Hydrology

17 pages, 15530 KiB

Open AccessArticle

Exploring Seasonality Indices for Low-Flow Analysis on Tibagi Watershed (Brazil)

by Alexandre Sokoloski de Azevedo Delduque de Macedo and Michael Männich

Hydrology 2025, 12(1), 19; https://doi.org/10.3390/hydrology12010019 - 17 Jan 2025

Viewed by 401

This study investigated the seasonality of low-flow discharges in the Tibagi watershed, Paraná, Brazil, through the analysis of three indices: Seasonality Ratio (

S R

), Seasonality Index (

S I

), and Seasonality Histogram (

S H

). The indices were computed [...] Read more.

This study investigated the seasonality of low-flow discharges in the Tibagi watershed, Paraná, Brazil, through the analysis of three indices: Seasonality Ratio (

S R

), Seasonality Index (

S I

), and Seasonality Histogram (

S H

). The indices were computed and compared using previously calculated low-flow discharge data (

Q_{95}

) and physiographic information on sub-watersheds. A ‘Seasonality Calendar’ was developed, illustrating the period and intensity of low-flow discharge occurrences in the watershed. The results indicate that, despite the watershed not presenting a strong seasonality, there is a tendency for low-flow discharges to concentrate in certain months, notably in August, September, and October. Spatial analysis reveals varied patterns with a certain trend of increased seasonality intensity (parameter r) towards downstream (north) and as the watershed area increases. These indices emerge as valuable tools for water resource management, aiding decision-making for allocation and hydrological regionalization, such as optimizing granting water resource distribution during dry seasons based on the identified low-flow patterns and establishing different reference low-flow values throughout the year. Full article

(This article belongs to the Section Statistical Hydrology)

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17 pages, 10357 KiB

Open AccessArticle

Performance Assessment of a Permeable Reactive Barrier on Reducing Groundwater Transport of Nitrate from an Onsite Wastewater Treatment System

by Charles P. Humphrey Jr., Guy Iverson and Mike O’Driscoll

Hydrology 2025, 12(1), 18; https://doi.org/10.3390/hydrology12010018 - 17 Jan 2025

Viewed by 936

Abstract

Elevated concentrations of nitrate in potable water supplies have been linked to negative health outcomes such as methemoglobinemia and various cancers. Groundwater can become contaminated with nitrate from sources including onsite wastewater treatment systems (OWTSs). A groundwater well down-gradient from an OWTS serving [...] Read more.

Elevated concentrations of nitrate in potable water supplies have been linked to negative health outcomes such as methemoglobinemia and various cancers. Groundwater can become contaminated with nitrate from sources including onsite wastewater treatment systems (OWTSs). A groundwater well down-gradient from an OWTS serving an elementary school in Eastern North Carolina USA had 15 consecutive water samples collected over a 5-year period that exceeded the maximum contaminant level of 10 mg/L for nitrate. Corrective actions were required. A permeable reactive barrier (PRB) filled with woodchips was installed between the OWTS drainfield and the contaminated well. The concentration of nitrate in groundwater from the well steadily decreased after the PRB was installed, and a significant (p = 0.001) inverse correlation (−0.859) was observed between the mean annual nitrate concentration and years after the PRB. The nitrate concentration in groundwater from the well has been below 10 mg/L for the last 17 consecutive sampling events. The median nitrate concentration in the well was significantly lower (p = 0.007) post (6.93 mg/L) relative to pre (12.66 mg/L) PRB. The PRB has not required any maintenance over the past 10 years. The implemented PRB directly influences the sampling results from a monitoring well, but it is not necessarily confirmed that it intercepts the entire groundwater flow or fully prevents aquifer contamination. To confirm this, additional monitoring wells would need to be installed. This research has shown that PRBs can be an effective, low-maintenance, best-management practice to reduce the groundwater transport of nitrate. Full article

(This article belongs to the Special Issue Novel Procedures and Methodologies for Surface and Underground Water Quality Analysis: Theory and Application)

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23 pages, 25140 KiB

Open AccessArticle

Flood Risk Assessment and Zoning for Niamey and Lokoja Metropolises in Niger and Nigeria

by Youssoufa Doulla Nouhou, Martins Yusuf Otache, Salamatou Abdourahamane Illiassou, Olasunkanmi Habeeb Okunola, Appollonia Aimiosino Okhimamhe and Thanh Thi Nguyen

Hydrology 2025, 12(1), 17; https://doi.org/10.3390/hydrology12010017 - 15 Jan 2025

Viewed by 806

Abstract

With the increasing frequency of floods in recent decades, particularly in West Africa, many regions have faced unusual and recurrent flooding events. Communities in flood-prone areas experience heightened insecurity, loss of property, and, in some cases, serious injuries or fatalities. Consequently, flood risk [...] Read more.

With the increasing frequency of floods in recent decades, particularly in West Africa, many regions have faced unusual and recurrent flooding events. Communities in flood-prone areas experience heightened insecurity, loss of property, and, in some cases, serious injuries or fatalities. Consequently, flood risk assessment and mitigation have become essential. This comparative study between Niamey and Lokoja employs Geographic Information Systems (GIS) and the Analytical Hierarchy Process (AHP) to delineate flood susceptibility, vulnerability, and risk zones. The study utilized a comprehensive range of thematic layers, with weight percentages assigned to each parameter as follows: 29% for elevation, 24% for slope, 15% for the Topographic Wetness Index (TWI), 9% for drainage density, 9% for distance from rivers, 4% for both precipitation and the Normalized Difference Water Index (NDWI), and 2% each for the Normalized Difference Vegetation Index (NDVI) and soil type. To validate these weightings, a consistency ratio was calculated, ensuring it remained below 10%. The findings reveal that 32% of the Niamey study area is at risk of flooding, compared to approximately 15% in Lokoja. The results highlight a very high flood potential, particularly in areas near the Niger River, with this potential decreasing as elevation increases. Given the current prevalence of extreme weather events in West Africa, it is crucial to employ effective tools to mitigate their adverse impacts. This research will assist decision-makers in quantifying the spatial vulnerability of flood-prone areas and developing effective flood risk assessment and mitigation strategies in the region. Full article

(This article belongs to the Section Water Resources and Risk Management)

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18 pages, 4329 KiB

Open AccessArticle

Integrating Nature-Based Solutions for Increased Resilience to Urban Flooding in the Climate Change Context

by George Radu, Maria Ilinca Chevereșan, Sorin Perju and Alina Bărbulescu

Hydrology 2025, 12(1), 16; https://doi.org/10.3390/hydrology12010016 - 15 Jan 2025

Viewed by 552

Abstract

As climate change intensifies with more frequent and severe flood events, urban areas face increasing challenges to protect population wellbeing. Amid urban development challenges, political uncertainty, and socioeconomic pressures, finding sustainable solutions to enhance urban resilience has become urgent and complex. This article [...] Read more.

As climate change intensifies with more frequent and severe flood events, urban areas face increasing challenges to protect population wellbeing. Amid urban development challenges, political uncertainty, and socioeconomic pressures, finding sustainable solutions to enhance urban resilience has become urgent and complex. This article explores the limitations of traditional drainage systems in an urban zone of Bucharest, Romania, and the integration of nature-based solutions for flood mitigation. We compare the existing situation with those simulated in a climate change scenario before and after implementing green solutions. The imperviousness of parking lots was set at 60%, that of green roofs at 65%, and that of parking lots at 85%. A hydraulic model was used for this purpose. The results demonstrate that the current stormwater systems struggle to meet the demands of increasing rainfall intensity and highlight how sustainable strategies can effectively address extreme weather challenges while contributing to the restoration of natural environments within the city. In the case of using ‘gray’ solutions, only 10–20% of the area affected by floods is reduced. In comparison, a combination of gray and green infrastructure achieved an average reduction in peak water levels of 0.76 m. Full article

(This article belongs to the Special Issue Sustainable Urban Water Resources Management)

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23 pages, 9846 KiB

Open AccessArticle

Assessing Groundwater Connection/Disconnection to Waterholes Along the Balonne River and in the Barwon–Darling River System in Queensland and New South Wales, Australia, for Waterhole Persistence

by Harald Hofmann and Jonathan Marshall

Hydrology 2025, 12(1), 15; https://doi.org/10.3390/hydrology12010015 - 14 Jan 2025

Viewed by 430

Abstract

Waterholes in semi-arid environment are sections of rivers that fill during high river flows or floods and keep water once flow ceases. They are essential water sources for rive ecosystems. Some waterholes remain even during prolonged droughts. The resilience of ecosystems in these [...] Read more.

Waterholes in semi-arid environment are sections of rivers that fill during high river flows or floods and keep water once flow ceases. They are essential water sources for rive ecosystems. Some waterholes remain even during prolonged droughts. The resilience of ecosystems in these environments depends on the persistence of the waterholes. While most semi-arid, ephemeral river systems are disconnected from regional groundwater and losing in most parts there may be some sections that can be connected to localised groundwater or parafluvial areas. To assess the persistence of waterholes the groundwater contribution to the water balance needs to be addressed. This study assesses groundwater connectivity to waterholes in a part of the Murray-Darling Basin, one of the largest watersheds in the world, using environmental tracers radon and stable isotopes. Approximately 100 samples were collected from 27 waterholes along the Narran, Calgoa, Barwon and Darling rivers, as well as 8 groundwater bore samples. The assessment of groundwater connectivity or the lack of is necessary from water balance modelling and estimation of persistence of these waterholes. As expected, the results indicate consistently low radon concentrations in the waterholes and very small deviation in stable isotopes

δ^{18}

O and

δ^{2}

H. In general, most of these waterholes are losing water to groundwater, indicated by low salinity (EC values) and low radon concentrations. While radon concentrations are small in most cases and indicative of little groundwater contributions, some variability can be assigned to bank return and parafluvial flow. It indicates that these contributions may have implications for waterhole persistence in ephemeral streams. The study demonstrates that in some cases local bank return flow or parafluvial flow may contribute to waterhole persistence. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Integrated Surface Water and Groundwater Resources Management)

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44 pages, 6676 KiB

Open AccessReview

Advancing Slope Stability and Hydrological Solutions Through Biocementation: A Bibliometric Review

by Armstrong Ighodalo Omoregie, Tariq Ouahbi, Fock-Kui Kan, Qurratu Aini Sirat, Hafsat Omolara Raheem and Adharsh Rajasekar

Hydrology 2025, 12(1), 14; https://doi.org/10.3390/hydrology12010014 - 13 Jan 2025

Viewed by 931

Abstract

Biocementation is an innovative and sustainable technique with wide-ranging applications in slope stabilization, watershed management, and erosion control. Despite its potential, comprehensive evaluations of its use in hydrology and geotechnical engineering are limited. This study addresses this gap through a bibliometric analysis of [...] Read more.

Biocementation is an innovative and sustainable technique with wide-ranging applications in slope stabilization, watershed management, and erosion control. Despite its potential, comprehensive evaluations of its use in hydrology and geotechnical engineering are limited. This study addresses this gap through a bibliometric analysis of 685 articles (2013–2023) from the Scopus database, employing VOSviewer and RStudio to explore global research trends, key contributors, and emerging themes. The analysis reveals that China, the United States, and Japan are leading contributors to this field, with significant advancements in microbial-induced (MICP) and enzyme-induced calcium carbonate precipitation (EICP) techniques. These methods have demonstrated effectiveness in improving soil strength, reducing erosion, and enhancing hydrological properties such as infiltration, runoff control, and water retention. Co-occurrence analysis identifies interdisciplinary connections between geotechnics and hydrology, highlighting research clusters focused on biomineralization, erosion resistance, and durability. The findings underscore biocementation’s pivotal role in addressing sustainability challenges by providing environmentally friendly alternatives to traditional soil stabilization techniques. This study not only maps the current research landscape but also offers valuable insights into the practical implications of biocementation for slope stability and hydrological management, laying the foundation for future advancements in sustainable engineering practices. Full article

(This article belongs to the Section Soil and Hydrology)

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19 pages, 11754 KiB

Open AccessArticle

Assessing the Impacts of Climatic and Water Management Scenarios in a Small Mountainous Greek River

by Angeliki Mentzafou, Anastasios Papadopoulos and Elias Dimitriou

Hydrology 2025, 12(1), 13; https://doi.org/10.3390/hydrology12010013 - 11 Jan 2025

Viewed by 786

Abstract

The water resource management of transboundary mountainous river basins under climate change is expected to be challenging. In order to contribute to the better understanding of climate change effects on the water resources of the mountainous and transboundary Prespa Lakes basin, a hydrological [...] Read more.

The water resource management of transboundary mountainous river basins under climate change is expected to be challenging. In order to contribute to the better understanding of climate change effects on the water resources of the mountainous and transboundary Prespa Lakes basin, a hydrological model of the Agios Germanos River, one of the main rivers discharging to Great Prespa Lake, was developed, and two water management plans under two different climate scenarios were examined. Based on the results, the impact of climate change on surface water resources was evident in all climate change scenarios examined, even under the most favorable water abstraction practices. Nevertheless, sensible water management can moderate the impact of climate change by up to 10% in an optimistic scenario in both the near- and long-term, and by up to 6% and 1% for the near- and long-term, respectively, in a pessimistic scenario. Integrated water management practices that moderate the impact of climate change on the water ecosystem services should be prioritized. Nature-based approaches could provide solutions regarding climate change adaptation and mitigation. Transboundary cooperation, data exchange mechanisms, common policy frameworks, and monitoring, reporting, and evaluation systems, could reduce human and ecosystems’ vulnerabilities and improve the water security of the area. Full article

(This article belongs to the Special Issue Runoff Modelling under Climate Change)

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22 pages, 14251 KiB

Open AccessArticle

The Development of Drawdown Dolines and Subsidence Dolines with the Comparison of Their Bedrock Resistivities—A Case Study

by Márton Veress

Hydrology 2025, 12(1), 12; https://doi.org/10.3390/hydrology12010012 - 10 Jan 2025

Viewed by 398

Abstract

The effect of the epikarst on the development of drawdown dolines and subsidence dolines is described. For this, the resistivity values of the bedrock determined by Vertical Electrical Sounding (VES) measurements were used. The higher resistivities below drawdown dolines are explained by the [...] Read more.

The effect of the epikarst on the development of drawdown dolines and subsidence dolines is described. For this, the resistivity values of the bedrock determined by Vertical Electrical Sounding (VES) measurements were used. The higher resistivities below drawdown dolines are explained by the deeper position of the piezometric surface, while the low resistivity values below subsidence dolines can be traced back to the more elevated position of the piezometric surface. Resistivities increasing towards the centre of drawdown dolines refer to cavity heterogeneity increasing towards the centre and increasing vertical percolation rate, while decreasing resistivity values indicate an increasing degree of cavity fill above the piezometric level. At their asymmetrical variety, the bedrock of their opposite slope is of asymmetric resistivity, which is explained by the different elevations of the piezometric surface and the latter by different infiltration that took place on slopes with different inclinations. The same resistivity values of the doline with a flat floor indicate the homogeneous cavity formation of the epikarst. This latter results in homogeneous vertical infiltration, which favours horizontal dissolution. The piezometric surface is not deflecting below the subsidence dolines because resistivity differences are small between the bedrock below the doline and the bedrock of its environment. Below subsidence doline, above the piezometric surface, cavities develop (the resistivity is higher relative to the resistivity of the environment), and then the cavities become filled by suffosion (therefore, the resistivity below the doline is lower relative to its environment). The passage below the doline develops into a shaft as a result of its concentrated water supply and the epikarst is separated into parts. Full article

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24 pages, 1884 KiB

Open AccessReview

Modeling Groundwater Resources in Data-Scarce Regions for Sustainable Management: Methodologies and Limits

by Iolanda Borzì

Hydrology 2025, 12(1), 11; https://doi.org/10.3390/hydrology12010011 - 9 Jan 2025

Viewed by 545

Abstract

Groundwater modeling in data-scarce regions faces significant challenges due to the lack of comprehensive, high-quality data, impacting model accuracy. This systematic review of Scopus-indexed papers identifies various approaches to address these challenges, including coupled hydrological-groundwater models, machine learning techniques, distributed hydrological models, water [...] Read more.

Groundwater modeling in data-scarce regions faces significant challenges due to the lack of comprehensive, high-quality data, impacting model accuracy. This systematic review of Scopus-indexed papers identifies various approaches to address these challenges, including coupled hydrological-groundwater models, machine learning techniques, distributed hydrological models, water balance models, 3D groundwater flow modeling, geostatistical techniques, remote sensing-based approaches, isotope-based methods, global model downscaling, and integrated modeling approaches. Each methodology offers unique advantages for groundwater assessment and management in data-poor environments, often combining multiple data sources and modeling techniques to overcome limitations. However, these approaches face common challenges related to data quality, scale transferability, and the representation of complex hydrogeological processes. This review emphasizes the importance of adapting methodologies to specific regional contexts and data availability. It underscores the value of combining multiple data sources and modeling techniques to provide robust estimates for sustainable groundwater management. The choice of method ultimately depends on the specific objectives, scale of the study, and available data in the region of interest. Future research should focus on improving the integration of diverse data sources, enhancing the representation of complex hydrogeological processes in simplified models, and developing robust uncertainty quantification methods tailored for data-scarce conditions. Full article

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10 pages, 599 KiB

Open AccessArticle

Study on the Stage Method of the Water Environmental Capacity Flood Season in the Ningxia Section of the Yellow River

by Yu Song and Hongrui Wang

Hydrology 2025, 12(1), 10; https://doi.org/10.3390/hydrology12010010 - 8 Jan 2025

Viewed by 471

Abstract

The rational use of the water environmental resources of the main stream of the Yellow River, which is the mother river of the Chinese nation, and the control of and reduction in water environmental pollution, especially in relation to water quality safety, have [...] Read more.

The rational use of the water environmental resources of the main stream of the Yellow River, which is the mother river of the Chinese nation, and the control of and reduction in water environmental pollution, especially in relation to water quality safety, have become important issues that must be considered in Ningxia’s economic and social development. Due to the influence of monsoons, river runoff in most of the river basins in China is mainly concentrated in the flood season, and its distribution is extremely uneven within and among years. Therefore, an analysis of the seasonal change law of heavy rainfall and flooding and a scientific and rational staging of the flood season can fully demonstrate the comprehensive benefits of the river and also address the inevitable need to master and utilize the capacity of the water environment. In this study, the abundant, level, and absent year division of the Ningxia section of the main stream of the Yellow River was carried out using the percentage of parity and the guarantee rate methods. Several commonly used flood periods staging methods were studied, and their applicable conditions were preliminarily analyzed. The research results not only provide a reference for the relevant management departments, a decision-making basis for rational planning, and the scientific and appropriate development of river basins but they also have scientific research significance. Full article

(This article belongs to the Special Issue Advances in Urban Hydrology and Stormwater Management)

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17 pages, 1919 KiB

Open AccessArticle

Design Flood Calculation Model for Extra-Small Watersheds in Ungauged Basin

by Yun Wang, Zengchuan Dong, Xinhua Zhu, Wenzhuo Wang, Yupeng Liu, Ronghao Chen and Yunjia He

Hydrology 2025, 12(1), 9; https://doi.org/10.3390/hydrology12010009 - 7 Jan 2025

Viewed by 532

Abstract

Designing floods in ungauged watersheds with limited data is a significant challenge in water conservancy projects. To address this, the method of calculating the design flood peak and flood volume using the weighted average method was proposed, which is based on the instantaneous [...] Read more.

Designing floods in ungauged watersheds with limited data is a significant challenge in water conservancy projects. To address this, the method of calculating the design flood peak and flood volume using the weighted average method was proposed, which is based on the instantaneous unit hydrograph method and the inference formula method, combined with the characteristics of heavy rainfall floods in ungauged watersheds. The calculation results are analyzed in terms of reasonableness through the distribution pattern of the flood peak modulus under different frequencies of the constructed reservoirs, the relative error analysis, and the HEC-RAS model. Based on the one-day flood process of the adjacent basin, the calculation of deducing the design flood process using the hydrological comparison method was proposed. Taking the “Stormwater Runoff Chart” as the data source, the runoff generation, and concentration model was established with the design flood of Baludi Reservoir in the Gelangram River basin of Menglian, Yunnan Province as the research object. A comparative study of the results of the design floods calculated by different methods was carried out. The results show that the new method can well describe the rainstorm process. The method has better performance in the application to the design flood calculation of ungauged basins due to its consideration of the influence of subsurface conditions. The method not only reduces the construction cost but also improves the safety of the reservoir through a better-fitted design flood calculation. Full article

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21 pages, 5692 KiB

Open AccessArticle

Kinetic Column Evaluation of Potential Construction Options for Lessening Solute Mobility in Backfill Aquifers in Restored Coal Mine Pits, Powder River Basin, USA

by Jeff B. Langman and Julianna Martin

Hydrology 2025, 12(1), 8; https://doi.org/10.3390/hydrology12010008 - 7 Jan 2025

Viewed by 432

Abstract

Following open-pit coal mining in the Powder River Basin, landscape reconstruction includes the construction of backfill aquifers from overburden waste rock. With overburden disaggregation and the re-introduction of groundwater, the weathering of newly available mineral surfaces and mobilization of nanomaterials can impact groundwater [...] Read more.

Following open-pit coal mining in the Powder River Basin, landscape reconstruction includes the construction of backfill aquifers from overburden waste rock. With overburden disaggregation and the re-introduction of groundwater, the weathering of newly available mineral surfaces and mobilization of nanomaterials can impact groundwater quality even when such issues were not previously detected in the overburden’s groundwater. Kinetic columns of Powder River Basin waste rock were used to evaluate backfill construction options—zeolite amendment, and soil amendment, compaction, rinse—that could reduce potential groundwater quality impacts. The leachate from each column was collected twice weekly for 20 weeks. The Eh and pH of the leachate substantially varied during an initial high-weathering period indicative of the traditional weathering of newly exposed mineral surfaces and the weathering and flushing of mobile particles. Correspondingly, select elements, such as arsenic and cadmium, were present in relatively high concentrations during this initial weathering period. Waste rock that was compacted or rinsed produced leachate with less solutes and potential contaminants when compared to the unaltered and zeolite- and soil-amended waste rock. Greater compaction during backfilling is possible but may require additional consideration for connecting the surface drainage network to the surrounding area. Rinsing of the waste rock is a viable construction option because of the temporary storage of the waste rock prior to backfilling but would require leachate collection for contaminant treatment. Full article

(This article belongs to the Topic Transport, Transformation and Cycling of Elements in Water and Soil and Their Response to Human Activities)

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22 pages, 7144 KiB

Open AccessArticle

Attribution of the Climate and Land Use Change Impact on the Hydrological Processes of Athabasca River Basin, Canada

by Sharad Aryal, Mukand S. Babel, Anil Gupta, Babak Farjad, Dibesh Khadka and Quazi K. Hassan

Hydrology 2025, 12(1), 7; https://doi.org/10.3390/hydrology12010007 - 7 Jan 2025

Viewed by 651

Abstract

Climate change (CC) and land use/land cover change (LULCC) are significant drivers of hydrological change, and an effective watershed management requires a detailed understanding of their individual and the combined impact. This study focused on the Athabasca River Basin (ARB), Canada, and investigated [...] Read more.

Climate change (CC) and land use/land cover change (LULCC) are significant drivers of hydrological change, and an effective watershed management requires a detailed understanding of their individual and the combined impact. This study focused on the Athabasca River Basin (ARB), Canada, and investigated how the basin responded to their changes using the MIKE SHE-MIKE Hydro River. Our findings revealed novel insights into ARB hydrological changes, including increment in non-vegetated lands (0.26%), savannas (1.28%), forests (0.53%), and urban areas (0.02%) while grasslands (2.07%) and shrublands (0.03%) decreased. Moreover, the basin experienced rising annual minimum (1.01 °C) and maximum (0.85 °C) temperatures but declining precipitation (6.2%). The findings suggested a significant impact of CC compared to LULCC as CC caused annual reduction in streamflow (7.9%), evapotranspiration (4.8%), and recharge (6.9%). Meanwhile, LULCC reduced streamflow (0.2%) and recharge (0.4%) but increased evapotranspiration (0.1%). The study revealed spatiotemporal variability across the ARB, with temperature impacts stronger in winter and precipitation influencing other seasons. Full article

(This article belongs to the Special Issue Hydrological Modelling for the Sustainable Management of Water Resources in River Basins)

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21 pages, 2112 KiB

Open AccessArticle

Climatic Factors Influencing Aleppo Pine Sap Flow in Orographic Valleys Under Two Contrasting Mediterranean Climates

by Ana M. Sabater, José Antonio Valiente, Juan Bellot and Alberto Vilagrosa

Hydrology 2025, 12(1), 6; https://doi.org/10.3390/hydrology12010006 - 6 Jan 2025

Viewed by 567

Abstract

Global climate change projections highlight the Mediterranean Basin as one of the most susceptible areas to the effects of intense and prolonged droughts, as well as increasing air temperatures. Accordingly, the productivity and survival of forests in this area will depend on their [...] Read more.

Global climate change projections highlight the Mediterranean Basin as one of the most susceptible areas to the effects of intense and prolonged droughts, as well as increasing air temperatures. Accordingly, the productivity and survival of forests in this area will depend on their ability to resist and adapt to increasingly drier conditions. Different climatic conditions across the Mediterranean Basin could drive differences in forest functioning, requiring trees to acclimate to them. Sea breeze dynamics along orographic valleys can also influence climatic conditions, accentuating differences between inland and coastal forests. However, there is limited information on whether the climatic factors regulating tree transpiration in Aleppo pine forest in orographic valleys vary according to climate. This study aims to identify and compare the climatic factors that regulate tree transpiration along a gradient and determine the thresholds at which these factors affect transpiration rates. This study was carried out by means of sap flow gauges, since this technique is a key feature for quantifying and understanding tree transpiration. It was conducted in two Aleppo pine dry sub-humid forests (inland and coastal, 750 and 675 trees ha⁻¹, respectively) and in two pine semi-arid forests (inland and coastal, 600 and 400 trees ha⁻¹, respectively) in the western Mediterranean basin during January–November of 2021. No significant rainfall events or droughts were recorded during the period of study, indicating a standard climatic condition in these areas. The main findings demonstrated that the variability in sap flow could be attributed to the interaction between soil water content and vapour pressure deficit in all the forests studied. However, the highest threshold values of these climatic factors in relation to the increase or decrease in maximum sap flow (i.e., less sensitivity) were exhibited in semi-arid forests, highlighting the adaptability of Aleppo pine to more limiting climatic conditions. These findings are relevant for the consequences of the predicted increase in harsh climatic conditions and the balance among vapour pressure deficit, temperature and soil water availability. Future research will be essential to confirm forest acclimatisation in the transitional dry to semi-arid forest ecosystems predicted by global climate change projections, given their potential to strongly alter ecosystem function and water cycles. Full article

(This article belongs to the Section Ecohydrology)

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16 pages, 4228 KiB

Open AccessArticle

Spatial and Temporal Variability of Extreme Hydroclimatic Events in the Bani River Basin

by Fousseini Kouyaté, François Kossi Guédjé, Assane Ndiaye and Orou Moctar Ganni Mampo

Hydrology 2025, 12(1), 5; https://doi.org/10.3390/hydrology12010005 - 5 Jan 2025

Viewed by 613

Abstract

Severe hydroclimatic events affect ecosystems and human livelihoods, creating significant challenges for managing water resources. This study analyzed the rainfall and river flow trends in the Bani River Basin (BRB) from 1991 to 2020. Using indices such as the maximum rainfall over a [...] Read more.

Severe hydroclimatic events affect ecosystems and human livelihoods, creating significant challenges for managing water resources. This study analyzed the rainfall and river flow trends in the Bani River Basin (BRB) from 1991 to 2020. Using indices such as the maximum rainfall over a one-day period (RX1DAY), maximum rainfall over a five-day period (RX5DAY), rainfall exceeding the 95th percentile (R95P), simple daily precipitation intensity (SDII), and peak discharge (Qmax), the modified Mann–Kendall test and Pettitt’s test were applied to assess the trends and identify potential breakpoints. The results revealed spatial variability, with southern regions showing reduced rainfall, while northeastern areas exhibit increasing extreme rainfall and river flow. The RX5DAY declined significantly after 2000, reflecting reductions in prolonged rainfall events, followed by the RX1DAY, which declined significantly after 2012, indicating a reduction in short-duration extremes. In contrast, the R99P, SDII, and Qmax exhibited positive trends, indicating intensifying rainfall intensity and extremes in discharge. A notable breakpoint was detected in 1993, marking a transition to increased extreme flows. The highest values of the rainfall indices (R95P, R99P, RX1DAY, RX5DAY, SDII) were concentrated in the southern part of the basin, while the north recorded lower values. These results highlight the basin’s vulnerability to climate variability and provide insights into hydroclimatic changes, serving as a basis for informed decision-making and future research. Full article

(This article belongs to the Section Statistical Hydrology)

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21 pages, 2960 KiB

Open AccessArticle

Comparison of Precipitation Rates from Global Datasets for the Five-Year Period from 2019 to 2023

by Heike Hartmann

Hydrology 2025, 12(1), 4; https://doi.org/10.3390/hydrology12010004 - 1 Jan 2025

Viewed by 947

Abstract

Precipitation is a fundamental component of the hydrologic cycle and is an extremely important variable in meteorological, climatological, and hydrological studies. Reliable climate information including accurate precipitation data is essential for identifying precipitation trends and variability as well as applying hydrologic models for [...] Read more.

Precipitation is a fundamental component of the hydrologic cycle and is an extremely important variable in meteorological, climatological, and hydrological studies. Reliable climate information including accurate precipitation data is essential for identifying precipitation trends and variability as well as applying hydrologic models for purposes such as estimating (surface) water availability and predicting flooding. In this study, I compared precipitation rates from five reanalysis datasets and one analysis dataset—the European Centre for Medium-Range Weather Forecasts Reanalysis Version 5 (ERA-5), the Japanese 55-Year Reanalysis (JRA-55), the Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2), the National Center for Environmental Prediction/National Center for Atmospheric Research Reanalysis 1 (NCEP/NCAR R1), the NCEP/Department of Energy Reanalysis 2 (NCEP/DOE R2), and the NCEP/Climate Forecast System Version 2 (NCEP/CFSv2)—with the merged satellite and rain gauge dataset from the Global Precipitation Climatology Project in Version 2.3 (GPCPv2.3). The latter was taken as a reference due to its global availability including the oceans. Monthly mean precipitation rates of the most recent five-year period from 2019 to 2023 were chosen for this comparison, which included calculating differences, percentage errors, Spearman correlation coefficients, and root mean square errors (RMSEs). ERA-5 showed the highest agreement with the reference dataset with the lowest mean and maximum percentage errors, the highest mean correlation, and the smallest mean RMSE. The highest mean and maximum percentage errors as well as the lowest correlations were observed between NCEP/NCAR R1 and GPCPv2.3. NCEP/DOE R2 showed significantly higher precipitation rates than the reference dataset (only JRA-55 precipitation rates were higher), the second lowest correlations, and the highest mean RMSE. Full article

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22 pages, 4867 KiB

Open AccessArticle

Characteristics of Precipitation, Streamflow, and Sediment Transport of the Hangman Creek in the Pacific Northwest, USA: Implication for Agricultural Conservation Practice Implementation

by Yongping Yuan and Sean Kanyuk

Hydrology 2025, 12(1), 3; https://doi.org/10.3390/hydrology12010003 - 31 Dec 2024

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Abstract

Anthropogenic climate change and changes to land use and land management practices can have significant impacts on streamflow and sediment transport. In this study, we investigated long-term precipitation, streamflow, and suspended sediment load patterns within the Hangman Creek watershed, draining from the Rocky [...] Read more.

Anthropogenic climate change and changes to land use and land management practices can have significant impacts on streamflow and sediment transport. In this study, we investigated long-term precipitation, streamflow, and suspended sediment load patterns within the Hangman Creek watershed, draining from the Rocky Mountains in Idaho to Washington, to identify the magnitude of changes with the goal of better understanding the links between these processes and the potential effects of agricultural conservation practices (ACPs) implemented since the 1990s. Comparing the study periods of 1991 to 2020 with 1961 to 1990, 1991 to 2020 had lower streamflow/precipitation ratios in the highest flow months such as February and March. Most streamflow occurred during winter and spring, so did suspended sediment. In addition, 2018 had much lower suspended sediment load compared to earlier years (1999 and 2000) during high flow seasons (January to April) given that streamflow was higher in 2018 than in 1999 and 2000. These changes may be attributed to the adoption of agricultural conservation practices because land cover remained almost unchanged from 2001 to 2021 and ACP adoption increased. Finally, the flow frequency analysis showed a strong linkage between higher streamflow events and increased suspended sediment load, with between 81% and 96% of total annual suspended sediment loads transported during the highest 10% of flows. Full article

(This article belongs to the Special Issue Hydrological Processes in Agricultural Watersheds)

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45 pages, 12393 KiB

Open AccessArticle

Enhancing Tropical Cyclone Risk Assessments: A Multi-Hazard Approach for Queensland, Australia and Viti Levu, Fiji

by Jane Nguyen, Michael Kaspi, Kade Berman, Cameron Do, Andrew B. Watkins and Yuriy Kuleshov

Hydrology 2025, 12(1), 2; https://doi.org/10.3390/hydrology12010002 - 29 Dec 2024

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Abstract

Tropical cyclones (TCs) are natural hazards causing extensive damage to society, infrastructure, and the natural environment. Due to the multi-hazardous nature of TCs, comprehensive risk assessments are essential to understanding how to better prepare for potential impacts. This study develops an integrated methodology [...] Read more.

Tropical cyclones (TCs) are natural hazards causing extensive damage to society, infrastructure, and the natural environment. Due to the multi-hazardous nature of TCs, comprehensive risk assessments are essential to understanding how to better prepare for potential impacts. This study develops an integrated methodology for TC multi-hazard risk assessment that utilises the following individual assessments of key TC risk components: a variable enhanced bathtub model (VeBTM) for storm surge-driven hazards, a random forest (RF) machine learning model for rainfall-induced flooding, and indicator-based indices for exposure and vulnerability assessments. To evaluate the methodology, the regions affected by TC Debbie (2017) for Queensland and TC Winston (2016) for Fiji’s main island of Viti Levu were used as proof-of-concept case studies. The results showed that areas with the highest risk of TC impacts were close to waterbodies, such as at the coastline and along riverine areas. For the Queensland study region, coastal populated areas showed levels of “high”, “very high”, and “extreme” risk, specifically in Bowen and East Mackay, driven by the social and infrastructural domains of TC risk components. For Viti Levu, areas classified with an “extreme” risk to TCs are primarily areas that experienced coastal inundation, with Lautoka and Vuda found to be especially at risk to TCs. Additionally, the Fiji case study was validated using post-disaster damage data, and a statistically significant correlation of 0.40 between TC Winston-attributed damage and each tikina’s overall risk was identified. Ultimately, this study serves as a prospective framework for assessing TC risk, capable of producing results that can assist decision-makers in developing targeted TC risk management and resilience strategies for disaster risk reduction. Full article

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21 pages, 3618 KiB

Open AccessArticle

Operativity of the Taunsa Barrage, Pakistan: Experimental Investigation on the Subsidiary Weir

by Muhammad Zahid Ullah, Habib-Ur-Rehman Mughal, Noor Yaseen, Noor Muhammad Khan, Giada Varra, Luca Cozzolino and Renata Della Morte

Hydrology 2025, 12(1), 1; https://doi.org/10.3390/hydrology12010001 - 29 Dec 2024

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Abstract

River barrages ensure water availability for enhanced irrigation and human consumption. Of course, effective and sustainable management of existing barrages requires controlling riverbed erosion through appropriately designed stilling basins with their appurtenances. The present study assesses the stilling basin performance of the Taunsa [...] Read more.

River barrages ensure water availability for enhanced irrigation and human consumption. Of course, effective and sustainable management of existing barrages requires controlling riverbed erosion through appropriately designed stilling basins with their appurtenances. The present study assesses the stilling basin performance of the Taunsa Barrage, a vital water resources infrastructure built in 1958 in Punjab, Pakistan, and rehabilitated between 2004 and 2008 through the construction of a subsidiary weir (SW) downstream of the main weir. A physical modeling approach was employed, consisting of two distinct phases of laboratory experiments. Phase 1 replicated the Taunsa Barrage before rehabilitation, assessing the need for SW construction under different discharge rates and downstream bed elevations. Phase 2 reproduced the post-rehabilitation conditions, including varying discharge values, heights and positions of the SW, to evaluate the stilling basin design concerning the ability to dissipate flow energy. The results demonstrated (i) inadequate tailwater levels and oscillating hydraulic jump formation under increased discharges in pre-rehabilitation conditions (highlighting the poor performance of the original Taunsa Barrage stilling basin and the need for an SW to address these hydraulic deficiencies), and (ii) that the SW, under the design conditions, achieved optimal head loss for discharge values near the design discharge. However, the head loss efficiency was highly sensitive to variations in the distance and height of the SW due to hydraulic jump pulsations. Moreover, the head loss efficiency rapidly degraded for discharges greater than the design discharge. These findings indicate that the Taunsa barrage stilling basin may lack the capacity to accommodate higher discharges resulting from the interplay between climate change and land use alterations within the upstream Indus River basin. Future research should focus on developing a design that enhances energy dissipation robustness, reducing susceptibility to potential discharge increases. Full article

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Hydrology, Volume 12, Issue 1 (January 2025) – 19 articles

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