Hydrology

11 pages, 2322 KiB

Open AccessArticle

Impact of Gravel Pits on Water Quality in Alluvial Aquifers

by Igor Karlović, Tamara Marković, Andrew C. Smith and Krešimir Maldini

Hydrology 2023, 10(4), 99; https://doi.org/10.3390/hydrology10040099 - 21 Apr 2023

Cited by 1 | Viewed by 3325

Gravel pits are considered potentially hazardous in terms of groundwater quality protection as they represent an open part of the aquifer system, increasing the aquifer’s vulnerability to contamination from the surface. The aim of this research was to determine the biogeochemical processes in [...] Read more.

Gravel pits are considered potentially hazardous in terms of groundwater quality protection as they represent an open part of the aquifer system, increasing the aquifer’s vulnerability to contamination from the surface. The aim of this research was to determine the biogeochemical processes in gravel pits that have a positive effect on the groundwater quality in the alluvial aquifer in NW Croatia. The aquifer is situated below developed agricultural land, with high groundwater nitrate concentrations having been recorded over the last decades. The differences between two gravel pits and the surrounding groundwater were studied using in situ, hydrochemical, and isotopic parameters (δ¹⁵N-NO₃ and δ¹⁸O-NO₃), together with existing microbial data. The analyses of nitrogen species indicated that nitrate attenuation processes take place in gravel pits. Bacterial denitrification and nitrate uptake by algae were responsible for significant decreases in nitrate concentration. These processes were more effective in the inactive gravel pit, which has a longer water residence time and during warm periods, when microbial biomass, abundance, and activity were high. The seasonally variable microbial activity also affected trace metals, removing them from groundwater, possibly through the biosorption of metal ions. The presented research shows that the observed biogeochemical processes are associated with seasonal changes that affect the types and number of microbial communities and the chemical composition of water, resulting in gravel pits being groundwater remediation points. Full article

(This article belongs to the Special Issue Novel Approaches in Contaminant Hydrology and Groundwater Remediation)

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12 pages, 2066 KiB

Open AccessArticle

Thermally Enhanced Spreading of Miscible Plumes in Porous Media

by Ryan G. Tigera, Whitney L. Benson and David C. Mays

Hydrology 2023, 10(4), 98; https://doi.org/10.3390/hydrology10040098 - 21 Apr 2023

Viewed by 1267

Abstract

In situ groundwater remediation often calls for a chemical or biological amendment to be injected as an aqueous solution into a contaminated groundwater aquifer. Accordingly, remediation depends on mixing the amendment into the contaminated groundwater, which, in turn, depends on spreading the plume [...] Read more.

In situ groundwater remediation often calls for a chemical or biological amendment to be injected as an aqueous solution into a contaminated groundwater aquifer. Accordingly, remediation depends on mixing the amendment into the contaminated groundwater, which, in turn, depends on spreading the plume of the injected amendment effectively. Here, we present proof-of-principle results from a laboratory study showing that amendment plume spreading can be enhanced by heating the injected water, which is consistent with the mechanism of miscible viscous fingering. The heated water has a lower viscosity, rendering a mobility ratio (i.e., log viscosity ratio) of 1.2 that generates elongated plume perimeters for essentially consistent plume areas. Using a quasi-two-dimensional apparatus and recording photographs after each increment of the injection volume, two image analysis techniques were employed to measure the area and perimeter of the injected plume, and the results are compared to isothermal controls, showing that the plume perimeter increased by 47% when determined by binary image analysis or 56% when determined by morphological image analysis. Accordingly, this study offers evidence that heating the injected water enhances miscible plume spreading in porous media. Full article

(This article belongs to the Special Issue Novel Approaches in Contaminant Hydrology and Groundwater Remediation)

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12 pages, 2106 KiB

Open AccessArticle

Rainfall Partitioning in Amazon Forest: Implications of Reduced Impact Logging on Litter Water Conservation

by Jeferson Alberto de Lima and Kelly Cristina Tonello

Hydrology 2023, 10(4), 97; https://doi.org/10.3390/hydrology10040097 - 21 Apr 2023

Cited by 2 | Viewed by 1566

Abstract

This study aimed to investigate how sustainable forest management can affect litter hydrological properties. We investigated the net precipitation, litter mass, water-holding capacity, effective water-holding and retention capacity, maximum water retention and water content in unlogged and logged forests over 13 months in [...] Read more.

This study aimed to investigate how sustainable forest management can affect litter hydrological properties. We investigated the net precipitation, litter mass, water-holding capacity, effective water-holding and retention capacity, maximum water retention and water content in unlogged and logged forests over 13 months in the Amazon Forest, where reduced-impact logging is allowed. The mean litter mass was similar for unlogged and logged forests. The litter water-holding capacity was 220% for unlogged and 224% for logged forests, and for fractions followed: unstructured > leaves > seeds > branches for both forests. The effective water-holding capacity was 48.7% and 49.3% for unlogged and logged, respectively, and the effective water retention was 10.3 t·ha⁻¹ for both forests. The effective water retention in the rainy and dry seasons accounted for 12.5 t ha⁻¹ and 7.2 t ha⁻¹ for unlogged and logged, respectively. The maximum water retention was slightly greater for logged forests (16.7 t ha⁻¹) than unlogged (16.3 t ha⁻¹). The litter water content had 40% less water in the dry season than in the rainy in both forests. In general, there were no significant differences in litter storage and hydrological properties between stands. This suggests that reduced-impact logging did not significantly affect the hydrological dynamics of the litter layer in the Amazonian forests studied. Full article

(This article belongs to the Topic Hydrology and Water Resources in Agriculture and Ecology)

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17 pages, 2534 KiB

Open AccessArticle

Mapping Projected Variations of Temperature and Precipitation Due to Climate Change in Venezuela

by Jesús A. Viloria, Barlin O. Olivares, Pedro García, Franklin Paredes-Trejo and Aníbal Rosales

Hydrology 2023, 10(4), 96; https://doi.org/10.3390/hydrology10040096 - 17 Apr 2023

Cited by 3 | Viewed by 3804

Abstract

The impacts of climate change will not be homogeneous in all countries or between regions within each country. Mapping projected changes in temperature and precipitation is crucial for formulating region-specific agricultural adaptation measures. The spatial variation of projected changes in temperature and annual [...] Read more.

The impacts of climate change will not be homogeneous in all countries or between regions within each country. Mapping projected changes in temperature and precipitation is crucial for formulating region-specific agricultural adaptation measures. The spatial variation of projected changes in temperature and annual precipitation for 1970–2000 and 2041–2060 in Venezuela was analyzed using the WorldClim 2.1 data. Both variables have been analyzed in fourteen physiographic regions that differ in climate, geology, geomorphology, soils, and land use. The results reveal that western regions experience higher temperature increases, while the regions located in the east and center of the country are projected to experience greater decreases in rainfall. Likewise, temperature and precipitation will increase from north to south. Thus, there are differences in how different regions will be affected by variations in temperature and annual precipitation associated with climate change. It is concluded that physiographic regions can be used as large spatial units to plan future land use and design agricultural adaptation measures to climate change at the national scale. Full article

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18 pages, 29981 KiB

Open AccessArticle

A Machine-Learning Framework for Modeling and Predicting Monthly Streamflow Time Series

by Hatef Dastour and Quazi K. Hassan

Hydrology 2023, 10(4), 95; https://doi.org/10.3390/hydrology10040095 - 17 Apr 2023

Cited by 1 | Viewed by 1813

Abstract

Having a complete hydrological time series is crucial for water-resources management and modeling. However, this can pose a challenge in data-scarce environments where data gaps are widespread. In such situations, recurring data gaps can lead to unfavorable outcomes such as loss of critical [...] Read more.

Having a complete hydrological time series is crucial for water-resources management and modeling. However, this can pose a challenge in data-scarce environments where data gaps are widespread. In such situations, recurring data gaps can lead to unfavorable outcomes such as loss of critical information, ineffective model calibration, inaccurate timing of peak flows, and biased statistical analysis in various applications. Despite its importance, predicting monthly streamflow can be a complex task due to its connection to random dynamics and uncertain phenomena, posing significant challenges. This study introduces an ensemble machine-learning regression framework for modeling and predicting monthly streamflow time series with a high degree of accuracy. The framework utilizes historical data from multiple monthly streamflow datasets in the same region to predict missing monthly streamflow data. The framework selects the best features from all available gap-free monthly streamflow time-series combinations and identifies the optimal model from a pool of 12 machine-learning models, including random forest regression, gradient boosting regression, and extra trees regressor, among others. The model selection is based on cross-validation train-and-test set scores, as well as the coefficient of determination. We conducted modeling on 26 monthly streamflow time series and found that the gradient boosting regressor with bagging regressor produced the highest accuracy in 7 of the 26 instances. Across all instances, the models using this method exhibited an overall accuracy range of 0.9737 to 0.9968. Additionally, the use of either a bagging regressor or an AdaBoost regressor improved both the tree-based and gradient-based models, resulting in these methods accounting for nearly 80% of the best models. Between January 1960 and December 2021, an average of 40% of the monthly streamflow data was missing for each of the 26 stations. Notably, two crucial stations located in the economically significant lower Athabasca Basin River in Alberta province, Canada, had approximately 70% of their monthly streamflow data missing. To address this issue, we employed our framework to accurately extend the missing data for all 26 stations. These accurate extensions also allow for further analysis, including grouping stations with similar monthly streamflow behavior using Pearson correlation. Full article

(This article belongs to the Special Issue Traditional Statistics vs. Modern Machine Learning Approaches in Hydrology)

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19 pages, 7546 KiB

Open AccessEditor’s ChoiceArticle

Application of Running Water-Type Retarding Basin to Old Kinu River Floodplain, Japan

by Tadaharu Ishikawa and Ryosuke Akoh

Hydrology 2023, 10(4), 94; https://doi.org/10.3390/hydrology10040094 - 15 Apr 2023

Cited by 1 | Viewed by 1370

Abstract

In the upper and middle reaches of rivers in Japan, river channels used to meander in a comparatively narrow floodplain and heavy rain runoff used to naturally expand over the entire floodplain, retarding floods toward the downstream. Recent continuous levee building to prevent [...] Read more.

In the upper and middle reaches of rivers in Japan, river channels used to meander in a comparatively narrow floodplain and heavy rain runoff used to naturally expand over the entire floodplain, retarding floods toward the downstream. Recent continuous levee building to prevent river overflow has had two kinds of negative effects, namely an increase in flood damage in areas of a floodplain closed by levees and river terraces at the time of runoff over the river channel capacity, and an increase in the flood peak toward the downstream. This study introduces the concept of a running water-type retarding basin that mitigates flood damage by allowing excess runoff to pass through the floodplain, restoring a natural hydrological process. After a description of the concept of the facility design, a design example is presented for a closed floodplain of the Kinu River Floodplain, where excess runoff caused severe flood damage in 2015, to quantify the performance and effects of the running water-type retarding basin. Full article

(This article belongs to the Special Issue Flood Inundation Mapping in Hydrological Systems)

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20 pages, 3120 KiB

Open AccessArticle

Temporal Variations in Temperature and Moisture Soil Profiles in a Mediterranean Maquis Forest in Greece

by Athanassios Bourletsikas, Nikolaos Proutsos, Panagiotis Michopoulos and Ioannis Argyrokastritis

Hydrology 2023, 10(4), 93; https://doi.org/10.3390/hydrology10040093 - 14 Apr 2023

Cited by 5 | Viewed by 1682

Abstract

Soil moisture (SM) and temperature (ST) are critical factors in forest eco-hydrological research. In this study, we investigated the inter- and intra-annual changes in SM and ST profiles in a mixed Mediterranean maquis forest stand together with soil and meteorological parameters. Hourly data [...] Read more.

Soil moisture (SM) and temperature (ST) are critical factors in forest eco-hydrological research. In this study, we investigated the inter- and intra-annual changes in SM and ST profiles in a mixed Mediterranean maquis forest stand together with soil and meteorological parameters. Hourly data from three field measurements points at four depths (−5, −20, −40 and −70 cm) for 6 years were interpolated using the kriging method to produce annual SM and ST profiles. The results indicate that air temperature highly affects the upper 5 cm of the mineral soil. In general, it increases with depth in winter at an average rate of 0.036 °C/cm and decreases in summer (0.035 °C/cm), presenting higher values compared to air temperature from April to August and lower ones during the rest of the period. Precipitation is the main factor driving SM variations up to a superficial soil depth of 40 cm. The upper soil layer (0–40 cm) infiltrates water faster and presents high SM variability, especially in monthly and seasonal (year to year) time steps. The maquis forest stands are likely to be strongly affected by climate change, therefore the results of this study could be useful in hydrological and climate change studies focused on maquis vegetation water management. Full article

(This article belongs to the Special Issue Forest Hydrometeorology)

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12 pages, 1931 KiB

Open AccessArticle

Spatial Variability of Best Management Practices Effectiveness on Water Quality within the Yazoo River Watershed

by Vivek Venishetty, Prem B. Parajuli and Dipesh Nepal

Hydrology 2023, 10(4), 92; https://doi.org/10.3390/hydrology10040092 - 14 Apr 2023

Viewed by 1393

Abstract

Best management practices (BMPs) are management operations that reduce pollution and improve water quality. This study assessed the spatial variability of BMPs effectiveness within the Yazoo River Watershed (YRW) using Soil and Water Assessment Tool (SWAT). Two field-scale watersheds, Merigold Watershed (MW) from [...] Read more.

Best management practices (BMPs) are management operations that reduce pollution and improve water quality. This study assessed the spatial variability of BMPs effectiveness within the Yazoo River Watershed (YRW) using Soil and Water Assessment Tool (SWAT). Two field-scale watersheds, Merigold Watershed (MW) from the Delta and Skuna River Watershed (SRW) in the Bluff Hills, were selected within the YRW. The SWAT model was calibrated and validated for monthly streamflow, and daily total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). Monthly evaluated streamflow Nash–Sutcliffe efficiency indices were in the range from 0.60 to 0.86; daily evaluated TSS indices were in the range from 0.11 to 0.15, TN from 0.11 to 0.12, and TP from 0.05 to 0.26 during model calibration and validation periods. BMPs were implemented in MW and SRW to analyze the spatial variability effect on water quality. Cover crops (CC), vegetative filter strips (VFS), and a combination of VFS and CC were applied as BMP scenarios. Overall, a larger reduction in streamflow was about 15%, sediment about 26%, and nutrient loads, which was about 39% (TN) and 50% (TP), was determined in the MW, whereas in the large watershed (YRW) the reductions in streamflow, sediment, TN, and TP loads were about 4%, 5%, 30%, and 24%, respectively. Therefore, the novelty of this research is to compare the efficiency of a BMP in pollutant reduction at two different geographic scales. The results from this study could help farmers, scientific researchers, precision management planning, and implementing agencies select appropriate BMP for field-scale water resources management in minimizing sediment and nutrient quantities in surface water. Full article

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27 pages, 16811 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Evaluation of Various Resolution DEMs in Flood Risk Assessment and Practical Rules for Flood Mapping in Data-Scarce Geospatial Areas: A Case Study in Thessaly, Greece

by Nikolaos Xafoulis, Yiannis Kontos, Evangelia Farsirotou, Spyridon Kotsopoulos, Konstantinos Perifanos, Nikolaos Alamanis, Dimitrios Dedousis and Konstantinos Katsifarakis

Hydrology 2023, 10(4), 91; https://doi.org/10.3390/hydrology10040091 - 12 Apr 2023

Cited by 7 | Viewed by 2681

Abstract

Floods are lethal and destructive natural hazards. The Mediterranean, including Greece, has recently experienced many flood events (e.g., Medicanes Zorbas and Ianos), while climate change results in more frequent and intense flood events. Accurate flood mapping in river areas is crucial for flood [...] Read more.

Floods are lethal and destructive natural hazards. The Mediterranean, including Greece, has recently experienced many flood events (e.g., Medicanes Zorbas and Ianos), while climate change results in more frequent and intense flood events. Accurate flood mapping in river areas is crucial for flood risk assessment, planning mitigation measures, protecting existing infrastructure, and sustainable planning. The accuracy of results is affected by all simplifying assumptions concerning the conceptual and numerical model implemented and the quality of geospatial data used (Digital Terrain Models—DTMs). The current research investigates flood modelling sensitivity against geospatial data accuracy using the following DTM resolutions in a mountainous river sub-basin of Thessaly’s Water District (Greece): (a) open 5 m and (b) 2 m data from Hellenic Cadastre (HC) and (c) 0.05 m data from an Unmanned Aerial Vehicle (UAV) topographical mission. RAS-Mapper and HEC-RAS are used for 1D (steady state) hydraulic simulation regarding a 1000-year return period. Results include flood maps and cross section-specific flow characteristics. They are analysed in a graphical flood map-based empirical fashion, whereas a statistical analysis based on the correlation matrix and a more sophisticated Machine Learning analysis based on the interpretation of nonlinear relationships between input–output variables support and particularise the conclusions in a quantifiable manner. Full article

(This article belongs to the Special Issue Modern Developments in Flood Modelling)

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18 pages, 6697 KiB

Open AccessEditor’s ChoiceArticle

Development of Multi-Inflow Prediction Ensemble Model Based on Auto-Sklearn Using Combined Approach: Case Study of Soyang River Dam

by Seoro Lee, Jonggun Kim, Joo Hyun Bae, Gwanjae Lee, Dongseok Yang, Jiyeong Hong and Kyoung Jae Lim

Hydrology 2023, 10(4), 90; https://doi.org/10.3390/hydrology10040090 - 11 Apr 2023

Cited by 4 | Viewed by 1476

Abstract

Accurate prediction of dam inflows is essential for effective water resource management and dam operation. In this study, we developed a multi-inflow prediction ensemble (MPE) model for dam inflow prediction using auto-sklearn (AS). The MPE model is designed to combine ensemble models for [...] Read more.

Accurate prediction of dam inflows is essential for effective water resource management and dam operation. In this study, we developed a multi-inflow prediction ensemble (MPE) model for dam inflow prediction using auto-sklearn (AS). The MPE model is designed to combine ensemble models for high and low inflow prediction and improve dam inflow prediction accuracy. We investigated the impact of datasets assigned to flow regimes on the ensemble composition and compared the performance of the MPE model to an AS-based ensemble model developed using a conventional approach. Our findings showed that the MPE model outperformed the conventional model in predicting dam inflows during flood and nonflood periods, reducing the root mean square error (RMSE) and mean absolute error (MAE) by 22.1% and 24.9% for low inflows, and increasing the coefficient of determination (R²) and Nash–Sutcliffe efficiency (NSE) by 21.9% and 35.8%, respectively. These results suggest that the MPE model has the potential to improve water resource management and dam operation, benefiting both the environment and society. Overall, the methodology of this study is expected to contribute to the development of a robust ensemble model for dam inflow prediction in regions with high climate variability. Full article

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

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17 pages, 6374 KiB

Open AccessArticle

Search for a Relevant Scale to Optimize the Quality Monitoring of Groundwater Bodies in the Occitanie Region (France)

by Meryem Jabrane, Abdessamad Touiouine, Vincent Valles, Abdelhak Bouabdli, Said Chakiri, Ismail Mohsine, Youssouf El Jarjini, Moad Morarech, Yannick Duran and Laurent Barbiero

Hydrology 2023, 10(4), 89; https://doi.org/10.3390/hydrology10040089 - 10 Apr 2023

Cited by 4 | Viewed by 1493

Abstract

In France, and more generally in Europe, the high number of groundwater bodies (GWB) per administrative region is an obstacle for the management and monitoring of water for human consumption by regional health agencies. Moreover, GWBs show a high spatial, temporal, physico-chemical, and [...] Read more.

In France, and more generally in Europe, the high number of groundwater bodies (GWB) per administrative region is an obstacle for the management and monitoring of water for human consumption by regional health agencies. Moreover, GWBs show a high spatial, temporal, physico-chemical, and bacteriological variability. The objective is to establish homogeneous groupings of GWB from the point of view of water quality and the processes responsible for this quality. In the Occitanie region in southwestern France, the cross-referencing of two databases, namely the French reference system for groundwater bodies and SISE-EAUX, provided a dataset of 8110 observations and 15 parameters distributed over 106 GWB. The 8-step approach, including data conditioning, dimensional reduction by Principal Component Analysis, and hierarchical clustering, resulted in 20 homogeneous groups of GWB over the whole region. The loss of information caused by this grouping is quantified by the evolution of the explained variance. Splitting the region into two large basins (Adour-Garonne and Rhône Méditerranée) according to the recommendations of the European community does not result in a significant additional loss of information contained in the data. A quick study of a few groups allows to highlight the specificities of each one, thus enabling targeted guidelines or recommendations for water quality management and monitoring. In the future, the method will have to be tested on the scale of large European watersheds, as well as in the context of an increase in the number of parameters. Full article

(This article belongs to the Special Issue Groundwater Management)

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10 pages, 5558 KiB

Open AccessCommunication

Effects of the Time Period Length on the Determination of Long-Term Mean Annual Discharge

by Jana Poórová, Katarína Jeneiová, Lotta Blaškovičová, Zuzana Danáčová, Katarína Kotríková, Katarína Melová and Zuzana Paľušová

Hydrology 2023, 10(4), 88; https://doi.org/10.3390/hydrology10040088 - 08 Apr 2023

Cited by 3 | Viewed by 1345

Abstract

Currently, the 40-year-long reference period 1961–2000 is used in Slovakia for systematic assessment of the hydrological regime. The World Meteorological Organization recommends unifying the climatic normal 1991–2020 with a reference period for hydrological characteristics for the purpose of climate change research. We have [...] Read more.

Currently, the 40-year-long reference period 1961–2000 is used in Slovakia for systematic assessment of the hydrological regime. The World Meteorological Organization recommends unifying the climatic normal 1991–2020 with a reference period for hydrological characteristics for the purpose of climate change research. We have analyzed changes in the long-term mean annual discharges at 113 water-gauging stations over different time periods. Considering the history of the reference periods used in Slovakia, we have focused on the analysis of the 10, 20, 30, 40, and 50-year-long moving averages of the long-term mean annual discharges in the period 1961–2020 in comparison with the 1961–2000 reference period and the whole selected and analyzed period. The deviations of the annual flow rates for the area of Slovakia and river sub-basins have been analyzed. The results indicate that the new reference period to be used in Slovakia should include the time period after the year 2000. To determine its precise length, a more detailed analysis is needed. Full article

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22 pages, 34505 KiB

Open AccessFeature PaperArticle

Modeling Large River Basins and Flood Plains with Scarce Data: Development of the Large Basin Data Portal

by Riham K. Abu-Saymeh, Adil Godrej and Kathleen A. Alexander

Hydrology 2023, 10(4), 87; https://doi.org/10.3390/hydrology10040087 - 06 Apr 2023

Viewed by 1877

Abstract

Hydrological modeling of large river basins and flood plains continues to be challenged by the low availability and quality of observed data for modeling input and model calibration. Global datasets are often used to bridge this gap, but are often difficult and time [...] Read more.

Hydrological modeling of large river basins and flood plains continues to be challenged by the low availability and quality of observed data for modeling input and model calibration. Global datasets are often used to bridge this gap, but are often difficult and time consuming to acquire, particularly in low resource regions of the world. Numerous calls have been made to standardize and share data to increase local basin modeling capacities and reduce redundancy in efforts, but barriers still exist. We discuss the challenges of hydrological modeling in data-scarce regions and describe a freely available online tool site developed to enable users to extract input data for any basin of any size. The site will allow users to visualize, map, interpolate, and reformat the data as needed for the intended application. We used our hydrological model of the Upper Zambezi basin and the Chobe-Zambezi floodplains to illustrate the use of this online toolset. Increasing access and dissemination of hydrological modeling data is a critical need, particularly among users where data requirements and access continue to impede locally driven management of hydrological systems. Full article

(This article belongs to the Special Issue Advances in River and Floodplain Interactions)

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15 pages, 6126 KiB

Open AccessArticle

Simulation of Surface and Subsurface Water Quality in Hyper-Arid Environments

by Ahmed Mohamed, Ahmed Asmoay, Saad S. Alarifi and Musaab A. A. Mohammed

Hydrology 2023, 10(4), 86; https://doi.org/10.3390/hydrology10040086 - 06 Apr 2023

Cited by 5 | Viewed by 1441

Abstract

Forty-eight water samples (30 groundwater and 18 surface water samples) were collected from the study region. Physical and chemical examinations were performed on the water samples to determine the values of various variables. Several graphs, sheets, and statistical measures, including the sodium solubility [...] Read more.

Forty-eight water samples (30 groundwater and 18 surface water samples) were collected from the study region. Physical and chemical examinations were performed on the water samples to determine the values of various variables. Several graphs, sheets, and statistical measures, including the sodium solubility percentage (SSP), the sodium absorption ratio (SAR), and Piper’s diagram, were used to plot the concentration of the principal ions and the chloride mass balance (CMB). The contents of the variables were compared with the contents in other local areas and the standard allowable safe limits as recommended by the World Health Organization (WHO). Water pH values were neutral for all water samples. Electric conductivity (EC) readings revealed that water samples vacillated from slightly mineralized to excessively mineralized. Water salinities were fresh and very fresh according to the total dissolved solids (TDS) amounts. The hardness of water ranged from medium to hard in the surface water and from medium to very hard in the groundwater samples. Bicarbonate, sodium, and calcium made up the highest amounts in the surface water samples. The highest concentrations of bicarbonate, sulfate, chloride, and sodium were found in the groundwater. Diagrams show the major ion relationships as well as the type and origin of the water. According to Piper’s plots, most of the water samples under investigation were Ca-HCO₃ type, Mg water types, followed by SO₄.Ca-Cl water types. This highlighted the elemental preponderance of bicarbonate and alkaline earth (Ca²⁺ + Mg²⁺). This dominance is caused by evaporite and carbonate minerals dissolving in water because of anthropogenic activities and interaction processes. The groundwater recharge was estimated to be 0.89–1.6 mm/yr based on Chloride Mass Balance. The examined water samples can also be used for cattle, poultry, and irrigation. Additionally, the groundwater is of poorer quality than the surface water, although both types of water are adequate for various industries, with a range of 14 to 94 percent. With the exception of a few groundwater samples, the tested water samples are suitable for a number of applications. Full article

(This article belongs to the Topic Groundwater Pollution Control and Groundwater Management)

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17 pages, 4953 KiB

Open AccessArticle

Influence of Dissolved Oxygen, Water Level and Temperature on Dissolved Organic Carbon in Coastal Groundwater

by Thilagavathi Rajendiran, Chidambaram Sabarathinam, Banajarani Panda and Vetrimurugan Elumalai

Hydrology 2023, 10(4), 85; https://doi.org/10.3390/hydrology10040085 - 06 Apr 2023

Cited by 7 | Viewed by 2322

Abstract

The quality of groundwater has been severely impacted by urbanization around coasts. The change in climate and land use patterns has deteriorated the quality and availability of groundwater. One of the main issues in contemporary groundwater quality research is dissolved organic carbon (DOC) [...] Read more.

The quality of groundwater has been severely impacted by urbanization around coasts. The change in climate and land use patterns has deteriorated the quality and availability of groundwater. One of the main issues in contemporary groundwater quality research is dissolved organic carbon (DOC) in the water. The influence of DO, water level and water temperature on DOC in groundwater was identified in the current study by sampling 68 groundwater samples. The analytical results revealed that ~18% of total samples have DOC > 5 mg/L. The groundwater samples represented in the urban regions show high DOC. The samples with higher DOC correlated positively with dissolved inorganic ions, such as Ca, K, NO₃, Fe and DO. Domestic wastewater, agricultural runoff and local geology all have an impact on the DOC of groundwater. Groundwater chemistry is shown to be controlled by both aerobic and anaerobic conditions based on the DOC’s interactions with other ions. The study interrelates various sources, such as land use, geology, water level and temperature, to the DOC in groundwater and infers that the levels are higher in shallow groundwater, predominantly around the built-up region followed by the agricultural region. The temperature changes enhance the DOC in groundwater due to the variation in microbial activity. The shallow water level with a lower temperature shows the maximum DOC. Apart from the sediment organic matter and microbes, the study also attributes land use pattern to the source of DOC in groundwater. Full article

(This article belongs to the Special Issue Groundwater Decline and Depletion)

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15 pages, 6440 KiB

Open AccessArticle

Application of the Iber Two-Dimensional Model to Recover the Water Quality in the Lurín River

by Omayra Luzmila Mori-Sánchez, Lia Ramos-Fernández, Willy Eduardo Lluén-Chero, Edwin Pino-Vargas and Lisveth Flores del Pino

Hydrology 2023, 10(4), 84; https://doi.org/10.3390/hydrology10040084 - 05 Apr 2023

Cited by 2 | Viewed by 1606

Abstract

The Lurín River is one of the main sources of water for the city of Lima. However, the discharge of domestic wastewater, the presence of dumps, and long periods of drought cause the deterioration of the water resource. In this study, DO, [...] Read more.

The Lurín River is one of the main sources of water for the city of Lima. However, the discharge of domestic wastewater, the presence of dumps, and long periods of drought cause the deterioration of the water resource. In this study, DO, BOD₅, E. coli, T, EC, TSS,

U

, and h were monitored at 13 monitoring points spread over 20 km of river influence. This information was used to calibrate the parameters of

K_{d b o}

,

K_{a i r e}

,

K_{d o s}

, and

K_{d e c}

in the Iber two-dimensional numerical model, obtaining values of 0.55

d^{- 1}

, [4.84

d^{- 1}

–80.65

d^{- 1}

], 10 g O₂

m^{- 2} d^{- 1}

, and [1.49

d^{- 1}

–15.42

d^{- 1}

], respectively, with efficiencies ranging from “very good” to “satisfactory”. In the hydraulic model, a discretization of the channel, banks, and plains of 3, 5, and 7 m, respectively, was considered, resulting in a computational calculation time of 4 days in each simulation. The greatest contamination occurs in July at km 5 + 400 up to the Pan-American bridge. Therefore, it is proposed to recover the river by optimizing the San Bartolo Wastewater Treatment Plant (WWTP) and a new WWTP in Pachacámac to avoid diffuse contamination, with discharge flows of 0.980

m^{3} s^{- 1}

and 0.373

m^{3} s^{- 1}

, respectively, and 4 mg

L^{- 1}

, 15 mg

L^{- 1}

and 1000 NMP/100 mL for DO, BOD₅, and E. coli, respectively. Full article

(This article belongs to the Topic Research on River Engineering)

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16 pages, 9324 KiB

Open AccessArticle

Soil–Water–Atmosphere Effects on Soil Crack Characteristics under Field Conditions in a Semiarid Climate

by Jacques Carvalho Ribeiro Filho, Eunice Maia de Andrade, Maria Simas Guerreiro, Helba Araújo de Queiroz Palácio and José Bandeira Brasil

Hydrology 2023, 10(4), 83; https://doi.org/10.3390/hydrology10040083 - 04 Apr 2023

Cited by 2 | Viewed by 1670

Abstract

Soil’s physical and hydrological properties influence the proper modeling, planning, and management of water resources and soil conservation. In areas of vertic soils subjected to wetting and drying cycles, the soil–water–atmosphere interaction is complex and understudied at the field scale, especially in dry [...] Read more.

Soil’s physical and hydrological properties influence the proper modeling, planning, and management of water resources and soil conservation. In areas of vertic soils subjected to wetting and drying cycles, the soil–water–atmosphere interaction is complex and understudied at the field scale, especially in dry tropical regions. This work quantifies and analyzes crack development under field conditions in an expansive soil in a semiarid region for both the dry and rainy seasons. Six 1 m² plots in an experimental 2.8 ha watershed were photographed and direct measurements were taken of the soil moisture and crack area, depth and volume once a week and after a rainfall event from July 2019 to June 2020. The rainfall was monitored for the entire period and showed a unimodal distribution from December to May after five months without precipitation. The cracks were first sealed in the plots with a predominance of sand and when the soil moisture was above 23% and had an accumulated precipitation of 102 mm. The other plots sealed their cracks when the soil moisture was above 32% and with an accumulated precipitation in the rainy season above 222 mm. The cracks redeveloped after sealing upon a reduction of 4% in the soil moisture. The depth of the cracks showed a better response to climatic variations (total precipitation, soil moisture and continuous dry and wet days). The higher clay content and the higher plasticity index plots developed more cracks with greater depth and volume. Full article

(This article belongs to the Topic Hydrology and Water Resources in Agriculture and Ecology)

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23 pages, 8484 KiB

Open AccessArticle

Investigating Nitrate with Other Constituents in Groundwater in Two Contrasting Tropical Highland Watersheds

by Feleke K. Sishu, Seifu A. Tilahun, Petra Schmitter and Tammo S. Steenhuis

Hydrology 2023, 10(4), 82; https://doi.org/10.3390/hydrology10040082 - 03 Apr 2023

Cited by 2 | Viewed by 1512

Abstract

Nitrate is globally the most widespread and widely studied groundwater contaminant. However, few studies have been conducted in sub-Saharan Africa, where the leaching potential is enhanced during the rainy monsoon phase. The few monitoring studies found concentrations over drinking water standards of 10 [...] Read more.

Nitrate is globally the most widespread and widely studied groundwater contaminant. However, few studies have been conducted in sub-Saharan Africa, where the leaching potential is enhanced during the rainy monsoon phase. The few monitoring studies found concentrations over drinking water standards of 10 mg N-NO₃⁻ L⁻¹ in the groundwater, the primary water supply in rural communities. Studies on nitrate movement are limited to the volcanic Ethiopian highlands. Therefore, this study aimed to evaluate the transport and fate of nitrate in groundwater and identify processes that control the concentrations. Water table height, nitrate, chloride, ammonium, reduced iron, and three other groundwater constituents were determined monthly in the groundwater in over 30 wells in two contrasting volcanic watersheds over two years in the Ethiopian highlands. The first watershed was Dangishta, with lava intrusion dikes that blocked the subsurface flow in the valley bottom. The water table remained within 3 m of the surface. The second watershed without volcanic barriers was Robit Bata. The water table dropped rapidly within three months of the end of the rain phase and disappeared except near faults. The average nitrate concentration in both watersheds was between 4 and 5 mg N-NO₃⁻ L⁻¹. Hydrogeology influenced the transport and fate of nitrogen. In Dangishta, water was blocked by volcanic lava intrusion dikes, and residence time in the aquifer was larger than in Robit Bata. Consequently, nitrate remained high (in several wells, 10 mg N-NO₃⁻ L⁻¹) and decreased slowly due to denitrification. In Robit Bata, the water residence time was lower, and peak concentrations were only observed in the month after fertilizer application; otherwise, it was near an average of 4 mg N-NO₃⁻ L⁻¹. Nitrate concentrations were predicted using a multiple linear regression model. Hydrology explained the nitrate concentrations in Robit Bata. In Dangishta, biogeochemistry was also significant. 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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13 pages, 5103 KiB

Open AccessArticle

The Role of Water and Weathering Processes in Landslides in Hungarian Loess Sediments

by Csilla Király, Dóra Cseresznyés, Norbert Magyar, István Gábor Hatvani, Tamás Egedy, Zsuzsanna Szabó-Krausz, Beatrix Udvardi, Gergely Jakab, György Varga and Zoltán Szalai

Hydrology 2023, 10(4), 81; https://doi.org/10.3390/hydrology10040081 - 01 Apr 2023

Viewed by 1484

Abstract

Loess-paleosol bluffs can be unstable, but in the course of urbanization, houses may be built in such locations to take advantage of the view. One factor affecting the stability of such bluffs is water, the role of which in mass movements is well [...] Read more.

Loess-paleosol bluffs can be unstable, but in the course of urbanization, houses may be built in such locations to take advantage of the view. One factor affecting the stability of such bluffs is water, the role of which in mass movements is well established. In this study, the connection of mass movements to meteorological conditions, such as rainfall and subsequent water level changes, was researched using new statistical methods. The periodicity of the water level of the Danube was analyzed using wavelet spectrum analyses, while changepoint analysis was used to determine variations in the quantity of precipitation. These results were compared to the chronology of six mass movements in Kulcs, Hungary. This study also focused on the changes in geochemical properties of loess in different weather conditions (dry periods, wet periods, and flooding). The results showed that only two mass movements were connected to hydrological conditions, and in the other case human activity and geochemical changes may have been factors. The results of geochemical models created using PHREEQC showed calcite and kaolinite precipitation, and albite and dolomite dissolution as the main mineral changes over the course of a year. Albite was found to dissolve only in wet periods, and kaolinite precipitation was significant during flood periods. Full article

(This article belongs to the Topic Hydrological Modeling and Engineering: Managing Risk and Uncertainties)

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16 pages, 3843 KiB

Open AccessEditor’s ChoiceArticle

Modeling a Metamorphic Aquifer through a Hydro-Geophysical Approach: The Gap between Field Data and System Complexity

by Francesco Chidichimo, Michele De Biase, Francesco Muto and Salvatore Straface

Hydrology 2023, 10(4), 80; https://doi.org/10.3390/hydrology10040080 - 31 Mar 2023

Cited by 2 | Viewed by 1334

Abstract

The productivity of metamorphic aquifers is generally lower than that of the more common alluvial and carbonates ones. However, in some Mediterranean areas, such as the Calabria region (Italy), water scarcity combined with the presence of extensive metamorphic water bodies requires the development [...] Read more.

The productivity of metamorphic aquifers is generally lower than that of the more common alluvial and carbonates ones. However, in some Mediterranean areas, such as the Calabria region (Italy), water scarcity combined with the presence of extensive metamorphic water bodies requires the development of further studies to characterize the hydrodynamic properties of these groundwater systems in order to achieve their sustainable exploitation. The interest in this goal becomes even greater if climate change effects are considered. The purpose of this study was to provide the geological-structural and hydrogeological numerical modeling of a metamorphic aquifer, using direct and indirect data measurement, in a large area of the Sila Piccola in Calabria. The hydrodynamic characterization of the crystalline-metamorphic aquifer, constituted by granite and metamorphic rocks, is extremely complex. The MODFLOW-2005 groundwater model was used to simulate flow phenomena in the aquifer, obtaining hydraulic conductivity values of 2.7 × 10⁻⁶ m/s, which turned out to be two orders of magnitude higher than those obtained from the interpretation of the slug-tests performed in the study area. The mathematical model was also able to estimate the presence of a lateral recharge from a neighboring deep aquifer providing a significant water supply to the system under investigation. Full article

(This article belongs to the Topic Groundwater Pollution Control and Groundwater Management)

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13 pages, 6437 KiB

Open AccessArticle

Comparison between the Effects of Normal Rain and Acid Rain on Calcareous Stones under Laboratory Simulation

by Indira Rodríguez, Almudena Ortiz, Pablo Caldevilla, Sara Giganto, Gabriel Búrdalo and María Fernández-Raga

Hydrology 2023, 10(4), 79; https://doi.org/10.3390/hydrology10040079 - 31 Mar 2023

Cited by 3 | Viewed by 3058

Abstract

Acid rain is a problem that despite efforts to reduce atmospheric pollution, continues to impact not only countries where there is a high production of pollutants, but also transboundary areas to which the pollutants are transported. In addition to its effects on human [...] Read more.

Acid rain is a problem that despite efforts to reduce atmospheric pollution, continues to impact not only countries where there is a high production of pollutants, but also transboundary areas to which the pollutants are transported. In addition to its effects on human health, there are also the effects on infrastructure and the consequences that this entails. This study on the effect of rain and acid rain on calcareous materials highlights the need for protection of buildings constructed from these materials, many of which are part of the cultural heritage. The effects caused by rain and acid rain were studied using a rain simulator whose features allow the simulation of natural conditions as realistically as possible. In the same way, the effect of a coating synthesized from nanomaterials, which has been shown to serve as protection against the degradation caused by rain, was analyzed. In addition to a long-lasting protection of the stone material, this type of coating avoids the need for the replacement of elements and the recurrent cleaning of degraded parts. It also avoids the accumulation of parts on the ground, the transport of personnel, work materials and raw materials, thereby contributing to the reduction of the carbon footprint and water savings, which in turn reduces the production of pollutants that cause acid rain. Full article

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21 pages, 8575 KiB

Open AccessArticle

Integrating Satellite Imagery and Ground-Based Measurements with a Machine Learning Model for Monitoring Lake Dynamics over a Semi-Arid Region

by Kenneth Ekpetere, Mohamed Abdelkader, Sunday Ishaya, Edith Makwe and Peter Ekpetere

Hydrology 2023, 10(4), 78; https://doi.org/10.3390/hydrology10040078 - 31 Mar 2023

Cited by 3 | Viewed by 1911

Abstract

The long-term variability of lacustrine dynamics is influenced by hydro-climatological factors that affect the depth and spatial extent of water bodies. The primary objective of this study is to delineate lake area extent, utilizing a machine learning approach, and to examine the impact [...] Read more.

The long-term variability of lacustrine dynamics is influenced by hydro-climatological factors that affect the depth and spatial extent of water bodies. The primary objective of this study is to delineate lake area extent, utilizing a machine learning approach, and to examine the impact of these hydro-climatological factors on lake dynamics. In situ and remote sensing observations were employed to identify the predominant explanatory pathways for assessing the fluctuations in lake area. The Great Salt Lake (GSL) and Lake Chad (LC) were chosen as study sites due to their semi-arid regional settings, enabling the testing of the proposed approach. The random forest (RF) supervised classification algorithm was applied to estimate the lake area extent using Landsat imagery that was acquired between 1999 and 2021. The long-term lake dynamics were evaluated using remotely sensed evapotranspiration data that were derived from MODIS, precipitation data that were sourced from CHIRPS, and in situ water level measurements. The findings revealed a marked decline in the GSL area extent, exceeding 50% between 1999 and 2021, whereas LC exhibited greater fluctuations with a comparatively lower decrease in its area extent, which was approximately 30% during the same period. The framework that is presented in this study demonstrates the reliability of remote sensing data and machine learning methodologies for monitoring lacustrine dynamics. Furthermore, it provides valuable insights for decision makers and water resource managers in assessing the temporal variability of lake dynamics. Full article

(This article belongs to the Special Issue Trends and Variations in Hydroclimatic Variables)

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14 pages, 12805 KiB

Open AccessArticle

Scour Reduction around Bridge Pier Using the Airfoil-Shaped Collar

by Lav Kumar Gupta, Manish Pandey, P. Anand Raj and Jaan H. Pu

Hydrology 2023, 10(4), 77; https://doi.org/10.3390/hydrology10040077 - 30 Mar 2023

Cited by 10 | Viewed by 1920

Abstract

Scouring around the bridge pier is a natural and complex phenomenon that results in bridge failure. Failure of bridges have potential devastation and public safety and economic loss, which lead to political consequences and environmental impacts. Therefore, it is essential to countermeasure the [...] Read more.

Scouring around the bridge pier is a natural and complex phenomenon that results in bridge failure. Failure of bridges have potential devastation and public safety and economic loss, which lead to political consequences and environmental impacts. Therefore, it is essential to countermeasure the scour around the bridge pier. This paper studies the effects of four different airfoil-shaped collars (i.e.,

b_{c 1}

= 1.5b,

b_{c 2}

= 2.0b,

b_{c 3}

= 2.5b and

b_{c 4}

= 3.0b, where

b_{c}

and

b

are the diameter of the airfoil-shaped collar and pier, respectively) as a scour countermeasure. All the experiments are conducted under clear water conditions with uniform sediment and a constant water depth (y) of 10 cm. Airfoil-shaped collar is placed at four elevations, i.e., bed level, y/4, y/2 and 3y/4 above the sediment bed level. It is observed that the maximum percentages of scour reduction of 86, 100 and 100% occurred due to protection provided by the collar

b_{c 2}

,

b_{c 3}

and

b_{c 4}

, respectively, at sediment bed level. So, collars

b_{c 2}

,

b_{c 3}

and

b_{c 4}

are efficient at the sediment bed level. The profiles of scour hole show that the length of the transverse scour hole is greater than that of the longitudinal one. Numerical investigation of the morphological changes in sediment bed and scour depth contours is developed using the FLOW-3D for the pier with and without the airfoil-shaped collar. Full article

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

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20 pages, 55822 KiB

Open AccessFeature PaperArticle

Comprehensive Analysis of Hydrological Processes in a Programmable Environment: The Watershed Modeling Framework

by Nicolás Velásquez, Jaime Ignacio Vélez, Oscar D. Álvarez-Villa and Sandra Patricia Salamanca

Hydrology 2023, 10(4), 76; https://doi.org/10.3390/hydrology10040076 - 29 Mar 2023

Cited by 4 | Viewed by 2771

Abstract

Distributed hydrological modeling has increased its popularity in the community, leading to the development of multiple models with different approaches. However, the rapid growth has also opened a gap between models, interfaces, and advanced users. User interfaces help to set up and pre-process [...] Read more.

Distributed hydrological modeling has increased its popularity in the community, leading to the development of multiple models with different approaches. However, the rapid growth has also opened a gap between models, interfaces, and advanced users. User interfaces help to set up and pre-process steps. Nevertheless, they also limit the implementation of more complex experiments. This work presents the Watershed Modeling Framework (WMF) as a step forward in closing the interface–usage gap. WMF is a Fortran-Python module designed to provide tools to perform hydrological analysis and modeling that conceptualizes the watershed as an object with a defined topology, properties, and functions. WMF has a built-in hydrological model, geomorphological analysis functions, and a QGIS plugin. WMF interacts with other popular Python modules, making it dynamic and expandible. In this work, we describe the structure of WMF and its capabilities. We also provide some examples of its implementation and discuss its future development. Full article

(This article belongs to the Topic Hydrological Modeling and Engineering: Managing Risk and Uncertainties)

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9 pages, 1984 KiB

Open AccessArticle

Evaluating Methods of Streamflow Timing to Approximate Snowmelt Contribution in High-Elevation Mountain Watersheds

by Anna K. D. Pfohl and Steven R. Fassnacht

Hydrology 2023, 10(4), 75; https://doi.org/10.3390/hydrology10040075 - 25 Mar 2023

Viewed by 1144

Abstract

Current streamflow timing metrics, such as the center of volume, or COV, use flow days, which are days at which a specific total streamflow volume, such as 50% for COV, has passed a given point. These metrics have been used as indicators for [...] Read more.

Current streamflow timing metrics, such as the center of volume, or COV, use flow days, which are days at which a specific total streamflow volume, such as 50% for COV, has passed a given point. These metrics have been used as indicators for changes in the timings of snowmelt contributions to streamflow, but they may not be indicating changes to snowmelt timings as they have a fixed volume. Using manually extracted start and end days for high-elevation, mountainous watersheds, which are regarded as true values, we developed a new method to estimate when snowmelt is entering streams. Based on RMSE and NSE values, this new method is a better model for snowmelt-driven streamflow than using flow days or the COV. In general, the trend analysis results from the different timing metrics indicate an earlier timing in the year. This method was suitable for 40 different-sized watersheds in Colorado, USA; these are all snow-dominated watersheds in a semi-arid climate. This method could be used to assess watersheds in different climates, including those that are not as snow-dominated. Full article

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12 pages, 1173 KiB

Open AccessFeature PaperArticle

Utilization of Tryptophan-like Fluorescence as a Proxy for E. coli Contamination in a Mixed-Land-Use Karst Basin

by Ryan T. Dapkus, Alan E. Fryar, Benjamin W. Tobin, Diana M. Byrne, Shishir K. Sarker, Leonie Bettel and James F. Fox

Hydrology 2023, 10(4), 74; https://doi.org/10.3390/hydrology10040074 - 23 Mar 2023

Cited by 1 | Viewed by 2000

Abstract

Karst aquifers are susceptible to contamination by pathogenic microorganisms, such as those found in human and animal waste, because the surface and subsurface drainage are well integrated through dissolution features. Fecal contamination of water is commonly assessed by the concentration of thermotolerant coliform [...] Read more.

Karst aquifers are susceptible to contamination by pathogenic microorganisms, such as those found in human and animal waste, because the surface and subsurface drainage are well integrated through dissolution features. Fecal contamination of water is commonly assessed by the concentration of thermotolerant coliform bacteria, especially E. coli. This method is time-consuming, taking ≥18 h between the start of incubation and subsequent enumeration, as well as the time required to collect and transport samples. We examined the utility of continuous monitoring of tryptophan-like fluorescence (TLF) as a real-time proxy for E. coli in a mixed-land-use karst basin in the Inner Bluegrass region of central Kentucky (USA). Two logging fluorometers were sequentially deployed at the outlet spring. During storm flow, TLF typically peaked after discharge, which suggests that TLF transport in the phreatic conduit is likely related to sediment transport. The ability of TLF and other parameters (48 h antecedent precipitation, turbidity, and air temperature) to predict E. coli concentrations was assessed using the Akaike information criterion (AIC) applied to linear regression models. Because both the models and baseline concentrations of TLF differed between fluorometers, TLF and instrument interaction were accounted for in the AIC. TLF was positively correlated with E. coli and, in conjunction with antecedent precipitation, was the best predictor of E. coli. However, a model that included air temperature and antecedent precipitation but not TLF predicted E. coli concentrations similarly well. Given the expense of the fluorometers and the performance of the alternate model, TLF may not be a cost-effective proxy for E. coli in this karst basin. Full article

(This article belongs to the Special Issue Hydro-Geology of Karst Areas)

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