Water-saturated Soil Research Articles

Extensive Pineapple Production Constraints and Land Suitability in the Centre Region of Cameroon

The low level of productivity observed in pineapple fields in Centre Came-roon must be sustainably reduced in order to increase producers’ income while using the same resources. The identification and control of production constraints are key steps in optimizing the use of limited resources. To this end, the FAO land assessment methodology following the Fuzzy-MCDM pro-tocol was used for the two pineapple production basins in the Centre, namely Awae and Bokito. It was found that the land in Awae Basin is moderately suitable S2sf with constraints imposed by texture, pH and base saturation. In the Bokito Basin, 25% of the land is suitable S1wf and 75% is moderately suitable S2wsf with constraints imposed by soil texture (27%), temporary soil water saturation (99%), pH, base saturation and exchangeable sodium. Constraint correction improves the land index (potential suitability) and re-mains limited by permanent constraints that cannot be corrected. Improve-ment of the technical itinerary through modification of plant densities, selec-tion of improved cultivars and balanced fertilization must be undertaken to optimize pineapple production in Centre Cameroon.

Получение физико-механических характеристик лимногляциальных отложений Санкт-Петербурга для математической модели грунта

The article considers the problems of using existing mathematical models (Mohr-Coulomb, Hardening Soil, Soft Soil) for calculating bases of soft soils of the lacustrine-glacial complex lg III. In addition, in geotechnical calculations there has developed the practice of forming local soil models taking into account the features of a particular region. A detailed study of the physical and mechanical properties of soils is a necessary aspect for the validation of models in software systems. In this regard, the authors have carried out a study of the weak clayey water-saturated soil of St. Petersburg to regulate the program of its laboratory tests and values for mathematical models in the regional geotechnical software systems.

Constructive and technological solutions for underground space safety amidst dense historical buildings and weak foundation soils

The article considers the issues of geotechnical substantiation and application of constructive and technological measures for the construction of underground space up to 4.4 m deep in the closed courtyard of the Palace built in the 18th century in conditions of weak water-saturated soils in the historical center of St. Petersburg. The underground space of 18.4 x 29.4 m was arranged in close proximity to the enclosing structures of civil buildings built in the 18th - 19th centuries. The article presents design solutions based on the finite element calculation method for strengthening the foundations of existing buildings, enclosing the pit and the foundations of the new structures, which comprehensively ensure compliance with the required safe additional deformations of the surrounding buildings. The results of geotechnical monitoring are presented in comparison with the results of a numerical calculation of the main load-bearing structures of new and existing buildings of the surrounding development during the construction process.

Surfactant-mediated mobility of carbon dots in saturated soil: comparison between anionic and cationic surfactants.

Understanding the mobility, retention, and fate of carbon dots (CDs) is critical for the risk management of this emerging carbon material. However, the influences of surfactants on CDs' transport through subsurface media are still poorly understood. Herein, column experiments were conducted to explore the different influences of an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), on the CDs' transport in water-saturated soil. In the Na+ background electrolyte, both surfactants facilitated the transport of CDs at pH 7.0. The trend stemmed from steric hindrance, a decline in the straining effect, and competitive deposition between CDs and surfactant molecules. Additionally, SDBS increased the electrostatic repulsion of CDs and soil. Interestingly, in the divalent cation background electrolytes (i.e., Ca2+ or Cu2+), SDBS suppressed CDs' mobility, whereas CTAB had the opposite effect. The transport-inhibited effect of SDBS was mainly due to anionic surfactant ion (DBS-) precipitation with metal cations and the formation of adsorbed SDBS-Cu2+/Ca2+-CDs complexes. The enhanced effect of CTAB resulted from the CTAB coating on soil grains, which suppressed the cation bridging between CDs and soil. Furthermore, the magnitude of the SDBS promotion effect was pH-dependent. Surprisingly, CTAB could inhibit CDs' mobility at pH 9.0, owing to the binding cationic surfactant's strong hydrophobicity effect on the soil surface. Moreover, the experimental breakthrough curves of CDs were well described using a two-site transport model. Overall, the observations obtained from this study shed light on the relative mobility of CDs with different surfactants in typical groundwater conditions.

Assessment of the stress-strain state of pile foundations of a multi-story building with possible water saturation of loess soil

The increase in the density of buildings leads to the need to set aside for development areas that were previously considered unfavorable from the point of view of the quality of the geological conditions. Deposits of loess rocks cover almost 80% of the territory of Ukraine. Such soils are characterized by a negative feature - the ability to rapidly reduce their mechanical properties in contact with liquid and to cause additional subsidence deformations. Based on this, a significant part of buildings and structures is erected in conditions of the possible occurrence of uneven deformations due to water saturation of subsidence soils. Therefore, the foundation structures of these structures must be designed with taking into account the occurrence of subsidence of loess soils.
 In their natural state, loess soils have sufficiently high mechanical characteristics due to structural connections. However, as the moisture content increases, the resistance to compression rapidly decreases, structural bonds are destroyed, and soil subsidence is observed.
 The modern level of foundation structures design involves the search for a reliable and cost-effective foundation option. This is especially relevant in the conditions of construction on soils that have the property of settling with possible increase in moisture content.
 The paper presents the results of a comparison of foundation options, taking into account the influence of possible water saturation of loess soils on the stress-strain state of foundation structures. Different schemes of possible water saturation of loess soils were considered depending on their size and location.
 This publication is a continuation of the previously published work [4]. It was about the results of the research, which was devoted to the variant design of foundations using numerical simulation of the joint work of the elements of the "soil base - foundation - above-ground structures" system. According to the results of the study, the choice of a rational option of foundations was substantiated, based on its indicators of reliability and economic efficiency. The conducted research confirms that the size and location of the soaking zones of the subsiding soil affect the nature of the stress distribution in the foundation structures. It is shown that the variant design of foundations, taking into account the negative factors related to the soil conditions of the construction site, as well as man-made situations that may arise during the operation of the building, make it possible to design a reliable and at the same time cost-effective option of the foundations.

Mammals of Hazeldell Nature Preserve, Pulaski County, Kentucky: A Rare Highland Rim Ecosystem

Hazeldell Nature Preserve is a rare ecosystem on the Highland Rim of south-central Kentucky. It is the only state-protected site of its kind. This preserve is comprised of two distinct plant communities, including wet flatwoods and wet meadow. Despite its uniqueness, no ecological studies have been conducted on mammals in the past. Currently, two separate studies are underway on mammals. Here we present the results from the first of these that used camera traps set in the wet flatwoods community from 1 February to 28 March 2020. A total of 34,071 photos were taken with 553 having images of 12 species of mammals. The four most photographed species were eastern gray squirrel, Virginia opossum, white-footed deermouse, and white-tailed deer. These four species appeared in 91% of photos. The remaining 49 photos were of eight species including: eastern cottontail, coyote, bobcat, northern raccoon, striped skunk, southern flying squirrel, common gray fox, and eastern fox squirrel. Woodchuck and eastern chipmunk were not photographed during the study, yet each have ranges that include the preserve. These burrowers may avoid the preserve because of the secondary water table and saturated soil that occur during extended periods. The results of this study serve as baseline data for comparison to future camera trapping. Continued photo documentation will be used to identify changes in the mammal species composition of the preserve caused by species range changes in response to various factors, including habitat fragmentation and climate change.

Residual plastic film exerts dual effects of blocking and preferential flow on soil water movement

Plastic-film mulching (PFM) significantly improves farmland productivity in arid and semi-arid regions. However, the residual plastic film (RPF), also named “white pollution”, has become a serious concern. The effect of RPF on soil water flow is unclear, but it has negatively impacted the use of PFM. This study evaluated the effects of RPF on soil physical and hydraulic properties. The impact on infiltration uniformity and preferential flow was examined based on dye tracer technology. The experiments were carried out with 5 RPF levels (0, 150, 300, 450, and 600 kg ha−1), and 4 infiltration amounts (20, 40, 60, and 80 mm). The results showed that increasing RPF amounts decreased soil bulk density and saturated hydraulic conductivity, but increased soil porosity and saturated soil water content in the RPF layer (0–30 cm). RPF accumulation enhanced the blocking effect in the RPF layer promoting preferential flow in the deeper soil layers. In general, with more RPF in soil, dye-stained coverage (DC) and uniform infiltration depth (UniFr) decreased, while the coefficient of variation (CVd), preferential flow fraction (PFF), dye-stained depth (MDD), length index (LI), and the difference of soil water storage between before and after dyeing (∆SWS) increased, especially in the deeper soil layers with high infiltration amount. 450 kg ha−1 RPF produced the strongest preferential flow with a maximum MDD 32.9 cm, PFF 39.2 %, LI 136.8, CVd 0.73 %, and minimum UniFr 8.8 cm. Furthermore, the phenomenon became prominent if higher infiltration amounts were applied; under 450 kg ha−1 RPF, the average CV was 8.0 % higher for 80 mm infiltration compared with 20 mm infiltration. Finally, correlation analysis shows that the RPF was the main driving factor of preferential flow.

Calculation of effective properties of geocomposites based on computed tomography images

Biot’s parameter is included in the formula for calculating effective stresses and should be taken into account when assessing the stress-strain state of a water-saturated rock mass. A method for calculating Biot’s tensor parameter based on asymptotic averaging of the equilibrium equation for a fluid-saturated porous medium is proposed. Calculations of elastic properties and Biot’s coefficient were carried out on various types of rocks - limestone, dolomite, hyaloclastite, basalt. The calculations were carried out using 3D models of geocomposites built from X-ray computed tomography images. The results of 3D calculations of Young's modulus and Biot’s coefficient coincided with the results of experimental determinations of these properties by the ultrasonic method. This fact shows the expediency of using a computational approach that implements asymptotic averaging to estimate the effective properties using 3D models of the real rock structure. The results of 3D and 2D simulation of effective properties of geocomposites are compared. 2D models were built using photographs of rock sections. It was found that the values of Young's modulus and Biot’s parameter for 2D models differ from the corresponding experimental and 3D calculation results by 20-30 %. Therefore, 2D modeling is not suitable for evaluating the effective properties of porous geomaterials. Based on the results of calculations and experiments, the dependences of Young's modulus and Biot’s coefficient on porosity were obtained and studied. These dependencies are used in non-linear numerical simulation of the consolidation of water-saturated soils. The results of the study showed that Biot’s coefficient does not depend on Young's modulus of the rock skeleton material. The influence of the pore shape on Young's modulus and Biot’s coefficient was studied using 2D calculations. A method for predicting the shape of pores from the values of porosity and Young's modulus using neural networks is proposed. Using this method, a specific algorithm for predicting the shape of pores in hyaloclastites has been implemented and studied.

The Simulation of the Nonlinear Consolidation of Porous Media

In this paper, the general formulation of the problem of coupled deformation of a porous deformable medium with a fluid flowing through the pores is formulated, mathematically investigated and numerically implemented within the framework of physical and geometric nonlinearity. We present the formulation of the problem in velocities of solid phase displacements and the rate of pore pressure change in differential and variational forms. A phenomenological approach was used to formulate the mechanical model. The equations of the coupled consolidation model were derived from the general conservation laws of continuum mechanics using spatial averaging over a representative volume element. The consolidation model took into account the change in the porosity and permeability of the medium during deformation. The equations of filtration and porosity change, originally presented in Euler approach, were reformulated in Lagrangian coordinates of the solid phase using the relative fluid velocity according to ALE (Arbitrary Lagrangian - Eulerian) approach. The Gâteaux differentiation technique was used to linearize the variational equilibrium equations. For spatial discretization of the saddle system of equations, the finite element method (FEM) was used: quadratic serendipity elements for approximating the equilibrium equations and Brick type elements for approximating the filtration equation. To solve the system of equilibrium and filtration equations, a generalization of the implicit scheme with internal iterations at each time step by the Uzawa method was used. The results of numerical simulation of elastoplastic deformation of a water-saturated soil under load with fluid outflow are presented. To simulate the constitutive relations of elastoplastic deformation of soil under short-term loads, a generalization of S.S. Grigoryan's model to large deformations is proposed. The calculations were carried out in our own program code. The developed consolidation model can be used to simulate the formation of tracking ruts and unevenness of natural roads, as well as to calculate the uneven settlement of engineering structures.

Bayesian Calibration and Uncertainty Assessment of HYDRUS-1D Model Using GLUE Algorithm for Simulating Corn Root Zone Salinity under Linear Move Sprinkle Irrigation System

Soil salinization is one of the significant concerns regarding irrigation with saline waters as an alternative resource for limited freshwater resources in arid and semi-arid regions. Thus, the investigation of proper management methods to control soil salinity for irrigation with saline waters is inevitable. The HYDRUS-1D model is a well-known numerical model that can facilitate the exploration of management scenarios to mitigate the consequences of irrigation with saline waters, especially soil salinization. However, before using the model as a decision support system, it is crucial to calibrate the model and analyze the model’s parameters and outputs’ uncertainty. Therefore, the generalized likelihood uncertainty estimation (GLUE) algorithm was implemented for the HYDRUS-1D model in the R environment to calibrate the model and assess the uncertainty aspects for simulating soil salinity of corn root zone under saline irrigation with linear move sprinkle irrigation system. The results of the study have detected a lower level of uncertainty in the α, n, and θs (saturated soil water content) parameters of water flow simulations, dispersivity (λ), and adsorption isotherm coefficient (Kd) parameters of solute transport simulations comparing to the other parameters. A higher level of uncertainty was found for the diffusion coefficient as its corresponding posterior distribution was not considerably changed from its prior distribution. The reason for this phenomenon could be the minor contribution of diffusion to the solute transport process in the soil compared with advection and hydrodynamic dispersion under saline water irrigation conditions. Predictive uncertainty results revealed a lower level of uncertainty in the model outputs for the initial growth stages of corn. The analysis of the predictive uncertainty band also declared that the uncertainty in the model parameters was the predominant source of uncertainty in the model outputs. In addition, the excellent performance of the calibrated model based on 50% quantiles of the posterior distributions of the model parameters was observed in terms of simulating soil water content (SWC) and electrical conductivity of soil water (ECsw) at the corn root zone. The ranges of NRMSE for SWC and ECsw simulations at different soil depths were 0.003 to 0.01 and 0.09 to 0.11, respectively. The results of this study have demonstrated the authenticity of the GLUE algorithm to seek uncertainty aspects and calibration of the HYDRUS-1D model to simulate the soil salinity at the corn root zone at field scale under a linear move irrigation system.

EXPERIENCE IN STRENGTHENING UNDERGROUND PEDESTRIAN CROSSINGS IN WATER-SATURATED CITY SOILS

Purpose: to analyze the problem of subsidence of vertical and horizontal elements of underground pedestrian crossings in the conditions of the city of Kyiv (Intersection of Mineralna – Ukrainian streets) taking into account the water-logged structure of the soil. Find a modern solution to this problem using a scientific approach. Using the example of an underground pedestrian crossing, identify the most deformed areas in the elements of the joints of vertical and horizontal structures for further processing and drawing a conclusion for the elimination of similar ones in the future.Methodology: in order to establish the reasons that caused the deformation of structures, to solve the task of engineering survey of the technical condition of their reinforced concrete structures with an instrumental survey of the actual strength, geometry and monitoring of uneven precipitation. Based on the results of field and chamber work, a complex ofstrengthening and restoration engineering and technical measures was developed and recommended to the customer for implementation, taking into account the requirements. Originality: the article provides an example of the implementation of the construction of the foundations of underground pedestrian crossings erected on water-saturated soils in complex engineering and geological conditions using construction water subsidence, usingtechnological methods, with the aim of excluding uneven deformations of foundation sediments above the zones of depression funnels from water subsidence or artificial foundations from vertical cement-soil reinforcing elements, the frontal part of which must be wrapped in reliable base soils.Findings and practical implications. The sealing of horizontal and vertical technological and sedimentary-temperature seams in the construction of foundations, walls and the covering of underground structures should be carried out using modern types of hydraulic plugs that perceive the hydraulic pressure from underground water and exhibit the property of swelling when in contact with flooding water. Such technological solutions can be used in the construction of underground pedestrian crossings in the conditions of dense urban development, in the presence of significant possible vertical deformations in water-saturated soils.Keywords: subsidence, sediment, crack, depression curve, mountain pressure, waterproofing, pile, cement-soil reinforcing element, monitoring

Justification of the application of low-viscus polyurethane in conditions of poorly water-saturated soils

Purpose. Analytical justification of the method of strengthening the stability of the water-saturated alluvial soil massif around the subway tunnel by the method of jet cementation using low-viscosity polyurethane. Consider the advantages of this material and present the strength characteristics. The methods. Analytical justification of the method of strengthening the stability of the water-saturated alluvial soil massif around the subway tunnel by the method of jet cementation using low-viscosity polyurethane. Consider the advantages of this material and present the strength characteristics. Findings. The use of a mixture of concrete and low-viscosity polyurethane during jet cementing allows to increase the strength characteristics of piles, thanks to the advantages of polyurethane. The material has a high density, ozone resistance, stability at high and low temperatures, the possibility of use under significant mechanical loads, with a high density, it does not have a large mass, it is elastic. When filling wells with a mixture of cement and polyurethane solution in interaction with water-saturated soil, the physical and mechanical characteristics of the soil and the load on the structure of the metro tunnel change. Based on the analysis of the data on the consolidation of the soil massif, it can be highlighted that to increase the stability of the water-saturated soil massif, it is advisable to use the jet cementation method with the addition of low-viscosity polyurethane. The originality. The use of low-viscosity polyurethane as a cementing material by jet cementation is highly effective in cementing weak water-saturated soils. The use of polyurethane will make it possible to shorten the period of work, reduce the amount of material, and increase operational characteristics. Practical implementation. The silicification method is common and convenient for strengthening underground soil in the case of dense urban development, but the use of piles as a result of mixing soil with polyurethane will not only reduce the duration of work, but also reduce the cost and increase the speed of pile hardening, increase the range of coverage of the water-saturated massif near the tunnel, will reduce the possibility of the formation of an anti-filtration cushion, which is safer for urban development

The Liquifaction Modeling to Analysis of Soil Structure Composition

Indonesia is a country that is prone to natural disasters, one of which is liquefaction. The earthquake that occurred in Palu City in 2018 was a tsunami, and the ground moved or also known as liquefaction. The purpose of this study is to analyze the results of modelling the liquefaction potential using a shaking table test tool based on the composition of the soil structure and based on the groundwater level. The type of research used is descriptive qualitative research with modelling using a table test tool. The soil samples used were beach sand and clay soil with dry soil conditions and diameter based on the results of sieve no. 20 with a hole diameter of 0.85 mm. The water volume used is 4 L, 4.5 L, and 5 L. The result of this research is sand soil which is water-saturated soil liquefaction occurs and based on the groundwater level shows sand soil whit a volume of 5L, which is assumed to be a shallow groundwater level experiencing greater and faster liquefaction. One of the factors that occur in a liquefaction area is a water-saturated which has a shallow groundwater level.

The assessment of liquefication potential of water-saturated soils

The liquefaction potential of soils with a content of fine-grained fraction from 14.72 to 66.88% and unit weight from 20.1 to 22.5 kN/m3 in the vicinity of Sofia was evaluated. The assessment was carried out using the cyclic shear stress method. The analysis was performed for a seismic impact with magnitude Ms = 7.5 and at the maximum reference horizontal acceleration at the ground surface αmax(g) = 0.23 and for free field conditions without load from buildings and facilities.

Prediction of the soil saturated hydraulic conductivity in a mining area based on CT scanning technology

In an open-cast mining area, large-scale machinery compaction causes severe soil degradation. Exploring the soil hydraulic characteristics at different bulk densities is of tremendous significance for soil restoration and soil hydrological balance in the reclamation area of the destructed land. Saturated hydraulic conductivity (Ks) is one of the important parameters to characterize soil infiltration capacity. The soil compaction in the mining area significantly affects soil saturated hydraulic conductivity, and its field measurement is very difficult due to the severe soil compaction. Precise prediction of soil saturated hydraulic conductivity is a prerequisite for understanding water movement and solute transport processes. In this study, soil samples taken from the dump site of the Antaibao open-pit coal mine in the Pingshuo mining area of China were prepared in laboratory according to different bulk densities (1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, and 1.8 g cm−3), and the soil saturated water conductivity was measured in laboratory using constant head method. Moreover, the CT scanning technology was used to obtain soil macropore structure, and the fractal dimension of soil macropores was calculated, and the soil saturated water conductivity was predicted based on the fractal dimension. The number of macropores and macroporosity decreased with the increase in the bulk density, and the soil compaction resulted in poor connectivity of the soil macropores. The trend of the soil saturated water conductivity predicted using the CT scanning technique was consistent with that of the measured values in the laboratory under different bulk densities. With the increase of bulk density, the difference between the predicted value and the measured value increased slightly. Overall, a good prediction effect was achieved (R2 > 0.84). The prediction of the soil hydraulic characteristics of compacted soil in mining area based on CT scanning technology was feasible, and it can be applied to the study of practical problems in soil science.

ENERGY-EFFICIENT INSULATION SYSTEMS FOR LOW-RISE BUILDINGS

Statement of the problem. Low-rise construction is characterized by a relatively low cost and a possibility of forming effective insulating structure shells. Frames and massive walls are used as load-bearing structures, it is also possible to use concrete. Taking into account the current realities, the most relevant is the orientation of systems to the use of domestic materials including those capable of functioning effectively in harsh climatic conditions. Results. It was established that the properties of polyethylene foam and products based on it make it possible to recommend this material both in facade and roof insulation systems as well as in those in contact with the ground. It was found out that polyethylene foam causes almost no changes in the properties under freezing conditions down to minus 70 °C and in the range of sign-variable temperatures from -60 to +70 °C. With prolonged contact with water or water-saturated soil, the properties of the material are also stable. Conclusion. The use of rolled polyethylene foam is promising both in terms of the properties of the material itself and in view of the possibility of forming seamless insulating shells. The formation of seamless insulating shells creates practically impenetrable heat-vapor- and water-insulating barriers along the perimeter of the insulated object. The study of the properties of polyethylene foam in various operating conditions and insulation systems was the goal of the research described in the article. Methods approved by domestic standards were adopted as the basis for the research.

Approximate analytical solution to equation for two-dimensional soil-water movement in ponding infiltration based on numerical simulation

A simple analytical solution to two-dimensional (2D) ponding infiltration is essential for designing line-source or drip irrigation. We propose a new and simple approximate analytical method for calculating the 2D distribution of soil water with a 1-cm radius of ponding and uniform initial conditions and for estimating the horizontal and vertical distances of wetting fronts based on soil hydraulic parameters. The method assumes a semi-elliptical soil-wetting pattern and a one-dimensional profile of soil water at an arbitrary infiltration angle to solve the equation for the 2D movement of soil water and cumulative infiltration. We applied the numerical data simulated using HYDRUS-3D to validate the proposed method's parameters and evaluate the relationship between the wetting front and hydraulic parameters. The simulated results indicated that the assumptions were propitious to the fine-texture soils with air-entry suction larger than 10 cm. The ratio between the distances of the horizontal and vertical wetting fronts could be approximately predicted using the air-entry suction by analyzing the numerical results. The fitted results indicated that the parameters of the power function of the relationship between the distances of the horizontal and vertical wetting fronts and infiltration time could be described as polynomial and power functions of the diffusivity of saturated soil water. The approximate analytical solutions for the distance of the horizontal wetting front, depth of the vertical wetting front, and cumulative infiltration agreed well with other numerical simulations.

What makes soil landscape robust? Landscape sensitivity towards land use changes in a Swiss southern Alpine valley

Landscape sensitivity is a concept referring to the likelihood that changes in land use may affect in an irreversible way physical and chemical soil properties of the concerned landscape. The objective of this study is to quantitatively assess the sensitivity of the southern Alpine soil landscape regarding land use change-induced perturbations. Alpine soil landscapes can be considered as particularly sensitive to land use changes because their effects tend to be enhanced by frequent extreme climatic and topographic conditions as well as intense geomorphologic activity. In detail, the following soil key properties for soil vulnerability were analysed: (i) soil texture, (ii) bulk density, (iii) soil organic carbon (SOC), (iv) saturated hydraulic conductivity (Ksat), (v) aggregate stability and (vi) soil water repellency (SWR). The study area is characterized by a steep, east-west oriented valley, strongly anthropized in the last centuries followed by a progressive abandonment. This area is particularly suitable due to constant lithological conditions, extreme topographic and climatic conditions as well as historic land use changes. The analysis of land use change effects on soil properties were performed through a linear mixed model approach due to the nested structure of the data. Our results show a generally high stability of the assessed soils in terms of aggregate stability and noteworthy thick soils. The former is remarkable, since aggregate stability, which is commonly used for detecting land use-induced changes in soil erosion susceptibility, was always comparably high irrespective of land use. The stability of the soils is mainly related to a high amount of soil organic matter favouring the formation of stable soil aggregates, decreasing soil erodibility and hence, reducing soil loss by erosion. However, the most sensitive soil property to land use change was SWR that is partly influenced by the amount of soil organic carbon and probably by the quality and composition of SOM.

Hydropedological Characteristics of the Cathedral Peak Research Catchments

It has long been recognised that the role of soils is critical to the understanding of the way catchments store and release water. This study aimed to gain an understanding of the hydropedological characteristics and flow dynamics of the soils of three mountain catchment areas. Digital soil maps of the hydropedological characteristics of the catchments were interpreted and a conceptual response of these watersheds to precipitation was formed. This conceptual response was then tested with the use of site-specific precipitation and streamflow data. Furthermore, piezometers were installed in soils classified as the interflow hydropedological soil group as well as the saturated responsive hydropedological soil group and water table depth data for the three catchments were analysed. Climatic data indicated that there is a lag time effect in the quantity of precipitation that falls in the catchment and the corresponding rise in streamflow value. This lag time effect coupled with data obtained from the piezometers show that the various hydropedological soil groups play a pivotal role in the flow dynamics. Of importance is the unique influence of different wetland systems on the streamflow dynamics of the catchments. The drying and wetting cycles of individual wetland systems influenced both the baseflow connectivity and the overland flow during wetter periods. They are the key focus in understanding the connectivity between the hydropedological flow paths and the contribution of soil water to the stream networks of the three catchments.

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.