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Low-cost ceramic water filters are a very effective point-of-use technology for removing bacteria and protozoa from drinking water. The filters are made from locally sourced clay and a porogen materials such as sawdust. It is recommended that the sawdust be sieved to 30-sieve (600 μm) to make reliable filters. However, the size distribution of sawdust is usually broad and can extend below 100 μm. This study divided 30-sieve sawdust into four narrower size distributions and made filter disks for measurement of hydraulic conductivity and bulk density. Additionally, the microstructure of the materials was examined in three dimensions by micro-CT. The results showed that, independent of sawdust particle size, the void volume fraction in the filter increased linearly with the weight fraction of sawdust. In contrast, the permeability coefficient increased non-linearly as the fraction of sawdust increased. The magnitude of the permeability was higher for the larger sawdust particles when the sawdust fraction was 10 wt% or higher. Three-dimensional imaging of the pore structure in the filters suggested that the non-linear increase in permeability with increasing weight fraction of sawdust may be associated with increased interaction of the cavities created by the sawdust. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new in situ fracturing-enhanced oxidative remediation method is recommended. • New method helps KMnO 4 efficiently remediate low-permeability PHE-contaminated soil. • A systematic evaluation method is provided to obtain optimal engineering parameters. • KMnO 4 migration between fractures follows piecewise first-order reaction kinetics. • Possible degradation products and pathways of PHE oxidized by KMnO 4 are proposed. For low-permeability contaminated sites, existing combined fracturing-oxidation remediation technologies rely on diffusive migration of the oxidant to remediate only a small area near the fracture, resulting in long site-wide remediation times. Therefore, this study proposed a new fracturing-enhanced oxidative remediation method aimed at achieving rapid remediation of low-permeability polycyclic aromatic hydrocarbon-contaminated sites. Specifically, this study investigated the effect of potassium permanganate (KMnO 4) oxidation on the remediation time, total oxidant demand, phenanthrene (PHE) removal, oxidation kinetics, and physicochemical properties of low-permeability PHE-contaminated soil under fracturing conditions through one-dimensional rigid-wall hydraulic conductivity tests and a series of laboratory experiments. The results indicate that according to systematic evaluation, the optimal Darcy velocity was ≥ 5.95 × 10-6 m/s, and the optimal KMnO 4 concentrations for remediation of contaminated soils with low and medium–high PHE concentrations were 1 g/L and 2 g/L, respectively. The migration of KMnO 4 within the soil matrix between two adjacent parallel fractures followed piecewise first-order reaction kinetics. Additionally, KMnO 4 oxidation under fracturing conditions had less impact on the physicochemical properties of low-permeability PHE-contaminated soils while significantly reducing their ecotoxicity. Overall, this new remediation method shows promise for the rapid and efficient cleanup of low-permeability contaminated sites. Further research is warranted to evaluate the influence of other factors (e.g., permeability) on the oxidation effectiveness and kinetics of KMnO 4 in low-permeability PHE-contaminated soils. [ABSTRACT FROM AUTHOR]

• Porosity increased with freeze–thaw cycles (FTCs) when water content was below 30%. • Bulk density decreased with FTCs but increased at high water content and erosion. • Field capacity decreased with FTCs but increased at high bulk density. • Hydraulic conductivity increased with FTCs but decreased at high water content. • Erosion degree was the most critical factor affecting physical properties. Freeze-thaw cycles (FTCs) extensively and intensely occur in cold regions, significantly affecting soil properties. However, quantifying the impacts of FTCs at different initial conditions on soil properties is challenging due to the complex interactive responses. In this study, porosity, bulk density, field capacity and saturated hydraulic conductivity (K s) were measured to evaluate the responses of soil to FTCs. Eight FTCs (0, 1, 3, 5, 7, 10, 15 and 20 cycles), five initial soil mass water contents (10, 20, 30, 40 and 45 %), four eroded soils (original, degraded, deposited and parent), two initial bulk densities (1.2 and 1.3 g cm−3) and two freezing temperatures (−10 and −15 ℃) were employed to quantify the impacts of FTCs on physical properties. Results showed that repeated FTCs had a cumulative effect on soil physical properties, which generally entered a steady state after 10–15 FTCs. Changes in soil physical properties were highlighted after the initial 1–3 FTCs, and the effects of FTCs on physical properties diminished when the soil water content was below 20 %. Soil physical properties with different initial conditions responded differently to FTCs. Porosity increased with FTCs in increments ranging from about 0.2 to 8.7 %; however, the opposite result was observed when the initial soil water content exceeded 30 %. The bulk density decreased by 1.1–3.7 % with increasing FTCs, whereas the bulk density of the soils with high water content and severe soil erosion increased by 0.2–7.5 %. Compared to the initial state, the field capacity decreased by 0.1–15.3 % after 20 FTCs; however, the field capacity increased by 10.4 % under high bulk density. The K s increased by 21.8–249.5 % with the increase of FTCs, whereas the K s of the soils with 40 % and 45 % water content decreased by 28.7 % and 90.4 %, respectively. Overall, soil physical properties responded more strongly to FTCs at high water content, severe soil erosion, moderate bulk density and low freezing temperature. In comparison, the degree of soil erosion was the most critical factor influencing soil physical properties. These findings can help to improve the understanding of soil dynamic processes and provide new insight into mechanisms of erosion caused by seasonal FTCs. [ABSTRACT FROM AUTHOR]

• Sixteen soils from Central Chile were heated at 100 °C and 300 °C. • Hydraulic properties were monitored after heating. • Most hydraulic properties showed a significant change at 300 °C. • Relationships between hydraulic parameters and soil properties were explored. • Models based on OM and texture are useful for predicting hydraulic parameters. Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 °C and 300 °C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 °C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 °C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 °C and 300 °C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM. 1 1 Ca2+ = Calcium cations (meq/ 100g); CEC = Cation exchange capacity (meq/ 100g); CM = Chilean Matorral; EC = Electrical conductivity (μS/cm); I = Cumulative infiltration (cm); K = Unsaturated hydraulic conductivity (mm/h); K+ = Potassium cations (meq/ 100g); Ks = Saturated hydraulic conductivity (mm/h); Mg2+ = Magnesium cations (meq/100g); Na+ = Sodium cations (meq/100g); OM = Organic matter (g/100g); R index = Water repellency index; Se = Ethanol sorptivity (cm/s05); Sw = Water sorptivity (cm/s05); VTF = Valdivian Temperate Forest; WSA = Water-stable aggregates (%). [ABSTRACT FROM AUTHOR]

• Wood anatomical traits exhibit clear variations in the three target tree species. • Wood anatomical traits can be categorized into two functional groups related to growth and hydraulics. • High temperatures detriment tree growth, but benefit xylem-specific hydraulic conductivity (Ks). • Ks has different effects on tree growth, drought resistance and drought recovery among tree species. • Pinus tabuliformis in semi-arid mixed forests should be protected as a priority. With the intensification of climate warming, drought has become increasingly severe. Drought seriously impacts tree growth and may even result in tree mortality. However, our understanding of how the hydraulic structure of xylem in different tree species regulates growth and drought resistance remains incomplete. Here, we collected tree-ring samples from three semi-arid natural Chinese pine (Pinus tabuliformis)-broadleaf mixed forests in northern China. We selected Chinese pine (non-porous wood), white birch (Betula platyphylla , diffuse-porous wood), and Liaodong oak (Quercus liaotungensis , ring-porous wood) as target tree species. Using dendrochronology and wood anatomy methods, we evaluated interspecies differences in tree growth, climate sensitivity, and drought resistance, and analyzed the relationships between tree growth, drought resistance, and theoretical xylem-specific hydraulic conductivity (Ks). Our findings revealed distinct differences in the hydraulic structure of xylem among these three tree species as well as their resilience to drought. Liaodong oak exhibited less sensitive to drought compared to Chinese pine and white birch. Meanwhile both Chinese pine and Liaodong oak demonstrated greater resistance to drought than white birch. The positive correlation between specific xylem hydraulic conductivity and both tree growth and drought resistance were observed for Chinese pine, but Liaodong oak was the opposite. This suggested that specific hydraulic conductivity of xylem cannot serve as a consistent or robust predictor of tree growth or drought resistance across different species. As climate warming intensifies, it is anticipated that white birch may experience severe and significant irreversible decline in growth, while Liaodong oak may exhibit the highest potential growth performance. Given the projected intensification of future warming trends along with more frequent extreme climate events, safeguarding biodiversity and productivity within semi-arid Chinese pine-broadleaf mixed forests may hinge on the prioritizing protection efforts for Chinese pine. [ABSTRACT FROM AUTHOR]

In this study, we focused on the 3D dispersion of colloids. To our knowledge, we were the first to do so. Thereto, we injected silica encapsulated DNA tagged superparamagnetic particles (SiDNAmag) in a homogeneous coarse grain sand tank. At four downstream locations, SiDNAmag concentrations were determined as a function of time. Longitudinal and transverse dispersivity values and associated uncertainties of SiDNAmag were determined using Monte Carlo modelling approach. The parameter associated uncertainties of hydraulic conductivity as well as of the effective porosity estimated from SiDNAmag breakthrough curves were statistically similar to those estimated from salt tracer breakthrough curves. Further, the SiDNAmag dispersivity uncertainty ranges were then statistically compared with the salt tracer (NaCl, and fluorescein) dispersivities. Our results indicated that time to rise, time of peak concentration and shape of the breakthrough curves of SiDNAmag were similar to those of the salt tracer breakthrough curves. Despite the size difference between the salt tracer molecules and SiDNAmag, size exclusion did not occur, probably due to the large pore throat diameter to SiDNAmag diameter ratio. The median longitudinal dispersivity (α L) of salt tracer and SiDNAmag were 4.9 and 5.8 × 10−4 m, respectively. The median ratio of horizontal and vertical transverse dispersivities to α L , (α TH /α L and α TV /α L , respectively), for salt tracer and SiDNAmag ranged between 0.52 and 0.56. Through the statistical tests, we concluded that the longitudinal and traverse dispersivities of SiDNAmag were not statistically significantly different from salt tracer in 3 dimensions and could be used to characterize the dispersive properties of the medium we used. Our work contributes to a better understanding of 3D dispersion of SiDNAmag in saturated porous media. • 3D dispersive behaviour of SiDNAmags was investigated in a homogeneous sand tank. • SiDNAmag dispersivity and associated uncertainty was statistically not different from the conservative salt tracer. • SiDNAmag and Salt tracer showed similar time of peak concentration in homogeneous coarse grain sand. [ABSTRACT FROM AUTHOR]

Inverse grading structures are commonly found in landslide accumulations of high-speed and long-runout landslides. However, there is limited research on the internal erosion of inverse grading deposits. This study developed a program called discontinuous deformation analysis (DDA) and Darcy's law coupling program (DDCP) using C language to investigate the failure mechanism associated with internal erosion in inverse grading sand. The results indicate that as the hydraulic gradient increases, the internal erosion phenomenon becomes more pronounced. The failure of the inverse grading sand due to internal erosion can be attributed to three processes: loss of fine particles in the lower layer, accumulation of the particles from the upper layer in the lower layer, and flow of fine particles from the upper layer through the lower layer and exit from the bottom. During the internal erosion process, both the hydraulic conductivity and porosity initially decrease and then increase. Similarly, the average velocity of fine particles exceeds that of coarse particles in each layer. The stability of the inverse grading sand during the internal erosion increases with a higher content of fine particles in the lower layer. These findings are significant in understanding the mechanism of internal erosion within inverse grading deposits. [ABSTRACT FROM AUTHOR]

Clay-amended barriers are widely used to prevent hazardous leachate percolation from landfill to subsurface. The performance of these barriers is mostly evaluated through numerical simulations with limited experimental investigation through leachate flushing experiments. To bridge this gap, contaminant loading and its flushing experiments were carried out to assess the performance of clay-amended composite materials as landfill liners. River sand (Sa), loamy soil (Ns), and alternative waste materials like fly ash (Fa) and flushed silt (Si) were used to prepare the composites. Composites fulfilling the hydraulic conductivity (<10−7 cm/s) and compressive strength (200 kPa) criteria were selected for contaminant loading and its flushing experiments to understand the fate of fluoride ions. The experimentally determined hydraulic conductivity (K s) values for all the composites were in the order of 10−8 cm/s. The experimental breakthrough curves exhibited skewed shape, long tailing, and dual peaks. Dual porosity and dual permeability with immobile water models were employed to simulate these curves, revealing that preferential flow pathways and random chemical sorption sites significantly affect solute transport in clay-amended barriers. Further, scanning electron microscopy and energy-dispersive X-ray spectroscopy were employed to trace the preferred path of fluoride ions through the barrier. The removal efficiency and temporal moments were used to determine the percentage mass retained, mean arrival time, and spreading within the barrier. The highest solute mass was retained by sand-clay barrier (SaB30) (91%), followed by loam-clay barrier (NsB30) (59%), fly ash-clay barrier (FaB30) (38%), and silt-clay barrier (SiB30) (4%) with the least mass. The lowest mean arrival time was calculated for NsB30 (269 h) and the highest for SaB30 (990 h), with FaB30 (384 h) and SiB30 (512 h) having values in between. This study concludes that validating the design hypothesis of clay-amended barriers through contaminant loading and its flushing studies leads to an effective and sustainable design. [Display omitted] • Composite liners using soils and wastes offer high waste containment potential. • Physical non-equilibrium significantly affected solute transport in clay barriers. • Experimental BTCs exhibited skewed shape, long tailing, and dual peaks. • SEM-EDS analysis showed the presence of preferential flow pathways. • Clay bridges enhanced the containment efficiency of composite liners. [ABSTRACT FROM AUTHOR]

Macrodispersivity is critical for predicting solute behaviors with dispersive transport models. Conventional methods of estimating macrodispersivity usually need to solve flow equations and are time-consuming. Convolutional neural networks (CNN) have recently been proven capable of efficiently mapping the hydraulic conductivity field and macrodispersivity. However, the mapping accuracy still needs further improvement. In this paper, we present a new network shortcut connection style called weighted multi-scale connections (WMC) for convolutional neural networks to improve mapping accuracy. We provide empirical evidence showing that the WMC can improve the performance of CNN in macrodispersivity estimation by implementing the WMC in CNNs (CNN without short-cut connections, ResNet, and DenseNet), and evaluating them on datasets of macrodispersivity estimation. For the CNN without short-cut connections, the WMC can improve the estimating R2 by at least 3% on three datasets of conductivity fields. For ResNet18, the WMC improved the estimated R2 by an average of 2.5% on all three datasets. For ResNet34, the WMC improved the estimated R2 by an average of 5.6%. For ResNet50, the WMC improved the estimated R2 by an average of 16%. For ResNet101, the WMC improved the estimating R2 by an average of 30%. For DenseNets, the improved estimated R2 ranges from 0.5% to 5%. The WMC can strengthen feature propagation of different sizes and alleviate the vanishing-gradient issue. Moreover, it can be implemented to any CNN with down-sampling layers or blocks. • We proposed a short-cut connection (WMC) to improve the performance of CNN in macrodispersivity estimation. • We validated the effectiveness of WMC in ResNet and DenseNet. • The WMC can be implemented in any CNN with down-scaling layers. [ABSTRACT FROM AUTHOR]

The organic pollutants disposed at the Sardas landfill in Sabiñánigo (Huesca, northeastern Spain) by the INQUINOSA lindane factory have reached the Gállego alluvial aquifer and could affect the Sabiñánigo reservoir. The daily oscillations of the reservoir water level produce a tidal effect on the piezometric heads of the aquifer. These oscillations are transmitted in a damped way with a time lag, thus attesting that the silting sediments of the reservoir and the natural silts of the Gállego alluvial are interposed between the reservoir water and the layer of sands and gravels. A 2D finite element groundwater flow and total dissolved hexachlorocyclohexane (HCH) transport model through the Gállego alluvial aquifer is presented here. The flow model was constructed to: (1) Quantify the tidal effect, produced by the daily fluctuations of the reservoir water level on the aquifer; (2) Estimate the hydrodynamic parameters of the layer of sands and gravels; and 3) Estimate the vertical hydraulic conductivity of the silting sediments and silts; and (4) Quantify aquifer/reservoir interactions. The flow model reproduces the dynamics of the tidal effect and attests that groundwater velocity and flow direction changes daily in response to the oscillations of the reservoir level. Model results reproduce the measured well hydrographs and the Darcy velocity derived from tracer tests and confirm the validity of the conceptual model. The transport model of total dissolved HCH simulates the time evolution of the contaminant plume. The computed concentrations of total dissolved HCH and the contaminant mass outflux are very sensitive to changes in the source terms and the distribution coefficient, K d of HCH. The best fit to the measured HCH plumes in September 2010 and December 2020 is obtained with a K d ranging from 1 to 3 L/kg. The computed flux of dissolved HCH leaving the Sardas site in 2020 towards the Sabiñánigo reservoir ranges from 0.6 kg/year for K d = 3 L/kg to 3.1 kg/year for K d = 1 L/kg. The findings of this study will be most useful for planning and designing remedial and containment actions at the Sardas site and other similar lindane-affected sites. [Display omitted] • Oscillations of the reservoir level produce a tidal effect in the aquifer. • Groundwater flow changes from E -W to W-E direction when reservoir level is high. • Polluted groundwater does not discharge directly into the reservoir. • Computed concentrations of dissolved HCH are very sensitive to the K d. • The best fit to measured HCH data is achieved with K d [1, 3] L/kg. [ABSTRACT FROM AUTHOR]

A reasonable layout of subsurface drainage systems is considered essential for maximizing its drainage and salt control effectiveness. In the saline-alkali farmland of arid regions in Northwest China, low-permeability interlayers (clay, clay-loam or silty-loam) within the soils are common. However, the influence of the low-permeability interlayers on the layout of the subsurface drainage has not been extensively considered in the literature. This study investigated the process of subsurface drainage and salt discharge in salt-affected fields with silty-loam interlayers using field experiments and numerical simulations. Four field experiments were conducted, considering three different relative positions between the drainage pipes and silty-loam interlayers. The results showed that the silty-loam interlayers hindered water infiltration, and the distribution of soil salinity in the soil profile varied with the buried depth of drainage pipes at different positions relative to the silty-loam interlayer. When the buried depth of drainage pipes increased, the amount of water and salt discharged from drainage pipes increased, and the increase rate in salt discharge was greater than water drainage. A numerical model was calibrated and validated using the field experiment data, and 25 orthogonal numerical experiments were conducted to investigate the soil desalination effects of buried depth of drainage pipes, spacing between the pipes, saturated hydraulic conductivity of the interlayer, and position of the low-permeability interlayer. The results showed that the drainage pipe buried depth, spacing, and saturated hydraulic conductivity of the low-permeability interlayer had significant effects on the desalination rate (P < 0.01), while the position of the low-permeability interlayer had no significant effect (P > 0.05). Subsurface drainage pipes should be placed below the low-permeability interlayer. The desalination rate linearly increased with the buried depth of drainage pipe and saturated hydraulic conductivity of the interlayer, and it increased exponentially with decreased spacing. An empirical formula for soil desalination rate considering interlayer and subsurface drainage pipe layout parameters was fabricated and used to determine the appropriate layout parameters. • Field experiment with a silty-loam interlayer and different drain depth pipes was conducted. • The soil desalination rate was significantly influenced by the K s of the interlayer. • The effects of subsurface pipe layout parameters and interlayer on N were analyzed. • A formula considering the interlayer and subsurface pipe layout parameters was built. [ABSTRACT FROM AUTHOR]

The flow through saturated porous soil is described by Darcy equation that generally has no analytical solution. Therefore, we have to use numerical methods to solve it. There exist several numerical methods and the well-known most used one is the finite elements method. In this work, we use a Diamond finite volumes scheme characterized with its conservation property to simulate Darcy equation in the linear and the non linear case in two dimensional case, based on permeability tensor. Different test cases are studied to validate the accuracy and the efficiency of the numerical model. The numerical scheme proves, through the obtained results, high level of accuracy comparing with the exact solution. The diamond finite volumes scheme for its ability to ensure the mass conservation of our model, knowing that the finite elements or the finite differences methods are less efficient on this side, our finite volumes method is the most suited to the Darcy flow and more faithful to physical problems comparing to other methods. We focused in our study on different aspects of the finite volumes scheme, the mass conservation, the non-linearity of the hydraulic conductivity and their interaction with the finite volumes method. [ABSTRACT FROM AUTHOR]

At present, the state has introduced the policy of forest Chinese herbal medicine planting planning, strictly prohibiting the planting of Chinese herbal medicine in basic farmland, coupled with the fact that the continuous cropping obstacles of Panax notoginseng have not yet been solved, which makes the area of arable land suitable for planting become less and less. However, the effect of soil moisture regulation on the growth of Panax notoginseng cultivated on sloping arable land has not been reported. Thus, the aim of this study was to investigate the impact of various irrigation levels and slopes on Panax notoginseng agronomic traits, physiological characteristics, disease attributes, biomass, and quality characteristics. During 2018–2020, a field experiment was conducted in the Panax notoginseng growing seasons with three irrigation levels (I1: 70–75% θ FC , I2: 75–80% θ FC , I3: 80–85% θ FC) and three slopes (S1: 2.43°, S2: 6.38°, S3: 16.38°). The results evidenced that the photosynthetic characteristics, root hydraulic conductivity characteristics, biomass and PNS of Panax notoginseng reached the maximum value in the I2S2 treatment, and at the same time, the incidence rate of Panax notoginseng root rot was the lowest. Therefore, based on the results of this study, irrigation volume I2S2 should be regarded as the optimal slope and irrigation management strategies for reducing Panax notoginseng diseases and realizing stable yield and quality improvement of Panax notoginseng. A multi-objective optimization model was established through binary quadratic regression analysis. The findings evidenced that when the irrigation interval was 187–203 mm and the slope interval was 5–10.7°, Panax notoginseng had the lowest incidengce rate, and the root biomass and saponin content reached > 95% of the maximum values at the same time. [Display omitted] • Moisture and slope coupling reduces root rot in Panax notoginseng • Panax notoginseng had the worst hydraulic conductivity under I1S3 treatment • The most suitable slope for planting Panax notoginseng is 5–10.7° • Irrigation 152–193 mm balanced the relationship between morbidity, yield, and PNS [ABSTRACT FROM AUTHOR]

A cracked rock mass can be idealized using a three-set model of orthogonal cracks. By varying the number of cracks per set, the structural anisotropy caused by the cracks is represented, and by rotating the principal axes of the structural anisotropy a more realistic model is constructed following field observations. A constitutive law for closing a crack aperture is formulated based on the results of the extensive laboratory tests previously reported. Parameter H , which controls stress-dependent hydraulic behaviors of cracked rock masses, can be determined by a laboratory test, and its mechanical significance is explained as an index of the pseudo-elastic modulus related to crack closing. The value of H experimentally determined highly depends on the number of loading cycles and whether it is loading or unloading. Information regarding the stress history is required to estimate H for cracks in the field. The depth-dependent hydraulic conductivity tensor for a cracked rock mass is formulated in a closed form, in which the effects of structural anisotropy, non-hydrostatic stress, and rotation of crack system are considered. If the stress field is hydrostatic, the hydraulic conductivity tensor exhibits unique depth dependence, despite its structural anisotropy and rotation of its principal axes. Non-hydrostatic stress exerts a significant influence on the hydraulic conductivity tensor. Hydraulic anisotropy is determined by interference among the following three factors: (a) structural anisotropy caused by cracks, (b) non-hydrostatic stress, and (c) discordance between the principal axes of the structure and stress. The importance of the second and third factors is that hydraulic anisotropy cannot be discussed solely in terms of structural anisotropy. The depth-dependent mean hydraulic conductivity obtained by the current theory corresponds well with field measurements at two sites. [ABSTRACT FROM AUTHOR]

The issue of pressurized tunnels has been sufficiently investigated in the literature; nevertheless, the long-term behavior of the problem, which is the case in very squeezing conditions, remains unexplored. From a practical standpoint, the development of a damaged zone around the tunnel, due to the poor quality of blasting for excavation, imposes an additional challenge in predicting tunnel responses. This paper introduces an analytical approach addressing both water seepage and the excavation damaged zone (EDZ) concerning the long-term behavior of lined circular pressurized tunnels. To achieve this goal, the rheological behaviors of the initial rock mass and damaged zone are modeled using the Burgers model, along with considering the time-dependent variation in the rock mass hydraulic conductivity. After the validation of the model, the conducted parametric studies reveal that rock mass and lining hydraulic conductivities, EDZ radius, and the Burger shear modulus are the most influential parameters. [ABSTRACT FROM AUTHOR]

Although grass waterways are an effective conservation practice to reduce soil erosion, less is known about their subsurface hydrogeology. New research is highlighting the potential for NO 3 -N load reductions in waterways, but studies have not been done to characterize regional patterns. In this study, we used field investigation and numerical modeling to evaluate subsurface hydrogeological conditions beneath grass waterways found in major landform regions of Iowa. Our goal was to identify waterways that could be best utilized in a new conservation practice aimed at reducing tile NO 3 -N export from cropped fields. Waterway stratigraphy consisted of a layer of fine-textured, nutrient-rich sediment overlying glacial or post-glacial parent material. The mean hydraulic conductivity (K) of the alluvial sediments reflected a dominantly silty matrix and it was highest in northeast Iowa where sand contents were higher. Groundwater was largely anaerobic in lowland waterway areas, where high water tables contributed to low dissolved oxygen and NO 3 -N concentrations in shallow groundwater. Numerical modeling parameterized using the field data showed that in terms of annual water balance, more water is exported from grass waterways in surface runoff compared to subsurface tile and groundwater flow. In terms of subsurface flow, tile water yields were higher in smaller and steeper catchments and when the K of the waterway alluvium was higher. Based on regional patterns of sedimentology and landscape topography, smaller and steeper catchments within a landform region found in NE Iowa may be most appropriate to test a new conservation practice aimed to capture and remediate tile NO 3 -N export from grass waterways. • Grass waterway stratigraphy in Iowa consist of fine-textured, nutrient-rich sediment overlying glacial parent material. • Waterways have high water table and hydraulic conductivity consistent with silt-dominated matrix. • Groundwater quality is anaerobic with low dissolved oxygen and nitrate concentrations. • Numerical modeling shows that more subsurface water flow occurs in smaller and steeper catchments with higher alluvial K. [ABSTRACT FROM AUTHOR]

Groundwater exploitation in a riparian zone causes water infiltration from the river into the aquifer. Owing to adsorption and redox reactions along the flow path, the quality of water flowing from the river to groundwater wells is variably altered. The riverbed composition often involves spatiotemporal differences due to frequent changes in hydrological conditions. These changes create uncertainties in the transport and removal of solutes in the river water. In this study, the hydrodynamic field associated with riparian groundwater, changes in the structure of riverbed sediments caused by erosion and deposition, fluctuations in surface water and groundwater levels, and the removal efficiency of pollutants from groundwater through pumping were investigated. This involved in situ monitoring and sample testing of the composition of the river water, riverbed sediments, riverbed pore water, and groundwater during dry and wet seasons. Implementation of field in situ column experiments and molecular biology evidences were conducive to identifying the main biogeochemical processes occurring in the riverbed. The findings indicated that riparian groundwater exploitation alters the natural groundwater flow field, while fine sand deposition and microbial adsorption can reduce river recharge to aquifers by diminishing riverbed hydraulic conductivity. Shallow sediments within 1 m depth mainly involve NO 3 − reduction and E. coli adsorption. Reductive dissolution of Mn dominates in the deeper sediments. Additionally, reductive dissolution of Fe and dissimilatory nitrate reduction to ammonium (DNRA) drive high Fe2+ and NH 4 + concentrations in groundwater. The findings can improve the management of riparian groundwater and aid in the optimization of a plan for its exploitation. [Display omitted] • More than 90% of nitrates and E.coli are removed within 1m of the riverbed. • Reduction dissolution of minerals increases iron and manganese levels in groundwater. • Nitrate reduction drives high concentrations of NH 4 + in riparian groundwater. • Iron, manganese and ammonium are potential risks for riverbank filtration systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Root penetration into soils result in increased gas permeability. • Biochar addition alters pore-filling and increases soil capillarity. • Gas permeability function is dependent on root length density. Biochar amendment have been explored recently for improving hydro-mechanical properties of landfill cover system and enhancing the vegetation for the ecological restoration of post closure landfills. Existing studies have predominantly focused on the hydro-mechanical properties of biochar-amended rooted soils and yet few studies have comprehensively investigated their gas permeability functions in response to unsaturated conditions. The objective of this study is to experimentally and theoretically investigate the coupled effects of biochar and root intensity on CO 2 gas permeability in unsaturated soil. Biochar-amended rooted soil was prepared by growing Chrysopogon zizanioides on granite residual soils with biochar at a mas ratio of 5 %. Gas permeability and unsaturated soil properties (i.e., suction and degree of saturation) were monitored simultaneously. Due to the presence of roots, the maximum gas permeability, hydraulic conductivity, and suction increased by 200 %, 600 %, and 50 %, respectively, compared with bare soil. This was attributed to preferential flow, micropore increasement and negative pressure induced by root growth. However, biochar addition decreased the maximum gas permeability and hydraulic conductivity by 21 % and 33 %, respectively. This was attributed to the pore filling function of biochar, increased capillarity due to intrapore of biochar, and presence of surface functional groups in biochar promoting CO 2 adsorption. A newly developed model was proposed to predict gas permeability with respected to unsaturated soil properties. It was revealed that the gas permeability function of rooted soils showed a strong dependence on the measured root length density. This study highlights the significance of adopting biochar in mitigation of gas emissions in vegetated landfill cover system. [ABSTRACT FROM AUTHOR]

The unsaturated behavior of permeable reactive barriers (PRB) is a critical component in predicting the removal efficiency through the adsorption of contaminants. This study investigates the framework to estimate the soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) for iron oxide-coated sand (IOCS) and zeolite, which are common materials used in PRBs. A multistep outflow (MSO) experiment was performed and the results of the MSO experiment were used to optimize associated parameters in Kosugi's SWCC and HCF. In addition, three scenarios of optimization analysis were investigated to evaluate the best-fitting model for estimating SWCC and HCF. The low root mean square error (RMSE) of fitted parameters indicates the Kosugi model well described the observed suction profiles in MSO experiments. In addition, the lowest RMSE and coefficient of variation suggested the inclusion of the additional parameter β provided the best estimation of the three materials (clean sand, IOCS, and zeolite). The physically reasonable estimation of SWCC and HCF of the three materials from the optimized parameters suggests the proposed framework is a reasonable model for the unsaturated behavior of PRBs. [Display omitted] • Multistep outflow experiment of soils was performed for predicting SWCC. • Iron oxide coated sand and zeolite were selected for PRB applications. • Fitting parameters in Kosugi's SWCC was optimized from MSO experiment. • Reliable prediction of SWCC and HCF of clean sand, IOCS, and zeolite was obtained. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties are essential for understanding soil hydrological and erosion processes. The importance of roots on soil hydraulic parameters has been widely recognized, but current studies have focused mainly on the root effect of a single plant species. However, few studies have been carried out to investigate the effect of mixed plant roots on soil hydraulic parameters. Undisturbed soil samples were collected from three natural sampling sites with single plant types and four sites with mixed plant types. Both soil hydraulic parameters were measured: soil saturated hydraulic conductivity (Ks) and soil saturated water content (SW). Then the root effects on Ks and SW were subsequently evaluated. The results showed that the Ks and SW at the sites with mixed plants were higher than those at the sites with a single plant species. At all the sites, Ks and SW both exhibited a decreasing-increasing-decreasing trend with increasing root density. The critical root density for the above change was quantified. When fibrous roots were mixed with tap roots, Ks was mainly affected by tap roots, while SW was mainly affected by fibrous roots. The influence of roots on Ks and SW was mainly achieved by affecting soil organic matter, not by directly affecting Ks and SW. Based on the root density, the herbaceous coverage with optimal saturated hydraulic conductivity and water content was estimated to be 66.71%. • The roots effect of mixed plants on soil hydrology were stronger. • The roots affect soil hydrology mainly by affecting soil properties. • The root density with the optimal soil hydrology were obtained. [ABSTRACT FROM AUTHOR]

Treated wastewater (TWW) is increasingly used for irrigation, but its higher salt content compared to conventional water sources can induce soil salinization and sodification. This, in turn, may result in structural degradation and deterioration of soil hydraulic properties. The practice of using TWW for irrigation is not new, and it has long been applied in arid countries, with limited other water resources, while in recent years it is also getting used elsewhere given the worldwide influence on water resources. However, comparing and extrapolating results from existing studies on the use of TWW for irrigation is challenging due to the heterogeneity between experimental setups in terms of water quality, irrigation techniques applied, and pedo-climatic conditions. To explore the effect of TWW quality on soil hydraulic and physio-chemical following TWW irrigation and to examine to what extent these effects are soil type dependent, we compiled a database with results from 24 peer-reviewed studies across different soil types containing information on the link between TWW irrigation, and hydraulic and physio-chemical properties through various measurements. The meta-analysis revealed that application of TWW significantly increases sodium adsorption ratio (on average 71 ± 6%) and electrical conductivity (on average 51 ± 5%) of soil as compared to the use of conventional water source. Overall, there were no significant effects on the soil pore space (bulk density, soil total porosity) or pH. Interestingly, the application of TWW significantly increased soil organic carbon and aggregate stability, potentially even benefiting soil structure. In addition, the organic compounds in TWW also might lead to hydrophobicity. Yet, the effects of TWW on soil hydraulic and physio-chemical properties are not consistent across different TWW types and soil classes. A larger number of studies is required to draw sound conclusions on this topic. Anyway, this analysis already indicated that different soil textures might react differently to TWW irrigation. While in medium-textured soils, salt accumulation was observed and TWW significantly increased soil organic carbon and saturated hydraulic conductivity, fine-textured soils are more prone to clogging and reduced in saturated hydraulic conductivity. We also noticed an impact of the type of TWW, since the degree of treatment has a big impact on the remaining components added to the soils together with the water. Primary TWW, from which settleable and floatable solids are removed, resulted in the highest accumulation of salts and significantly increased soil organic carbon and improved soil aggregate stability. However, the elevated biochemical oxygen demand or chemical oxygen demand in this type of TWW leads to an accumulation of organic materials in the soil, negatively affecting its permeability and reducing soil saturated hydraulic conductivity. This study stresses the need for more standardized experiments quantifying the effect of TWW not only in terms of transfer of contaminants and biosafety, but also an effect on soil quality, and more specifically soil physical quality, especially at the longer term. • TWW irrigation significantly increased soil salinity and sodicity levels. • Despite increasing soil organic matter content, TWW use decreased saturated hydraulic conductivity. • Primary TWW irrigation induced a higher salt accumulation, and caused lower hydraulic conductivity than secondary and tertiary TWW. • Fine-textured soils exhibited a greater susceptibility to clogging and reductions in hydraulic conductivity than medium-textured or coarse-textured soils. [ABSTRACT FROM AUTHOR]

This paper describes a comprehensive investigation to accurately determine the hydraulic permeability k and the specific storage S s of a shale sample. One-dimensional pressure transient tests were conducted on a cylindrical sample under various levels of pore and confining pressures. For the boundary conditions, the upstream pressure was kept constant using a syringe pump, and the downstream storage was minimized for reducing the test duration. Both the downstream pressure and the upstream fluid flow into the sample were continuously recorded throughout the transient period. To estimate the hydraulic properties, the curve fitting technique was applied to the pressure and flow data using theoretical curves. We found that the pressure curve was sensitive to the ratio of hydraulic permeability to the specific storage (k / S s), but not sufficient to determine the individual components (k and S s). The upstream flow curve was sensitive to the specific storage but less sensitive to the permeability. Based on our sensitivity analysis, we present a combination of two objective functions of flow and pressure data to optimize both hydraulic properties with reasonable uncertainty. An alternative is to first use the flow data to determine S s and then use pressure data with the predetermined S s to obtain the remaining k. [ABSTRACT FROM AUTHOR]

[Display omitted] The evolution and change in jointed rock mass hydraulic conductivity (k rm ) during triaxial compression was investigated using the discrete element method code 3DEC bonded block model approach. The code's fluid flow logic was used to simulate flow tests at various stages, from the initial confined state through to the post-peak (i.e., failed) state. A target percent of joint contacts were randomly "broken" to produce different initial fracture intensities. The rock mass fluid flow behaviour was compared with laboratory flow tests of thermally brecciated granular marble. A new joint constitutive model was developed to account for nonlinear, hysteretic load–displacement behaviour to accurately reproduce changes in joint aperture due to complex inter-block stress changes. The simulations provided quantifiable measurements of k rm evolution with axial strain throughout the test for several rock mass quality conditions. The evolution of k rm with loading was found to be nonlinear, with significant increases associated with yielding-induced dilation, followed by relatively minor changes in the post-peak loading range. These trends are similar to the laboratory tests conducted on intact rock and on rock joints. The findings will be useful for improving groundwater flow models for stability assessment of rock slopes, particularly where significant shearing is expected. [ABSTRACT FROM AUTHOR]

Seawater intrusion in coastal aquifers is a significant problem that can be addressed through the construction of subsurface dams or physical cut-off barriers. An alternative method is the use of microbially induced carbonate precipitation (MICP) to reduce the hydraulic conductivity of the porous medium and create a physical barrier. However, the effectiveness of this method depends on various factors, and the scientific literature presents conflicting results, making it challenging to generalise the findings. To overcome this challenge, a statistical and machine learning (ML) approach is employed to infer the causes for the reduction in hydraulic conductivity and identify the optimum MICP parameters for preventing seawater intrusion. The study involves data curation, exploratory analysis, and the development of various models to fit the input data (k-Nearest Neighbours – kNN, Support Vector Regression – SVR, Random Forests – RF, Gradient Boosting – XgBoost, Linear model with interaction terms, Ensemble learning algorithms with weighted averages – EnL-WA and stacking – EnL-Stack). The models performed reasonably well in the region where permeability reduction is sensitive to carbonate increase capturing the permeability reduction profile with respect to cementation level while demonstrating that they can be used in initial assessments of the specific conditions (e.g., soil properties). The best performing algorithms were the EnL-Stack and RF followed by XgBoost and SVR. The MICP method is effective in reducing hydraulic conductivity provided that the various biochemical parameters are optimised. Critical biochemical parameters for successful MICP formulations are the bacterial optical density, the urease activity, calcium chloride concentration and flow rate as well as the interaction terms across the properties of the porous media and the biochemical parameters. The models were used to identify the optimum MICP formulation for various porous media properties and the maximum permeability reduction profiles across cementation levels have been derived. • MICP effectively reduces hydraulic conductivity to generate cut-off walls. • Machine learning models predict hydraulic conductivity for various MICP parameters. • Critical biochemical factors are OD 600 , urease activity and CaCl 2 concentration. • Interactions between porous media properties and biochemical factors are critical. [ABSTRACT FROM AUTHOR]

Synthetic geotextile envelope can be used as a replacement of sand filters for subsurface drainage pipes. However, clogging and blocking can occur if the filter does not match the soils properly. This paper presents a laboratory study on hydraulic performance of nonwoven geotextile as subsurface drain filter for silty loam soil in eastern China. Two selected synthetic geotextiles were tested. Results showed that Typar SF27 satisfied the filtration requirements compared to the traditional sand filters. Typar SF20 exhibited a clogging risk of about 50% more than SF27; it also exposed to soil loss about 10 times more than SF27. The results indicate that choosing geotextile envelope material for the targeted soils need to consider O90 of the geotextile material and soil size distribution. Findings from this study may provide technical reference for selecting proper geotextile filtering material for subsurface drainage pipes in the study area and regions with similar soil conditions. [ABSTRACT FROM AUTHOR]

An experimental investigation of multiple seepage-induced suffusion and its impact on the mechanical responses of internally unstable gap-graded soil, with a fines content of 25%, is presented in this paper. Using a modified triaxial erosion apparatus, with a redesigned seepage control system, erosion tests under multiple seepage conditions, as well as undrained monotonic and cyclic compression tests, are performed. It is found that multiple seepages cause an eroded mass without a marked change in volume and with a change in hydraulic conductivity as the number of seepage cycles increases. The monotonic compression tests show that eroded soil presents a smaller peak strength, residual strength, and a greater contractive response than non-eroded soil. The peak strength and stiffness of eroded soil are seen to decrease considerably as the number of seepage cycles increases. Multiple seepage-induced suffusion may create a collapsible soil structure in eroded soil, as shown by sudden decreases in deviator stress and stiffness, coupled by sharp increases in pore water pressure at small strain levels. As eroded soil might already be unstable, cyclic loading causes it to collapse, revealing a sudden increase in the generation of cyclic pore water pressure and a decrease in liquefaction resistance. The results highlight the importance of conducting laboratory tests to determine the impact of internal erosion on the strength and liquefaction resistance. [ABSTRACT FROM AUTHOR]

This paper assesses the Quaternary aquifer behavior in Assuit governorate under different management discharge/recharge scenarios. The four discharge scenarios represent 1.25, 1.5, 2.0, and 2.5 of the current abstraction rate. The two proposed discharge scenarios represent 0.5 and 1.0 m reduction in surface water levels in the Nile River and main canals in the study area. The sensitivity analysis was performed, identifying hydraulic conductivity as the most sensitive parameter. The model was calibrated with 28 observation wells with a good agreement with measured data. The reductions in groundwater heads are 0.17, 0.35, 0.72, 1.11 m for the four discharge scenarios, respectively, while 0.22 and 0.46 m obtained as a reduction in groundwater heads for the two proposed discharge scenarios, respectively. The recharge from the Nile and canals was reduced by 58.078, 114,800 m3/day, respectively. Sustainable management plan is recommended for long-term analysis of the Quaternary aquifer in the study area. [ABSTRACT FROM AUTHOR]

• Performances of 45 pedotransfer functions of K sat were evaluated using soil databases from U.S.A. • Pedotransfer functions were classified into four groups according to its input requirements. • Best performing PTFs were identified for each group at different texture classes. • Results of the study were compared to the results of five recent studies evaluated the same PTFs. Direct measurements of saturated hydraulic conductivity (K sat) are costly and time-consuming. Alternatively, pedotransfer functions (PTFs) have been developed to estimate K sat in terms of readily available soil properties. The goal of this study is to evaluate forty-five PTFs of K sat. The functions were divided into four groups according to their input requirements: EP-K sat group (F1.1-F1.9) require the effective porosity as inputs; SSC-K sat group (F2.1-F2.12) require (sand, silt, clay contents); SSCBD-K sat group (F3.1-F3.8) require (sand, silt, clay contents), bulk density; and SSCBDOM-K sat group (F4.1-F4.16) require (sand, silt, clay contents), bulk density, and organic matter content. The results showed that the best PTFs were F1.9 and F1.5 in EP-K sat group. For the SSC-K sat group, the PTFs F2.1, F2.11. For the SSCBD-K sat group, the PTFs F3.5, F3.6. For SSCBDOM-K sat group, the PTFs F4.13 and F4.8. Results of this study are helpful for predicting K sat inputs required for large scale hydrologic models with reliability. [ABSTRACT FROM AUTHOR]

Earth canals are subjected to seepage losses during the conveyance and distribution of irrigation water. With the current conditions of climate change and water scarcity, it is becoming crucial to conserve water. Canal lining is a common solution to minimize seepage losses. In this study SEEP/W model is used to investigate the effect of compacted earth lining characteristics on seepage from trapezoidal earth canals. The amount of reduction in seepage due to lining is quantified. Different scenarios for the hydraulic conductivity, thickness, and orientation (position) of compacted earth lining are evaluated. The results show that compacted earth lining is an efficient method to reduce conveyance losses. 99.8% of the water lost by seepage can be saved if highly compacted soil is used on the bed and sides. Partial lining can also be used, the most efficient orientation of lining depends on the canal's width. Design charts and equations are suggested. [ABSTRACT FROM AUTHOR]

The high-level nuclear waste, HLW, from Swedish and Finnish reactors will be deposited in crystalline rock at depths around 500 m. The waste is enclosed in steel canisters protected against corrosion by a 5 cm thick copper shell, which ensures a lifetime far longer than 100 000 years. Should some canister be breached any leaking nuclides will have decayed to so low activity that even if they reached the biosphere, they would cause minimal risk to humans. The cost of the copper is significant. The dismantling of the nuclear reactors, with induced activity must also be disposed of and this waste volume is much larger than that of the HLW, which makes it impossible to protect it in the same way. This paper explores if by locating the waste at larger depth where the ground water is more saline, and where the hydraulic conductivity of the rock is lower up-flow of contaminated water can be ensured to be negligible because the denser water at larger depth counteracts up-flow due to negative buoyancy. Several processes that could cause local up-flow are addressed, such as infiltration of meteoric water, impact of surface topology, heat production of the waste, geothermal gradient, salinity gradient, hydraulic conductivity heterogeneities and salt migration between seeping water and salt in matrix pore water. Flow and transport simulations using data from extensive field investigations over more than ten years with scores of km deep boreholes suggest that a HLW repository at around one km depth may be sufficient to hinder up-flow to the biosphere. • Natural saline water gradients hinder contaminant up-welling. • Narrow channels in fractures form dense 3D channel networks, which promotes mass exchange between mobile water and matrix pore water and retards solute transport. • Contaminants in waters at large depths are delayed from reaching the biosphere for very long times. [ABSTRACT FROM AUTHOR]

[Display omitted] • The potential and limitations of Borehole NMR in peatland environments are studied. • Borehole NMR data from 163 boreholes across four Danish peatlands are collected. • It is found that peat decomposition level can be tracked by NMR data. • Correlation of common lab measurements of peat samples with NMR data is examined. • NMR-derived hydraulic conductivity estimations are evaluated against slug tests. The potential and limitations of the Borehole Nuclear Magnetic Resonance (BNMR) technique as an in situ measurement for peatland soil characterization was tested in 163 boreholes at four selected peatlands in Denmark. The BNMR data effectively differentiated various geological units in peatland environments due to their distinct NMR responses. Moreover, field-scale variations of the porosity and pore size distribution (e.g., porosity variations within a single geological unit) were mapped to reveal possible trends reflecting geological or hydrogeological conditions in a peatland. Additionally, some of the NMR parameters were found to be correlated with peat decomposition or the degree of humification. The estimation of hydraulic conductivity (K) based on NMR data was also examined for various geological units and compared with slug test measurements. While NMR-based hydraulic conductivity estimations for sand and gyttja (fine-grained sediment with high organic matter) geological units fall within an acceptable range of error, we encountered challenges in achieving reliable estimations for peat. This study showed the potential of BNMR as a robust, rapid, and reliable in situ tool for soil characterization in peatland research. [ABSTRACT FROM AUTHOR]

Anisotropic permeability of bentonite mixtures governs water flow regime in buffer materials such as landfill cover systems, cutoff walls, and high-level waste repositories. Because of its widespread application, a series of 48 permeability tests were conducted in this study on specimens prepared from bentonite-sand mixtures with three bentonite contents. The tests were run along both isotropic loading and unloading paths to explore the evolution of anisotropic ratio from three distinct fabric anisotropy states. Accordingly, a new cubic sample-type, large-scale triaxial permeameter was introduced and employed. The results revealed an enhancement of as-compacted anisotropy ratio from 1 to almost 7 with bentonite contents. The anisotropy ratio was suppressed with isotropic loading for 40% and 70% bentonite while it was enhanced for 10% bentonite content. Unloading was revealed to reduce the anisotropy of higher bentonite contents due to the enhancement of fissures along horizontal and vertical directions. The practical implication in terms of the long-term performance of a landfill liner with medium to high bentonite contents is that despite a 10- to 30-fold reduction in permeability with loading, the leachate flow would be less anisotropic compared with the initial condition as supported by a reduction in the anisotropy ratio up to 3.5. • A new large-scale cubic sample-type triaxial permeameter is designed and introduced. • Anisotropy ratio evolves from 1 to 4 with a reduction in porosity of 10% bentonite. • Anisotropy of soils with 40% and 70% bentonite is declined when porosity is reduced. • Isotropic unloading suppressed the anisotropy ratio of soils with higher bentonite. • SEM observation revealed the unloading-induced fissures along orthogonal directions. [ABSTRACT FROM AUTHOR]

Physical clogging of porous media plays an important role in controlling their hydraulic conductivity. This study investigates how uniformly graded medium-to-coarse sand in a reservoir's bed performs in response to the inflow of turbid water with fine suspended sediments. Different particle sizes, heads, and concentrations were simulated to cover a range of hydrologic conditions. A 1D sand column was used with three bed material sizes and three suspended particle sizes. Seven particle size ratios were tested under a constant head. Four heads and three suspended sediment concentrations are also evaluated. It was concluded that the decline in the relative hydraulic conductivity of the bed material is directly proportional to the ratio of sediments-to-bed particle sizes. Increasing the concentration of suspended sediments accelerated the rate of clogging, while bigger heads increased the depth of clogging. The study highlights how physical clogging affects the water balance in surface reservoirs and threatens the safety of dams. [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) has been extensively studied at both lab and field scales for its functional applications, such as the shear strength enhancement or the hydraulic conductivity reduction for geological engineering. However, investigating the pore-scale interaction between calcite formation and hydraulic properties has been a challenge. In this study, we proposed an effective methodology that allows for non-destructive direct numerical simulations based on three-dimensional X-ray computed tomographic images of MICP-treated sands to capture those pore-scale interactions at from mm- to sub-mm scales. The lattice Boltzmann model was implemented to quantitatively evaluate the fluid velocity field through the realistic pore structures in the MICP-treated sands. It was confirmed that the calcite formation naturally led to a reduction in hydraulic conductivity, following a linear relationship with porosity. The spatial variability in hydraulic conductivity was finely mapped at different reaction stages, with vertical variation along the height being predominant over three orders of magnitude even for a 12 mm-length specimen. Additionally, we discussed the contribution of changes in hydraulic tortuosity and specific surface area to hydraulic conductivity variation and newly evaluated geometric factor in the Kozeny-Carman model for MICP-treated sands. Overall, the presented methodology demonstrated the feasibility of image-based characterization for 3D spatiotemporal changes during MICP via 'direct numerical simulation' and X-ray CT imaging, and the observation can be readily applied to porous geomaterials. • Pore-scale spatiotemporal change in MICP-treated sands were observed by X-ray CT. • Local hydraulic features of MICP-treated sands were estimated by image-based DNS. • Distribution of hydraulic properties of MICP-treated sands were mapped in 3D. • Geometric factor for Kozeny-Carman model was evaluated for MICP-treated sands. [ABSTRACT FROM AUTHOR]

• Faxon fir showed a preferentially nutrient allocation to needles than other organs. • With the elevation increasing, Faxon fir may be limited by P. • As the climate warms, high-altitude Faxon fir will be increasingly with N-restricted. • Faxon fir made a cooperative change among nutrient, hydraulic, and morphological. High-altitude mountain plants are at risk of extinction due to global warming. Our study examined the stoichiometric characteristics of high-altitude plants in response to a progressively warming climate, as well as exploring potential relationships between hydraulic conductivity efficiency, stoichiometric characteristics, and morphological traits. As the research object, it was decided to conduct this investigation using the Faxon fir, a dominant species in the Minjiang River Basin with better water conditions. The sampling time was four months. In July 2019, October 2019, January 2020, and April 2020, the stoichiometric characteristics (N and P) in needles, branches, stems, and roots of Faxon fir were measured along an altitude gradient at 200 m intervals from 2800 m to 3600 m. We also measured morphological traits and hydraulic traits. This study showed that the Faxon fir N P stoichiometric preferentially to needles, followed by branches and roots, and finally at the trunk, and the Faxon fir was in an N-restricted state. N and P elements exhibit a significant correlation with morphological traits, while the relationship between P elements and hydraulic characteristics is mediated indirectly through morphological traits. At high altitudes, climate warming will increase the N limitation of Faxon fir, but the effect on P limitation will be relatively limited. Climate environment and water status are closely related to the distribution of N P nutrients in the organs. Undoubtedly, climate change will directly affect the survival of high-altitude plants, and appropriate survival strategies can encourage plants to adapt to climate changes by balancing energy distribution among different organs and tissues. [ABSTRACT FROM AUTHOR]

Species' drought resistance is determined by a combination of multiple traits and their plastic response. However, a clear understanding of how these traits are coordinated and modulate plant responses to drought is still lacking. Here we used a water exclusion experiment on 20 Mediterranean woody species to evaluate a new framework to study plant drought responses, in which relatively constant functional traits modulate the physiological responses to a given drought exposure. In particular, we assessed how the response of stomatal conductance (G s), leaf relative water content (RWC) and leaf water potential difference (Δ Ψ) to leaf predawn water potential (Ψ pd) were modulated by commonly used functional traits. The latter included hydraulic and water relations attributes such as turgor loss point in leaves (Ψ tlp), vulnerability to xylem embolism in stems (Ψ 50), hydraulic conductivity per unit sapwood (K s), hydraulic conductivity per unit leaf area (K l , hydraulic sufficiency) and Huber value (H v), as well as specific leaf area (SLA) as a proxy for the leaf economics spectrum. Our results show that functional traits are highly coordinated, defining two main axes: the first related to drought tolerance and resource-use strategies and the second characterising the hydraulic sufficiency of leaves. These two axes, as well as many of the underlying functional traits, showed a significant interaction with Ψ pd in explaining physiological responses to drought, thus modulating G s , RWC, and Δ Ψ responses. Drought-tolerant species showed a less stringent regulation of water use and leaf water potential but were more effective at regulating leaf RWC. Also, the leaf water potential at turgor loss (Ψ tlp) emerged as an important trait orchestrating plant responses to drought. This study highlights that a clear separation between slow-varying traits (Ψ tlp , Ψ 50 , K s , K l , H v , SLA), physiological responses (G s , RWC, Δ Ψ) and tissue-level exposure to drought (Ψ pd) improves our understanding of plant drought resistance strategies. • Plant physiological responses to drought are modulated by functional traits. • Species-level variability in functional traits can be summarised in two main axes. • Hydraulic sufficiency contributes to defining the drought resistance strategy. • Leaf water potential at turgor loss point is a central modulator of physiological responses. [ABSTRACT FROM AUTHOR]

• The measured hydraulic conductivity of hydrophilic porous media was independent of the column outlet condition. • The measured hydraulic conductivity of hydrophobic porous media was dependent on the column outlet condition. • The traditional hydraulic conductivity formula is not suitable for hydrophobic porous media. Under certain conditions of natural or anthropogenic origin, the wettability properties of soils change from hydrophilic to hydrophobic. Such a transition results in substantial changes in water flow dynamics and soil hydraulic properties. Among them, the dependence of the hydraulic conductivity of hydrophobic porous media on the ponded water depth has been measured with the constant water head method and traditional hydraulic conductivity formula. A mechanism that can essentially explain the dependence is still missing. The current study aims to narrow this knowledge gap. Hydraulic conductivities of hydrophobic and hydrophilic glass beads were measured with two column outlet conditions: open to air and immersed in water. The measured hydraulic conductivity of hydrophobic glass beads depended on the ponded water depth with an open-to-air outlet. However, it was independent of the ponded water depth with an immersed outlet. The measured hydraulic conductivity of hydrophilic glass beads was independent of the ponded water depth for both outlet conditions. Surface tension effects at the column outlets decreased the volumetric flow rate of hydrophobic glass beads. Introducing the low volumetric flow rate into the traditional hydraulic conductivity formula without considering the surface tension effects leads to a dependence of hydraulic conductivity on the ponded water depth. This result calls for a new approach to calculate the hydraulic conductivity in hydrophobic porous media. [ABSTRACT FROM AUTHOR]

• We develop a new fractal capillary model accounting for the hysteresis effect. • The immobile water in the pores of frozen soil is considered in the prediction model. • The immobile water has a significant influence on the hydraulic conductivity at lower saturation. • The proposed fractal model can be simplified to a power function. The hydraulic conductivity of frozen soil is crucial for predicting water migration and frozen heave. Many models have been proposed to estimate the hydraulic conductivity, which involves factors such as unfrozen water content, specific surface area, grain size distribution, and pore size distribution. However, the bottleneck effect on the hysteresis of unfrozen water has not been adequately considered. This study proposed a hydraulic conductivity model based on the fractal theory by assuming the capillary tubes with a pore throat. Subsequently, the hydraulic conductivity was expressed as the product of the saturated and relative hydraulic conductivity, both of which can be determined from the microscopic fractal characteristics. Finally, the proposed model was verified using the experimental data and existing models, and a sensitivity analysis of the relative hydraulic conductivity was conducted. The validation showed that the predicted results agree well with the experimental data. Meanwhile, the proposed model can better describe the hysteresis effect of unfrozen water content during the freezing-thawing process than other commonly used models. Relative hydraulic conductivity is sensitive to pore structure characteristics and unfrozen water content. Immobile water saturation evidently influenced the relative hydraulic conductivity when it reached 0.7. The proposed model can be simplified as a power function in which the exponent can be calculated using the fractal dimension. The results help simulate the dynamic process of unfrozen water in frozen soil and may help understand the complex mechanisms of hysteresis and transport processes in frozen soil. [ABSTRACT FROM AUTHOR]

• Mine reclamation compacted glacial parent materials, impeding reforestation. • Deep ripping lowers soil bulk density within rips, below the surface. • Deep ripping increases variability in hydraulic conductivity and creates pipes. • Deep ripping may create soils that better support tree growth within, but not outside, the rips. Surface mining and reclamation activities can substantially affect the soil physical properties that mediate water movement and root growth, impeding the re-establishment of native vegetation and ecosystem function. Deep ripping is a promising approach to mitigate compaction using long shanks dragged through the soil, but little is known about its effectiveness in fine-textured glacial parent material. In five reclaimed surface mines and four reference forests on glacial parent material, we measured soil bulk density and saturated hydraulic conductivity. Two mine sites were subsequently subjected to deep ripping in a grid pattern and soil properties were remeasured within and outside of the rips. Before ripping, near-surface bulk density was higher and saturated hydraulic conductivity was lower at the reclaimed mines than the reference forests, and mine soils deeper than 20 cm were often denser than ideal for plant growth (>1.4 g cm−3). Ripping increased variability in bulk density and saturated hydraulic conductivity, with the intersection of perpendicular rips becoming denser than pre-rip conditions in the top 5 cm. Below the surface, soils in the rips were generally less dense than pre-rip conditions, and soil piping was observed within some rips. Between the rips, bulk density decreased in the top 5 cm, but remained constant or increased relative to pre-rip conditions at greater depths. These results emphasize the importance of fine-scale, spatially explicit sampling when assessing the effects of mine reclamation and ripping. Our data support strategies of planting trees within rip intersections, though cast doubt on the potential for root expansion into areas between rips. [ABSTRACT FROM AUTHOR]

• Particle batch smoother can identify the variations of soil hydraulic parameters. • Variations of soil hydraulic parameters correlated with soil organic matter. • Soil organic matter was replenished by litterfall and consumed by respiration. Soil hydraulic parameters are influenced by various inherent soil properties, such as pore structure and organic matter content, which can vary with changes in the ecosystem. However, identifying the temporal variations of soil hydraulic parameters in a co-evolving soil-vegetation system remains a challenge. This study focused on a tropical forest with significant seasonal variations in vegetation attributes, evaporation, and carbon fluxes over a five-year monitoring period. The particle batch smoother algorithm was integrated with an unsaturated flow model to identify the seasonally varied soil hydraulic parameters through assimilation of in-situ measured soil moisture. As a benchmark, the Generalized Likelihood Uncertainty Estimation method was applied to optimize soil hydraulic parameters without considering temporal variation. The results indicated that the temporally varying soil hydraulic parameters exhibited regular seasonal patterns and outperformed the unvaried soil hydraulic parameters in terms of reducing the errors in modeling of soil moisture and evaporation. Moreover, the seasonal variations in soil hydraulic parameters were closely linked to changes in the litterfall and terrestrial carbon fluxes over time. Specifically, due to the hysteresis of the transformation from litterfall to soil organic matter, the accumulated litterfall in Hot-dry season can replenish the soil organic matter, resulting in an increase in field capacity and saturated hydraulic conductivity in the Hot-rainy season. However, the intense decomposition of soil organic matter under high temperature in Hot-dry season led to a decrease in field capacity and saturated hydraulic conductivity. This study emphasizes the value of the particle batch smoother algorithm in detecting temporal variations in soil hydraulic parameters within a coevolving soil-vegetation system, thereby contributing to a more comprehensive understanding of the intricate dynamics within the ecohydrological system under a changing environment. [ABSTRACT FROM AUTHOR]

Grouting is an essential technique for reducing the hydraulic conductivity and enhancing the strength of rock mass used in the Dongzhuang hydro-junction project. The rheological properties of grout are not to be disregarded during grouting. In this study, a numerical grouting model is established by combining a modified Herschel–Bulkley (H B) rheology model with the level set method. The effects of rheological parameters (power-law index n , consistency coefficient k , and yield stress τ 0) on distribution pattern and flow characteristics of the grout are investigated. The H B model is more effective and precise than the Bingham model for predicting rheological characteristics. Numerical results indicated that distribution pattern and grout volume are primarily determined by n. A low shear rate inhibits the horizontal distribution and reduces the filling capacity of the grout, thus resulting in minimal deposition in the fracture. Grouts with a higher n and k require higher pressure to distribute around the fracture. The reduction in water volume in the fracture is calculated to provide comprehensive understanding into the sealing efficiency of the grout by varying the rheological parameters. This study provides valuable guidance regarding the different rheological parameter of grout in fractures, in addition to a novel concept for the optimal design of grouting distribution. • The effect of rheological parameters with Herschel-Bulkley model on grout distribution is investigated. • Distribution pattern and grout volume are mainly determined by the power-law index. • The low shear rate inhibits the horizontal distribution and reduces the filling capacity of grout. • The yield stress is not sensitive to sealing efficiency. [ABSTRACT FROM AUTHOR]

Natural slopes often exhibit tilted stratification with rotated transverse anisotropy in multiple soil properties, including the mechanical (e.g., friction angle φ and cohesion c) and hydraulic properties (e.g., saturated hydraulic conductivity k s). This phenomenon indicates that to achieve an accurate assessment of slope reliability under rainfall infiltration, the anisotropic spatial variation of the shear strength parameters and k s should be incorporated in a combined manner. Thus, this paper discusses the combined influence of rotated transverse anisotropy in the shear strength parameters and k s on the reliability and failure mechanism of an unsaturated slope under rainfalls. It is found that for a slope with tilted stratification, the failure mechanism and reliability estimator are dominantly influenced by the rotated transverse anisotropy in the shear strength parameters, while the influence induced by that in k s is slight. In particular, only incorporating the rotated transverse anisotropy in k s may lead to an incorrect reliability estimator of a slope with tilted stratification. Herein, the reliability index β would be estimated to be dramatically higher, and β of a slope with horizontal bedding would be higher than that of an anti-dip slope, which is inconsistent with the engineering experiences. Nonetheless, the rotated transverse anisotropy in k s should not be ignored in slope reliability assessment, because ignoring the rotated transverse anisotropy in k s would lead to overestimation of the reliability index β , which is adverse to the safety design of a slope. [ABSTRACT FROM AUTHOR]

• The concept of tunable fracture conductivity is presented to address thermal short-circuiting in EGS. • Utilizing this technique may increase heat extraction by 214 % over 50 years. • Using this technique can reduce an extra 1.05- 3.65 mt of greenhouse gas emissions. • Partial utilization of this technique can still effectively improve the efficiency of an EGS. The efficiency of an enhanced geothermal reservoir (EGS) depends on the effective circulation of the working fluid through the geothermal formation. To remove the thermal shortcut that leads to thermal short-circuiting in the EGS, we present a method of fracture hydraulic conductivity management and present some practical ways to implement it in the field. The core idea is to correlate the flow resistance in different flow channels with temperature, in order to make uniform heat extraction through each flow path. The presented technique is an adaptive and reversible system and is trying to engineer the fracture system for effective delay of the early thermal breakthrough in EGS. Results indicate that the proposed fracture conductivity tuning technique (FCTT) can help to avoid flow and thermal shortcuts between the wells and maintain high heat extraction rates. The autonomous management of fracture conductivity may increase cumulative heat extraction by more than 214 %, and reduce an extra 1.06 – 3.65 Mt of greenhouse gas emission through electricity generation after 50 years of EGS development, which is highly considerable for EGS development. Besides, we found that it could be still beneficial to apply such methods solely to the injection wells, which can also bring a heat extraction improvement of 201.9 %. Furthermore, we look at the situations when the special conductivity tuning agents are placed in the middle between the wells, it is still very effective to control the fluid flow in the reservoir and enhance heat extraction. By proposing the tunable fracture conductivity, we are trying to revisit the old problem of thermal short-circuiting and provide new insight into the efficient EGS operation. [ABSTRACT FROM AUTHOR]

Point sources with contaminants, such as chlorinated solvents, per - and polyfluoroalkyl substances (PFAS), or pesticides, are often located in low-permeability aquitards, where they can act as long-term sources and threaten underlying groundwater resources. We demonstrate the use of a 3D numerical model integrating comprehensive hydrogeological and contamination data to determine the contaminant mass discharge (CMD) from an aquitard into the underlying aquifer. A mature point source with a dissolved chlorinated solvent in a clayey till is used as an example. The quantitative determination is facilitated by model calibration to high-resolution vertical concentration profiles obtained by direct-push sampling techniques in the aquifer downgradient of the contaminant source zone. The concentration profiles showed a plume sinking with distance from the source characteristic for such aquitard/aquifer settings. The sinking is caused by the interplay between infiltrating water and horizontal groundwater flow. The application of 3D solute transport modeling on high-resolution profiles allowed for determining the infiltration rate, the hydraulic conductivity in the aquitard, and, ultimately, the CMD. Different source zone conceptualizations demonstrate the potential effects of fractures and sorption in source zones in aquitards on CMD development. Fractures in the aquitard had a minor influence on the current CMD determined with the presented approach. Still, fractures with hydraulic apertures larger than 10 μm were crucial for the temporal development of the CMD and plume. A thorough characterization of the source zone conditions combined with high-resolution concentration profiles and detailed modeling is valuable for shedding light on the probable future development of groundwater contamination arising from sources in aquitard/aquifer settings and evaluating remedial actions. • 3D solute transport modeling of chlorinated ethenes in source and plume. • High-resolution vertical concentration profiles by direct-push field methods. • Model calibration to concentration profiles reproduces characteristic plume sinking. • Quantification of contaminant mass discharge, infiltration, hydraulic conductivity. • Source conceptualization and fractures crucial for temporal CMD evolution. [ABSTRACT FROM AUTHOR]

Saturated hydraulic conductivity (Ksat) is a key performance variable in nature-based solutions for managing stormwater such as bioretention. Ksat is well understood from a soils perspective, but not an ecological one, despite growing recognition that plant traits and soil characteristics influence one-another and may co-regulate Ksat. There are myriad plant traits that potentially influence Ksat, which makes it difficult to know where attention should be focused to inform hydrologic design. We address this knowledge gap by 1) evaluating adaptive strategy theory as an overarching framework for characterizing plant effects on Ksat, assessing fifteen bioretention systems across three U.S. states and 2), exploring the implications of this theory for spatial and temporal patterns in plant effects on Ksat driven by regional variability in planting guidance and trajectories of plant succession. Our results illustrate that adaptive strategy significantly influences Ksat, with ruderal plants tending to decrease it and stress tolerant or competitive/stress tolerant plants increasing it. These relationships are indirect, reflecting the impact of adaptive strategy on root traits and soil organic matter, which influence Ksat directly. When these relationships are evaluated in the context of established planting guidance, we find that plants recommended in arid climates tend to increase Ksat relative to bare filter media whereas plants in humid climates do not. Small biases in planting preferences can dramatically change these outcomes. For instance, established vegetation in our bioretention sites was more competitive/stress tolerant than expected, significantly increasing Ksat. We also find that plant effects on Ksat are likely to vary in response to ruderal recruitment as bioretention systems age, reducing Ksat up to 15 %. Collectively, these results illustrate that plants play an important role in bioretention hydrology, and warrant consideration during hydrologic design. They also suggest that adaptive strategy theory is a promising design tool, providing useful insights into plant effects on Ksat, both geographically and over time. [Display omitted] • Ruderal plant strategies decrease saturated hydraulic conductivity (Ksat). • Competitive and stress tolerant plant strategies increase Ksat. • The effects of adaptive strategy are indirect through root and soil attributes. • Design guidance emphasizes plants that increase Ksat in arid (not humid) climates. • Ruderal recruitment is expected to decrease Ksat as bioretention systems age. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is a crucial macronutrient for plants and serves as a significant measure of soil productivity. The leaching of N-nitrate creates significant hazards for human health and ground water quality. Supplemental irrigation applied to various field crops significantly alters crop yield and nitrate (NO 3 –) leaching within the soil. Determining the influence of various N rates and irrigation levels on yield and NO 3 – leaching could help to select the optimum combination of irrigation and N. The influence of various irrigation levels and N rates on NO 3 – leaching, soil physicochemical characteristics and grain yield of wheat crop was investigated. Two irrigation levels, i.e., I 1 and I 2 (60% and 75% of field capacity) and three N levels, i.e., 105, 130 and 160 kg/ha named as N 1 , N 2 and N 3 were included in the study. The irrigation and N levels were optimized in preliminary studies. Data relating to yield-related characteristics of wheat and soil physicochemical properties were recorded. The growth and yield traits of the wheat crop were considerably influenced by varying degrees of irrigation N application. The interactive effect of I 2 N 3 resulted in the highest numbers of tillers m−2 (18.9), 1000-grain weight (40.3 g), and straw (5.87 t ha−1) and grain (4.17 t ha−1) yields. Irrigation significantly affected infiltration rate, hydraulic conductivity of the saturated soil and soil strength. The bulk density of soil increased, while soil porosity decreased with increasing depth. Economic analysis revealed that higher irrigation and N levels, i.e., I 2 N 3 resulted in the highest net economic returns. The NO 3 – concentration was significantly affected by soil depth and time after application of fertilizer. The NO 3 – concentration exhibited its greatest value at a depth of 0.35 m, while its lowest value was seen at a depth of 1 m. In addition, the concentration of NO 3 – exhibited a decline throughout the course of time after the administration of N. It is concluded that higher application of irrigation water and N fertilizer increased wheat yield and economic returns, and NO 3 – leaching. Therefore, alternative N sources with lower NO 3 – leaching must be used to reduce the adverse impacts on groundwater and environment. [ABSTRACT FROM AUTHOR]

The complexity of fractures in rocks results in heterogeneity and anisotropy of their hydraulic properties. The existence of hydraulic conductivity representative elementary volume (KREV) is a fundamental question in comprehending the hydraulic behavior of fractured rock masses. This article introduces an analytical procedure for determining the existence of KREV in fractured rock masses, which considers the distribution of underground apertures using a discrete fracture network (DFN) model. The procedure follows four basic steps: inverse modeling to generate a 3D DFN; calibration of the effective aperture by combining the results of packer tests and flow simulation using finite difference methods; calculation of the equivalent conductivities in 10 domains and 31 different flow directions; analysis of the fit error between the conductivity ellipsoid to determine the existence of KREV. The proposed approach is applied to the fractured rocks surrounding the 3013 exploration adit near the underground powerhouse of the Three Gorges Project as a case study. The results show that most fractures in the study area have apertures ranging from 0.06 to 0.25 mm and follow a lognormal distribution. The KREV size is 14–16 times the fracture spacing. Investigation of this model has significant implications for understanding flow through fracture networks in related fields. [ABSTRACT FROM AUTHOR]

A multi-exponential function (ME) is proposed to depict the highly nonlinear soil water retention curve and hydraulic conductivity function. Then, semi-analytical solution of pore-water pressure in an unsaturated infinite slope at steady state is derived using ME to depict soil hydraulic properties. The solution is verified with experimental and numerical results. It is found that ME can better describe the highly nonlinear hydraulic properties of soil than the single exponential function (SE), which is commonly-used previously. At steady state, the adoption of SE results in overestimating negative pore-water pressure (PWP; i.e., matric suction) by about 25 kPa and slope's factor of safety (FOS) by 100% under rainfall, but underestimating negative PWP by about 50 kPa under evaporation. The difference between PWP and FOS calculated by using SE and ME becomes more significant for soil with bimodal hydraulic conductivity function than that with unimodal one. This difference reduces at a larger slope angle and deeper depth. Moreover, this difference generally increases at a lower S ME /S SE , where S ME and S SE represent the suction at which the unsaturated hydraulic conductivity expressed by ME and SE equals the applied rainfall intensity or evaporation rate, respectively. When S ME /S SE is greater than 0.1, the difference basically diminishes. [ABSTRACT FROM AUTHOR]