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Previous studies have found that self-esteem is linked to subjective well-being (SWB), but little is known about the longitudinal relationship between self-esteem and the bi-factor structure of SWB which has been demonstrated to include three specific factors and a general factor of SWB. This study used four competing structural models of SWB (i.e., the three-factor model, the causal model, the hierarchical model and the bi-factor model) to investigate the relationships between self-esteem and SWB in a total of 997 emerging Chinese adults (Mage = 19.79 years; 65.20% females) through a two-wave longitudinal study. From the point of view of the fit index, the results showed that the bi-factor model fitted our data better than the other three models. Importantly, results for the vast majority of models demonstrated the existence of the reciprocal link between self-esteem and subjective well-being in emerging Chinese adults. Specially, the results of bi-factor model suggested that there was a bidirectional link between self-esteem and the general factor of subjective well-being. To sum up, our findings provide new support for studying the longitudinal relationship between self-esteem and SWB using four models including the bi-factor model. [ABSTRACT FROM AUTHOR]

To stop the spread of COVID-19, a number of public health policies and restrictions were implemented during the pre-vaccination phase of the pandemic. This study provides a quantitative assessment of how these policies impacted subjective well-being (SWB) in the United States over a 6-month period spanning March to August 2020. We study two specific research objectives. First, we aim to quantify the impacts of COVID-19 public health policies at different levels of stringency on SWB. Second, we train and implement a conditional inference tree model for predicting individual SWB based both on socio-demographic characteristics and policies then in place. Our results indicate that policies such as enforcing strict stay-at-home requirements and closing workplaces were negatively associated with SWB, and that an individual's socio-demographic characteristics, including income status, job, and gender, conditionally interact with policies such as workplace closure in a predictive model of SWB. Therefore, although such policies may have positive health implications, they also have secondary environmental and social implications that need to be taken into account in any cost-benefit analysis of such policies for future pandemic preparedness. Our proposed methodology suggests a way to quantify such impacts through the lens of SWB, and to further advance the science of pandemic preparedness from a public health perspective. [ABSTRACT FROM AUTHOR]

The article discusses new models from Alfa Romeo and Fiat that combine practicality with Italian style. The Fiat Doblo, a small van, has been introduced to the Irish market and offers various features such as enhanced suspensions, sliding side doors, and a flexible three-seat configuration. It is available in diesel or electric form, catering to different driving needs. The Alfa Romeo Tonale, a premium compact SUV, is now the entry model in the Alfa range and offers hybrid power options. It is known for its sportiness, attractive styling, and roomy cabin. The article also mentions the Renault Scenic E-Tech winning Car of the Year at the Geneva Motor Show and provides information about upcoming veterinary events. [Extracted from the article]

With the continuous development in drilling and blasting technology, smooth wall blasting (SWB) has been widely applied in tunnel construction to ensure the smoothness of tunnel profile, diminish overbreak and underbreak, and preserve the tunnel's interior design shape. However, the complexity of the actual engineering environment and the deficiency of current optimization theories have posed certain challenges to the optimization of SWB parameters under arbitrary geological conditions, on the premise that certain control targets are satisfied. Against the above issue, a genetic algorithm (GA) and back propagation (BP) neural network-based computational model for SWB design parameter optimization is proposed. This computational model can comprehensively reflect the relation among geological conditions, design parameters, and results by training and testing the 285 collected sets of test data samples at different conditions. Moreover, it automatically searches optimal blasting design parameters through the control of SWB targets to acquire the optimal design parameters based on specific geological conditions of surrounding rocks and under the specified control targets. When the optimization algorithm is compared with other current optimization algorithms, it is shown that this algorithm has certain computational superiority over the existing models. When the optimized results are applied in practical engineering, it is shown that in overall consideration of the geological conditions, control targets, and other influencing factors, the proposed GA_BP-based model for SWB parameter optimization has high feasibility and reliability, and that its usage can be generalized to analogous tunneling works. [ABSTRACT FROM AUTHOR]

Much scholarly attention is paid to understanding subjective well-being (SWB) from a spatial perspective. Various features of a city including social capital may have significant impacts on SWB in addition to individual attributes and national characteristics. However, the extant empirical studies of SWB tend to focus on the national- or regional-scale analysis rather than the city-scale analysis. Particularly, few studies inquire into the impacts of social capital and urban amenities on SWB along with the spatial dependence at the city level. This paper aims to examine the spatial effects of social capital and urban characteristics on the SWB of cities. For this purpose, we construct a series of spatial panel models for SWB using data for 219 cities in South Korea, from the Korean Community Health Survey (KCHS) conducted in 2011, 2013, 2015, and 2017. The results show that income, Gini-coefficient, social trust, social networks with friends, participation in charity activities, open space, and cultural opportunities all affect the SWB. Particularly, social capital and open space have spatial spillover effects on the SWB, even after controlling for socio-demographic variables. These findings will not only draw some important policy implications for urban planning and public management to improve the level of urban SWB, but also provide a piece of significant evidence for follow-up studies of its kind. [ABSTRACT FROM AUTHOR]

This paper analyzes the channels of change of subjective well-being (SWB), and how are the effects of a social intermediation program. We develop a simple theoretical model to link SWB with the individual and reference wealth, the effort and the level of aspirations. After to overcome selection issues with an instrumental variable to identify causal effects, we find a negative impact on SWB being the main channel of this change is subjective relative wealth, i.e., the relation between the individual and the reference wealth. There is no effect through other theoretical channels, but the results on SWB are heterogeneous by psychological features; they are higher among those with low aspiration levels and external locus of control. Finally, we disentangle the main program characteristics that might generate this effect giving relevant information for the policymakers. [ABSTRACT FROM AUTHOR]

Purpose: The increased population aging has resulted in a growing need for longitudinal studies about the quality of life among older people. Nevertheless, the results of these investigations could be biased because more disadvantaged people leave the original sample. The purpose of this study is to examine how the selective attrition observed in a panel survey affect multivariate models of subjective well-being (SWB). The question is if we could do reliable longitudinal investigations concerning the predictors of SWB in old age. Methods: This paper examines attrition in a panel of older people in Chile. Attrition was evaluated in the variables that affect elderly SWB. Probit models were fitted to compare dropouts with nondropouts. Then, multivariate probit models were estimated on satisfaction and depressive symptoms, comparing dropouts and nondropouts. Finally, we compared weighted and unweighted multivariate probit models on SWB. Results: The attrition rate in 2 years was 38.8%, including deaths and 32.9%, excluding them. Survey dropouts had lower satisfaction but not higher depressive symptoms. Among SWB predictors, people without a partner and with lower self-efficacy abandoned more the study. When applying the Becketti, Gould, Lillard, and Welch test, the probit coefficients of the predictor variables on SWB outcome variables were similar for dropouts and nondropouts. Finally, the comparison of multivariate models on SWB with weighting methods did not find substantial differences in the explanatory coefficients. Conclusion: Although some predictors of attrition were associated with SWB, attrition did not produce biased estimates in multivariate models of life satisfaction life or depressive symptoms in old age. [ABSTRACT FROM AUTHOR]

Soil–Water characteristic Curve (SWCC) is meant to describe the mechanical behavior of unsaturated soil. The present paper focuses on the internal multi-scale microstructure of Xining untreated loess and lime-treated loess with the use of scanning electron microscopy (SEM) and image processing technique. A new SWCC model was presented based on the fractal dimension of pore size distribution. The SWCC of untreated loess was calculated from fractal dimension and fitted well with curve tested from Fredlund SWCC device. The SWCC of lime-treated loess was then calculated. Two curves of Xining untreated loess and lime-treated loess have been compared and reasons for the difference have also been discussed. The results indicate that the content of large pores in lime-treated loess decreased and the content of micro-pore increased. The bracket pores were changed into cement pores. The pore fractal dimension D of Xining untreated loess is 1.39 and the pore fractal dimension D of Xining lime-treated loess is 1.53. Air-entry value of untreated loess is 12.16 kPa, while lime-treated Loess—35.15 kPa. In transition region, matric suction of lime-treated loess was in the range of 35.15 kPa ~ 4000 kPa, while matric suction of untreated loess—12.16 kPa ~ 2600 kPa. The range of the transition region in lime-treated loess is larger than that in the loess, while in the range of saturation region, the reverse applies. Under the condition of the same matrix suction, the saturation of lime-treated loess is greater than that of untreated loess. In the residual region, the difference of SWCC of soil samples is small. [ABSTRACT FROM AUTHOR]

Paddy fields play a critical role as storage for the retention of surface water in hydrological processes, but their water balance is complicated by irrigation and drainage management. Studies have proposed flow routing methods for paddy fields by simplifying the hydrological and hydraulic complexity associated with drainage processes. However, the performance of paddy field routing schemes has not yet been sufficiently evaluated to assist in the selection of routing methods for a water balance analysis. This study evaluated three common drainage routing schemes developed for paddy fields, including the simple water balance (SWB), linear reservoir with threshold (LRT), and broad-crested weir (BCW) models, in terms of complexity and performance. This study also compared the accuracy of irrigation water requirement and sediment load estimates simulated using the three schemes. Results showed that the BCW model produced the best statistical accuracy when predicting daily flow, but the three routing methods performed similarly over a 10-day time scale. Results suggested that the simple structure of the SWB model was not accurate enough to reproduce high and low flow on a daily scale, which produced relatively higher irrigation water requirements and sediment loads compared with those of LRT and BCW. LRT provided performance statistics similar to those of BCW using fewer calibration parameters. The comparison confirmed a trade-off relationship between model complexity and performance, highlighting the importance of model selection for hydrological analysis. [ABSTRACT FROM AUTHOR]

Crop water productivity (CWP) is a measure of crop yield per unit of water consumed and plays a crucial role in evaluating the role of alternate management practices for sustainable production. This study investigates the crop water and yield dynamics of rice (Oryza sativa L.) subjected to three (low, moderate, and high water stress) deficit irrigation scenarios. Factorial experiments were conducted in four paddy fields in a command area of south India during the 2017–18 growing seasons with farmers' current irrigation practice used as the control (T1). Seasonal total and irrigation water application of rice was ranged from 803 and 175 mm for high stress to 978 and 350 mm for T1 conditions. Cumulative potential evapotranspiration (ETo) for the growing seasons was observed to be 326.65 ± 2.51 mm. The FAO-56-based SIMDualKc model was parameterized to partition the evapotranspiration (ET) fluxes and to obtain site-specific crop coefficients for each scenario. Model-simulated root zone soil moistures were in agreement with the observations for all irrigation treatments (R2 > 0.80, RMSE < 0.04 cm3 cm−3, n = 20). Stage-specific single (Kc) and basal crop (Kcb) coefficients for rice with T1 are, respectively, 1.1, 1.09, 0.79, and 0.9, 0.97, 0.57, which are slightly lower than FAO tabulated values. The calibrated soil–water balance model was further applied to simulate crop yield using a simple crop growth algorithm. Our results conclude that crop yield is sensitive to water stress during vegetation (ky = 1.14 ± 0.10) followed by transplantation (ky = 1.07 ± 0.16) and reproduction stages (ky = 1.02 ± 0.17). We observed a marginal increase in CWP (12% in 2017 and 3% in 2018) and a reduction in deep percolation losses (29% in 2017 and 14% in 2018) through controlled water-saving strategies. [ABSTRACT FROM AUTHOR]

Village collectives are important providers of rural public goods in developing countries with dual urban-rural structures. However, few studies have investigated the relationship between the public goods provided by village collectives and the subjective well-being (SWB) of rural residents. This study aims to fill that gap. Based on the 2014 round of China Family Panel Studies (CFPS) survey data, this study estimates an ordered logit model of a SWB function to examine the role of the public goods provided by village collectives. The results indicate that village collectives' provision of public goods has a significantly positive effect on the SWB of rural residents by promoting the dual growth of household income and consumption. Village collectives' public expenditures on production, education, and public services also positively affect the SWB of rural residents. The public goods provided by village collectives have a significantly positive effect on the SWB of young and middle-aged rural residents but not on the SWB of elderly rural residents. Finally, rural residents with low levels of education and health obtain more SWB effects than do residents with high levels. [ABSTRACT FROM AUTHOR]

Domain-specific measures of subjective wellbeing are valuable tools for assessing the mental health of college students. In this study, we examined relations between Big Five personality traits and college students' subjective wellbeing (SWB) using a college-specific measure: The College Student Subjective Wellbeing Questionnaire. Using a latent variable modeling approach called bifactor analysis, we found that the general college wellbeing factor was best predicted by agreeableness and extraversion whereas the specific dimensions of college SWB were differentially predicted by conscientiousness and neuroticism. Specifically, conscientiousness best predicted academic satisfaction and efficacy whereas neuroticism best predicted students' connectedness to the university. The results suggest that the profile of a flourishing college student is extraverted and agreeable. This study illustrates the methodological advantage of using a domain-specific measure of SWB and bifactor modeling to shed light on the unique relations between personality and various aspects of college students' mental health. [ABSTRACT FROM AUTHOR]

The Indian subcontinent is vulnerable to natural disasters, predominantly devastating floods. The north-eastern region of India, especially the state of Assam, is endowed with many natural water resources, making the area highly flood-prone. However, very few studies have investigated the population's subjective well-being (SWB) in these areas despite such recurrent adversity. An integrated model of SWB is proposed and tested by combining the SWB homeostasis theory and the theory of conservation of resources. The integrated model indicated both subjective as well as objective variables as significant predictors of the SWB. A sample of 306 participants was randomly selected from two severely flood-affected areas in the state of Assam in India using a cross-sectional survey study design. Structural equation modeling was used to test two hypothesized integrated models (a direct and mediational path model). The results indicated that SWB homeostasis is maintained within the normative range of 60-65 points when measured on a 100-point continuum. Analysis of the direct path model showed that education, safe shelter, personality traits (extraversion, neuroticism, agreeableness, and openness), object and condition resources, psychological buffers (optimism and perceived control), and negative affect significantly predicted SWB. The mediational path model indicated that optimism is a significant mediator between personality traits (agreeableness, conscientiousness, and neuroticism), positive affect, resources (object resources and condition resources), and SWB. The study findings may have implications for counselling in addressing internal psychological buffers such as optimism and perceived control for maintaining the SWB of the disaster victims. [ABSTRACT FROM AUTHOR]

The present study is focused on a theoretical model of unsaturated soil based on elastic spherical particle arrangement, which can be considered to be a simplified DEM method. The model is presented with a large graded soil. This approach follows a new research method so that the physical phenomena are explained and the number of experimental parameters is limited. The theoretical model takes into account the different arrangements of soil particles so that the entire void ratio scale is covered. The wetting and drying paths are modelled. A comparison with the Brooks and Corey (1962) theory and the new theory is achieved on experimental results with a sample of glass micro-sphere and two natural soils, the Livet-Gavet sandy-loam and the Livet-Gavet loam. It shows that this new theory improves precision of the prediction using only simple physical parameters. [ABSTRACT FROM AUTHOR]

The relative hydraulic conductivity is one of the key parameters for unsaturated soils in numerous fields of geotechnical engineering. The quantitative description of its variation law is of significant theoretical and technical values. Parameters in a classical hydraulic conductivity model are generally complex; it is difficult to apply these parameters to predict and estimate the relative hydraulic conductivity under deformation condition. Based on the fractal theory, a simple method is presented in this study for predicting the relative hydraulic conductivity under deformation condition. From the experimental soil-water characteristic curve at a reference state, the fractal dimension and air-entry value are determined at a reference state. By using the prediction model of air-entry value, the air-entry values at the deformed state are then determined. With the two parameters determined, the relative hydraulic conductivity at the deformed state is predicted using the fractal model of relative hydraulic conductivity. The unsaturated hydraulic conductivity of deformable Hunan clay is measured by the instantaneous profile method. Values of relative hydraulic conductivity predicted by the fractal model are compared with those obtained from experimental measurements, which proves the rationality of the proposed prediction method. [ABSTRACT FROM AUTHOR]

Background: The detrimental effects of caregiving have been well documented. In order to compensate for the disadvantages of caring, research has also tried to identify factors associated to caregivers' subjective well-being (SWB).Aims: We aim at presenting an integrative model of SWB.Methods and Procedures: Sample consisted of 228 staff working with people with intellectual disabilities. Measures employed included three different components of self-care (social, internal and physical), mental and physical health, conscientiousness, hope, and life satisfaction. The model aimed to explain SWB, measured by life satisfaction, by several variables (self-care, mental and physical health, and conscientiousness), while checking for the role of hope as a partial mediator of these relationships.Outcomes and Results: Results show an overall good fit of the model: χ2(6) = 12.274, p =  .056; CFI = .953; RMSEA = .077 [.000, .139], hence establishing the first model of prediction of SWB of staff in services for people with intellectual disabilities.Conclusions and Implications: Social self-care, mental health and conscientiousness were capable of explaining life satisfaction but only through hope, that is, these factors did not have significant direct effects. The presence of hope may be then necessary for these factors to benefit staff. Strengths and limitations are discussed. [ABSTRACT FROM AUTHOR]

An increasing number of crops are being considered as potential sources of biomass for both conventional (e.g., maize/corn) and cellulosic (e.g., switchgrass, miscanthus, and hybrid poplar) biofuels. Studies investigating the hydrologic characteristics of these crops are often conducted at either the field scale with a focus on evapotranspiration (ET) or at the plot scale where experiments generally rely on soil water storage dynamics and residual water balances. While this has led to many important insights into crop–soil water interactions under these crops, there does not appear to be any multiyear direct comparisons of the drainage fluxes under this range of biofuel crops. Furthermore, important advancements in drainage flux measurement technologies have yet to be applied to quantify hydrologic fluxes below a range of biofuel crops. Here, we use soil water content (SWC) probes and automated equilibrium tension lysimeters (AETL) to characterize detailed differences in soil water storage and drainage fluxes under conventional and cellulosic biofuel crops. The results of this study suggest that there are significant differences between subsurface water fluxes under some conventional and cellulosic biofuel crops, such as 75% greater average annual drainage and more rapid drainage accumulation under switchgrass relative to maize. An increasing number of crops are being considered as potential sources of biomass for conventional (e.g., maize/corn) and cellulosic (e.g., switchgrass, miscanthus, and hybrid poplar) biofuels. This study uses soil water content probes and automated equilibrium tension lysimeters to characterize detailed differences in soil water storage and drainage fluxes under conventional and cellulosic biofuel crops. The results of this study suggest that there are significant differences between subsurface water fluxes under these biofuel crops, such as 75% greater average annual drainage and more rapid drainage accumulation under switchgrass relative to maize. [ABSTRACT FROM AUTHOR]

Highlights • Soil-water carrying capacity of three revegetation species was determined. • Optimal plant cover (LAI) or biomass (NPP) varied across the Loess Plateau. • Climate, soil texture and elevation drive variations in LAI and NPP. • A revegetation threshold was recommended for future revegetation activities. Abstract Re-vegetation is a necessary control measure of soil erosion in the Loess Plateau. However, excessive re-vegetation can aggravate soil water shortage, which can in turn threaten the health and services of restored ecosystems. An optimal plant cover or biomass (i.e., soil-water carrying capacity for vegetation, SWCCV) is important for regional water balance, soil protection and vegetation sustainability. The objective of this study was to determine the spatial distribution of SWCCV for three non-native tree (Robinia pseudoacaia), shrub (Caragana korshinskii) and grass (Medicago sativa) species used in the re-vegetation of the Loess Plateau. The dynamics of actual evapotranspiration (AET), net primary productivity (NPP) and leaf area index (LAI) were simulated using a modified Biome-BGC (Bio-Geochemical Cycles) model. Soil and physiological parameters required by the model were validated using field-observed AET for the three plant species at six sites in the study area. The validated model was used to simulate the dynamics of AET, NPP and LAI for the three plant species at 243 representative sites in the study area for the period 1961–2014. The results show that spatial distributions of mean AET, NPP and LAI generally increased from northwest to southeast, much the same as mean annual precipitation (MAP) gradient. In terms of maximum LAI, the ranges of optimal plant cover were 1.1–3.5 for R. pseudoacaia , 1.0–2.4 for C. korshinskii and 0.7–3.0 for M. sativa. The corresponding SWCCV, expressed as NPP were 202.4–616.5, 83.7–201.7 and 56.3–253.0 g C m−2 yr−1. MAP, mean annual temperature, soil texture and elevation were the main variables driving SWCCV under the plant species; explaining over 86% of the spatial variations in mean NPP in the study area. Further re-vegetation therefore needs careful reconsideration under the prevailing climatic, soil and topographic conditions. The results of the study provide a re-vegetation threshold to guide future re-vegetation activities and to ensure a sustainable eco-hydrological environment in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Abstract Meticulous research has been done to observe and measure the impact of biochar on soil-water retention properties. On the contrary, very little research is conducted on quantifying cracking in soil biochar composites. Investigation of crack intensity factor is essential as it affects permeability and hence, overall water balance in agricultural fields. It is well known that cracking of soil is influenced by suction and water content but their interactive effects are not very well understood. This technical note aims to investigate the cracking of soil amended with biochar made out of water hyacinth, an invasive weed, with focus on analysing interactive effects of water content and soil suction. An integrated reduced scale monitoring and modelling using artificial neural networks have been adopted. A series of tests were conducted to monitor suction, water content and crack intensity factor in soils mixed with four different compositions i.e. 0%, 2%, 5% and 10% by weight of biochar for around 3 months. The measured results have been evaluated first, and eventually modelled using artificial neural networks to predict crack intensity factor as function of water content and suction for all composites. In most of the cases it has been found that suction is more influential than water content. However, the relative significance of suction to water content in determining crack intensity factor decreases with increase in biochar content of soil. It is concluded that the optimum biochar content is 10% for most of the agricultural purposes based on the water retention capacity and cracking. The probability distribution of crack intensity factor is found to be normal for case with 5% biochar and while for others, it is skewed negatively. A simple cost based analysis taking in context of a small developing urban city of India, showcased a cost savings in irrigation of urban infrastructure by around 63,000 US dollars for a particular summer. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Highlights • We extend the Landsberg and Fowkes (1978) model of water uptake to root networks. • Dichotomous branching pattern is more efficient in water uptake than herringbone. • Network topology affects uptake over reported ranges of hydraulic parameters. • Total water uptake responded more to radial flow in lupin but axial floow in wheat. • Axial flow limitation may affect monocot root habit evolution. Abstract Current theory and supporting research suggests that radial transport is the most limiting factor to root water uptake, raising the question whether only absorbing root length and radial conductivity matter to water uptake. Here, we extended the porous pipe analytical model of root water uptake to entire root networks in 3D and analysed the relative importance of axial and radial characteristics to total uptake over parameter ranges reported in the literature. We found that network conductance can be more sensitive to axial than radial conductance of absorbing roots. When axial transport limits uptake, more dichotomous topology, especially towards the base of the network, increases water uptake efficiency, while the effect of root length is reduced. Whole root system conductance was sensitive to radial transport and length in model lupin (Lupinus angustifolius L.), but to axial transport and topology in wheat (Triticum aestivum L.), suggesting the root habit niche space of monocots may be constrained by their loss of secondary growth. A deep tap root calibrated to oak (Quercus fusiformis J. Buchholz) hydraulic parameters required 15 times more xylem volume to transport comparable amounts of water once recalibrated to parameters from juniper (Juniperus ashei Small 1901), showing that anatomical constraints on axial conductance can lead to significant trade-offs in woody roots as well. Root system water uptake responds to axial transport and can be limited by it in a biologically meaningful way. [ABSTRACT FROM AUTHOR]

This paper examines the current procedure for determining the soil-water characteristic curve (SWCC) model with a particular focus on its application to slope stability analysis under transient unsaturated seepage conditions. A series of laboratory experiments was performed to determine the SWCC of different soils, ranging from high plasticity clay to silty sand, found across the Korean Peninsula. The experimental results were utilized to identify the suitable SWCC model for each soil type based on the fitting criterion. Also, this paper developed a numerical framework for infinite slope stability analysis under transient unsaturated seepage conditions. The significant advantage of the proposed framework, from the practical viewpoint, is to directly predict the timing of failure and potential failure plane based on rainfall recording. The effect of choice of SWCC models on predictability in stability analysis was evaluated by adopting the present framework along with the identified SWCC models. Furthermore, a case study of landslides after a 3-month rainfall in Pohang, Korea, was revisited to assess the performance of the proposed framework. The obtained results demonstrate the significant role of SWCC model on the results of slope stability analysis. The analysis using the SWCC model satisfying the fitting criterion could still not capture the real behavior of unsaturated soil. The comprehensive transient analysis is strongly suggested as a complementary means to the current fitting criterion for determining the suitable SWCC model for stability analysis under transient seepage conditions. [ABSTRACT FROM AUTHOR]

Depending on the nature of the material and suction range, laboratory measurements of the soil-water characteristic curve (SWCC) can be time-consuming and expensive, especially for residual soils, in which a wide range of particle sizes and soil structures typically results in SWCCs that cover a wide range of suction. Investigations of the SWCCs of residual soil from flysch rock masses are rare, and so far, no results were presented in the literature which were obtained by performing measurements on undisturbed specimens. In this paper, a detailed examination of water retention characteristics is performed for a specific type of residual soil (CL) formed by the weathering of a flysch rock mass. Measurements performed by using different techniques and devices on intact specimens were successfully combined to obtain the SWCC during both drying and wetting processes, under different stress conditions, and from saturated to air-dried conditions. Used procedures are suitable for the determination of SWCCs of soils that undergo volume changes during the drying or the wetting process, since instantaneous volumetric water content can be determined. Results presented in this paper can be used to assess the influence of desaturation of the residual soil covering flysch slopes during dry summer periods by providing key-in material properties required to analyze the transient rainfall infiltration process. [ABSTRACT FROM AUTHOR]

Three-dimensional DEM (discrete element method) simulations of triaxial tests and wetting tests on unsaturated silt were carried out in order to analyse the macro and microscopic behaviour under triaxial stress conditions. Interparticle adhesive forces were incorporated into a rolling and twisting resistance model to represent the van der Waals and capillary forces. A loose DEM sample was first produced considering rolling and twisting resistance and van der Waals forces to sustain an open structure. A series of pseudo-constant water content triaxial tests were simulated by controlling adhesive forces at contacts using the matric suction and a group of representative soil-water characteristic curves. The wetting tests were performed by quickly and gradually wetting (QW and GW) the unsaturated sample at different deviator stress levels. By introducing adhesive forces at contacts, the simulation reproduces the main mechanical behaviour. In the triaxial tests, Z m (mechanical coordination number) for the unsaturated sample increases rapidly during shear until becoming approximately constant. The induced structural anisotropy (under deviatoric loading) reduces with decrease in water content due to the higher interparticle adhesive forces. In the gradual wetting tests, the deviatoric fabric increases gradually during wetting. The deviator strains induced by QW and GW (loading-wetting sequence) are much larger than for the saturated sample at the same stress state in triaxial tests (wetting-loading sequence). [ABSTRACT FROM AUTHOR]

We systematically evaluated the effect of model complexity and calibration strategy on estimated recharge using four varyingly complex models and a unique long-term recharge data set. A differential split sample test was carried out by using six calibration periods with climatically contrasting conditions in a constrained Monte Carlo approach. All models performed better during calibration than during validation due to differences in model structures and climatic conditions. The two more complex, physically-based models predicted the observed recharge with relatively small uncertainties, even when calibration and prediction periods had different climatic conditions. In contrast, the more simplistic soil-water balance model significantly underestimated the recharge rates. The fourth, semi-mechanistic model captured the observed recharge rates, but with a larger uncertainty range than the physically-based models. Our results may have relevant implications for a broad range of applications when recharge models are used as decision-making tools. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ETc) partitioning and obtaining of FAO56 dual crop coefficient (Kc) for olive was carried out with the SIMDualKc software application for root zone and topsoil soil water balance based on the dual crop coefficients. A simplified two source-energy balance model (STSEB), based on daily remotely sensed soil and canopy thermal infrared data and retrieval of surface fluxes, also provided information on partitioning ETc for the olive orchard. Both models were calibrated and validated with ground-based, sap flow-derived transpiration rates, and their performance was compared in partitioning ETc for incomplete cover, intensive olive grown in orchards (≥300 trees ha-1). The SIMDualKc proved adequate in partitioning ETc. The STSEB model underestimated ETc mostly by inadequately simulating soil evaporation and its contribution to the total latent heat flux. Such results suggest difficulties in using information from the STSEB algorithm for assessing ETc and dual Kc crop coefficients of intensive olive orchards with incomplete ground cover. [ABSTRACT FROM AUTHOR]

Knowledge on pore functionality is important for the management of soils in the environment. The present study considered the hypothesis that Bt horizons with cohesive character have a different porous network regarding its functionality because, among other aspects, their pores are preferentially oriented in the horizontal direction. This study aimed to evaluate pore functionality in cohesive and non-cohesive Bt horizons, including the functional evaluation of pores arranged vertically and horizontally in soils of the Coastal Tablelands of the Ceará state, Brazil. In an Argissolo Vermelho-Amarelo Distrófico típico (PVAd) and in an Argissolo Amarelo Eutrocoeso abrúptico (PAex), soil samples were collected in cohesive and non-cohesive Bt horizons (two soil collection arrangements: horizontal and vertical), in seven replicates, considering undisturbed soil structure (28 samples in each soil, a total of 56 samples in both soils). A disturbed sample was collected from each soil horizon for grain size analysis. The following variables were analyzed: granulometry, soil air intrinsic permeability ( K air ), pore continuity, soil-water characteristic curve and average pore length. The data of each soil profile were analyzed considering the completely randomized design, with seven replicates. For soil air intrinsic permeability, a 2 × 2 × 5 factorial scheme was used (two horizons: cohesive Bt and non-cohesive Bt; two pore arrangements: horizontal and vertical; five matric potentials: − 2, − 6, − 10, − 33 and − 100 kPa); for average pore length, a 2 × 2 factorial scheme was used (two horizons: cohesive Bt and non-cohesive Bt; two pore arrangements: horizontal and vertical). The data were subjected to the Shapiro-Wilk test to verify normality, to F test for the analysis of variance, and to the Tukey test for the comparison of means, all at 0.05 probability level. The sand fraction prevailed in both soils. Horizons with cohesive character have lower K air in comparison to the non-cohesive ones. For pore orientation, in general, K air was superior for those arranged horizontally. Pores in cohesive horizons are less continuous compared with horizons without cohesive character. As to the arrangement, in general, pores are more continuous horizontally. Regarding soil water characteristic curve, the expressive difference between cohesive and non-cohesive horizons is within the matric potential range from saturation up to approximately − 8 kPa to − 10 kPa. In the rest of the curve, in cohesive horizons, especially in the situation where pores are vertically arranged, there is more water available to plants at the same matric potential. It was concluded that pores in Bt horizons with cohesive character are less functional than those in Bt horizons without cohesive character, with lower permeability to air, length and connection between them. Regardless of how well the pores are oriented, the highest percentage of blocked pores, i.e., those that do not contribute to gas and heat fluxes, occurs in the horizons with cohesive character. In horizons with cohesive character, horizontal porosity proved to be functionally better than vertical porosity. The fact that the pores in cohesive horizons show lower permeability to the air, shorter length and less connectivity evidences the limitation of these soils for the exploration by plant roots, since they characterize an environment with restriction to gas and heat exchanges - although they can function as a barrier to water drainage, supplying water in greater amount in comparison to a non-cohesive soil. [ABSTRACT FROM AUTHOR]

Tempe cell with a self-developed horizontal hanging column attachment was used to measure the soil water characteristic curves (SWCCs) of granular materials initially saturated with either water or polymer solutions. For SWCCs of six poorly graded granular materials with d50 ranging from 0.04 to 0.7 mm in water, it was found that (1) as grain size decreases, air entry value increases, and matric suction (ψ) for the funicular and pendular regimes increases and that (2) steep desaturation curves over narrow ψ range in the funicular regime were observed. Air entry values obtained from the fitting parameter 1/α in van Genuchten SWCC equation fall in the boundaries calculated from the pore throat sizes in both simple cubic and face-centered cubic packings. A toroidal meniscus water model, which incorporates the measured surface tension and contact angle values between aqueous solutions and solid surfaces, was proposed for the SWCC in pendular regime and was compared to well-received numerical methods. This toroid model successfully depicts SWCC of poorly graded granular materials in water. However, SWCCs predicted by this toroid model underestimate the degree of saturation in the pendular regime for Ottawa 20–30 sands in polymer solutions. Herschel–Bulkley fluid, which is a type of non-Newtonian fluids, is postulated to increase the ψ needed to drain the polymer solution due to the nonzero shear stress intercept. In addition, it is also postulated by scanning electron microscopy and optical confocal imaging results that the rough surfaces of Ottawa 20–30 sand, which have many micron-sized “kinks”, together with the possible chemical attractions, help retain the polymer solutions on the solid surfaces, or water film. [ABSTRACT FROM AUTHOR]

The coefficient of permeability function is an important unsaturated soil property required when modeling seepage and contaminant transport phenomena. Inaccuracies in the estimation of the permeability function can lead to significant errors in numerical modeling results. Changes in void ratio and degree of saturation are factors that influence the permeability function. Presently available methodologies for estimating the unsaturated permeability function make the assumption that there is no volume change as soil suction is changed. As a result, volume changes are interpreted as changes in degree of saturation. The commonly used estimation techniques for the permeability function are reasonable for soils such as sands that experience little volume change as soil suction is changed. On the other hand, inaccurate results are generated when soils undergo volume change as is the case with oil sands tailings. Revisions to previous methodologies are proposed to render the estimation of the permeability function more suitable for simulating the drying process associated with soils that undergo high volume changes. The revised methodology independently analyzes the effect of volume changes (i.e., changes in void ratio) and degree of saturation changes (i.e., changes in S-SWCC (degree of saturation - soil-water characteristic curve)). Laboratory data on thickened oil sands tailings are presented and interpreted within the context of the proposed methodology. [ABSTRACT FROM AUTHOR]

Due to the formational environment and climatic variability, granite residual soils with grain-size distribution ranging from gravel to clay undergo multiple drying-wetting cycles. The influences of multiple drying-wetting cycles on the soil-water characteristic curve (SWCC) and pore-size distribution (POSD) of undisturbed granite residual soils are investigated using the pressure plate test and nuclear magnetic resonance (NMR) spin-spin relaxation time ( T2) distribution measurement, respectively. Results show that the water-retention capacity and air-entry value decrease and pores become more uniform with increasing drying-wetting cycles. After four drying-wetting cycles, the soil reaches a nearly constant state. The POSD change of multiple drying-wetting cycle samples is consistent with the SWCC of the soils. Furthermore, a modified van Genuchten model in terms of cumulative pore volume is used to obtain the best-fit POSD of the drying-wetting cycle samples. The shape and changing tendency of both curves of SWCC and POSD are quite similar and achieved a better correlation. It can be concluded that the SWCC is strongly dependent on the POSD of the soil and NMR T2 relaxometry can be used as an alternative to the assessment of microstructural variation of residual soils subjected to the periodic drying and wetting process. [ABSTRACT FROM AUTHOR]

Population growth and changes in climate and diets will likely further increase the pressure on agriculture and water resources globally. Currently, staple crops are obtained from annuals plants. A shift towards perennial crops may enhance many ecosystem services, but at the cost of higher water requirements and lower yields. It is still unclear when the advantages of perennial crops overcome their disadvantages and perennial crops are thus a sustainable solution. Here we combine a probabilistic description of the soil water balance and crop development with an extensive dataset of traits of congeneric annuals and perennials to identify the conditions for which perennial crops are more viable than annual ones with reference to yield, yield stability, and effective use of water. We show that the larger and more developed roots of perennial crops allow a better exploitation of soil water resources and a reduction of yield variability with respect to annual species, but their yields remain lower when considering grain crops. Furthermore, perennial crops have higher and more variable irrigation requirements and lower water productivity. These results are important to understand the potential consequences for yield, its stability, and water resource use of a shift from annual to perennial crops and, more generally, if perennial crops may be more resilient than annual crops in the face of climatic fluctuations. [ABSTRACT FROM AUTHOR]

Water retention, unsaturated permeability, and deformation-failure characteristics induced by infiltration were studied by analyzing stress-dependent soil–water characteristics and the wetting stress path of unsaturated intact clayey loess in Baoji, China. Test results in Baoji and Heifangtai were compared. The results show the following: (1) The soil–water characteristic shape is related to stress, and suction decreases with water content; (2) the van Genuchten model is applicable to the clayey loess in Baoji, (3) the unsaturated permeability coefficient is related to stress, which increases with axial net stress; (4) under certain confining stress, hydraulic properties of loess vary considerably by region and, compared with loess in Heifangtai, the water retention capacity of clayey loess in Baoji is greater; (5) brittle deformation is dominant in Baoji but plastic deformation is dominant in Heifangtai; and (6) deformation behavior and the strength of loess is related to the confining stress, and the combined action of that stress and suction cause breakage of loess cementation bonds. The decrease of matric suction is not necessary for loess deformation, but the breakage of cementation bonds is the essence of the decreasing strength and final deformation failure of loess. [ABSTRACT FROM AUTHOR]

Recently planted intensive almond plantations may have access to limited water supply due to water scarcity thus, information on almond water use under limited irrigation is needed. Here, the soil water balance was used to assess the consumptive use (ET) of full irrigated, moderately stressed and severely stressed almond trees over a three-year study, as well as the relation between applied water and ET. Sap flow measurements in eight experimental trees were used to obtain independent transpiration (T) measurements. Evaporation from soil (E S ) was modelled to estimate tree T from the water balance. Relative consumptive use in the deficit irrigation (DI) treatments largely exceeded the relative applied water, highlighting the need to measure ET in stressed treatments for hydrologic purposes. The moderately stressed treatments (irrigated at 65.5% of full irrigation) consumed 79.0% of maximum evapotranspiration (ET of 897 mm), while the severely stressed treatment consumed 63.6% of ETc (ET of 722 mm) when applied water was only 39.6% of control. On average, almond ETc approached 1200 mm, Seasonal evolution of the transpiration coefficient yielded maximum peak values ranging from 0.99 to 1.08, and minimum peak values of 0.33 attained with a severe deficit irrigation strategy. Transpiration measured by Compensated Heat Pulse-Calibrated Average Gradient sap-flow (x), was compared to water balance T estimates (y), and yielded a very good relation over the three years of study (y = 0.90x + 4.23, r 2 = 0.81). The sap flow measurements proved to be useful to overcome the limitations of the soil water balance technique, revealing that almond trees were able to extract water from below the monitored depths and suggesting that deep percolation event must have occurred in spring and autumn. [ABSTRACT FROM AUTHOR]

As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying soil and water. To analyze the spatio-temporal changes of humidifying effect of green lands at the spring daytime, the authors monitored the air humidity within 1.8 m high from various underlying surfaces, including arbor-grass lands, shrub lands, herb lands and a cement pavement, from late February to late April in 2015 and 2016, when it was sunny and windless, in the Yuxi park of Shijazhuang. The results were compared with the monitoring data of a bare land (190 m × 120 m) without environmental interventions such as vegetation and water. The results could be summarized as follows: ① The humidifying effect of green spaces was the weakest at 8:00 a.m. during the late February, whereas it was the strongest at 10:00 a.m.; from late March to late April, the humidifying effect of green spaces strengthened with the increase of air temperature, and the strongest was noted around 12:00-16:00. ②The humidifying effect of various types of green lands was the strongest close to the ground, and reduced from 0.2 m to 1.8 m. This vertical stratification became apparent after the plants sprouted, the vertical difference of humidifying effect was the most significant in the herb lands, less significant in arbor-grass lands, and least in the shrub lands. ③ Multiple comparison analysis of the humidity data showed that relative humidity of all green lands achieved the significant level (P < 0.05), indicating the strong effect of landscape plants in adjusting atmospheric humidity in spring. ④The humidifying effect of the artificial lake was more remarkable before the plants sprouted, however, with the rapid growth of plant leaves, the effect gradually reduced and became even weaker than the effect of vegetation. Although the humidifying effect in spring was weaker than that in summer and autumn, the effect of humidification was more complicated during the growth of green leaves in spring than in summer and autumn. This is useful to construct the theory system of ecological environment effect of green lands in spring, summer and autumn. [ABSTRACT FROM AUTHOR]

Characterizing the spatiotemporal variability of soil-water content (SWC) is of paramount importance in many scientific fields and operational applications. We present a case study of the temporal stability and variability of SWC in a gravel-mulched field, a form of mulching that has been widely used by farmers on the loessial area of China for over 300 years, using Spearman correlation coefficients, frequency distributions and an index of temporal stability. SWC was measured weekly from May to August 2013 in the 0–10, 10–20, 20–30 and 30–50 cm layers. SWC was more variable in the surface soil, due to several environmental factors, and the variability gradually decreased with depth. A large sample size was needed for estimating the mean SWC of the field under dry conditions. High Spearman correlation coefficients between the SWCs measured on different sampling campaigns indicated a high temporal stability. The stability of the SWC spatial patterns over time and along the soil profile allowed us to identify a location representative of the field-mean SWC, with high coefficients of determination ranging between 0.8564 and 0.9325. The large-scale monitoring of SWC from few observations is thus feasible, which will aid the management of soil moisture in gravel-mulched fields in arid regions. [ABSTRACT FROM AUTHOR]

The filling of the Three Gorges Reservoir in China inevitably deteriorated the slope stability near the reservoir and triggered many landslides, which have become a serious geo-hazard. The fluctuation of the water level and the changes in pore water pressure in the slope lead to stability changes of the reservoir slopes. Taking the Huangtupo Riverside No.2 Landslide (HR2L) as a case study, a comprehensive geotechnical investigation is performed. First, the soil-water characteristics curve (SWCC) and the long-term strength of the slip zone soils and landslide soils are obtained based on the experiments. Second, a numerical simulation is used to obtain the distribution characteristics of the saturation line. Finally, the reliability of the landslide is evaluated. The results show the following: (1) At the same reservoir level, the saturation line will change with different reservoir statuses. (2) When considering the matric suction, the safety factor of the landslide is larger (by 3%) than that without considering this component. (3) As the reservoir water level rises, the safety factor of the slope increases. (4) The slip zone soils of the landslide show significant creep characteristics. Under the effect of creep, the long-term strength decreases gradually. (5) Considering the long-term strength of the slip zone soils, the variation of landslide reliability decreases gradually. The slope stability gradually changes from a less-stable state to a worse state. [ABSTRACT FROM AUTHOR]

The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin ( UCRB), particularly during low-flow periods. Understanding impacts on groundwater in the basin from projected climate change will assist water managers in the region in planning for potential changes in the river and groundwater system. A previous study on changes in basin-wide groundwater recharge in the UCRB under projected climate change found substantial increases in temperature, moderate increases in precipitation, and mostly periods of stable or slight increases in simulated groundwater recharge through 2099. This study quantifies projected spatial and seasonal changes in groundwater recharge within the UCRB from recent historical (1950 to 2015) through future (2016 to 2099) time periods, using a distributed-parameter groundwater recharge model with downscaled climate data from 97 Coupled Model Intercomparison Project Phase 5 ( CMIP5) climate projections. Simulation results indicate that projected increases in basin-wide recharge of up to 15% are not distributed uniformly within the basin or throughout the year. Northernmost subregions within the UCRB are projected an increase in groundwater recharge, while recharge in other mainly southern subregions will decline. Seasonal changes in recharge also are projected within the UCRB, with decreases of 50% or more in summer months and increases of 50% or more in winter months for all subregions, and increases of 10% or more in spring months for many subregions. [ABSTRACT FROM AUTHOR]

With the pressure to ban or limit the use of bisphenol A (BPA), production of alternatives such as bisphenol AF (BPAF) and bisphenol S (BPS) are increasing, but little is known on their partitioning behavior for use in assessing distribution in the ecosystem. Octanol-water (D owpH) and soil-water partitioning were measured at several pH values for BPA, BPAF, and BPS. Sorption isotherms were constructed from measured aqueous and soil phase concentrations and were fit sufficiently well with a linear sorption model. pH-dependent distribution was observed in both octanol-water and soil-water systems particularly for BPS and BPAF, which have lower estimated pK a values than those for BPA. Accounting for soil organic carbon (OC) content and pH was sufficient to describe sorption reasonable well across the four soils (%OC 0.1-2.5, pH 3.8-8.6); no other soil properties correlated well with bisphenol sorption. However, for a given soil especially for the two high clay low OC soils, BPS sorbed much more than expected relative to observed trends in D owpH and magnitude appeared correlated to % kaolinite; therefore, Ca2+-bridging of BPS to clay edge sites was assessed by comparing sorption from 0.01 N KCl and 0.01 N CaCl2; however, no significant differences were observed. [ABSTRACT FROM AUTHOR]

The relation between the soil-water characteristic curve (SWCC) and the soil freezing characteristic curve (SFCC) is investigated based on the similarity between the freezing/thawing and drying/wetting behaviors of soils. The SWCCs of clay and silt are obtained by the pressure plate extractor and vapor pressure method, while the SFCCs are determined from the unfrozen water content measurement using the nuclear magnetic resonance (NMR) and temperature measurement. The pore water potential of the frozen soil is derived from a generalized Clapeyron equation, which addresses the effects of capillarity, sorption, and osmosis, and compared to that of unsaturated soils. Our experimental results show that at low water content the matric potential in the soil saturated with pore water and pore ice is generally different from that in the soil saturated with pore water and pore gas. A series of experiments on the soil samples saturated by NaCl solutions of different concentrations were performed to determine the osmotic potential and the water retention characteristics. Based on the principles of surface chemistry, a relationship between the adsorptive forces and the water film thickness is developed, which is capable of describing the soil water characteristic when the sorption effect is significant. Our results indicate that the freezing-point depression method should be applied with caution in determining the soil water retention characteristics of unsaturated soils at lower water content. [ABSTRACT FROM AUTHOR]

Porous models are built using the current pore-size distribution of the material and can reproduce the phenomenon of hysteresis during wetting-drying cycles. The term current pore-size distribution means that the size of the pores is being updated as the soil deforms. This type of model can be used advantageously for the development of fully coupled hydromechanical constitutive models for unsaturated soils. Also, because the volumetric deformation affects the pore-size distribution of the soil, the influence of the former on the retention curves can be easily assessed. This paper presents a porous-solid model that simulates the hydraulic hysteresis of soils and the influence of the volumetric deformation on the soil-water retention curves. The precision obtained in numerical and experimental comparisons shows the adequacy of the model. [ABSTRACT FROM AUTHOR]

The soil-water characteristic curve (SWCC) is an important tool in the interpretation of the properties of unsaturated soil, and is widely applied in Geotechnical and Geo-environmental engineering. The SWCC uses several fitting parameters to express the best fit equations, and the fitting parameters depend on the experimental data. The reliability and predictability of SWCC are always being questioned. In this paper, Fredlund and Xing model is used to fit the experimental data of loamy sand and sandy clay loam in the UNSODA database, the fitting parameters values are discussed. Bayesian framework and the Markov Chain Monte Carlo simulation method are applied to estimate the uncertainty of SWCC from the errors and variance of the fitting parameters, and SWCC of different levels of confidence is obtained. Applications of the confidence on slope stability analysis are presented by a simplified finite element program. [ABSTRACT FROM AUTHOR]

This study was focused on modeling soil water, carbon (C), and nitrogen (N) dynamics in soil and crop emphasizing uncertainties in model parameterization and the evaluation of potential water stress for silage maize cultivations on a drained field. The CoupModel was applied on different management systems for silage maize ( Zea mays ) in monoculture and undersown with grass ( Lolium perenne L.) on a sandy-humic soil. Four different fertilization levels with 0, 150 kg of mineral-N, 40 m 3 of cattle slurry (72–148 kg N ha −1 year −1 ), and combined slurry/mineral-N (222–298 kg N ha −1 year −1 ) were simulated over five years. Results were based on most plausible parameter combinations regarding simulated biomass obtained from 10,000 runs by the Generalized Likelihood Uncertainty Estimation (GLUE) approach. The uncertainty in model parameterization was reduced significantly by limiting the number of simulations for each treatment sequentially resulting in quartile coefficients of variation ( CV *) < 25% for 26% and 36% of selected input parameters in bi-cropping and monoculture systems, respectively. Average soil temperatures in upper soil depths, the groundwater level, water potentials, and water contents between 10 and 80 cm of depth were reproduced plausibly with the model as well as plant C and N contents. The CV * values of evapotranspiration and total runoff ranged between 0 and 26% and 8–21%, respectively, on half-yearly basis. Significant differences between the cropping systems were found, even though the soil water balance was positive for all systems, and the potential water stress was only minor in bi-cropping systems. [ABSTRACT FROM AUTHOR]

Pitfalls in the common approaches to obtaining material parameters from soil-water characteristic curves (SWCCs) are discussed, and the typical mistakes made in the literature are highlighted. Particular attention is given to the evaluation of the air-entry value (AEV) from the gravimetric water content–based SWCCs. A consistent graphical approach for the determination of AEV based on an understanding of the effects of stress history and volume change on gravimetric water retention behavior is presented. The robustness and application of the approach are demonstrated using an extensive set of experimental data from the literature. [ABSTRACT FROM AUTHOR]

A series of experiments were performed to investigate the hydraulic and mechanical behavior of an unsaturated silt obtained from the Yellow River Delta. To identify the key factors that influence the soil-water characteristics (SWC), an experimental program was designed to study the SWC of the soil at different void ratios and vertical pressures. It was shown that an apparent hysteresis phenomenon occurred on the SWC curves when the soil experienced drying/wetting cycles. It was also shown that the influence of void ratio on the SWC was significant, and the stress state influenced the SWC only through changing the void ratio. Isotropic compression tests were conducted at different constant matric suctions, using a suction-controlled double cell triaxial apparatus. The soil under shearing showed apparent dilatant and softening behavior, in a way similar to medium to dense sand. In addition, the hardening effect of matric suction was significant, and both the stiffness and peak strength of the soil increased with matric suction. Based on the experimental observations, an elastoplastic constitutive model coupling capillary hysteresis and plastic deformation was developed, in which a hysteretic SWC relationship was introduced to characterize the influence of hydraulic history on the skeletal deformation. To better simulate the volumetric change of the soil, a nonassociated flow rule was adopted. The effect of the plastic volumetric strain on water-retention behavior was also taken into consideration. The proposed model was used to simulate the behavior of unsaturated silt under constant-suction, isotropic compression and constant-suction, triaxial shearing conditions, showing the capability of the new model in describing the behavior of unsaturated silt. [ABSTRACT FROM AUTHOR]

A common underlying assumption in the development of soil-water characteristic curves (SWCCs) is that the soil is sufficiently stiff such that no changes occur in the volume of the soil associated with soil-suction change. A number of researchers recently recognized the importance of considering soil-volume changes in SWCCs; however, few researchers have evaluated the effect of volume change on the computed rate and degree of wetting/drying of unsaturated soils and the associated impact on computed soil-volume change response. This paper focuses on the impacts of considering soil-volume change in the determination of SWCCs for high-volume-change soils, with emphasis on the estimated unsaturated hydraulic conductivity function and response to wetting. Numerical simulations of unsaturated flow and suction-induced volume change were used to study the effect of consideration of volume change in the determination of SWCCs. Numerical analyses used laboratory-determined SWCCs with and without the inclusion of volume change measurements. The study results demonstrate that the impact of volume change consideration on SWCCs and the estimated unsaturated hydraulic conductivity function can be quite substantial for high-volume-change soils such as expansive clays. [ABSTRACT FROM AUTHOR]

In order to simulate soil erosion and sedimentation processes of debris flow, a depth-integrated particle method with soil-water mixing model is proposed. In the model, each numerical particle represents a mixture of soil grains and water with a certain soil volume concentration and can exchange the soil mass with the neighboring particles according to the diffusion equation. A unique relationship is also assumed between the soil volume concentration and its critical deposition angle to compute the bottom shear stress acting on the flowing numerical particles. Therefore, the model only contains three major mechanical parameters: the classical Manning coefficient, the critical slope angle for the loose soil deposit at the base of valley, and the diffusion coefficient to control the soil water mixing process. In addition, a two-step simulation method is proposed to evaluate the initial distribution of the loose soil deposit in the valley bottom. The model is initially validated by a laboratory flume experiment taken from the open literature, and adequate values of the mechanical parameters are determined. Next, the model is applied into the case study of the 2010 debris flow event in Zhouqu, and the simulation results are compared with the field investigation, as well as the post-event satellite images. The affected area, the travel distance, and the flow velocity statistics exhibit good agreement. [ABSTRACT FROM AUTHOR]

The concept of available water holding capacity (AWHC) is important to many aspects of soil water management, particularly those involving a soil water balance calculation. In New Zealand AWHC estimates are commonly based directly or indirectly on laboratory measured pressure plate data. Such retentivity based values for AWHC are relatively similar across a range of soil types. Less often, AWHC values have been measured under rye grass/white clover pasture in the field. We critically discuss an important earlier New Zealand study. It noted that field-measured values are commonly about twice the laboratory-based estimates. We conclude that variable rooting depth, due to the presence or absence of compacted soil at depth and/or variable pasture vigour or species composition, usually has a greater effect on the AWHC than does the soil properties in the top 760 mm depth. Finally, it is claimed that this uncertainty around the exact size of AWHC need not undermine its utility. The one exemption to this assurance is where reliable predictions of drainage (and leaching) below the root zone are required: in this case there is the likelihood that use of the often quoted values for AWHC in the water balance will result in a significant overestimation of drainage (and leaching). [ABSTRACT FROM AUTHOR]

The small-strain shear modulus G0 is a fundamental property governing shear wave propagation in soil. It depends on fabric of soil particles, soil water content, and stress state. The dependency of G0 on stress and water content was assessed by using the suction stressbased effective stress principle. Here the variation of G0 with water content was compared with soil-water retention (SWR) behavior and suction stress behavior for 12 soils under zero total stress conditions. A recently established SWR model enables the distinction of capillary and adsorption regimes for better interpretation of the correlation between G0 and suction stress. It is demonstrated experimentally that the variations of both G0 and suction stress follow the same pattern but differ by a dimensionless scalar. Further correlation of the scalar with SWR provides good predictions of suction stress for different soils in the capillary regime. The established correlations among SWR, suction stress, and G0 further confirm the validity of the suction stress-based effective stress principle. [ABSTRACT FROM AUTHOR]

The snow pack of Sierra Nevada, southern Spain, melts during spring and early summer, feeding ancestral irrigation channels in the region known as the Alpujarra. This simulation study compares the traditional irrigation water supply, based on proportional division, with the actual supply, based on up-downstream priority, in one watershed in the Alpujarra. A combination of three models was used for the analysis. Water supply was simulated using the snowmelt-runoff model. The snow cover required by that model was determined using satellite images. A second model simulated the distribution of water based on proportional division and on up-downstream priority. Irrigation requirements and return flows were simulated using a soil-water balance. Proportional division is an inherently equitable mechanism for distributing water, but can lead to water deficits for different crops in a command area. The analysis demonstrated this premise not be true. The superiority of proportional division was magnified in dry years. Because of the internal reuse of return flows, irrigation consumptive use coefficient (the ratio of irrigation water that is evapotranspirated by the crops to the total amount of irrigation water that leaves the area of concern during the period of analysis) at the watershed scale was significantly greater than at the irrigation-channel scale. This result illustrated, based on tradition in ancestral irrigation community, the notion of integrated water resources management. [ABSTRACT FROM AUTHOR]

The goal of this work was to develop an easy-to-use and engaging irrigation scheduling tool for cotton which operates on a smartphone platform. The model which drives the Cotton SmartIrrigation App (Cotton App) is an interactive ET-based soil water balance model. The Cotton App uses meteorological data from weather station networks, soil parameters, crop phenology, crop coefficients, and irrigation applications to estimate root zone soil water deficits (RZSWD) in terms of percent as well as of inches of water. The Cotton App sends notifications to the user when the RZSWD exceeds 40%, when phenological changes occur, and when rain is recorded at the nearest weather station. It operates on both iOS and Android operating systems and was released during March 2014. The soil water balance model was calibrated and validated during 2012 and 2013 using data from replicated plot experiments and commercial fields. The Cotton App was evaluated in field trials for three years and performed well when compared to other irrigation scheduling tools. Its geographical footprint is currently limited to the states of Georgia and Florida, United States, because it is enabled to use meteorological data only from weather station networks in these states. A new version is currently under development which will use national gridded meteorological data sets and allow the Cotton App to be used in most cotton growing areas of the United States. [ABSTRACT FROM AUTHOR]