Search Results (62)

Understanding long-term hydroclimatic variability in arid and semi-arid regions is essential for sustainable water resource management in the context of accelerating climate change. This study examines historical trends (1950–2024) and data-driven extrapolations to 2040 for precipitation and temperature across 30 secondary river basins in Iran using ERA5 reanalysis dataset and the Light Gradient Boosting Machine (LightGBM) model. Results reveal pronounced spatial heterogeneity in precipitation, with more than two-thirds of basins showing median values of 0 mm, reflecting extreme rainfall intermittency. Long-term analysis indicates significant precipitation increases in northern basins, whereas decadal trends show widespread drying since the early 2000s, particularly in eastern regions (30–60 mm per decade). Mean, maximum, and minimum temperatures exhibit significant upward trends (0.015–0.045 °C yr⁻¹), with stronger warming in northern and northwestern basins; however, minimum temperatures increased faster than maximum temperatures, reducing the diurnal temperature range and indicating a shift in regional thermal dynamics. Maximum temperature is negatively correlated with precipitation (R ≈ −0.27 to −0.34), suggesting enhanced evapotranspiration under warming conditions. LightGBM extrapolations to 2040 indicate continued warming (1–3 °C) and precipitation declines across more than 80% of Iran, underscoring intensifying hydroclimatic stress and increasing challenges for water resource management in dryland environments. Full article

Soil erosion is a significant environmental concern in arid regions, particularly in dam-regulated watersheds, where intermittent flows from sprinkler irrigation can exacerbate land degradation. This study assesses soil erosion susceptibility in the Sidi Aich watershed using a combined approach of the Revised Universal Soil Loss Equation (RUSLE) and the Analytic Hierarchy Process (AHP), enabling the integration of both regional characteristics and expert-driven weighting. The RUSLE model accounts for natural and human-induced factors, whereas AHP provides a hierarchical weighting system that highlights rainfall erosivity and the local impacts of dam-regulated discharges. Results show that 26.12% of the area falls into the very high susceptibility category, 25.45% into high, 23.91% into moderate, and 24.51% into low susceptibility. Model validation demonstrates satisfactory predictive performance, with Area Under the Curve (AUC) values of 0.85 for AHP and 0.78 for RUSLE. Overall, the findings emphasize the critical role of dam-controlled releases in increasing soil vulnerability, a factor that may not be fully captured when using RUSLE alone. By combining RUSLE and AHP, this research provides a more realistic and regionally tailored assessment of erosion risk, offering valuable guidance for watershed management and erosion mitigation strategies in arid environments. Full article

Rainfall is recognised as one of the major external factors affecting the stability of retaining walls. The magnitude of rainfall directly influences the overall stability of retaining walls, while rainfall patterns alter the infiltration process and the saturation state of the soil, thereby affecting soil shear strength and retaining wall stability. In order to investigate the effects of rainfall pattern and intensity on the stability of reinforced soil gabion retaining walls, numerical simulations were carried out to examine wall stability under two typical rainfall patterns (uniform and intermittent) and three rainfall intensities (20 mm/d, 50 mm/d, and 80 mm/d). The results indicate that: (1) under uniform rainfall conditions, the extent of the soil pore water pressure response zone is greater than that under intermittent rainfall of the same intensity, and as the uniform rainfall intensity increases from 20 mm/d to 80 mm/d, the pore water pressure response zone expands by approximately four times; (2) the rainfall pattern exerts a certain influence on the distribution characteristics of the time-history curves of lateral displacement of the retaining wall, with the horizontal displacement under intermittent rainfall exhibiting a non-uniform growth pattern associated with the rainfall pattern; (3) uniform heavy rainfall has a more pronounced effect on the horizontal displacement of reinforced soil gabion retaining walls, with the maximum absolute horizontal displacement reaching approximately 12.89 mm; and (4) rainfall pattern affects the evolution of the slope stability coefficient, which gradually decreases and eventually stabilises under uniform rainfall, whereas under intermittent rainfall it shows a continuous decreasing trend characterised by alternating rates of reduction, with a greater reduction observed under uniform rainfall conditions. These findings elucidate the influence of different rainfall patterns and intensities on the displacement behaviour and stability of reinforced soil gabion retaining walls, and provide a reference for risk assessment of reinforced soil gabion retaining walls. Full article

This study investigates the scaling properties of rainfall in Tunis over temporal scales ranging from 5 min to 2.5 years using high-resolution rain gauge data from three recording stations. We employ the Universal Multifractal (UM) framework to characterize scaling properties across multiple temporal regimes. The UM model was selected over alternative multifractal approaches because of its parsimonious three-parameter formulation (C₁, α, H). It explicitly accounts for non-conservative processes through the Fractionally Integrated Flux (FIF) extension and includes established bias correction methods for highly intermittent signals. This framework has demonstrated universality across diverse climatic conditions and enables direct comparison with existing rainfall studies in Mediterranean environments. Spectral analysis reveals three distinct scaling regimes: micro-scale (5 min–2 h 40 min), meso-scale (2 h 40 min–7 days), and synoptic scale (>7 days). The non-conservative nature of the micro-scale regime is addressed through a multifractal fractionally integrated flux model. A key challenge in applying UM analysis to rainfall data is the prevalence of low and zero rain rates (>98% zeros in our dataset). This extreme intermittency introduces significant bias in parameter estimation. Existing correction methods require either continuous rain sequences—scarce in semi-arid climates—or are limited to moderate intermittency levels. We propose an empirical correction method that extends the existing semi-empirical approach by explicitly linking the percentage of zero values to biased UM parameters through empirical relationships applicable to sequences with as few as 50% rainy observations. This advancement enables reliable parameter estimation from highly intermittent datasets. In such conditions, traditional event-by-event analysis yields insufficient samples (only five continuous events longer than 2 h 40 min over 2.5 years in Tunis). The corrected estimates (α = 1.63, C₁ = 0.16 for micro-scales) demonstrate strong consistency with continuous rainfall events and align well with high-resolution studies, validating our approach for extreme intermittency conditions characteristic of Mediterranean semi-arid climates. Full article

Driving rain or ‘wind-driven rain’ (WDR) arrives at the ground on an oblique trajectory, and drops may strike at a speed greater than their still-air terminal velocity. Oblique rain can affect a range of geomorphic processes including the splash dislodgment and transport of soil particles, and hydrological processes including overland flow, canopy interception, and the generation of stemflow. The mean rain inclination angle at which WDR strikes the ground has been estimated from the catch of paired gauges, one with a conventional horizontal orifice, and one with a vertical orifice, or by related forms of vectopluviometers. Such data allow the resolution of rain vectors to find the rain inclination. However, rain-collecting devices of this kind do not permit the real-time recording of the rain inclination from moment to moment. Here, a new acoustic method for measuring the rain inclination is introduced that provides an inexpensive tool for the continuous, real-time monitoring of WDR. Furthermore, the method also permits the simultaneous recording of rainfall duration and intermittency at a high temporal resolution, with no additional apparatus. Data on rain inclinations collected during showers on a tropical coast exposed to strong trade-winds are presented to illustrate the operation of the acoustic measurement system. However, the focus of this paper is the presentation of the new method itself, and not on the climatology of WDR. Full article

The potential for ‘Hass’ avocado production is predicted to increase with climate warming in New Zealand, a country where avocado orchards often lack irrigation because of a cooler and wetter climate compared to most other major growing regions. However, intermittent summer droughts are also predicted to increase in frequency and intensity. This study assessed the effects of summer soil water deficits on fruit growth of ‘Hass’ avocado in the Bay of Plenty, New Zealand, by comparing irrigated and non-irrigated treatments. Rainfall was variable over the three years of the study (2016–17, 2017–18, and 2018–19), but each summer there was a dry period without any rainfall for 2–3 weeks that decreased soil water content in the non-irrigated treatment. Fruit number and final yields were highly variable between trees and years, an effect of variable fruit set during the spring flowering period, and were not affected by the irrigation treatments because soil water deficits did not occur until later, during the summer. Increasing tree crop load caused decreasing individual fruit weight and dry matter content at harvest. However, in the year with the highest average crop load a dry period occurred during early fruit development, and mean fruit weight at harvest was decreased by 26.4 g (10%) in the non-irrigated treatment, an effect that was only apparent after accounting for the effects of variable crop load. The trees responded to dry conditions by reducing stomatal conductance (g_s) by 20%, preventing midday leaf water potential (Ψ_leaf) from decreasing below −0.25 MPa. Irrigation of avocado under the conditions at this site is therefore recommended when soil tension decreases below −30 kPa at 30 cm depth, and adverse effects on fruit growth are likely when tension decreases below −50 kPa. Irregular bearing of avocado under New Zealand growing conditions causes highly variable crop loads that obscure economically significant effects of mild to moderate water deficits on fruit growth. However, irrigation is still an important consideration for avocado production under current growing conditions and is likely to become more important under future climate scenarios as the risk of summer droughts increases. Full article

An extraordinary episode is a torrential rainfall event that produces significant societal impacts, which poses a major natural hazard in the western Mediterranean, particularly along the Valencia coast. This study evaluates the feasibility and added value of an explicitly spatial approach for estimating return periods of extraordinary precipitation in the Júcar and Turia basins, moving beyond traditional point-based or micro-catchment analyses. Our methodology consists of progressive spatial aggregation of time series within a basin to better estimate return periods of exceeding specific catastrophic rainfall thresholds. This technique allows us to compare 10 min rainfall data of a reference station (e.g., Turís, València, 29 October 2024 catastrophe) with long-term annual maxima from 98 stations. Temporal structure is characterized using the fractal–intermittency n-index, while tail behavior is modeled using several extreme-value distributions (Gumbel, GEV, Weibull, Gamma, and Pareto) and guided by empirical errors. Results show that $n\approx 0.3$–0.4 is consistent for extreme rainfall, while return periods systematically decrease as stations are added, stabilizing with about 15–20 stations, once the relevant spatial heterogeneity is sampled. Specifically, the probability of exceeding extraordinary thresholds is between 3 and 10 times higher for the areal than the point approach, so recurrence of a catastrophe would be once a few decades rather than centuries. Overall, the results demonstrate that spatially integrated return-period estimation is operational, physically consistent, and better suited for basin-scale risk assessment than purely point-based approaches, providing a relevant baseline for interpreting recent catastrophic events in the context of ongoing climatic warming in the Mediterranean region. Full article

Precipitation pulses refer to discrete and intermittent precipitation events that significantly influence ecosystem carbon and nitrogen cycling processes. However, the mechanisms by which different vegetation types modulate the sensitivity of carbon dioxide (CO₂) and nitrous oxide (N₂O) fluxes to short-term rainfall pulses remain poorly elucidated. To address this knowledge gap, we conducted a controlled rainfall simulation experiment across four representative surface types (moss-dominated biological soil crusts, Artemisia-ordosica-dominated soil, Caragana-korshinskii-dominated soil, and bare sandy soil), applying two precipitation pulses (5 mm and 10 mm) to quantify soil CO₂ and N₂O flux responses. The results showed that: (1) CO₂ emissions increased significantly with precipitation intensity, with the 10 mm treatment producing higher mean fluxes than the 5 mm treatment. Emission peaks (1200–1600 mg m⁻² h⁻¹) occurred within 24 h after rainfall and returned to baseline levels within three days; (2) Surface cover exerted a strong regulatory effect on CO₂ emissions, with moss crust soils (~400 mg m⁻² h⁻¹) and A. ordosica soils (~350 mg m⁻² h⁻¹) exhibiting CO₂ fluxes 2.5–3 times higher than those of bare sandy soils (~120 mg m⁻² h⁻¹); (3) Structural equation modeling indicated that precipitation indirectly enhanced CO₂ emissions by increasing soil carbon availability, with total organic carbon emerging as the strongest direct driver. Together, these findings clarify the primary controls on precipitation-induced CO₂ emissions in restored desert systems and highlight the decoupled and weak short-term response of N₂O, providing critical insights for managing carbon–nitrogen processes under increasing precipitation variability. Full article

The exploitation of hydrokinetic resources represents a sustainable and efficient alternative for renewable energy generation. This study presents the design and real-world implementation of a compact hydrokinetic system capable of converting rainwater runoff into electricity within smart homes. Unlike conventional large-scale hydrokinetic technologies, this system was specifically engineered for intermittent, low-flow conditions typical of residential rainwater collection networks. The turbine was manufactured using 3D-printed biodegradable materials to promote environmental sustainability and facilitate rapid prototyping. Through CFD simulations and laboratory testing, the system’s hydraulic behaviour and energy conversion efficiency were validated across different flow scenarios. The complete system, consisting of four turbines rated at 120 W each, was integrated into a real smart home without structural modifications. From an academic perspective, this study contributes a quantitatively validated hybrid hydrokinetic–low-head framework for residential rainwater energy recovery, addressing intermittent and low-flow urban conditions insufficiently explored in existing literature. Field tests demonstrated that the hydrokinetic system provides complementary energy during rainfall events, generating up to 6000 Wh per day and enhancing household energy resilience, particularly during periods of low solar availability. The results confirm the technical feasibility, sustainability, and practical viability of decentralized hydrokinetic energy generation for residential applications. Full article

Rainfall disaggregation is a key challenge in hydrology, especially in regions with limited high-resolution records. This study applies the Random Bartlett–Lewis Rectangular Pulse Model to four regions of Hellas to generate hourly rainfall from daily totals. The work is novel in evaluating the model under data-scarce Mediterranean conditions, incorporating a two-tiered uncertainty analysis, testing alternative pulse intensity distributions (Gamma and Exponential), and comparing its performance with a deterministic machine learning (ML) approach. Results show that the RBLRPM reproduces essential rainfall properties such as variance, autocorrelation, skewness, and dry spell probabilities, even when calibrated with as little as three years of data. The ML approach ensures perfect conservation of daily totals and computational efficiency, but it smooths temporal variability and underestimates extremes. By contrast, the stochastic RBLRPM captures clustering, intermittency, and heavy tails more realistically, which is crucial for hydrological design and flood risk analysis. The Gamma distribution consistently outperforms the Exponential form, though both remain applicable. Overall, the Gamma-based RBLRPM offers a robust and transferable method for rainfall disaggregation in data-limited contexts, highlighting the importance of stochastic approaches for water resource management, infrastructure resilience, and climate adaptation. Full article

Temporary wetlands are ecosystems formed by seasonal or intermittent inundation that provide habitats and support hydrological and biogeochemical processes. Despite their importance, they are often overlooked due to their small size and ephemeral nature. The lava forest of Jeju Island, known as Gotjawal, is a rare ecosystem where temporary wetlands occur despite the high permeability of basaltic terrain. This study reports an assessment of temporary wetlands in the Seonheul Gotjawal forest, focusing on identification, boundary delineation, and key characteristics. Wetlands were identified using four years (2020–2023) of water level monitoring and vegetation surveys. Hydrological boundaries were defined by maximum observed water levels, and ecological boundaries were delineated from plant distribution. Ecological boundaries consistently fell within hydrological ones, showing the value of vegetation indicators in wetland identification. Wetland areas ranged from 347–1214 m², with average depths of 0.2–0.9 m and hydroperiods of 13–76%. Water levels correlated with total rainfall. Three geomorphological wetland types were distinguished, with the shortest hydroperiods observed in small lava depressions functioning as forest microhabitats for endemic species. This study provides the first integrated evaluation of temporary wetlands in the Gotjawal lava forest and offers baseline data for classification and conservation. Full article

Rainfall deficits and erratic dry spells pose major challenges in rainfed ecosystem. In-situ moisture conservation practices (MCP) like ridge–furrow methods, improve soil moisture but are inadequate during 2–3 week dry spells at critical crop stages (flowering and maturity), leading to yield loss. Supplemental irrigation (SI) using an ex-situ rainwater harvesting (RWH) pond can mitigate these effects, but optimizing the pond design is challenging due to limited runoff and storage losses. This study aims to design RWH pond for small farm holders with a 1.0 ha area and evaluate its efficient use for SI during intermittent dry spells and critical crop stages. The design volume was estimated using the SCS-CN method based on daily rainfall data (1974–2010) for the northeast monsoon. A pond with a capacity of 487.5 m³, constructed for a 1 ha micro-watershed, was used to observe the runoff for design validation. The harvested runoff can be used as SI for a cultivable area of 0.4 ha, based on the watershed-to-cultivable area ratio. Statistical analysis of observed and estimated runoff data from 2011 to 2023 revealed a strong correlation (r = 0.87), confirming the pond design. Harvested rainwater, applied through micro-irrigation (rain gun) at a depth of 50 mm during moisture stress periods, significantly improved cotton productivity. The combined use of harvested rainwater and MCP increased yield in the range of 3.8 to 25.3%, improved rainwater use efficiency (1.52 to 3.13 kg ha⁻¹ mm⁻¹), and had a higher benefit-cost ratio (1.15 to 2.43) over a 13-year period. This study concludes that integrating in-situ MCP with ex-situ RWH with micro-irrigation significantly improves rainfed crop productivity in vertisols. Full article

For the design of stormwater pumping stations, there is often uncertainty regarding the selection of an appropriate rainfall event to determine the required pumping capacity and temporary storage volume for managing extreme events of a given magnitude. To account for the risk of system failure, the return period is considered, as recommended based on the size of the catchment’s drainage area or other considerations, depending on the local regulations of a country. This study focused on analysing the direct runoff volume from the catchment, the storage volume required for the operation of the pumping system, and the order of magnitude of the design flow rate. The results indicate that a rainfall event with a duration of at least twice the time of concentration should be used. The design flow rate should range between 50% and 70% of the peak discharge, and designing for flow rates near the peak is not advisable, as it can lead to intermittent pump operation and result in an oversized installed capacity. The methodology developed in this research was applied to the Coastal Protection Project located in the city of Cartagena, Colombia, which includes a 2045.6-m-long box culvert with a cross-sectional area of 2 × 2 m, and three pumping stations, each equipped with three pumps rated at 0.75 m³/s, for a total installed capacity of 6.75 m³/s. Full article

Focusing on the Lingshan section of Guangxi’s Pinglu Canal, this study addresses frequent waterlogging during construction under subtropical monsoon rainfall. Human disturbances alter hydrological processes, causing project delays and economic losses. We developed a coupled Storm Water Management Model (SWMM 1D hydrological) and Hydrologic Engineering Center—River Analysis System 2D (HEC-RAS 2D hydrodynamic) model. High-resolution Unmanned Aerial Vehicle—Light Detection and Ranging (UAV-LiDAR) Digital Elevation Model (DEM) delineated sub-catchments, while the Green-Ampt model quantified soil conductivity decay. Synchronized runoff data drove high-resolution HEC-RAS 2D simulations of waterlogging evolution under design storms (1–100-year return periods) and a real event (10 May 2025). Key results: Water depth exhibits nonlinear growth with return period—slow at low intensities but accelerating beyond 50-year events, particularly at temporary road junctions where embankments impede flow. Additionally, intensive intermittent rainfall causes significant ponding at excavation pit-road intersections, and optimized drainage drastically shortens recession time. The study reveals a “rapid runoff generation–restricted convergence–prolonged ponding” mechanism under construction disturbance, validates the model’s capability for complex scenarios, and provides critical data for real-time waterlogging risk prediction and drainage optimization during the canal’s construction. Full article

More than half of the world’s rivers are intermittent, and climate change is increasing their intermittency, affecting water resources and ecosystems. In Taiwan, steep topography and uneven rainfall have led to increased intermittency in some areas, reflecting changes in hydrological conditions. Using streamflow data, this study applied intermittency ratio (IR), modified 6-month dry period seasonality (SD6), and trend analysis, as well as watershed properties and climate indices. Results showed that 92% of stations had low flows for less than 20% of the time. The dry season was mainly from November to April, and intermittency was spatially affected mainly by upstream soil moisture, moderately by potential evapotranspiration and infiltration, and less by actual evapotranspiration and catchment area. Intermittency increased in the east and decreased in the west. It was negatively correlated with upstream soil moisture and strongly associated with rainfall frequency, especially the proportion of days with precipitation less than 1 mm. These patterns highlight regional differences in river responses to climate. Full article