Hydrology

23 pages, 3284 KiB

Open AccessArticle

Significance of Spring Inflow to Great Salt Lake, Utah, U.S.A.

by Lauren E. Bunce, Tim K. Lowenstein, Elliot Jagniecki and David Collins

Hydrology 2025, 12(6), 159; https://doi.org/10.3390/hydrology12060159 (registering DOI) - 19 Jun 2025

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Spring waters (n = 103) from locations surrounding Great Salt Lake (GSL) were mapped, collected, and analyzed to determine their chemical compositions. A ternary Ca-SO₄-alkalinity plot was used to group these waters into compositional types based on the principle of chemical [...] Read more.

Spring waters (n = 103) from locations surrounding Great Salt Lake (GSL) were mapped, collected, and analyzed to determine their chemical compositions. A ternary Ca-SO₄-alkalinity plot was used to group these waters into compositional types based on the principle of chemical divides. Different spring water types were mixed with Bear, Jordan, and Weber River waters to determine the amount of spring inflow needed to reproduce the chemical composition of GSL. The Pitzer-based computer program EQL/EVP was used to simulate evaporation of spring-river water mixtures. The goal was to find spring-river water mixtures that, when evaporated, reproduced the chemical composition of modern GSL. This approach yielded GSL brine composition from a starting mixture of 12% spring inflow and 88% river water, by volume. The calculated spring inflow–river water mixture contains, on a molar percentage basis, greater than 50% of the B, K, Li, Na, and Cl supplied by springs and greater than 50% of the Ba, Ca, Sr, SO₄, and alkalinity derived from rivers. Understanding GSL spring inflow and brine evolution as lake elevation drops is critical to lake environments, ecosystems, and industrial brine shrimp harvesting and mineral extraction. Full article

(This article belongs to the Special Issue Lakes as Sensitive Indicators of Hydrology, Environment, and Climate)

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21 pages, 1792 KiB

Open AccessArticle

Assessment of Baseflow Separation Methods Used in the Estimations of Design-Related Storm Hydrographs Across Various Return Periods

by Oscar E. Coronado-Hernández, Rafael D. Méndez-Anillo and Manuel Saba

Hydrology 2025, 12(6), 158; https://doi.org/10.3390/hydrology12060158 - 19 Jun 2025

Viewed by 133

Abstract

Accurately estimating storm hydrographs for various return periods is crucial for planning and designing hydrological infrastructure, such as dams and drainage systems. A key aspect of this estimation is the separation of baseflow from storm runoff. This study proposes a method for deriving [...] Read more.

Accurately estimating storm hydrographs for various return periods is crucial for planning and designing hydrological infrastructure, such as dams and drainage systems. A key aspect of this estimation is the separation of baseflow from storm runoff. This study proposes a method for deriving storm hydrographs for different return periods based on hydrological station records. The proposed approach uses three baseflow separation methods: constant, linear, and master recession curve. A significant advantage of the proposed method over traditional rainfall–runoff approaches is its minimal parameter requirements during calibration. The methodology is tested on records from the Lengupá River watershed in Colombia, using data from the Páez hydrological station, which has a drainage area of 1090 km². The results indicate that the linear method yields the most accurate hydrograph estimates, as demonstrated by its lower root mean square error (RMSE) of 0.35%, compared to the other baseflow separation techniques, the values of which range from 2.92 to 3.02%. A frequency analysis of hydrological data was conducted using Pearson Type III and Generalized Extreme Value distributions to identify the most suitable statistical models for estimating extreme events regarding peak flow and maximum storm hydrograph volume. The findings demonstrate that the proposed methods effectively reproduce storm hydrographs for return periods ranging from 5 to 200 years, providing valuable insights for hydrological design, which can be employed using the data from stream gauging stations in rivers. Full article

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19 pages, 4046 KiB

Open AccessArticle

Combining Hydrodynamic Modelling and Solar Potential Assessment to Evaluate the Effects of FPV Systems on Mihăilești Reservoir, Romania

by Gabriela Elena Dumitran, Elena Catalina Preda, Liana Ioana Vuta, Bogdan Popa and Raluca Elena Ispas

Hydrology 2025, 12(6), 157; https://doi.org/10.3390/hydrology12060157 - 19 Jun 2025

Viewed by 181

Abstract

Floating photovoltaic (FPV) systems are a new green technology emerging lately, having the indisputable advantage of not covering agricultural land but instead the surface of lakes or reservoirs. Being a new technology, even though the number of studies is significant, reliable results remain [...] Read more.

Floating photovoltaic (FPV) systems are a new green technology emerging lately, having the indisputable advantage of not covering agricultural land but instead the surface of lakes or reservoirs. Being a new technology, even though the number of studies is significant, reliable results remain limited. This paper presents the possible influence of an FPV farm installed on the surface of a reservoir in Romania in four scenarios of the surface being covered with photovoltaic panels. The changes in the water mass under the FPV panels were determined using mathematical modelling as a tool. For this purpose, a water quality model was implemented for Mihăilești Reservoir, Romania, and the variations in the temperature, the phytoplankton biomass, and the total phosphorus and nitrogen were computed. Also, by installing FPV panels, it was estimated that a volume of water of between 1.75 and 7.43 million m³/year can be saved, and the greenhouse gas emission reduction associated with the proposed solutions will vary between 15,415 and 66,066 tCO_2e/year; these results are in agreement with those reported in other scientifical studies. The overall conclusion is that the effect of an FPV farm on the reservoir’s surface is beneficial for the water quality in the reservoir. Full article

(This article belongs to the Special Issue Hydrodynamics and Water Quality of Rivers and Lakes)

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22 pages, 1288 KiB

Open AccessReview

The Status, Applications, and Modifications of the Snowmelt Runoff Model (SRM): A Comprehensive Review

by Ninad Bhagwat, Rohitashw Kumar, Mahrukh Qureshi, Raja M. Nagisetty and Xiaobing Zhou

Hydrology 2025, 12(6), 156; https://doi.org/10.3390/hydrology12060156 - 18 Jun 2025

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Abstract

In this review paper, we perform a comprehensive review of the current state of the art, worldwide applications, and modifications of the Snowmelt Runoff Model (SRM). Snow is a significant element of the hydrologic cycle and is sometimes regarded as the primary source [...] Read more.

In this review paper, we perform a comprehensive review of the current state of the art, worldwide applications, and modifications of the Snowmelt Runoff Model (SRM). Snow is a significant element of the hydrologic cycle and is sometimes regarded as the primary source of streamflow in watersheds at high latitudes and altitudes. Quantitative assessment of snowmelt runoff is crucial for real-world applications, including runoff projections, reservoir management, hydro-electricity production, irrigation techniques, and flood control, among others. Numerous hydrological modeling software have been developed to simulate snowmelt-derived streamflow. The SRM is one of the well-known modeling software developed to simulate snowmelt-derived streamflow. The SRM simulates snowmelt runoff with fewer data requirements and uses remotely sensed snow cover extent. This makes the SRM appropriate for use in data-scarce locations, particularly in remote and inaccessible mountain watersheds at higher elevations. It is a conceptual, deterministic, semi-distributed, and degree-day hydrological model that can be applied in mountainous basins of nearly any size. Recent advancements in remote sensing integration and climate model coupling have significantly enhanced the model’s ability to estimate snowmelt runoff. Additionally, numerous studies have recently improved the traditional SRM, further enhancing its capabilities. This paper highlights some of the global SRM research, focusing on the working of the model, input parameters, remote sensing data availability, and modifications to the original model. Full article

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21 pages, 4702 KiB

Open AccessArticle

Borehole Geophysical Time-Series Logging to Monitor Passive ISCO Treatment of Residual Chlorinated-Ethenes in a Confining Bed, NAS Pensacola, Florida

by Philip T. Harte, Michael A. Singletary and James E. Landmeyer

Hydrology 2025, 12(6), 155; https://doi.org/10.3390/hydrology12060155 - 18 Jun 2025

Viewed by 142

Abstract

In-situ chemical oxidation (ISCO) is a common method to remediate chlorinated ethene contaminants in groundwater. Monitoring the effectiveness of ISCO can be hindered because of insufficient observations to assess oxidant delivery. Advantageously, potassium permanganate, one type of oxidant, provides the opportunity to use [...] Read more.

In-situ chemical oxidation (ISCO) is a common method to remediate chlorinated ethene contaminants in groundwater. Monitoring the effectiveness of ISCO can be hindered because of insufficient observations to assess oxidant delivery. Advantageously, potassium permanganate, one type of oxidant, provides the opportunity to use its strong electrical signal as a surrogate to track oxidant delivery using time-series borehole geophysical methods, like electromagnetic (EM) induction logging. Here we report a passive ISCO (P-ISCO) experiment, using potassium permanganate cylinders emplaced in boreholes, at a chlorinated ethene contamination site, Naval Air Station Pensacola, Florida. The contaminants are found primarily at the base of a shallow sandy aquifer in contact with an underlying silty-clay confining bed. We used results of the time-series borehole logging collected between 2017 and 2022 in 4 monitoring wells to track oxidant delivery. The EM-induction logs from the monitoring wells showed an increase in EM response primarily along the contact, likely from pooling of the oxidant, during P-ISCO treatment in 2021. Interestingly, concurrent natural gamma-ray (NGR) logging showed a decrease in NGR response at 3 of the 4 wells possibly from the formation of manganese precipitates coating sediments. The coupling of time-series logging and well-chemistry data allowed for an improved assessment of passive ISCO treatment effectiveness. Full article

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

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Graphical abstract

17 pages, 3175 KiB

Open AccessArticle

Impact of Different Building Roof Types on Hydrological Processes at the Urban Community Scale

by Chaohui Chen, Hao Hou, Yongguo Shi, Ping Zhao, Yao Li, Yong Wang, Yindong Zhang and Tangao Hu

Hydrology 2025, 12(6), 154; https://doi.org/10.3390/hydrology12060154 - 18 Jun 2025

Viewed by 141

Abstract

As urbanization accelerates and urban hydrological cycles evolve, roof typology emerges as a pivotal role in water retention capacity and drainage efficiency. To systematically evaluate the influence of various roof types on urban hydrological processes, this study designed four distinct catchment scenarios: Thiessen [...] Read more.

As urbanization accelerates and urban hydrological cycles evolve, roof typology emerges as a pivotal role in water retention capacity and drainage efficiency. To systematically evaluate the influence of various roof types on urban hydrological processes, this study designed four distinct catchment scenarios: Thiessen Polygon Scenarios (TS), Roof Type Consideration Scenarios (RS), Full Flat-Roof Scenarios (FS), and Full Pitched-Roof Scenarios (PS). This study employed the Urban Flood Intelligent Model (UFIM) to simulate urban flooding scenarios, utilizing precipitation data from 21 August 2024 combined with four distinct return periods (1a, 5a, 10a, and 20a) as hydrological inputs. The results show that roof types significantly affected hydrological processes in urban communities. Flat roofs accumulate water and drain slowly, making it easy to form larger areas of accumulated water during peak rainfall periods, thereby increasing the risk of urban flooding. Pitched roofs drain quickly but experience a brief rise in water level during peak hours due to rapid drainage. Based on these insights, priority should be given to the use of sloped roof design in areas prone to accumulated water to accelerate drainage. In areas requiring runoff mitigation, the strategic integration of flat roofs with green roofs enhances rainwater retention capacity, thereby optimizing urban hydrological regulation and bolstering flood resilience. Full article

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

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20 pages, 2831 KiB

Open AccessArticle

Assessment of the Impact of Climate Change on Dam Hydrological Safety by Using a Stochastic Rainfall Generator

by Enrique Soriano, Luis Mediero, Andrea Petroselli, Davide Luciano De Luca, Ciro Apollonio and Salvatore Grimaldi

Hydrology 2025, 12(6), 153; https://doi.org/10.3390/hydrology12060153 - 17 Jun 2025

Viewed by 66

Abstract

Dam breaks can lead to important economic and human losses. Design floods, which are useful to assess possible dam breaks, are usually estimated through statistical analysis of rainfall and streamflow observed data. However, such available samples are commonly limited and, consequently, high uncertainties [...] Read more.

Dam breaks can lead to important economic and human losses. Design floods, which are useful to assess possible dam breaks, are usually estimated through statistical analysis of rainfall and streamflow observed data. However, such available samples are commonly limited and, consequently, high uncertainties are associated with the design flood estimates. In addition, climate change is expected to increase the frequency and magnitude of extreme rainfall and flood events in the future. Therefore, a methodology based on a stochastic rainfall generator is proposed to assess hydrological dam safety by considering climate change. We selected the Eugui Dam on the Arga river in the north of Spain as a case study that has a spillway operated by gates with a maximum capacity of 270 m³/s. The stochastic rainfall generator STORAGE is used to simulate long time series of 15-min precipitation in both current and future climate conditions. Precipitation projections of 12 climate modeling chains, related to the usual three 30-year periods (2011–2024; 2041–2070 and 2071–2100) and two emission scenarios of AR5 (RCP 4.5 and 8.5), are used to consider climate change in the STORAGE model. The simulated precipitation time series are transformed into runoff time series by using the continuous COSMO4SUB hydrological model, supplying continuous 15-min runoff time series as output. Annual maximum flood hydrographs are selected and considered as inflows to the Eugui Reservoir. The Volume Evaluation Method is applied to simulate the operation of the Eugui Dam spillway gates, obtaining maximum water levels in the reservoir and outflow hydrographs. The results show that the peak outflows at the Eugui Dam will be lower in the future. Therefore, maximum reservoir water levels will not increase in the future. The methodology proposed could allow practitioners and dam managers to check the hydrological dam safety requirements, accounting for climate change. 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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62 pages, 18163 KiB

Open AccessArticle

Regional Frequency Analysis Using L-Moments for Determining Daily Rainfall Probability Distribution Function and Estimating the Annual Wastewater Discharges

by Pau Estrany-Planas, Pablo Blanco-Gómez, Juan I. Ortiz-Vallespí, Javier Orihuela-Martínez and Víctor Vilarrasa

Hydrology 2025, 12(6), 152; https://doi.org/10.3390/hydrology12060152 - 16 Jun 2025

Viewed by 125

Abstract

The spatial distribution of precipitation is one of the major unknowns in hydrological modeling since meteorological stations do not adequately cover the territory, and their records are often short. In addition, regulations are increasingly restricting the amount of wastewater that can be discharged [...] Read more.

The spatial distribution of precipitation is one of the major unknowns in hydrological modeling since meteorological stations do not adequately cover the territory, and their records are often short. In addition, regulations are increasingly restricting the amount of wastewater that can be discharged each year. Therefore, understanding the annual behavior of rainfall events is becoming increasingly important. This paper presents Rainfall Frequency Analysis (RainFA), a software package that applies a methodology for data curation and frequency analysis of precipitation series based on the evaluation of the L-moments for regionalization and cluster classification. This methodology is tested in the city of Palma (Spain), identifying a single homogeneous cluster integrated by 7 (out of 11) stations, with homogeneity values less than 0.6 for precipitation values greater than or equal to 0.4 mm. In the evaluation of the prediction capacity, the selected cluster of 7 stations performed in the first quartile of the 120 possible combinations of 7 stations, both for the detection of the occurrence of rainfall—in terms of Probability of Detection (POD), False Alarm Ratio (FAR), Critical Success Index (CSI) and Bias Score (BS) statistics—and for the accuracy of rainfall—according to Root Mean Square Error (RMSE), Nash–Sutcliffe Efficiency coefficient (NSE) and Percent Bias (PBIAS). The cluster was also excellent for predicting different rainfall ranges, resulting in the best combination for both light—i.e., [1, 5) mm—and moderate—i.e., [5, 20) mm—rainfall prediction. The Generalized Pareto gave the best probability distribution function for the selected region, and it was used to simulate daily rainfall and system discharges over annual periods using Monte Carlo techniques. The derived discharge values were consistent with observations for 2023, with an average discharge of about 700,000 m³ of wastewater. RainFA is an easy-to-use and open-source software programmed using Python that can be applied anywhere in the world. Full article

(This article belongs to the Special Issue Advances in the Measurement, Utility and Evaluation of Precipitation Observations)

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31 pages, 8526 KiB

Open AccessArticle

Water-Sensitive Urban Design (WSUD) Performance in Mitigating Urban Flooding in a Wet Tropical North Queensland Sub-Catchment

by Sher Bahadur Gurung, Robert J. Wasson, Michael Bird and Ben Jarihani

Hydrology 2025, 12(6), 151; https://doi.org/10.3390/hydrology12060151 - 15 Jun 2025

Viewed by 166

Abstract

Existing wet tropical urban drainage systems often fail to accommodate runoff generated during extreme rainfall. Water-sensitive urban design (WSUD) systems have the potential to retrofit the existing urban drainage system by enhancing infiltration and retention functions. However, studies supporting this assumption were based [...] Read more.

Existing wet tropical urban drainage systems often fail to accommodate runoff generated during extreme rainfall. Water-sensitive urban design (WSUD) systems have the potential to retrofit the existing urban drainage system by enhancing infiltration and retention functions. However, studies supporting this assumption were based on temperate or arid climatic conditions, raising questions about its relevance in wet tropical catchments. To answer these questions, in this study a comprehensive modelling study of WSUD effectiveness in a tropical environment was implemented. Engineers Park, a small sub-catchment of 0.27 km² at Saltwater Creek, Cairns, Queensland, Australia was the study site in which the flood mitigation capabilities of grey and WSUD systems under major (1% Annual Exceedance Probability—AEP), moderate (20% AEP), and minor (63.2% AEP) magnitudes of rainfall were evaluated. A detailed one-dimensional (1D) and coupled 1D2D hydrodynamic model in MIKE+ were developed and deployed for this study. The results highlighted that the existing grey infrastructure within the catchment underperformed during major events resulting in high peak flows and overland flow, while minor rainfall events increased channel flow and shifted the location of flooding. However, the integration of WSUD with grey infrastructure reduced peak flow by 0% to 42%, total runoff volume by 0.9% to 46%, and the flood extent ratio to catchment area from 0.3% to 1.1%. Overall, the WSUD integration positively contributed to reduced flooding in this catchment, highlighting its potential applicability in tropical catchments subject to intense rainfall events. However, careful consideration is required before over-generalization of these results, since the study area is small. The results of this study can be used in similar study sites by decision-makers for planning and catchment management purposes, but with careful interpretation. Full article

(This article belongs to the Special Issue Advances in Nature-Based Solutions for Hydrometeorological Risk Reduction)

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17 pages, 6310 KiB

Open AccessArticle

An Evaluation of the Effects of the 1755 Lisbon Earthquake on Rivers and Their Tributaries in Mainland Portugal

by Alice Tavares, Aníbal Costa and Carlos S. Oliveira

Hydrology 2025, 12(6), 150; https://doi.org/10.3390/hydrology12060150 - 13 Jun 2025

Viewed by 440

Abstract

Historical earthquake records are crucial for analyzing high-intensity earthquakes that occur over long periods. Since good instrumental data only date back to 1980, there are gaps in our knowledge, and qualitative assessments remain essential to expand our knowledge and integrate more information into [...] Read more.

Historical earthquake records are crucial for analyzing high-intensity earthquakes that occur over long periods. Since good instrumental data only date back to 1980, there are gaps in our knowledge, and qualitative assessments remain essential to expand our knowledge and integrate more information into the number of variables under analysis. This study examined the hydrological and hydrogeological effects of the 1755 Lisbon earthquake, focusing on regions near rivers and proposing new insights for intensity scales. This information is relevant for seismic risk management and mitigation, to be discussed in regional and national territorial planning strategies. Mapping revealed that most phenomena occurred along the Porto–Tomar tectonic fault, with some extending to other probable faults or geological contrasts. A comparative chart between existing intensity scales and the proposed descriptors highlights agreements and discrepancies, emphasizing the need for more detailed descriptors for intensity levels below X for river-related phenomena. The proposed descriptors include a flow increase with course alterations (intensities VI–VIII), flow suppression and eventual reset (intensity VIII or higher), abnormal current agitation and vertical wave movements (intensities VI–VIII), and cloudy (turbid) water (intensities V–VIII). This work also highlights the need to cross-reference data and the complexity of establishing correlations between effects, ancient descriptions, and descriptors for these intensity scales. Full article

(This article belongs to the Topic Advances in Hydrogeological Research)

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24 pages, 3885 KiB

Open AccessArticle

Spatiotemporal Analysis of Available Freshwater Resources in Watersheds Across Northern New Jersey

by Toritseju Oyen and Duke Ophori

Hydrology 2025, 12(6), 149; https://doi.org/10.3390/hydrology12060149 - 12 Jun 2025

Viewed by 329

Abstract

Groundwater is a critical freshwater resource, yet its quality is increasingly threatened by anthropogenic activities, particularly in urbanized regions. This study employs geospatial analysis to evaluate the spatiotemporal variability of groundwater quality across 11 Watershed Management Areas (WMAs) in northern New Jersey, from [...] Read more.

Groundwater is a critical freshwater resource, yet its quality is increasingly threatened by anthropogenic activities, particularly in urbanized regions. This study employs geospatial analysis to evaluate the spatiotemporal variability of groundwater quality across 11 Watershed Management Areas (WMAs) in northern New Jersey, from 1999 to 2016. Using specific conductance (SC) as a proxy for salinity, we applied Ordinary Kriging interpolation to estimate SC values in unmonitored locations, leveraging data from 295 shallow wells within the New Jersey Ambient Groundwater Quality Monitoring Network. The results reveal significant spatial heterogeneity in groundwater quality, strongly associated with land use and road density. The Northeast water region, characterized by high urbanization and extensive road networks, exhibited the poorest water quality, with salinity levels exceeding the 750 μS/cm threshold for freshwater in WMAs such as Lower Passaic (WMA-4) and Hackensack (WMA-5). In contrast, the Northwest region, dominated by agricultural and undeveloped land, maintained better water quality. Temporal analysis showed a worrying decline in freshwater coverage, from 80% in 1999–2004 to 74% in 2014–2016, with deicing salts and aging sewer infrastructure identified as major contamination sources. The study highlights the efficacy of Kriging and GIS tools in mapping groundwater quality trends and highlights the urgent need for targeted water management strategies in vulnerable regions. These findings provide policymakers and stakeholders with actionable insights to mitigate groundwater degradation and ensure long-term freshwater sustainability in northern New Jersey. Full article

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20 pages, 3072 KiB

Open AccessArticle

Effectiveness of River Training Projects in Controlling Shoal Erosion: A Case Study of the Middle Yangtze River

by Yao Yue, Weiya Huang, Yaxin Guo, Junhong Zhang, Yunping Yang, Dongdong Zhang, Linshuang Liu and Xinxin Chen

Hydrology 2025, 12(6), 148; https://doi.org/10.3390/hydrology12060148 - 12 Jun 2025

Viewed by 393

Abstract

Reservoir regulation and river training works are significant factors influencing downstream channel evolution. However, there is still a lack of systematic studies on the evolution patterns under their synergistic impacts. In particular, the adaptability of shoal training works under hydrological variability conditions needs [...] Read more.

Reservoir regulation and river training works are significant factors influencing downstream channel evolution. However, there is still a lack of systematic studies on the evolution patterns under their synergistic impacts. In particular, the adaptability of shoal training works under hydrological variability conditions needs further investigation. The main purpose of this study is to undertake a thorough analysis of the efficacy of river training works related to shoal erosion control and to identify its underlying causes and potential mitigation strategies. By reviewing completed river training works and collecting and analyzing hydrological data of the middle Yangtze River, we developed and applied a hydro-morphological model to simulate the river evolution processes. A systematic evaluation was undertaken on the impact of training works on shoal erosion. The results indicate that the river training works can influence local hydrological and hydrodynamic conditions, thereby enhancing shoals’ resistance to erosion and decelerating shoal shrinkage. However, under altered hydrologic regimes, the effectiveness of training works wanes, thus failing to fully achieve its intended effects. Specifically, the bank protection project attenuated the intensity of scour at the head of the continent by 30% (average annual scour depth reduced from 2.1 m to 1.5 m) and increased the local stability index by 14.5% (from 0.744 to 0.852), but it is still below the critical threshold (1.024). The findings of this study are expected to provide a scientific basis for the planning and implementation of river training works in the Middle Yangtze River and serve as a reference for addressing similar issues in other regions. Full article

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23 pages, 2177 KiB

Open AccessArticle

Climatological Seasonal Cycle of River Discharge into the Oceans: Contributions from Major Rivers and Implications for Ocean Modeling

by Moncef Boukthir and Jihene Abdennadher

Hydrology 2025, 12(6), 147; https://doi.org/10.3390/hydrology12060147 - 12 Jun 2025

Viewed by 593

Abstract

This study presents a global assessment of the climatological seasonal variability of river discharge into the oceans, based on an expanded dataset comprising 958 gauging stations across 136 countries. Monthly discharges were compiled for 145 major rivers and tributaries, with a focus on [...] Read more.

This study presents a global assessment of the climatological seasonal variability of river discharge into the oceans, based on an expanded dataset comprising 958 gauging stations across 136 countries. Monthly discharges were compiled for 145 major rivers and tributaries, with a focus on improving the accuracy and spatial coverage of global freshwater flux estimates. Compared to previous datasets, this updated compilation includes a broader set of rivers, explicitly integrates tributary inflows, and quantifies both the absolute and relative seasonal amplitudes of discharge variability. The results reveal substantial differences among ocean basins. The Atlantic Ocean, although receiving the highest total runoff, shows relatively weak seasonal variability, with a coefficient of variation of CV = 12.6% due to asynchronous peak discharge from its major rivers (Amazon, Congo, Orinoco). In contrast, the Indian Ocean exhibits the most pronounced seasonal cycle (CV = 88.3%), driven by monsoonal rivers. The Pacific Ocean shows intermediate variability (CV = 62.1%), influenced by a combination of monsoon rains and snowmelt. At the river scale, Orinoco and Changjiang display high seasonal amplitudes, exceeding 89% of their mean flows, whereas more stable regimes are found in equatorial and temperate rivers like the Amazon and Saint Lawrence. In addition, the critical role of tributaries in altering discharge magnitude and seasonal variability is well established. This study provides high-resolution monthly discharge climatologies at global and basin scales, enhancing freshwater forcing in OGCMs. By improving the representation of land–ocean exchanges, it enables more accurate simulations of salinity, circulation, biogeochemical cycles, and climate-sensitive processes in coastal and open-ocean regions. Full article

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13 pages, 536 KiB

Open AccessOpinion

Understanding and Mitigating Urban Flood Risk

by Ezio Todini

Hydrology 2025, 12(6), 146; https://doi.org/10.3390/hydrology12060146 - 11 Jun 2025

Viewed by 254

Abstract

This opinion paper aims to clarify the interacting elements that affect the substantial consequences of urban floods. The main goal is to elucidate the assessment of risk and its mitigation by examining relevant elements, including the comprehension of the causes and characteristics of [...] Read more.

This opinion paper aims to clarify the interacting elements that affect the substantial consequences of urban floods. The main goal is to elucidate the assessment of risk and its mitigation by examining relevant elements, including the comprehension of the causes and characteristics of urban floods. This analysis addresses the challenges of informed urban flood management, emphasizing intelligent planning, operational efficiency, and community preparedness, with the objective of ensuring timely, resilient, and effective responses that maintain social and environmental equity. Ultimately, the unresolved issues that hinder decision makers from making informed decisions are succinctly delineated. Full article

(This article belongs to the Special Issue Understanding, Forecasting and Control of Flooding and Pollution in the Urban Environment: The 10th Anniversary of Hydrology)

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18 pages, 2811 KiB

Open AccessArticle

Numerical Simulation of Turbulent Flow in River Bends and Confluences Using the k-ω SST Turbulence Model and Comparison with Standard and Realizable k-ε Models

by Rawaa Shaheed, Abdolmajid Mohammadian and Alaa Mohammed Shaheed

Hydrology 2025, 12(6), 145; https://doi.org/10.3390/hydrology12060145 - 11 Jun 2025

Viewed by 586

Abstract

River bends and confluences are critical features in fluvial environments where complex flow patterns, including secondary currents, turbulence, and surface changes, strongly influence sediment transport, river morphology, and water quality. The accurate prediction of these flow characteristics is essential for hydraulic engineering applications. [...] Read more.

River bends and confluences are critical features in fluvial environments where complex flow patterns, including secondary currents, turbulence, and surface changes, strongly influence sediment transport, river morphology, and water quality. The accurate prediction of these flow characteristics is essential for hydraulic engineering applications. In this study, we present a numerical simulation of turbulent flow in river bends and confluences, with special consideration given to the dynamic interaction between free-surface variations and closed-surface constraints. The simulations were performed using OpenFOAM, an open-source computational fluid dynamics (CFDs) platform, with the k-ω SST (Shear Stress Transport) turbulence model, which is well-suited for capturing boundary layer behavior and complex turbulence structures. The finite volume method (FVM) is used to simulate and examine the behavior of the secondary current in channel bends and confluences. Two sets of experimental data, one with a sharply curved channel and the other with a confluent channel, were used to compare the numerical results and to evaluate the validity of the model. This study focuses on investigating to what extent the k-ω SST turbulence model can capture the effects of secondary flow and surface changes on flow hydrodynamics, analyzing velocity profiles and turbulence effects. The results are validated against experimental data, demonstrating the model’s ability to reasonably replicate flow features under both free- and closed-surface conditions. This study provides insights into the performance of the k-ω SST model in simulating the impact of geometrical constraints on flow regimes, offering a computationally robust and reasonable tool for river engineering and water resources management, particularly in the context of hydraulic structure design and erosion control in curved and confluence regions. Full article

(This article belongs to the Special Issue Hydrodynamics and Water Quality of Rivers and Lakes)

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18 pages, 3611 KiB

Open AccessArticle

Using Landsat 8/9 Thermal Bands to Detect Potential Submarine Groundwater Discharge (SGD) Sites in the Mediterranean in North West-Central Morocco

by Youssef Bernichi, Mina Amharref, Abdes-Samed Bernoussi and Pierre-Louis Frison

Hydrology 2025, 12(6), 144; https://doi.org/10.3390/hydrology12060144 - 10 Jun 2025

Viewed by 505

Abstract

The objective of this study is to detect the locations of submarine groundwater discharge (SGD) in the coastal area of the El Jebha region, located in northwestern Morocco. It is hypothesized that this zone is fed by one of the most rain-rich karstic [...] Read more.

The objective of this study is to detect the locations of submarine groundwater discharge (SGD) in the coastal area of the El Jebha region, located in northwestern Morocco. It is hypothesized that this zone is fed by one of the most rain-rich karstic aquifers in Morocco (the Dorsale Calcaire). The region’s geology is complex, characterized by multiple faults and fractures. Thermal remote sensing is used in this study to locate potential SGD zones, as groundwater emerging from karst systems is typically cooler than surrounding ocean water. Landsat satellite imagery was used to assess temperature variations and detect anomalies associated with the presence of freshwater in the marine environment. El Jebha’s geographical location, with a direct interface between limestone and sea, makes it an ideal site for the appearance of submarine groundwater discharges. This study constitutes the first use of Landsat-8/9 thermal-infrared imagery, processed with a multi-temporal fuzzy-overlay method, to detect SGD. Out of 107 Landsat scenes reviewed, 16 cloud-free images were selected. The workflow identified 18 persistent cold anomalies, of which three were classified as high-probability SGD zones based on recurrence and spatial consistency. The results highlight several potential SGD zones, confirming the cost-effectiveness of thermal remote sensing in mapping thermal anomalies and opening up new perspectives for the study of SGD in Morocco, where these phenomena remain rarely documented. Full article

(This article belongs to the Topic Karst Environment and Global Change)

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19 pages, 1734 KiB

Open AccessArticle

Future Dynamics of Drought in Areas at Risk: An Interpretation of RCP Projections on a Regional Scale

by Pietro Monforte and Sebastiano Imposa

Hydrology 2025, 12(6), 143; https://doi.org/10.3390/hydrology12060143 - 9 Jun 2025

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Abstract

The Mediterranean region is currently experiencing the effects of a climate crisis, marked by an increase in the frequency and intensity of drought events. Climate variability has led to prolonged periods of drought, even in areas not traditionally classified as arid. These events [...] Read more.

The Mediterranean region is currently experiencing the effects of a climate crisis, marked by an increase in the frequency and intensity of drought events. Climate variability has led to prolonged periods of drought, even in areas not traditionally classified as arid. These events have significant impacts on water resources, agricultural productivity, and socioeconomic systems. This study investigates the evolution of meteorological, hydrological, and socioeconomic droughts using the Standardized Precipitation Index (SPI) at time scales of 3, 12, and 24 months in a Mediterranean region identified as particularly vulnerable to climate change. Observational data from local meteorological stations were used for the 1991–2020 baseline period. Future climate projections were derived from the MPI-ESM model under the RCP 4.5 and RCP 8.5 scenarios, extending to the year 2080. Data were aggregated on a 0.50° × 0.50° spatial grid and bias-corrected using linear scaling. The Kolmogorov–Smirnov test was applied to assess the statistical compatibility between observed and projected precipitation data. Results indicate a substantial decline in annual precipitation, with reductions of up to 20% under the RCP 8.5 scenario for the period 2051–2080, compared to the reference period. The frequency of severe and extreme drought events is projected to increase by 30–50% in several grid meshes, especially during summer. Conversely, altered weather patterns in other areas may increase the likelihood of flood events. This study identifies the grid meshes most vulnerable to drought, highlighting the urgent need for adaptive water management strategies to ensure agricultural sustainability and reduce the socioeconomic impacts of climate-induced drought. Full article

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27 pages, 9650 KiB

Open AccessArticle

Impact of Spatio-Temporal Variability of Droughts on Streamflow: A Remote-Sensing Approach Integrating Combined Drought Index

by Anoma Srimali, Luminda Gunawardhana, Janaka Bamunawala, Jeewanthi Sirisena and Lalith Rajapakse

Hydrology 2025, 12(6), 142; https://doi.org/10.3390/hydrology12060142 - 7 Jun 2025

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Abstract

Understanding how spatial drought variability influences streamflow is critical for sustainable water management under changing climate conditions. This study developed a novel Combined Drought Index (CDI) and a method to assess spatial drought impacts on different flow components by integrating remote sensing and [...] Read more.

Understanding how spatial drought variability influences streamflow is critical for sustainable water management under changing climate conditions. This study developed a novel Combined Drought Index (CDI) and a method to assess spatial drought impacts on different flow components by integrating remote sensing and hydrological modelling frameworks with generic applicability. The CDI was constructed using Principal Component Analysis to merge multiple standardized indicators: the Standardized Precipitation Evapotranspiration Index, Temperature Condition Index, Vegetation Condition Index, and Soil Moisture Condition Index. The developed framework was applied to the Giriulla sub-basin of the Maha Oya River Basin, Sri Lanka. The CDI strongly correlated with standardized streamflow with a Pearson correlation coefficient of 0.74 and successfully captured major drought and flood events between 2015 and 2023. A semi-distributed hydrological model was used to simulate streamflow variations across sub-catchments under varying drought conditions. Results show upstream sub-catchments were more sensitive to droughts, with sharper declines in specific discharge. Spatial drought variability had different impacts under high- and low-flow conditions: wetter sub-catchments contributed more during high flows, while resilience during low flows varied with catchment characteristics. This integrated approach provides a valuable framework that can be generically applicable for enhanced drought impact assessments. 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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20 pages, 3135 KiB

Open AccessArticle

Dynamics of Runoff Quantity in an Urbanizing Catchment: Implications for Runoff Management Using Nature-Based Retention Wetland

by Lihoun Teang, Kim N. Irvine, Lloyd H. C. Chua and Muhammad Usman

Hydrology 2025, 12(6), 141; https://doi.org/10.3390/hydrology12060141 - 6 Jun 2025

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Abstract

Rapid suburbanization can alter catchment flow regime and increase stormwater runoff, posing threats to sensitive ecosystems. Applications of Nature-based Solutions (NbS) have increasingly been adopted as part of integrated water management efforts to tackle the hydrological impact of urbanization with co-benefits for improved [...] Read more.

Rapid suburbanization can alter catchment flow regime and increase stormwater runoff, posing threats to sensitive ecosystems. Applications of Nature-based Solutions (NbS) have increasingly been adopted as part of integrated water management efforts to tackle the hydrological impact of urbanization with co-benefits for improved urban resilience, sustainability, and community well-being. However, the implementation of NbS can be hindered by gaps in performance assessment. This paper introduces a physically based dynamic modeling approach to assess the performance of a nature-based storage facility designed to capture excess runoff from an urbanizing catchment (Armstrong Creek catchment) in Geelong, Australia. The study adopts a numerical modelling approach, supported by extensive field monitoring of water levels over a 2.5-year period. The model provides a decision support tool for Geelong local government in managing stormwater runoff to protect Lake Connewarre, a Ramsar-listed wetland under the Port Phillip Bay (Western Shoreline) and Bellarine Peninsula. Runoff is currently managed via a set of operating rules governing gate operations that prevents flows into the ecological sensitive downstream waterbody from December to April (drier periods in summer and most of autumn). Comparison with observed water level data at three monitoring stations for a continuous simulation period of May 2022 to October 2024 demonstrates satisfactory to excellent model performance (NSE: 0.55–0.79, R²: 0.80–0.89, ISE rating: excellent). Between 1670 × 10³ m³ and 2770 × 10³ m³ of runoff was intercepted by the nature-based storage facility, representing a 56–70% reduction in stormwater discharge into Lake Connewarre. Our model development underscores the importance of understanding and incorporating user interventions (gate operations and emergency pumping) from the standard operation plan to better manage catchment runoff. As revealed by the seasonal flow analysis for consecutive years, adaptive runoff management practices, capable of responding to rainfall variability, should be incorporated. Full article

(This article belongs to the Special Issue Advances in Nature-Based Solutions for Hydrometeorological Risk Reduction)

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23 pages, 6853 KiB

Open AccessArticle

Application of the Groundwater Data Mapper Tool to Assess Storage Changes in a Groundwater-Driven Basin in the Klamath Watershed, Oregon, USA

by Daniel Shepard, Norman L. Jones and Gustavious P. Williams

Hydrology 2025, 12(6), 140; https://doi.org/10.3390/hydrology12060140 - 6 Jun 2025

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Abstract

Streamflow in the Upper Williamson Basin of the Klamath Watershed is groundwater dominated with year-to-year fluctuations in both volume and duration, including multi-year periods with no streamflow. The relationship between precipitation, groundwater, and streamflow is difficult to characterize because of the limited number [...] Read more.

Streamflow in the Upper Williamson Basin of the Klamath Watershed is groundwater dominated with year-to-year fluctuations in both volume and duration, including multi-year periods with no streamflow. The relationship between precipitation, groundwater, and streamflow is difficult to characterize because of the limited number of monitoring wells, large data gaps, and a unique geologic structure that controls flow. To understand why surface flow has ceased entirely, we use the Groundwater Data Mapper Tool to impute gaps in the well data using machine learning and open-source Earth observation data and then compute changes in groundwater storage over time. Our research confirms that groundwater storage is correlated to streamflow and finds that there is a control groundwater storage below which flow does not occur. Furthermore, we find that groundwater storage is correlated to rainfall with a three- to four-year delay. This lag and the geologic structural control mean that even with several years of above-average precipitation, live flow may take years to resume. This insight allows water managers to understand and adjust for this highly irregular streamflow for better management decisions. 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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15 pages, 5961 KiB

Open AccessArticle

Calibration and Validation of an Operational Method to Estimate Actual Evapotranspiration in Mediterranean Wetlands

by Luca Fibbi, Nicola Arriga, Marta Chiesi, Alessandro Dell’Acqua, Maurizio Pieri and Fabio Maselli

Hydrology 2025, 12(6), 139; https://doi.org/10.3390/hydrology12060139 - 5 Jun 2025

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Abstract

A semi-empirical method for estimating actual evapotranspiration (ETa) based on ancillary and NDVI data, named NDVI-Cws, is currently being refined for improved applicability to wetlands. The investigation, in particular, addresses the case of semi-natural ecosystems where the impact of meteorological water stress (WS) [...] Read more.

A semi-empirical method for estimating actual evapotranspiration (ETa) based on ancillary and NDVI data, named NDVI-Cws, is currently being refined for improved applicability to wetlands. The investigation, in particular, addresses the case of semi-natural ecosystems where the impact of meteorological water stress (WS) is limited by groundwater resources. To adapt to this situation, the application of the NDVI-Cws method is preceded by a calibration phase based on spatially enhanced Land Surface Analysis Satellite Application Facility (LSA SAF) evapotranspiration products. This calibration is currently performed in the main wetlands of Tuscany (Central Italy) identified in the Ramsar Convention. The calibrated NDVI-Cws version is then applied to all regional Ramsar areas, yielding outputs that are first examined all over Tuscany. Next, the model estimates are quantitatively assessed versus ETa observations taken in a forest and a grassland Ramsar site. The results of these independent tests show the improvement achieved by the calibration phase with respect to the original model version. This supports the potential of the refined NDVI-Cws method to yield reasonably accurate daily ETa estimates for wetlands at a spatial resolution that is mainly dependent on the NDVI data used. Full article

(This article belongs to the Special Issue GIS Modelling of Evapotranspiration with Remote Sensing)

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25 pages, 4968 KiB

Open AccessArticle

Impact of Precipitation Uncertainty on Flood Hazard Assessment in the Oueme River Basin

by Dognon Jules Afféwé, Fabian Merk, Marleine Bodjrènou, Manuel Rauch, Muhammad Nabeel Usman, Jean Hounkpè, Jan-Geert Bliefernicht, Aristide B. Akpo, Markus Disse and Julien Adounkpè

Hydrology 2025, 12(6), 138; https://doi.org/10.3390/hydrology12060138 - 4 Jun 2025

Viewed by 909

Abstract

This study evaluates the impact of precipitation ensembles on flood hazards in the Ouémé River Basin by coupling the hydrological HBV and hydrodynamic HEC–RAS model. Both models were calibrated and validated to simulate hydrological and hydraulic processes. Meteorological and hydrometric data from 1994 [...] Read more.

This study evaluates the impact of precipitation ensembles on flood hazards in the Ouémé River Basin by coupling the hydrological HBV and hydrodynamic HEC–RAS model. Both models were calibrated and validated to simulate hydrological and hydraulic processes. Meteorological and hydrometric data from 1994 to 2016, along with flood maps and DEM are used. Evapotranspiration data are calculated using Hargreaves–Samani formula. The coupling HBV–HEC–RAS models enabled the generation of ensemble hydrographs, flood maps, flood probability maps and additional statistics in West Africa for the first time, offering a comprehensive understanding of flood dynamics under uncertainty. Ensemble hydrographs and maps obtained enhance decision-making by showing discharge scenarios, spatial flood variability, prediction reliability, and probabilities, supporting targeted flood management and resource planning under uncertainty. The findings underline the need for a comprehensive strategy to mitigate both common and rare flood events while accounting for spatial uncertainties inherent in hydrological and hydraulic modeling. Full article

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24 pages, 2384 KiB

Open AccessArticle

An Application of the Ecosystem Services Assessment Approach to the Provision of Groundwater for Human Supply and Aquifer Management Support

by Malgorzata Borowiecka, Mar Alcaraz and Marisol Manzano

Hydrology 2025, 12(6), 137; https://doi.org/10.3390/hydrology12060137 - 3 Jun 2025

Viewed by 756

Abstract

Increasing pressures on groundwater in the last decades have led to a deterioration in the quality of groundwater for human consumption around the world. Beyond the essential evaluation of groundwater dynamics and quality, analyzing the situation from the perspective of the Ecosystem Services [...] Read more.

Increasing pressures on groundwater in the last decades have led to a deterioration in the quality of groundwater for human consumption around the world. Beyond the essential evaluation of groundwater dynamics and quality, analyzing the situation from the perspective of the Ecosystem Services Assessment (ESA) approach can be useful to support aquifer management plans aiming to recover aquifers’ capacity to provide good quality water. This work illustrates how to implement the ESA using groundwater flow and nitrate transport modelling for evaluating future trends of the provisioning service Groundwater of Good Quality for Human Supply. It has been applied to the Medina del Campo Groundwater Body (Spain), where the intensification of agricultural activities and groundwater exploitation since the 1970s caused severe nitrate pollution. Nitrate status and future trends under different fertilizer and aquifer exploitation scenarios were modelled with MT3DMS coupled to a MODFLOW model calibrated with piezometric time series. Historical land use and fertilizer data were compiled to assess nitrogen loadings. Besides the uncertainties of the model, the results clearly show that: (i) managing fertilizer loads is more effective than managing aquifer exploitation; and (ii) only the cessation of nitrogen application by the year 2030 would improve the evaluated provisioning service in the long term. The study illustrates how the ESA can be incorporated to evaluate the expected relative impact of different management actions aimed at improving significant groundwater services to humans. 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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22 pages, 11891 KiB

Open AccessArticle

Evaluation of Rainfall Distribution Based on the Precipitation Concentration Index: A Case Study over the Selected Summer Rainfall Regions of South Africa

by Christina M. Botai, Joel O. Botai, Mxolisi B. Mukhawana, Jaco de Wit, Ndumiso S. Masilela, Nosipho Zwane and Henerica Tazvinga

Hydrology 2025, 12(6), 136; https://doi.org/10.3390/hydrology12060136 - 3 Jun 2025

Viewed by 631

Abstract

The Precipitation Concentration Index (PCI) is considered a powerful tool that can be used to analyse the spatial and temporal distribution and variability of precipitation over a region. It plays a significant role in planning and managing water resources, including monitoring and forecasting [...] Read more.

The Precipitation Concentration Index (PCI) is considered a powerful tool that can be used to analyse the spatial and temporal distribution and variability of precipitation over a region. It plays a significant role in planning and managing water resources, including monitoring and forecasting drought and flood risks. As such, the present study used the PCI to investigate the spatio-temporal distribution of precipitation in summer rainfall regions covering six selected South African provinces. Specifically, this study analysed monthly precipitation data from 49 rainfall districts spanning from 1979 to 2023 and assessed the spatio-temporal variability patterns of annual, seasonal and supra-seasonal PCI values and their trends based on the Mann–Kendall trend test. Pearson’s correlation was used to evaluate the relationship between the PCI values and precipitation across the provinces. Moderate annual PCI values were observed mainly in KwaZulu-Natal and the eastern regions of the Free State and Mpumalanga provinces. A large portion of the study site exhibited irregular annual precipitation concentrations. The PCI decreased by −1.5 and −1.2 magnitudes of change during 1979–1989 and 2000–2011 and increased by 2.1 and 2.8 magnitudes between 1990–2000 and 2012–2023, respectively. Uniform precipitation concentration was mostly recorded during the December–January–February (DJF) season. The entire study area recorded moderate precipitation concentration during the March–April–May (MAM) and September–October–November (SON) seasons (with exceptions for KwaZulu-Natal (KZN)). In addition, irregular precipitation concentration dominated during the June–July–August (JJA) rainy season. All provinces except KZN recorded positive trends in annual PCI. Also, positive trends in PCI were observed during the supra-wet season across the provinces, except KZN and in parts of the Free State. Furthermore, negative trends in seasonal PCI were mostly dominant during DJF and MAM, while positive trends were mostly observed during SON and JJA rainy seasons. The annual PCI values were positively correlated with annual precipitation in KZN, Free State and Limpopo, while negative correlations were observed in Mpumalanga and North West provinces. The results presented in this study contribute to drought and flood monitoring in support of water resource management and planning. Full article

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17 pages, 6573 KiB

Open AccessArticle

Balancing Hydrological Sustainability and Heritage Conservation: A Decadal Analysis of Water-Yield Dynamics in the Honghe Hani Rice Terraces

by Linlin Huang, Yunting Lyu, Linxuan Miao and Sen Li

Hydrology 2025, 12(6), 135; https://doi.org/10.3390/hydrology12060135 - 31 May 2025

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Abstract

The Honghe Hani Rice Terraces, a UNESCO World Heritage agroecosystem, embody a millennia-old synergy of cultural heritage and ecological resilience, yet face declining water yields amid land-use intensification and climate variability. This study employs the InVEST model and geographic detector analysis to quantify [...] Read more.

The Honghe Hani Rice Terraces, a UNESCO World Heritage agroecosystem, embody a millennia-old synergy of cultural heritage and ecological resilience, yet face declining water yields amid land-use intensification and climate variability. This study employs the InVEST model and geographic detector analysis to quantify water-yield dynamics from 2010 to 2020 and identify their spatial and mechanistic drivers. Annual water yield averaged 558 mm, with cultivated lands contributing 33% of total volume, while built-up areas reached 980 mm per unit in 2018. A 31% decline by 2020, driven by cropland fragmentation and tourism growth, revealed persistent-yield hotspots in forested central-eastern terraces and cold spots in southwestern dryland margins. Land-use pattern accounted for 80–95% of yield variability, exacerbated by temperature interactions. Forests, delivering 68.7 million m³ over the decade, highlight the hydrological significance of traditional landscape mosaics. These findings advocate reforestation in critical recharge zones, terrace restoration to preserve agroecological integrity, and regulated tourism integrating rainwater harvesting to sustain water security and cultural heritage. By blending hydrological modeling with socio-cultural insights, this study provides a scalable framework for safeguarding terraced agroecosystems worldwide, aligning heritage conservation with sustainable development. 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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20 pages, 5405 KiB

Open AccessArticle

Assessing the Risk of Natural and Socioeconomic Hazards Caused by Rainfall in the Middle Yellow River Basin

by Yufeng Zhao, Shun Xiao, Xinshuang Wu, Shuitao Guo and Yingying Yao

Hydrology 2025, 12(6), 134; https://doi.org/10.3390/hydrology12060134 - 29 May 2025

Viewed by 592

Abstract

Extreme rainfall events directly increase flood risks and further trigger environmental geological hazards (i.e., landslides and debris flows). Meanwhile, rainfall-induced risks are determined by climate and geographical factors and spatial socioeconomic factors (e.g., population density and gross domestic product). However, the middle stream [...] Read more.

Extreme rainfall events directly increase flood risks and further trigger environmental geological hazards (i.e., landslides and debris flows). Meanwhile, rainfall-induced risks are determined by climate and geographical factors and spatial socioeconomic factors (e.g., population density and gross domestic product). However, the middle stream of Yellow River Basin, where geological hazards frequently occur, lacks systematic analyses of rainfall-induced risks. In this study, we propose a comprehensive quantification framework and apply it to the Loess Plateau of northern China based on 40 years of climate data, streamflow measurements, and multiple spatial and geographical attribute datasets. A deep learning algorithm of long short-term memory (LSTM) was used to predict runoff, and the analytic hierarchy index was utilized to evaluate the comprehensive spatial risk considering natural and socioeconomic factors. Despite a decrease in annual precipitation in our study area of 1.46 mm per year, the intensity of heavy rainfall has increased since the 1980s, characterized by increases in rainstorm intensity (+4.68%), rainfall intensity (+7.07%), and rainfall amount (+5.34%). A comprehensive risk assessment indicated that high-risk areas accounted for 20.30% of the total area, with rainfall, geographical factors, and socioeconomic variables accounting for 53.90%, 29.72%, and 16.38% of risk areas, respectively. Rainfall was the dominant factor that determined the risk, and geographical and socioeconomic properties characterized the vulnerability and resilience of disasters. Our study provided an evaluation framework for multi-hazard risk assessment and insights for the development of disaster prevention and reduction policies. Full article

(This article belongs to the Special Issue Advances in the Measurement, Utility and Evaluation of Precipitation Observations)

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18 pages, 3073 KiB

Open AccessReview

Enhancing Flood Risk Management: A Review on Numerical Modelling of Past Flood Events

by José González-Cao, Helena Barreiro-Fonta, Diego Fernández-Nóvoa and Orlando García-Feal

Hydrology 2025, 12(6), 133; https://doi.org/10.3390/hydrology12060133 - 29 May 2025

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Abstract

Recent scientific literature has consistently highlighted a significant increase in both the frequency and intensity of flood events, primarily attributed to the effects of climate change. Projections suggest that this trend will likely intensify in the coming decades. In this context, enhancing our [...] Read more.

Recent scientific literature has consistently highlighted a significant increase in both the frequency and intensity of flood events, primarily attributed to the effects of climate change. Projections suggest that this trend will likely intensify in the coming decades. In this context, enhancing our understanding of flooding dynamics becomes not only necessary but urgent. A critical component of this advancement lies in the numerical analysis of historical flood events, which provides valuable insights into flood behaviour across extended temporal and spatial scales. This approach enables two key outcomes: a significant improvement in conventional methods for estimating return periods and a reduction in the uncertainties associated with historical flood events by simulating multiple plausible scenarios to identify the most likely one. This paper presents a comprehensive review of the scientific literature focused on the numerical simulation and reconstruction of past flood events. Two main conclusions emerge from this review: First, the temporal scope of the studies is notably wide, covering events ranging from glacial periods to those occurring in the mid-20th century. Second, there exists a pronounced spatial imbalance in the geographical distribution of these studies, with certain regions significantly underrepresented. This review provides a valuable resource for researchers and practitioners working in flood risk assessment and hydrological modelling. By consolidating existing knowledge, it supports the development and refinement of decision-support tools aimed at improving mitigation strategies to reduce the impact of flooding on both populations and infrastructure. Full article

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20 pages, 9562 KiB

Open AccessArticle

Study on the Surface Water Chemical Composition and Water Quality Pollution Characteristics of the Shiyang River Basin, China

by Haifeng Wang, Shaoqing Wu, Jihai Xu, Lixia Zhang, Kuijing Li, Jisheng Li, Heping Shu and Jihua Chu

Hydrology 2025, 12(6), 132; https://doi.org/10.3390/hydrology12060132 - 29 May 2025

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Abstract

The surface water quality issue in arid regions is becoming increasingly severe and has become a significant challenge for global environmental protection and water resource management. By continuously collecting surface water samples (2000~2024) and utilizing hydrochemical and principal component analysis, the changes in [...] Read more.

The surface water quality issue in arid regions is becoming increasingly severe and has become a significant challenge for global environmental protection and water resource management. By continuously collecting surface water samples (2000~2024) and utilizing hydrochemical and principal component analysis, the changes in the chemical composition of surface water and its water quality pollution characteristics are examined in the Shiyang River Basin. The surface water anion concentrations are characterized by HCO₃⁻ > SO₄²⁻ > Cl⁻, with average concentrations of 214.11 mg/L, 117.31 mg/L, and 21.61 mg/L, respectively. The cation concentrations follow the trend of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺, with average concentrations of 56.22 mg/L, 33.75 mg/L, 22.91 mg/L, and 5.33 mg/L, respectively. The dominant water types are Ca-HCO₃ and Ca (Mg)-HCO₃ in the mountainous area and in the plains, respectively. The weathering of carbonates and silicates is the main controlling factor for the evolution process of surface water. Strong evaporation leads to significant differences in ion concentrations, which is manifested as low in mountainous areas and high in plain areas. In addition, the surface water quality in the plains is worse than that of the mountainous areas. The main pollution indicators include DO, CODM_n, COD, BOD₅, NH₄⁺-N, TP, TN, and fecal coliforms. The surface water quality of Hongyashan Reservoir and Caiqi has improved significantly, reflecting the impact of the water diversion project. The results of this study are of great significance for improving water resource management and ensuring the sustainability of the ecological environment in arid regions. Full article

(This article belongs to the Special Issue Hydrodynamics and Water Quality of Rivers and Lakes)

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25 pages, 6290 KiB

Open AccessArticle

Precipitation-Related Atmospheric Nutrient Deposition in Farmington Bay: Analysis of Spatial and Temporal Patterns

by Gustavious P. Williams, A. Woodruff Miller, Amin Aghababaei, Abin Raj Chapagain, Pitamber Wagle, Yubin Baaniya, Rachel H. Magoffin, Xueyi Li, Taylor Miskin, Peter D. Oldham, Samuel J. Oldham, Tyler Peterson, Lyle Prince, Kaylee B. Tanner, Anna C. Cardall and Daniel P. Ames

Hydrology 2025, 12(6), 131; https://doi.org/10.3390/hydrology12060131 - 27 May 2025

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Abstract

This study quantifies the atmospheric deposition (AD) of nutrient loads into the Farmington Bay ecosystem via wet deposition over a three-year period. We analyzed nutrient concentrations from 509 total phosphorus (TP), 507 orthophosphate (OP), and 511 total nitrogen (TN) samples collected at seven [...] Read more.

This study quantifies the atmospheric deposition (AD) of nutrient loads into the Farmington Bay ecosystem via wet deposition over a three-year period. We analyzed nutrient concentrations from 509 total phosphorus (TP), 507 orthophosphate (OP), and 511 total nitrogen (TN) samples collected at seven locations around the Bay. We estimated AD loads using two different spatial interpolation methods, Kriging and Inverse Distance Weighting (IDW), as well as average concentrations. The loads computed using Kriging and IDW were similar, but the loads computed using sample averages were about 70% smaller. We estimated that annual atmospherically deposited nutrient loads range from 306 to 594 Mg for TN, 73 to 195 Mg for TP, and 43 to 144 Mg for OP. The loads in 2023 were significantly higher than those in 2021 and 2022, a phenomenon we attribute to higher precipitation and a major loading event that occurred on 13 April 2023. Based on comparison with studies concerning nearby Utah Lake, the total loads could be two to three times larger than our estimates. These studies suggest that fine particulate matter may significantly contribute to AD nutrient loads, but these loads are not captured by our sampling method. However, the inclusion of non-water surfaces in Farmington Bay may mitigate this difference. Full article

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22 pages, 3320 KiB

Open AccessArticle

Modeling Estuarine Algal Bloom Dynamics with Satellite Data and Spectral Index-Based Classification

by Mayya Podsosonnaya, Maria J. Schreider and Sergei Schreider

Hydrology 2025, 12(6), 130; https://doi.org/10.3390/hydrology12060130 - 26 May 2025

Viewed by 1094

Abstract

Macroalgae are an integral part of estuarine primary production; however, their excessive growth may have severe negative impacts on the ecosystem. Although it is generally believed that algal blooms may be caused by a combination of excessive nutrients and temperature, their occurrences are [...] Read more.

Macroalgae are an integral part of estuarine primary production; however, their excessive growth may have severe negative impacts on the ecosystem. Although it is generally believed that algal blooms may be caused by a combination of excessive nutrients and temperature, their occurrences are hard to predict, and quantitative monitoring is a logistical challenge which requires the development of reliable and inexpensive techniques. This can be achieved by implementation of processing algorithms and indices on multi-spectral satellite images. Tuggerah Lakes estuary on the Central Coast of NSW was studied because of the regular occurrences of blooms, primarily of green filamentous algae. The detection of algal blooms based on the red-edge effect of the chlorophyll provided consistent results supported by direct observations. The Floating Algae Index (FAI) was identified as the most accurate index for detecting algal blooms in shallow areas, following a comparative analysis of six commonly used algae detection indices. Logistic regression was implemented where FAI was used as a predictor of two clusters, “bloom” and “non-bloom”. FAI was calculated for multi-spectral satellite images based on pixels of 20 × 20 m, covering the entire area of the Tuggerah Lakes. Seven sample points (pixels) were chosen, and the optimal threshold was found for each pixel to assign it to one of the two clusters. The logistic regression model was trained for each pixel; then the optimal parameters for its coefficients and the optimal classification threshold were obtained by cross-validation based on bootstrapping. Probabilities for classifying clusters as either “bloom” or “non-bloom” were predicted with respect to the optimal threshold. The resulting model can be used to estimate probability of macroalgal blooms in coastal estuaries, allowing quantitative monitoring through time and space. 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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