipeline to calibrate our model with respect to a given root system.ResultsWhen applied to simulated root distributions, our model produced pore-water pressure profiles which agreed with those derived from experimental saturated hydraulic conductivity values of soils vegetated with willow and grass. Agreement improved for simulated root distributions where root segments were oriented in a more realistic way, suggesting that the hydraulic characteristics of vegetated soils are a consequence of root-oriented preferential flow.ConclusionBy incorporating root-oriented preferential flow, our model improves the ability to describe and analyse water infiltration through vegetated soil. This could help optimise irrigation, forecast flood events and plan landslide prevention strategies.

A simple method for correcting the effects of initial soil moisture on Modified Philip-Dunne Infiltrometer drawdown curves

The effect of varying initial soil moisture (θin) of a given soil on the drawdown curve measured using the Modified Philip-Dunne Infiltrometer (MPDI) and consequently on the estimated saturated hydraulic conductivity (Κs) value, was investigated. The laboratory tests completed using three different types of soil show that the drawdown curve was sensitive to θin for all three soils. This resulted in yielding Κs values that are sensitive to the values of θin. The lowest value of Κs was observed when the MPDI was used under wet conditions. To obtain a consistent estimate of Κs, a new correction factor was developed. This factor can be multiplied with the geometrical coefficient used in the governing equations of the MPDI to make appropriate corrections. After employing the correction factor, the variations in Κs values for all three tested soils decreased from 66%, 61% and 59%, to 26%, 16% and 26%, respectively. In situ experimental tests also show similar results and the coefficient of variation decreased from 81% to 61% after applying the correction factor. The performance was further validated by testing the relative performance of the MPDI against the results obtained using Minidisk Infiltrometer (MDI) under varying θin values. Results from the MDI show that the coefficient of variation for the Κs values of the three soils were 20%, 28%, and 32%, which are similar to the variations obtained after applying the correction factor in the MPDI model calculations. The aforementioned results indicate that the correction method proposed in this study is a useful method for improving the overall performance of MPDI.

Ecological Study of an Artificial Saline Lake Ecosystem in Wadi Al-Shatti, Libya

This study provided the first data related to the ecosystem of Ain Al-Mashashiya Lake. It is likely the new apperance of a saline artificial lake formed from agricultural drainage water from surounded local farms, small lakes provide an opportunity to understand intra-ecosystem connectivity and its dynamics. Water samples were collected representing two stations along edges and at the middle of the lake and other samples surrounded soil and vegetation. Lake depth was &gt; 5 meters, the pH was found to be relatively high at edge of the lake (7.46 &amp; 7.44) compared to at middle of the lake (7.38 &amp; 7.32). Highly saline water, i.e., 129.79 &amp; 125.48 dS/m &amp; 126.82 &amp; 133.74 dS/m at edge and middle of the lake respectively. The average level of PO4 and NO3 during winter is slightly lower than summer. The water cations abundances were typically Na &gt; K &gt; Ca &gt; Mg, where were for anions, Cl &gt; SO4 &gt; HCO3 &gt; PO4 &gt; NO3. The lake is valuable for biodiversity and provide habitat for many species. Five phytoplankton types have been registered, i.e., Cocconeis, Notholca Pandorina, Oscillatoria, Chlamydomonas. The most common species were Pandorina &amp; Oscillatoria. Soils of the study zone were classified as sandy loam, with a porosity of 44.53%. and saturated hydraulic conductivity (Ks) values was 4×10-3 cm/h and 6.4% of OM content. The soil reaction (pH) was 7.24 and its EC value was 19.42 dS/m that indicated high saline affected soil. The concentrations of Na, Ca &amp; Mg, were as high as 193, 48 &amp; 14.4 mg/kg, respectively, with low NO3 content 0.293 mg/kg. Tamarix (Tamarix aphylla) commonly found along the lake edges. The dry desert climate of the area played a main role in imposing the lake ecosystems.