Hydrology

24 pages, 3803 KB

Open AccessArticle

Surface Runoff Responses to Forest Thinning in Semi-Arid Oak–Pine Micro-Catchments of Northern Mexico

by Gabriel Sosa-Pérez, Argelia E. Rascón-Ramos, David E. Hermosillo-Rojas, Alfredo Pinedo Alvarez, Eduardo Santellano-Estrada, Raúl Corrales-Lerma, Sandra Rodríguez-Piñeros and Martín Martínez-Salvador

Hydrology 2026, 13(1), 27; https://doi.org/10.3390/hydrology13010027 - 9 Jan 2026

Abstract

Hydrological behavior plays a critical role in seasonally dry forest ecosystems, as it underpins water availability for multiple productive activities, including forestry, agriculture, grazing, and urban supply. This study evaluated the hydrological effects of thinning treatments in a semi-arid oak–pine forest of Chihuahua, [...] Read more.

Hydrological behavior plays a critical role in seasonally dry forest ecosystems, as it underpins water availability for multiple productive activities, including forestry, agriculture, grazing, and urban supply. This study evaluated the hydrological effects of thinning treatments in a semi-arid oak–pine forest of Chihuahua, Mexico, using a Before–After–Control–Impact (BACI) design. Three Micro-catchments (MC) with initially comparable tree density and canopy cover were monitored during the rainy seasons of 2018 (pre-thinning) and 2019 (post-thinning). Thinning treatments were applied at 20% and 60% canopy cover in two MC, while a third remained unthinned as a 100% control. Precipitation and surface runoff were recorded at the event scale, and data were analyzed using Weibull probability models with a log link to capture the frequency and magnitude of runoff events. Precipitation patterns were broadly comparable across years, although 2018 included an extreme storm event (59 mm). In contrast, runoff volumes in 2019 were lower despite marginally higher seasonal rainfall, reflecting the absence of large storms. Statistical modeling indicated that for each additional millimeter of precipitation, mean runoff increased by approximately 12%, although thinning significantly altered baseline conditions. Relative to 2018, mean runoff ratios were 0.087 in the 100% canopy catchment, 0.296 in the 60% treatment, and 0.348 in the 20% treatment, suggesting that reduced canopy cover retained proportionally more runoff than the control. BACI contrasts confirmed that thinned catchments maintained higher proportions of runoff than the unthinned control, although statistical significance was marginal for the 20% canopy treatment. Overall, the study provides ecohydrological insights relevant to the management of semi-arid forest ecosystems. Full article

(This article belongs to the Special Issue Advances in Catchments Hydrology and Sediment Dynamics (Second Edition))

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27 pages, 20617 KB

Open AccessArticle

Evaluation of a Computational Simulation Approach Combining GIS, 2D Hydraulic Software, and Deep Learning Technique for River Flood Extent Mapping

by Nikolaos Xafoulis, Evangelia Farsirotou, Spyridon Kotsopoulos and Aris Psilovikos

Hydrology 2026, 13(1), 26; https://doi.org/10.3390/hydrology13010026 - 9 Jan 2026

Abstract

Floods are among the most catastrophic natural disasters, causing severe impact on human lives and ecosystems. The proposed methodology integrates Geographic Information Systems, 2D hydraulic modeling, and deep learning techniques to develop a computational simulation approach for flood extent prediction and was implemented [...] Read more.

Floods are among the most catastrophic natural disasters, causing severe impact on human lives and ecosystems. The proposed methodology integrates Geographic Information Systems, 2D hydraulic modeling, and deep learning techniques to develop a computational simulation approach for flood extent prediction and was implemented in the Enipeas River basin, located within the Thessalia River Basin District, Greece. Hydrological analysis was performed using the HEC-HMS software (version 4.12), while hydraulic simulations were conducted with HEC-RAS 2D. The hydraulic modeling produced synthetic flood scenarios for a 1000-year return period, generating spatially distributed outputs of flood extents. The deep learning algorithm was based on a U-Net (CNN) architecture. The model was trained using multi-channel raster tiles, including open access geospatial data such as Digital Elevation Model, slope, flow direction, stream centerline, land use, and simulated flood extents. Model validation was carried out in two independent domains (TS1 and TS2) located within the same river basin. Model outputs are adequately compared with both 2D hydraulic simulations and official Flood Risk Management Plan maps, and the comparison indicates close spatial and quantitative agreement, with flood extent area differences below 8%. Based on the results, the proposed methodology presents a potential and efficient tool for rapid flood risk mapping. Full article

(This article belongs to the Special Issue Advances in Flood Studies: Enhancing Data Collection, Rating Curves, and Hydrological Analyses)

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28 pages, 8219 KB

Open AccessArticle

Rainfall–Groundwater Correlations Using Statistical and Spectral Analyses: A Case Study on the Coastal Plain of Al-Hsain Basin, Syria

by Mahmoud Ahmad, Katalin Bene and Richard Ray

Hydrology 2026, 13(1), 25; https://doi.org/10.3390/hydrology13010025 - 8 Jan 2026

Abstract

Climate change and irregular precipitation patterns have increasingly threatened groundwater sustainability in semi-arid regions like the Eastern Mediterranean. Specifically, in coastal Syria, the lack of quantitative understanding regarding aquifer recharge mechanisms hinders effective water resource management. To address this, this study investigates the [...] Read more.

Climate change and irregular precipitation patterns have increasingly threatened groundwater sustainability in semi-arid regions like the Eastern Mediterranean. Specifically, in coastal Syria, the lack of quantitative understanding regarding aquifer recharge mechanisms hinders effective water resource management. To address this, this study investigates the dynamic relationship between rainfall and groundwater levels in the Al-Hsain Basin coastal plain using 48 months of monitoring data (2020–2024) from 35 wells. We employed a unified analytical framework combining statistical methods (correlation, regression) with advanced time–frequency techniques (Wavelet Coherence) to capture recharge behavior across diverse Quaternary, Neogene, and Cretaceous strata. The results indicate strong climatic control on groundwater dynamics, particularly in shallow Quaternary wells, which exhibit rapid recharge responses (lag < 1 month). In contrast, deeper aquifers showed delayed and buffered responses. A dual-variable model incorporating temperature significantly improved prediction accuracy (R² = 0.97), highlighting the role of evapotranspiration. These findings provide a transferable diagnostic framework for identifying recharge zones and supporting adaptive groundwater governance in data-scarce semi-arid environments. Full article

(This article belongs to the Special Issue Impact of Climate Change on Groundwater Resources in Coastal Aquifers: Qualitative and Quantitative Assessments)

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12 pages, 1760 KB

Open AccessArticle

Mechanisms of Multi-Path Runoff Leakage Induced by Cracks at the Rock–Soil Interface on Bedrock-Exposed Slopes in Karst Critical Zones

by Xingya Chen, Xudong Peng, Longpei Cen, Wenping Meng, Quanhou Dai and Yanyi Huang

Hydrology 2026, 13(1), 24; https://doi.org/10.3390/hydrology13010024 - 8 Jan 2026

Abstract

As exposed bedrocks commonly interface with the soil directly, lacking a transition layer, cracks at rock–soil interface cracks (RSI-Cracks), are well-developed, particularly following wet–dry alternation in karst critical zones. However, inadequate understanding of the influence of RSI-Cracks on multi-path runoff generation around bedrocks [...] Read more.

As exposed bedrocks commonly interface with the soil directly, lacking a transition layer, cracks at rock–soil interface cracks (RSI-Cracks), are well-developed, particularly following wet–dry alternation in karst critical zones. However, inadequate understanding of the influence of RSI-Cracks on multi-path runoff generation around bedrocks has hindered an in-depth comprehension of subsurface-dominated hydrological processes in karst areas. To address this gap, we developed micro-slope models replicating rock–soil interfacial configurations by building upon field investigations. Two conditions, namely, the presence and absence of RSI-Cracks, were incorporated, with rain intensity and rock surface inclination as experimental conditions. Our results indicate that RSI-Cracks significantly alter the runoff output (p < 0.05), exacerbating subsurface water leakage. Compared with that on slopes without RSI-Cracks, the proportion of surface runoff on slopes with RSI-Cracks is reduced, with a reduction range of 4 to 46%. Conversely, RSI-Cracks promote an increase in the proportion of outflow at the rock–soil interface (RSI flow), with an increase range of 7 to 38%. This is an important reason for the aggravation of subsurface water leakage through RSI-Cracks. However, there is no significant change in the water loss caused by internal soil seepage on slopes with or without RSI-Cracks. These findings provide novel insights into underground water loss, with valuable implications for the construction and improvement of hydrological models in karst areas. Full article

(This article belongs to the Special Issue The Influence of Landscape Disturbance on Catchment Processes)

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21 pages, 4727 KB

Open AccessArticle

Effects of Groundwater Flux on Denitrification in a Steep Coastal Agricultural Island in Western Japan Using Push–Pull Tests

by Kelly Tiku Tarh, Shin-ichi Onodera, Mitsuyo Saito, Sharon Bih Kimbi and Miho Awamura

Hydrology 2026, 13(1), 23; https://doi.org/10.3390/hydrology13010023 - 7 Jan 2026

Abstract

This study investigated the influence of groundwater flux and temperature on denitrification in a steep coastal agricultural Island in western Japan. Push–pull tests (PPTs) were conducted at depths of 3 m, 15 m, and 30 m, during winter, spring, and summer to assess [...] Read more.

This study investigated the influence of groundwater flux and temperature on denitrification in a steep coastal agricultural Island in western Japan. Push–pull tests (PPTs) were conducted at depths of 3 m, 15 m, and 30 m, during winter, spring, and summer to assess denitrification under varying hydrogeological and seasonal conditions. The 3 m layer is silty loam, 15 m is granitic weathered soil, and 30 m is granitic weathered rock, each with distinct hydraulic conductivities and fluxes. The objectives were to assess denitrification rates and fluxes, assess depth- and season-related variability, and determine the relative roles of hydraulic flux and temperature on denitrification. Denitrification was higher at shallow (3 m) and deep (30 m) boreholes during low-flux periods, while low at the intermediate depth (15 m) where fluxes were highest. Temperature variation had weak correlations compared to hydraulic flux, which showed a strong inverse correlation with denitrification. These findings demonstrate that residence time, controlled by groundwater flux, is the dominant factor influencing nitrate attenuation in this steep coastal aquifer. The PPTs results indicate that denitrification rates derived from PPTs decrease under higher hydraulic fluxes, as these conditions promote more oxic conditions. The study highlights the potential for natural denitrification to mitigate nitrate contamination during low-flux periods, providing insights for sustainable groundwater management in agricultural island environments. Full article

(This article belongs to the Special Issue Impact of Climate Change on Groundwater Resources in Coastal Aquifers: Qualitative and Quantitative Assessments)

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30 pages, 6524 KB

Open AccessArticle

Modeling and Assessment of Salinity Reduction Strategies in the Jarahi River, Iran

by Javad Ahadiyan, Narges Yarahamdi, Asghar Akbari, Seyed Mohsen Sajjadi, Hossein Azizi Nadian and Farhad Bahmanpouri

Hydrology 2026, 13(1), 22; https://doi.org/10.3390/hydrology13010022 - 6 Jan 2026

Abstract

This study investigates the spatial and temporal variations in salinity in the Jarahi River and its traditional channels using field measurements and numerical simulations. The primary objective is to assess the effectiveness of different management strategies for salinity reduction under minimum-discharge conditions. Salinity [...] Read more.

This study investigates the spatial and temporal variations in salinity in the Jarahi River and its traditional channels using field measurements and numerical simulations. The primary objective is to assess the effectiveness of different management strategies for salinity reduction under minimum-discharge conditions. Salinity dynamics were analyzed through electrical conductivity (EC) measurements collected over a one-year period and simulated using the MIKE 11 hydrodynamic model. Model performance was evaluated by comparing simulated and observed EC values at key monitoring stations. The results indicate that maximum salinity levels occur during March and April in both the main river and traditional channels, while the highest temporal variability in EC was observed in October. The comparison between observed and simulated data showed a relative error of less than 10%, confirming the reliability of the model simulations. Four management scenarios were evaluated: (1) preventing inflow from the Motbeg drainage, (2) blocking non-centralized drainage inputs, (3) removing all inlet drains, and (4) increasing discharge releases from the Ramshir Dam. The first and third scenarios led to the highest salinity reductions, reaching up to 39% (approximately 1266 µS/cm) in the Gorgor channel, while reductions of up to 53% were observed in traditional streams such as Mansuri and Omal-Sakher under the third scenario. Increasing dam releases resulted in a maximum reduction of 23% (724 µS/cm) at the Gorgor station. Finally, the proposed management strategies significantly reduced salinity levels along the river system, particularly at the entrance of the Jahangiri traditional stream, providing practical insights for salinity control and river basin management. Full article

(This article belongs to the Section Hydrological and Hydrodynamic Processes and Modelling)

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17 pages, 2944 KB

Open AccessArticle

Prolonged Dry Periods Associated with Riparian Vegetation Growth and Channel Simplification

by Michael Nones and Yiwei Guo

Hydrology 2026, 13(1), 21; https://doi.org/10.3390/hydrology13010021 - 6 Jan 2026

Abstract

Climate change is impacting rivers worldwide, with a reduction in normal flow conditions in temperate regions like Poland. Such changes might have a significant influence on riparian vegetation and channel planform dynamics. To better understand how these changes impact the river morphology, this [...] Read more.

Climate change is impacting rivers worldwide, with a reduction in normal flow conditions in temperate regions like Poland. Such changes might have a significant influence on riparian vegetation and channel planform dynamics. To better understand how these changes impact the river morphology, this research focuses on a 250 km-long reach of the Polish Vistula River and investigates variations of monthly maximum discharges and vegetation conditions over the period 1984–2023 by means of Landsat satellite images. These satellite data were handled via Google Earth Engine, looking at a common index such as the Normalized Difference Vegetation Index, considered as a proxy of vegetation coverage variations. Results point out an increase in the median NDVI over the study area from 0.2 in 1984 to 0.3 in 2023, connected with a reduction of monthly discharge from around 920 m³/s to 880 m³/s. This suggests that changes in flow discharge are associated with a process of riparian vegetation growth, leading to a reduction of planform and bars dynamics and closure of secondary channels (i.e., oversimplification). This is particularly evident over the last couple of decades, during which water availability has decreased significantly, as more humid years in the middle of the study period are now no longer existing, with an observed decrease in the maximum monthly discharge during the last 20 years, likely connected with a more severe impact of climate change. This reduction in flooding events allows more time for vegetation to establish on river bars and banks, eventually creating new islands and causing the observed oversimplification of the active channel. In summary, using the Vistula River as an exemplary case study, this research suggests that prolonged dry periods, more common in recent decades due to climate change, might impact large rivers located in temperate climates, favouring the development of vegetation on exposed sandbars, eventually resulting in a less dynamic active channel. Full article

(This article belongs to the Special Issue Current Challenges in Ecohydrology: Advanced Numerical and Experimental Analysis on Water Resources Management in Natural Watersheds, with a Special Focus on Flooding and Drought)

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30 pages, 9248 KB

Open AccessArticle

Groundwater and Surface Water Interactions in the Highwood River and Sheep River Watersheds: An Integrated Alpine and Non-Alpine Assessment

by Aprami Jaggi, Dayal Wijayarathne, Michael Wendlandt, Tiago A. Morais, Tatiana Sirbu, Andrew Underwood, Paul Eby and John Gibson

Hydrology 2026, 13(1), 20; https://doi.org/10.3390/hydrology13010020 - 6 Jan 2026

Abstract

Groundwater–surface water interactions were investigated in the Highwood River (3952 km²) and Sheep River watersheds (1568 km²), originating in the Rocky Mountains headwaters of the South Saskatchewan River (Alberta, Canada), to improve understanding of hydrological processes that potentially influence [...] Read more.

Groundwater–surface water interactions were investigated in the Highwood River (3952 km²) and Sheep River watersheds (1568 km²), originating in the Rocky Mountains headwaters of the South Saskatchewan River (Alberta, Canada), to improve understanding of hydrological processes that potentially influence water use and vulnerability to climatic change in representative, alpine-fed mixed-use watersheds. Similar to adjacent regions of the Bow, Red Deer and Oldman watersheds, the upper reaches of these watersheds are sparsely populated with significant seasonal glacier and snowmelt influence, while the lower watersheds are currently under increasing water supply pressure from competing agricultural–municipal interests, with notable risk of flooding during high-flow events and drought during the growing season. Investigations included mapping of hydrologic and hydrogeologic controls (aquifers, buried channels, colluvial deposits, etc.,) and synoptic geochemical and isotopic surveys (δ²H, δ¹⁸O, δ¹³C-DIC, ²²²Rn) to characterize evolution in water type and seasonal progression in streamflow sources and underlying mechanisms. Our findings confirm seasonal progression in streamflow water sources, characterized by a pronounced snowmelt-dominated spring freshet, but with a sustained recession fed by colluvial, moraine, fluvial, and fractured bedrock sources. Seasonal isotopic variations establish that shallow groundwater sources are actively maintained throughout the spring freshet, often accounting for a dominant portion of streamflow, which indicates active displacement of groundwater storage by snowmelt recharge during spring melt. The contrast in the proportion of alpine contributions in each watershed suggests these systems may respond very differently to climate change, which needs to be carefully considered in developing sustainable water-use strategies for each watershed. Full article

(This article belongs to the Section Surface Waters and Groundwaters)

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24 pages, 13069 KB

Open AccessArticle

China’s Seasonal Precipitation: Quantitative Attribution of Ocean-Atmosphere Teleconnections and Near-Surface Forcing

by Chang Lu, Long Ma, Bolin Sun, Xing Huang and Tingxi Liu

Hydrology 2026, 13(1), 19; https://doi.org/10.3390/hydrology13010019 - 4 Jan 2026

Abstract

Under concurrent global warming and multi-scale climate anomalies, regional precipitation has become more uneven and less stable, and extreme events occur more frequently, amplifying water scarcity and ecological risk. Focusing on mainland China, we analyze nearly 70 years of monthly station precipitation records [...] Read more.

Under concurrent global warming and multi-scale climate anomalies, regional precipitation has become more uneven and less stable, and extreme events occur more frequently, amplifying water scarcity and ecological risk. Focusing on mainland China, we analyze nearly 70 years of monthly station precipitation records together with eight climate drivers—the Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), Multivariate ENSO Index (MEI), Arctic Oscillation (AO), surface air pressure (AP), wind speed (WS), relative humidity (RH), and surface solar radiation (SR)—and precipitation outputs from eight CMIP6 models. Using wavelet analysis and partial redundancy analysis, we systematically evaluate the qualitative relationships between climate drivers and precipitation and quantify the contribution of each driver. The results show that seasonal precipitation decreases stepwise from the southeast toward the northwest, and that stability is markedly lower in the northern arid and semi-arid regions than in the humid south, with widespread declines near the boundary between the second and third topographic steps of China. During the cold season, and in the northern arid and semi-arid zones and along the margins of the Tibetan Plateau, precipitation varies mainly with interdecadal swings of North Atlantic sea surface temperature and with the strength of polar and midlatitude circulation, and it is further amplified by variability in near-surface winds; the combined contribution reaches about 32% across the Northeast Plain, the Junggar Basin, and areas north of the Loess Plateau. During the warm season, and in the eastern and southern monsoon regions, precipitation is modulated primarily by tropical Pacific sea surface temperature and convection anomalies and by related changes in the position and strength of the subtropical high, moisture transport pathways, and relative humidity; the combined contribution is about 22% south of the Yangtze River and in adjacent areas. Our findings reveal the spatiotemporal variability of precipitation in China and its responses to multiple climate drivers and their relative contributions, providing a quantitative basis for water allocation and disaster risk management under climate change. Full article

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30 pages, 9320 KB

Open AccessArticle

Flood Hazard Assessment Under Subsidence-Influenced Terrain Using Deformation-Adjusted DEM in an Oil and Gas Field

by Mohammed Al Sulaimani, Rifaat Abdalla, Mohammed El-Diasty, Amani Al Abri, Mohamed A. K. El-Ghali and Ahmed Tabook

Hydrology 2026, 13(1), 18; https://doi.org/10.3390/hydrology13010018 - 4 Jan 2026

Abstract

Flood hazards in arid oil-producing regions result from both natural hydrological processes and terrain changes due to land subsidence. In the Yibal field in northern Oman, long-term hydrocarbon extraction has caused measurable ground deformation, altering surface gradients and drainage patterns. This study presents [...] Read more.

Flood hazards in arid oil-producing regions result from both natural hydrological processes and terrain changes due to land subsidence. In the Yibal field in northern Oman, long-term hydrocarbon extraction has caused measurable ground deformation, altering surface gradients and drainage patterns. This study presents a deformation-adjusted flood hazard assessment by integrating a 2013 photogrammetric DEM with a 2023 subsidence-corrected DEM derived from multi-temporal PS-InSAR observations (RADARSAT-2 and TerraSAR-X). Key hydrological indicators—including slope, drainage networks, Height Above Nearest Drainage (HAND), floodplain depth, Curve Number, and extreme precipitation from the wettest monthly rainfall in a 10-year archive—were recalculated for both years. Flood hazard maps for 2013 and 2023 were generated using an AHP-based multi-criteria framework across five hydrologically motivated scenarios. Results indicate that while the total area of high- and very-high-hazard zones changed only slightly in most scenarios (within ±6%), these zones shifted into subsidence-affected depressions, reflecting deformation-driven redistribution of flood-prone areas. Low-hazard zones grew most significantly, especially in Scenarios S2–S4, with increases of 160–320% compared to 2013, while moderate-hazard areas showed smaller but consistent growth. Floodplain-dominated conditions (S5) produced the most pronounced nonlinear response, with a substantial increase in very low hazard and localized concentration of very high hazard in areas of deepest subsidence. Geomorphic analysis using the Geomorphic Flood Index (GFI) shows deepening of flow pathways and expansion of geomorphic depressions between 2013 and 2023, supporting the modeled redistribution of hazards. These findings demonstrate that even moderate subsidence can significantly alter hydrological susceptibility and underscore the importance of incorporating deformation-adjusted terrain modeling into flood hazard assessments in petroleum fields and other subsidence-prone areas. Full article

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34 pages, 11413 KB

Open AccessArticle

Hydrodynamic-Ecological Synergistic Effects of Interleaved Jetties: A CFD Study Based on a 180° Bend

by Dandan Liu, Suiju Lv and Chunguang Li

Hydrology 2026, 13(1), 17; https://doi.org/10.3390/hydrology13010017 - 2 Jan 2026

Abstract

Under the dual pressures of global climate change and anthropogenic activities, enhancing the ecological functions of hydraulic structures has become a critical direction for sustainable watershed management. While traditional spur dike designs primarily focus on bank protection and flood control, current demands require [...] Read more.

Under the dual pressures of global climate change and anthropogenic activities, enhancing the ecological functions of hydraulic structures has become a critical direction for sustainable watershed management. While traditional spur dike designs primarily focus on bank protection and flood control, current demands require additional consideration of river ecosystem restoration. Numerical simulations were performed using the RNG k-ε turbulence model to solve the three-dimensional Reynolds-averaged Navier–Stokes equations, a formulation that enhances prediction accuracy for complex flows in curved channels, including separation and reattachment. Following a grid independence study and the application of standard wall functions for near-wall treatment, a comparative analysis was conducted to examine the flow characteristics and ecological effects within a 180° channel bend under three configurations: no spur dikes, a single-side arrangement, and a staggered arrangement of non-submerged, flow-aligned, rectangular thin-walled spur dikes. The results demonstrate that staggered spur dikes significantly reduce the lateral water surface gradient by concentrating the main flow, thereby balancing water levels along the concave and convex banks and suppressing lateral channel migration. Their synergistic flow-contracting effect enhances the kinetic energy of the main flow and generates multi-scale turbulent vortices, which not only increase sediment transport capacity in the main channel but also create diverse habitat conditions. Specifically, the bed shear stress in the central channel region reached 2.3 times the natural level. Flow separation near the dike heads generated a high-velocity zone, elevating velocity and turbulent kinetic energy by factors of 2.3 and 6.8, respectively. This shift promoted bed sediment coarsening and consequently increased scour resistance. In contrast, the low-shear wake zones behind the dikes, with weakened hydrodynamic forces, facilitated fine-sediment deposition and the growth of point bars. Furthermore, this study identifies a critical interface (observed at approximately 60% of the water depth) that serves as a key interface for vertical energy conversion. Below this height, turbulence intensity intermittently increases, whereas above it, energy dissipates markedly. This critical elevation, controlled by both the spur dike configuration and flow conditions, embodies the transition mechanism of kinetic energy from the mean flow to turbulent motions. These findings provide a theoretical basis and engineering reference for optimizing eco-friendly spur dike designs in meandering rivers. Full article

(This article belongs to the Special Issue Advances in Catchments Hydrology and Sediment Dynamics (Second Edition))

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21 pages, 3405 KB

Open AccessArticle

Spatiotemporal Dynamics and Lagged Hydrological Impacts of Compound Drought and Heatwave Events in the Poyang Lake Basin

by Ningning Li, Yang Yang, Zikang Xing, Yi Zhao, Jianhui Wei, Miaomiao Ma and Xuejun Zhang

Hydrology 2026, 13(1), 16; https://doi.org/10.3390/hydrology13010016 - 30 Dec 2025

Abstract

Compound drought and heatwave (CDHW) events pose a rising threat to global water security and ecosystem stability. While their increased frequency under global warming is recognized, their spatiotemporal evolution and subsequent cascading impacts on hydrological processes in monsoonal lake basins remain poorly quantified. [...] Read more.

Compound drought and heatwave (CDHW) events pose a rising threat to global water security and ecosystem stability. While their increased frequency under global warming is recognized, their spatiotemporal evolution and subsequent cascading impacts on hydrological processes in monsoonal lake basins remain poorly quantified. This study investigates the characteristics and hydrological impacts of CDHW in the Poyang Lake Basin, China’s largest freshwater lake, from 1981 to 2016. Using a daily rolling-window approach with the Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI), we identified CDHW events and characterized them with metrics of frequency, severity, and intensity. Event coincidence analysis (ECA) was employed to quantify the trigger relationship between CDHW and subsequent hydrological droughts (streamflow and lake water level). Our results reveal a paradigmatic shift in the CDHW regime post-2000, marked by statistically significant increases in all three metrics and a fundamental alteration in their statistical distributions. ECA demonstrated that intensified CDHW events significantly enhance hydrological drought risk, primarily through a robust and increasing lagged influence at seasonal timescales (peaking at 40–90 days). Decomposition of compound events attributes this protracted impact predominantly to the heatwave component, which imposes prolonged hydrological stress, in contrast to the more immediate but rapidly decaying influence of drought alone. This study highlights the necessity of integrating compound extremes and their non-stationary, lagged impacts into water resource management and climate adaptation strategies for monsoonal basins. Full article

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24 pages, 2113 KB

Open AccessArticle

Half a Century of Civil Engineering in the Bahlui River Hydrographic System: The Unexpected Journey from Gray Structures to Hybrid Resilience

by Nicolae Marcoie, Șerban Chihaia, András-István Barta, Daniel Toma, Valentin Boboc, Mihai Gabriel Balan, Cătălin Dumitrel Balan and Mircea-Teodor Nechita

Hydrology 2026, 13(1), 15; https://doi.org/10.3390/hydrology13010015 - 29 Dec 2025

Abstract

Water reservoirs are critical components of hydrological systems that mitigate floods and droughts, but their long-term performance under climate change and variable socioeconomic conditions remain insufficiently documented. This study examines the Bahlui River basin (northeastern Romania), where 17 reservoirs constructed mainly between the [...] Read more.

Water reservoirs are critical components of hydrological systems that mitigate floods and droughts, but their long-term performance under climate change and variable socioeconomic conditions remain insufficiently documented. This study examines the Bahlui River basin (northeastern Romania), where 17 reservoirs constructed mainly between the 1960s and 1980s have been operational for more than five decades. Using the most recent technical reservoir reports, land-use evolution, and present operational functions, the contribution of man-made reservoirs to flood attenuation and drought buffering over time was appraised. Flood mitigation is the most consistent and reliable function, with peak-flow reductions commonly exceeding 60–90% of design discharges at the basin scale. Engineered drought mitigation functions (irrigation and industrial water supply) have decreased significantly as a result of socioeconomic changes started in 1989. However, the gradual expansion of green infrastructure, such as wetlands and riparian vegetation, has improved passive water retention and low-flow buffering capacity. These unanticipated developments have resulted in variable levels of hybrid hydrological resilience. The findings show that, while artificial reservoirs have strong flood-control capacity over long periods of time, their contribution to drought mitigation is increasingly dependent on the integration of ecological components, emphasizing the importance of green-gray interactions in long-term reservoir management. Full article

(This article belongs to the Special Issue Natural or Artificial Water Reservoirs' Impacts on Mitigating the Intensities of Floods and Droughts)

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39 pages, 8683 KB

Open AccessArticle

Abandonment Integrity Assessment Regarding Legacy Oil and Gas Wells and the Effects of Associated Stray Gas Leakage on the Adjacent Shallow Aquifer in the Karoo Basin, South Africa

by Murendeni Mugivhi, Thokozani Kanyerere, Yongxin Xu, Myles T. Moore, Keith Hackley, Tshifhiwa Mabidi and Lucky Baloyi

Hydrology 2026, 13(1), 14; https://doi.org/10.3390/hydrology13010014 - 29 Dec 2025

Abstract

Shale gas extraction is underway in the Karoo Basin. Previous oil and gas explorers abandoned several wells, and the abandonment statuses of these wells are unknown. Critically, improperly abandoned wells can provide a pathway for the leakage of stray gas into shallow aquifers [...] Read more.

Shale gas extraction is underway in the Karoo Basin. Previous oil and gas explorers abandoned several wells, and the abandonment statuses of these wells are unknown. Critically, improperly abandoned wells can provide a pathway for the leakage of stray gas into shallow aquifers and degrade water quality. To understand the abandonment integrity risk posed by these wells, a qualitative risk model was developed to assess the likelihood of well-barrier failure leading to a potential leak. The potential leak paths identified include zones with cement losses during grouting, casing corrosion, cement channels, failure to case and cement risk zones, uncased and uncemented sources, uncemented annuli, and unplugged wells. To confirm whether these wells are leaking, geochemical tracing of stray gas was integrated. Eleven of the fifty samples collected had dissolved hydrocarbon gas concentrations that were high enough to use isotopic analysis to determine the source. The results revealed microbial gas via fermentation and carbon dioxide reduction, thermogenic gas, and geothermal gas, as evidenced by larger δ¹³C₁ values and isotopic reversals associated with dolerite intrusions. The thermogenic-type gas detected in legacy abandoned wells and <1 km water boreholes adjacent to these wells serves as evidence that the downhole plugs did not maintain their integrity or were improperly plugged, whereas the thermogenic gas detected in >1 km water boreholes indicates leakage contamination due to natural fracture pathways. The presence of thermogenic gas in legacy wells and in groundwater boreholes <1 km from legacy wells implies that shale gas extraction using hydraulic fracturing cannot be supported in these situations. However, using safety buffer zones greater than 1 km from the legacy wells for shale gas drilling could be supported. Full article

(This article belongs to the Topic Advances in Groundwater Science and Engineering)

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28 pages, 2974 KB

Open AccessArticle

Climate Change Impacts on Agricultural Watershed Hydrology, Southern Ontario: An Integrated SDSM–SWAT Approach

by Rong Hu, Ramesh Rudra, Rituraj Shukla, Ashok Shaw and Pradeep Goel

Hydrology 2026, 13(1), 13; https://doi.org/10.3390/hydrology13010013 - 28 Dec 2025

Abstract

Understanding the local-scale impacts of climate change is critical for protecting water resources and ecosystems in vulnerable agricultural regions. This study investigates the Canagagigue Creek Watershed (CCW) in Southern Ontario, Canada, which is an area vital to the Grand River Basin yet threatened [...] Read more.

Understanding the local-scale impacts of climate change is critical for protecting water resources and ecosystems in vulnerable agricultural regions. This study investigates the Canagagigue Creek Watershed (CCW) in Southern Ontario, Canada, which is an area vital to the Grand River Basin yet threatened by sediment runoff, making it an ecologically sensitive area. We applied an integrated Statistical Downscaling Model (SDSM) and Soil and Water Assessment Tool (SWAT) (version 2012) approach under the IPCC A2 scenario to project impacts for the period 2025–2044. The results reveal a fundamental hydrological shift, and evapotranspiration is projected to claim nearly 70% of annual precipitation, leading to a ~30% reduction in total water yield. Seasonally, the annual streamflow peak is projected to shift from March to April, indicating a transition from a snowmelt-dominated to a rainfall-influenced system, while extended low-flow periods increase drought risk. Crucially, sediment yield at the watershed outlet is projected to decrease by 7.9–10.5%. The concomitant reduction in streamflow implies a weakened sediment transport capacity. However, this points to a heightened risk of increased in-stream deposition, which would pose a dual threat, (a) elevating flood risk through channel aggradation and (b) creating a long-term sink for agricultural pollutants that degrades water quality. By linking SDSM and SWAT, this study moves beyond generic predictions, providing a targeted blueprint for climate-resilient land and water management that addresses the complex, interacting challenges of water quantity. Full article

(This article belongs to the Special Issue Advances in Catchments Hydrology and Sediment Dynamics (Second Edition))

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21 pages, 4863 KB

Open AccessArticle

Revealing Emerging Hydroclimatic Shifts: Advanced Trend Analysis of Rainfall and Streamflow in the Navasota River Watershed

by Ali Fares, Ripendra Awal, Anwar Assefa Adem, Anoop Valiya Veettil, Taha B. M. J. Ouarda, Samuel Brody and Marouane Temimi

Hydrology 2026, 13(1), 12; https://doi.org/10.3390/hydrology13010012 - 25 Dec 2025

Abstract

Rainfall and streamflow analyses have long been central to hydrological research, yet traditional approaches often overlook the complexity introduced by changing climate signals, land-use dynamics, and human infrastructure. This study applies an integrated, data-driven framework to explore emerging hydroclimatic shifts in the Navasota [...] Read more.

Rainfall and streamflow analyses have long been central to hydrological research, yet traditional approaches often overlook the complexity introduced by changing climate signals, land-use dynamics, and human infrastructure. This study applies an integrated, data-driven framework to explore emerging hydroclimatic shifts in the Navasota River Watershed of east-central Texas. By combining autocorrelation analysis, Mann–Kendall and modified Mann–Kendall trend tests, and Pettitt’s change-point detection, we examine more than a century of precipitation and streamflow records alongside post-1978 reservoir operations. Results reveal an accelerating wetting tendency, particularly evident in decadal rolling averages and early-summer precipitation, accompanied by a statistically significant increase in 10-year moving averages of annual peak streamflow. While abrupt regime shifts were not detected, subtle but persistent changes point to evolving watershed memory and heightened flood risk in the post-dam era. This study reframes rainfall and streamflow trend analysis as a dynamic tool for anticipating hydrologic regime shifts, highlighting the urgent need for adaptive water infrastructure and flood management strategies in rapidly urbanizing and climate-sensitive watersheds. Full article

(This article belongs to the Special Issue Trends and Variations in Hydroclimatic Variables: 2nd Edition)

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21 pages, 1731 KB

Open AccessArticle

Hydrodynamic Parameter Estimation for Simulating Soil-Vegetation-Atmosphere Hydrology Across Forest Stands in the Strengbach Catchment

by Benjamin Belfort, Aya Alzein, Solenn Cotel, Anthony Julien and Sylvain Weill

Hydrology 2026, 13(1), 11; https://doi.org/10.3390/hydrology13010011 - 24 Dec 2025

Abstract

Modeling the water cycle in the critical zone requires understanding interactions between the soil–vegetation–atmosphere compartments. Mechanistic modeling of soil water flow relies on the accurate determination of hydrodynamic parameters that control hydraulic conductivity and water retention curves. These parameters can be derived either [...] Read more.

Modeling the water cycle in the critical zone requires understanding interactions between the soil–vegetation–atmosphere compartments. Mechanistic modeling of soil water flow relies on the accurate determination of hydrodynamic parameters that control hydraulic conductivity and water retention curves. These parameters can be derived either using pedotransfer functions (PTFs), using soil properties obtained from field samples, or through inverse modeling, which allows the parameters to be adjusted to minimize differences between simulations and observations. While PTFs are widely used due to their simplicity, inverse modeling requires specific instrumentation and advanced numerical tools. This study, conducted at the Hydro-Geochemical Environmental Observatory (Strengbach forested catchment) in France, aims to determine the optimal hydrodynamic parameters for two contrasting forest plots, one dominated by spruce and the other by beech. The methodology integrates granulometric data across multiple soil layers to estimate soil parameters using PTFs (Rosetta). Water content and conductivity data were then corrected to account for soil stoniness, improving the KGE and NSE metrics. Finally, inverse parameter estimation based on water content measurements allowed for refinement of the evaluation of α, Ks, and n. This framework to estimate soil parameter was applied on different time periods to investigate the influence of the calibration chronicles on the estimated parameters. Results indicate that our methodology is efficient and that the optimal calibration period does not correspond to one with the most severe drought conditions; instead, a balanced time series including both wet and dry phases is preferable. Our findings also emphasize that KGE and NSE must be interpreted with caution, and that long simulation periods are essential for evaluating parameter robustness. Full article

(This article belongs to the Section Hydrological and Hydrodynamic Processes and Modelling)

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19 pages, 2213 KB

Open AccessReview

Benefits and Challenges of Small Dams in Mediterranean Climate Region: A Review

by Alissar Yassin, Giovanni Francesco Ricci, Francesco Gentile and Anna Maria De Girolamo

Hydrology 2026, 13(1), 10; https://doi.org/10.3390/hydrology13010010 - 24 Dec 2025

Abstract

In Mediterranean climate regions, water scarcity, seasonal droughts and hydrological extremes are exacerbated by climate change. In these areas, small dams are increasingly used as decentralized water infrastructure for water supply, especially in agricultural areas. However, several challenges must overcome when planning and [...] Read more.

In Mediterranean climate regions, water scarcity, seasonal droughts and hydrological extremes are exacerbated by climate change. In these areas, small dams are increasingly used as decentralized water infrastructure for water supply, especially in agricultural areas. However, several challenges must overcome when planning and managing small reservoirs. This review combines evidence from case studies to analyze the benefits and challenges of small dams. The findings show that small reservoirs may offer a wide array of ecological, agricultural, hydrological, and socio-economic benefits when strategically planned and properly maintained, providing water and contributing to groundwater recharge, vegetative restoration, and biodiversity conservation, while simultaneously controlling flash floods in a cost-effective and participatory manner. On the other hand, evaporation losses and sedimentation may affect water quality and reduce storage capacity. In addition, small dams may negatively affect river ecosystems. Persistent disturbance of downstream flow and sediment regime contributes to altered river morphology and habitat, with effects on biota, and may reduce river system resilience. These impacts are context-dependent, influenced by dam density, geomorphic setting, and climate. Finally, this study highlighted the importance of governance and maintenance practices. Polycentric and participative systems may promote more adaptable responses to water stress, whereas fragmented institutions exacerbate trade-offs between water supply and ecological integrity. Full article

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10 pages, 251 KB

Open AccessEditorial

Editorial for Special Issue “Geographic Information System (GIS) Techniques and Applications for Sustainable Water Resource Management in Agriculture”

by Iolanda Borzì, Beatrice Monteleone and Hailong Yin

Hydrology 2026, 13(1), 9; https://doi.org/10.3390/hydrology13010009 - 24 Dec 2025

Abstract

Geographic Information Systems (GISs) and remote sensing technologies have undergone transformative advances over the past decade, fundamentally reshaping how hydrologists and water managers approach agricultural water resource challenges [...] Full article

(This article belongs to the Special Issue Geographic Information Systems (GIS) Techniques and Applications for Sustainable Water Resources Management in Agriculture)

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