Search Results (367)

Efficient irrigation management is crucial for optimizing crop development while minimizing resource use. This study aimed to assess the spatial variability of water distribution under conventional sprinkler irrigation, alongside soil moisture and infiltration dynamics, using multispectral sensors onboard Remotely Piloted Aircraft (RPAs). The experiment was conducted over a 466.2 m² area equipped with 65 georeferenced collectors spaced at 3 m intervals. Soil data were collected through volumetric rings (0–5 cm), auger sampling (30–40 cm), and 65 measurements of penetration resistance down to 60 cm. Four RPA flights were performed at 20 min intervals post-irrigation to generate NDVI and NDWI indices. NDWI values decreased from 0.03 to −0.02, indicating surface moisture reduction due to infiltration and evaporation, corroborated by gravimetric moisture decline from 0.194 g/g to 0.191 g/g. Penetration resistance exceeded 2400 kPa at 30 cm depth, while bulk density ranged from 1.30 to 1.50 g/cm³. Geostatistical methods, including Inverse Distance Weighting and Ordinary Kriging, revealed non-uniform water distribution and subsurface compaction zones. The integration of spectral indices within situ measurements proved effective in characterizing irrigation system performance, offering a robust approach for calibration and precision water management. Full article

This study examines the kinematic behavior of a large-scale colluvial landslide in a coastal low-elevation forest, where rainfall, geological formations, and hydrological conditions drive substantial slope displacement. The landslide comprises a colluvial layer overlying mudstone, with downslope movement toward the coastline induced by gravitational forces and infiltration. Using GPS surveys, inclinometers, soil moisture sensors, and numerical modeling, the temporal and spatial patterns of displacement were analyzed. Maximum horizontal displacements reach 8.1 cm/year, with deep-seated movements extending over 25 m into the mudstone. Key mechanisms include weakening of the colluvium–mudstone interface and creep within saturated mudstone, while a hydraulic barrier near the coastline restricts subsurface flow. Progressive upslope migration of the freshwater-bearing mudstone zone under annual rainfall further contributes to long-term deformation. These findings provide critical insights into the hydrologically controlled kinematics of coastal colluvial landslides. Full article

Optimizing seeding ratios in mixed cover crop species can maximize their ecological benefits, such as soil properties and weed suppression. A two-year field study assessed seven oat (O) and daikon radish (D) ratios (100:0 to 0:100) for their effects on soil quality, weed pressure, and subsequent spinach yield. Measured parameters included cover crop biomass, C:N ratio, land equivalence ratio (LER), soil organic carbon (SOC), microbial population, soil enzyme activities, bulk density, porosity, moisture, and water infiltration time. The impact of intercrop residues and two weeding strategies (hand weeding and no weeding) on weed pressure and spinach yield was also assessed. Oat monoculture produced the highest biomass (338.7 g m⁻²), while radish monoculture biomass was the lowest (256.1 g m⁻²). Yet the 30:70 (O:D) ratio contributed to the highest SOC (0.96). The C:N ratio of all intercropped combinations was below the critical threshold (25:1) that causes N immobilization, with oat monoculture having the highest value (23:1). The microbial population was highest with the 10:90 (O:D) ratio, with 12.8 × 10⁻⁴ most probable number per g⁻¹ soil. While urease and dehydrogenase enzyme activities were not affected by intercrop ratios, β-glucosidase and alkaline phosphatase activities were up to 30% higher in daikon radish-dominated intercrops. Bulk density decreased by 31.7% in oat monoculture, whereas infiltration time was shortened in daikon radish monoculture by 41.7% (4.6 s). Weed suppression was strongest in oat monoculture and the 90:10 (O:D) intercropping, reducing weed populations by over 30%. Spinach yield was highest in oat monoculture with hand weeding (842.9 g m⁻²), with a 40.2% increase over weeding alone. Overall, daikon radish-dominated intercropping ratios were more effective in enhancing soil properties, whereas oat-dominated intercropping improved spinach yield, mainly due to slower decomposition, thus better suppressing weeds. Full article

Granite residual soil is widely employed as subgrade fill material, but its tendency to undergo wetting-induced deformation under moisture infiltration poses significant challenges to pavement stability. To address this issue, this study introduces an innovative wetting device capable of precisely controlling moisture content increase, enabling multi-step wetting tests under controlled conditions. Saturated wetting tests were also conducted using both single-line and double-line methods, and the results were compared. Pore size distribution curves for granite residual soil samples with different initial states were measured using Mercury Intrusion Porosimeter (MIP) tests. Results indicate that for both the single-line method and the double-line method, the ${\epsilon }_V$-lgp curve for samples subjected to different compaction efforts remains parallel across varying initial moisture content. The increase in vertical stress will constrain the water adsorption and swelling potential. Whereas an increase in compaction effort leads to greater swelling potential, which is mitigated by an increase in initial moisture content. By integrating the test results of the soil water characteristic (SWCC) curve, the relationship between normalized wetting deformation and matric suction is primarily influenced by the initial state of the soil sample and remains unaffected by vertical stress during multi-step wetting. Based on the test results, an empirical wetting prediction model was formulated, accounting for the influence of vertical stress, initial matric suction, and matric suction after wetting. Fitting results confirmed that the established model achieved high prediction accuracy (R² > 0.9), supporting its application in practical engineering endeavors. Full article

Hydrological drought indices, while critical for monitoring, are often limited by their reliance on single variables, failing to capture the multidimensional complexity of water scarcity, particularly in data-scarce and climate-sensitive regions. This study addresses this critical gap by introducing a Composite Hydrological Drought Index (CHDI) for a northern watershed in Thailand, a region where drought risk is intensified by climatic shifts and intensive land use. The proposed methodology integrates multiple outputs from the Variable Infiltration Capacity (VIC) hydrological model, including precipitation, runoff, evapotranspiration, baseflow, and soil moisture layers, and employs Principal Component Analysis (PCA) to synthesize the dominant drivers of water-level variability. The first principal component (PC1), which accounted for over 50% of the total variance, served as the basis for the CHDI, and was strongly correlated with precipitation, surface runoff, and surface soil moisture. The performance of CHDI was rigorously evaluated against observed data from eight hydrological stations. The index demonstrated significant predictive skill, with Pearson’s correlation coefficients (R) ranging from 0.49 to 0.79 (p < 0.05), a maximum Nash–Sutcliffe Efficiency (NSE) of 0.63, and F1-scores for drought detection as high as 0.92. It effectively captured seasonal and interannual variability, including the accurate identification of low-flow events reported by the National Hydro Informatics Data Center (NHC). While the CHDI showed robust performance, particularly under high-flow conditions and in drought classification, some limitations were observed in complex or anthropogenically influenced sub-catchments. These findings highlight the potential of CHDI as a reliable and integrative tool for hydrological drought monitoring and for supporting water resource management in data-scarce and climate-sensitive regions. Full article

Water scarcity is a significant issue in arid and semi-arid regions and improving our understanding of infiltration and recharge processes is crucial for water resource management. In this study, weighing lysimeters were employed in Mu Us Sandy Land, China to continuously monitor soil water content and recharge rates during the non-freezing seasons from April 2021 to October 2023. The performance of three empirical weight functions, including Poisson, Rayleigh, and Gamma distributions in simulating the recharge process was evaluated. The results indicate that: (1) The process of groundwater recharge displays significant interannual and seasonal differences. Due to low initial soil moisture and scarce rainfall, recharge accounts for only 10.9% of the averaged annual rainfall in 2021. Due to extreme rainfall events (126.8 mm), groundwater recharge increased by 649.4% compared to 2021, accounting for 51.2% of the annual rainfall in 2022. Because of relatively high soil moisture, groundwater recharge accounted for 18.3% of the annual rainfall in 2023. (2) The Poisson empirical weight function is more suitable for simulating a gradual increase in recharge rate, while it fails to accurately capture the rapid rise in recharge rates associated with extreme rainfall events. (3) Compared to the Poisson empirical weight function, the Gamma distribution performs better under extreme rainfall conditions. This study provides a detailed analysis of groundwater recharge dynamics in semi-arid regions and offers technical support for a deeper understanding of groundwater recharge processes. Full article

This study investigates the combined impact of climate change and land use changes on water resources and soil conditions in the Litani River Basin (LRB) in Lebanon. The Mediterranean region, including the LRB, is highly vulnerable to climate change. This study utilizes the WiMMed (Water Integrated Management for Mediterranean Watersheds) model to assess hydrological variables such as infiltration, runoff, and soil moisture for the years 2009, 2014, and 2019. It considers 2019 climate conditions to project the 2040 scenarios for Representative Concentration Pathways (RCPs) 2.6 and 8.5, incorporating the unique characteristics of the Mediterranean watershed. Results indicate a concerning trend of declining infiltration, runoff, and soil moisture, particularly under the more severe RCP 8.5 scenario, with the most significant reductions occurring during summer. Land use changes, such as deforestation and urban expansion, are identified as key contributors to reduced infiltration and increased runoff. This study highlights the critical role of soil moisture in crop productivity and ecosystem health, showing how land cover changes and climate change intensify these effects. Soil moisture is highly sensitive to precipitation variations, with a 20% reduction in precipitation and a 5 °C temperature increase leading to substantial decreases in soil moisture. These findings highlight the urgent need for sustainable land management practices and climate mitigation strategies in the Litani River Basin (LRB) and similar Mediterranean watersheds. Protecting forests, implementing soil conservation measures, and promoting responsible urban development are crucial steps to maintain water resources and soil quality. Furthermore, this research offers valuable insights for policymakers, farmers, and environmentalists to prepare for potential droughts or flooding events, contributing to the preservation of this vital ecosystem. The data from this study, along with the recommended actions, can play a crucial role in fostering resilience at the national level, addressing the challenges posed by climate change. Full article

Investigating rainfall infiltration mechanisms and slope stability dynamics under varying vegetation cover conditions is essential for advancing ecological slope protection methodologies. This research focuses on large-scale outdoor slope models, with the objective of monitoring soil moisture variations in real-time during rainfall events on four types of slopes: bare, herbaceous, shrub, and mixed herb–shrub planting. Combining direct shear tests for unsaturated soil with numerical simulations, and considering the weakening effect of water on shear strength, this study analyzes slope stability. The findings reveal significant spatial variations in rainfall infiltration rates, with maximum values recorded at a burial depth of 0.2 m, declining as the burial depth increases. Different types of vegetation have distinct impacts on slope infiltration patterns: herbaceous increases cumulative infiltration by 21.32%, while shrub reduces it by 61.06%. The numerically simulated moisture content values demonstrate strong congruence with field-measured data. Compared with monoculture herbaceous or shrub root systems, the mixed herb–shrub root system exhibits the most significant enhancement effects on shear strength parameters. Under high water content conditions, root systems demonstrate substantially greater improvement in cohesion than in internal friction angle. Before rainfall, shrub vegetation contributed the most significant improvement to the safety factor, increasing it from 2.766 to 3.046, followed by herbaceous and mixed herb–shrub vegetation, which raised it to 2.81 and 2.948. After rainfall, mixed herb–shrub vegetation demonstrated the greatest enhancement of the safety factor, elevating it from 1.139 to 1.361, followed by herbaceous and shrub vegetation, which increased it to 1.192 and 1.275. The study offers preliminary insights and a scientific basis for the specific conditions tested for selecting and optimizing eco-friendly slope protection measures. Full article

Preferential flow in coal mining subsidence areas leads to shallow soil moisture loss, vegetation reducing and ecological degradation. However, the factors influencing the development of preferential flow remain unclear. This study analyzed the morphological characteristics of preferential flow using a staining tracer test in coal mining subsidence areas along the middle reaches of the Yellow River Basin. Characteristic parameters including the dye-stained area ratio, preferential flow ratio, length index, variation coefficient were comparatively evaluated under different initial soil moisture conditions. Results showed that shallow soils exhibited substrate flow, while preferential flow occurred in deeper soil layers below the matrix flow. As initial soil moisture increased, the extent of both substrate flow and preferential flow decreased. The dye-stained area ratio declined with increasing soil depth, and the relationship between dye-stained area and soil layer depth was best described by a cubic function. Higher initial soil moisture reduced maximum infiltration depth and length indices while increasing the coefficient of the stained pattern. Furthermore, a higher of initial soil water content corresponded to a lower preferential flow index. Overall, increased initial soil moisture may reduce the extent of preferential flow and the rapid infiltration of water into soil. These findings provides a basis for further hydrological studies in coal mining subsidence areas in arid and semi-arid regions and offer scientific support for ecological restoration efforts in mining areas. Full article

The Zigui Basin, located in the Three Gorges Reservoir Area, has developed numerous landslides due to its interlayering of sandstone and mudstone, geological structure, and reservoir operations. This study identifies a fourth type of landslide failure mode: an oblique-dip slope wedge (OdSW) landslide, based on the Wanshuitian landslide. Following four heavy rainfall events from 3 to 13 July 2024, this landslide exhibited significant deformation on the 17th and was completely destroyed within 40 min. The dimensions of the landslide were 350 m in length, 160 m in width, and 20 m in thickness, with a volume estimated at 8.0 × 10⁵ m³. The characteristics of landslide deformation and the changes in moisture content within the shallow slide body were ascertained using unmanned aerial vehicles, moisture meters, and mobile phone photography. The landslide was identified to have occurred within the weathered residual layer of mudstone, situated between two sandstone layers, with the eastern boundary defined by an inclined rock layer. Upon transitioning into the accelerated deformation stage, the landslide initially exhibited uniform overall sliding deformation, culminating in accelerated deformation destruction. The dip structure created terrain disparities, resulting in a step-like terrain on the left bank and gentler slopes on the right bank, with interbedded soil and rock in a shallow layer, because the interlayered soft and hard geological conditions caused varied weathering and erosion patterns on the riverbank slopes. The interbedded weak–hard stratum layer fostered the development of the oblique-dip slope wedge landslide. Based on the improved Green–Ampt model, we developed a stability prediction methodology for an oblique-dip slope wedge landslide and determined the rainfall infiltration depth threshold of the Wanshuitian landslide (9.8 m). This study aimed not merely to sharpen the evolution mechanism and stability prediction of the Wanshuitian landslide but also to formulate more effective landslide-monitoring strategies and emergency management measures. Full article

This study presents a scenario-based assessment of the future sensitivity of minimal low-water runoff to climate change in Western Kazakhstan. An ensemble of global climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), combined with dynamically downscaled projections for Central Asia, was applied to estimate minimal monthly runoff during the summer–autumn and winter low-water periods for the rivers of the Zhaiyk–Caspian water management basin. The analysis covers three future time horizons: 2040 (2031–2050), 2060 (2051–2070), and 2080 (2071–2090), under two greenhouse gas concentration scenarios: SSP3-7.0 (moderately high emissions) and SSP5-8.5 (high emissions). The results reveal a pronounced seasonal contrast in the projected hydrological response. During the winter low-water period, a steady increase in minimal runoff is projected for all rivers, with the most significant changes observed for the Or, Zhem, Temir, and Shagan rivers. This increase is primarily driven by higher winter precipitation, increased thaw frequency, and enhanced infiltration recharge. Conversely, despite modest increases in summer–autumn precipitation, minimal runoff during the summer–autumn low-water period is projected to decline significantly, particularly in the southern basins, due to elevated evapotranspiration rates and soil moisture deficits associated with rising air temperatures. These findings emphasize the importance of developing seasonally differentiated, climate-resilient water management strategies to mitigate low-flow risks and ensure water security under future climate conditions in arid and semi-arid regions. Full article

Accurate and reliable modeling of pavement deterioration is critical for effective infrastructure management. This study proposes a probabilistic machine learning framework using Bayesian-optimized Natural Gradient Boosting (BO-NGBoost) to predict the International Roughness Index (IRI) of asphalt pavements in cold climates. A dataset only for cold regions was constructed from the Long-Term Pavement Performance (LTPP) database, integrating multiple variables related to climate, structure, materials, traffic, and constructions. The BO-NGBoost model was evaluated against conventional deterministic models, including artificial neural networks, random forest, and XGBoost. Results show that BO-NGBoost achieved the highest predictive accuracy (R² = 0.897, RMSE = 0.184, MAE = 0.107) while also providing uncertainty quantification for risk-based maintenance planning. BO-NGBoost effectively captures long-term deterioration trends and reflects increasing uncertainty with pavement age. SHAP analysis reveals that initial IRI, pavement age, layer thicknesses, and precipitation are key factors, with freeze–thaw cycles and moisture infiltration driving faster degradation in cold climates. This research contributes a scalable and interpretable framework that advances pavement deterioration modeling from deterministic to probabilistic paradigms and provides practical value for more uncertainty-aware infrastructure decision-making. Full article

The usage of land on small farms in subtropical regions varies with climatic conditions. Agricultural cultivation typically occurs during the spring and summer (of the southern hemisphere), with tobacco being the primary crop on most small farms. During these seasons, livestock graze in pastures and woodlots. After the tobacco harvest (March), farmers plant winter cover crops, and by May, livestock is moved from the pastures to the agricultural areas. This study aimed to examine how grazing influences soil density, water infiltration rates, and animal behavior across different land types (pasture, native forest, eucalyptus reforestation, and agriculture) during the tobacco-growing season, and the off-season when grazing occurs on agricultural lands. It was found that forage availability and climatic conditions determined grazing duration in pastures and forests, under Integrated Crop–Livestock (ICL) systems. Higher forage volume in the agriculture area reduced grazing time and increased resting periods. Eucalyptus reforestation areas had the best soil conditions due to minimal grazing occurring there. An increase in soil bulk density and a decrease in water infiltration rates were observed at the end of the grazing period in both pasture and woodland areas. Year-round ICL systems appear to enhance soil quality through fallow periods, improving forage availability, soil moisture retention, and water infiltration as well. Full article

Previous studies have extensively applied the generalized consolidation theory, which incorporates a two-stress state variable framework, to predict the volumetric behavior of unsaturated expansive soils under varying mechanical stress and matric suction. A key requirement for this approach is a constitutive surface that links the soil void ratio to both net stress and matric suction. A large number of fitting parameters are typically needed to accurately fit a two-variable void ratio surface equation to laboratory test data. In this study, a single-stress state variable framework was adopted to describe the void ratio as a function of effective stress for unsaturated soils. The proposed approach was applied to fit void ratio–effective stress constitutive curves to laboratory test data for two different expansive clays. Additionally, a finite element model coupling variably saturated flow and stress–strain analysis was developed to simulate the volume change behavior of expansive clay subjected to moisture fluctuations. The model utilizes suction stress to compute the effective stress field and incorporates the dependency of soil modulus on volumetric water content based on the proposed void ratio–effective stress relationship. The developed numerical model was validated against a benchmark problem in which a layer of Regina expansive clay was subjected to a constant infiltration rate. The results demonstrate the effectiveness of the proposed model in simulating expansive soil deformations under varying moisture conditions over time. Full article

Soft soils, characterized by high compressibility, low shear strength, and high water sensitivity, pose serious challenges to geotechnical engineering in infrastructure projects. Traditional stabilization methods such as lime and cement face limitations, including environmental concerns and poor durability under chemical or cyclic loading. Ionic soil stabilizers (ISSs), which operate through electrochemical mechanisms, offer a promising alternative. However, their long-term performance—particularly under environmental stressors such as acid/alkali exposure and cyclic wetting–drying—remains insufficiently explored. This study evaluates the strength and durability of ISS-modified soil through a comprehensive experimental program, including direct shear tests, permeability tests, and cyclic wetting–drying experiments under neutral, acidic (pH = 4), and alkaline (pH = 10) environments. The results demonstrate that ISS treatment increases soil cohesion by up to 75.24% and internal friction angle by 9.50%, particularly under lower moisture conditions (24%). Permeability decreased by 88.4% following stabilization, resulting in only a 10–15% strength loss after water infiltration, compared to 40–50% in untreated soils. Under three cycles of wetting–drying, ISS-treated soils retained high shear strength, especially under acidic conditions, where degradation was minimal. In contrast, alkaline conditions caused a cohesion reduction of approximately 26.53%. These findings confirm the efficacy of ISSs in significantly improving both the mechanical performance and environmental durability of soft soils, offering a sustainable and effective solution for soil stabilization in chemically aggressive environments. Full article