Invasive species are often central to conservation efforts, particularly when concerns involve potential impacts on rare, endemic native species. The New River drainage, which represents the upper reaches of the ancient Teays River, is delineated by Kanawha Falls, a well-documented zoogeographic barrier to fish distributions. The New River drainage begins in North Carolina, flows through western Virginia, and ends in southern West Virginia. The lower New River system in West Virginia is naturally depauperate of native fish species and it is nearly saturated with nonnative fish species: 32 natives including at least 8 endemics, and 62 nonnatives. Herein, we conducted time-series data analysis to examine chronological shifts in fish species distributions. Specifically, we documented range contractions of four endemic species in the lower New River system: Kanawha Minnow (Phenacobius teretulus), New River Shiner (Miniellus scabriceps), Appalachia Darter (Percina gymnocephala), and Candy Darter (Etheostoma osburni). We contrasted these findings with five nonnative species that have recently undergone rapid range expansions: Telescope Shiner (Notropis telescopus), Whitetail Shiner (Cyprinella galactura), Rainbow Darter (Etheostoma caeruleum), Roanoke Darter (Percina roanoka), and Variegate Darter (Etheostoma variatum). The endemic species are of conservation concern given limited distribution ranges and documented population declines. Although among-species comparisons of range shifts do not support causal inference, the documentation of changes in distribution ranges of endemic and invasive species are critical to inform conservation efforts.

Riparian zones are transitional environments between terrestrial and freshwater ecosystems. Preserving and restoring natural habitats could be instrumental in maintaining and enhancing ecosystem services vital for both environmental health and human well-being. The aim of this study is the spatial analysis of ecosystem services in the hydrographic network of Pinios River basin, Greece. Initially, the riparian zones were delineated using the Riparian Buffer Delineation Model v6.1 (Abood and Maclean, 2011). The model creates variable-width riparian buffer zones that tend to vary in width based on the stream order. Ecosystem services were estimated using the Integrated Valuation of Ecosystem Services and Tradeoffs 3.1 (InVEST) software (Natural Capital Project, 2024). Mapping and valuing ecosystem services were conducted for the Habitat Quality Model, the Carbon Storage Model, and the Sediment Delivery Ratio Model (Natural Capital Project, 2024). Specifically, in order to create habitat quality maps, land cover maps were analyzed in conjunction with threats to species habitats. Regarding carbon storage, the model utilizes land use maps along with stocks in four carbon pools (aboveground biomass, belowground biomass, soil organic carbon, and dead organic matter) to estimate the quantity of carbon stored in a landscape. Furthermore, the Sediment Delivery Ratio (SDR) model was used to quantify and map the generation of sediment on land and its subsequent delivery to streams or water bodies. The required input data are Digital Elevation Model, erosivity factor, soil erodibility factor, land cover map cover-management factor (C), and support practice factor (P). The results demonstrated a clear correlation between the level of human intervention and the provision of these services. Specifically, forests and semi-natural areas were identified as significant contributors to ecosystem services, showcasing higher levels of habitat quality, carbon storage, and lower erosion.

Introduction

Unpolluted freshwater is a crucial component for maintaining human health. The present study aimed to investigate the bioaccumulation of heavy metal contaminants (Fe, Cd, Cr, Cu, and Pb) in water, sediments, and tissues of Tor putitora for assessing their suitability for human consumption.

Methods

Fish, water, and soil samples were collected from the Zhob River, and Flame Atomic Absorption Spectrometry (FAAS) was employed to assess the level of heavy metal contamination.

Results

Water quality parameters (temperature and pH) were within suitable ranges, but electric conductivity and turbidity exceeded permissible limits. High concentrations of Fe and Cd in soil and Pb in both water and soil were noted, surpassing WHO and USEPA standards. Despite elevated Fe levels, the examined metal concentrations in fish tissues were below FAO/WHO limits, indicating safe human consumption. Estimated daily intake (EDI) showed no health risk for the local population. Non-carcinogenic risk assessment indicated individual metal consumption safety, but combined metal intake may pose potential health risks. Carcinogenic risk assessment for Cd, Cr, and Pb revealed no cancer risk for consumers. Multivariate analysis, including the correlation matrix, revealed strong and significant correlations (P<0.05) among heavy metal pairs (Fe/Cr, Fe/Pb, Cr/Fe, Cr/Pb, Pb/Fe, and Pb/Cr). Hierarchical cluster analysis and principal component analysis (PCA) identified the origins of these metals, attributing their presence to the nearby weathering of rocks and mining, municipal, and agricultural activities. These factors were recognized as potential sources of heavy metal bioaccumulation in riverine fish.

Conclusions

This study concluded that the Zhob River was contaminated with heavy metals, emphasizing the need to prevent domestic and industrial sewage inflow. Monitoring these metals in the food chain is crucial for reducing associated health risks. This study provides the first report on heavy metal distribution in the Zhob River's highly abundant and edible mahseer fishes.

This study aims to investigate the impact of the dam breach mechanisms and characteristics on the flood wave effluxing through the breach. The failure mechanisms, the geometric characteristics, and the development time of the breach are estimated with the five empirical equations provided by HEC-RAS. The flood routing is simulated with the HEC–RAS 2D model using the Eulerian-Lagrangian Shallow Water equations (SWE-ELM), derived from St. Venant differential equations. A finite volume grid was utilized to discretize the St. Venant equations. Then, the routing of the flood wave through the inundated area is performed by estimating the flood depth and the flow velocities for every wet cell of the grid for a given period. As a case study, a hydraulic 2D routing model was built to examine various breach scenarios of the Tsiknias dam, an earthen dam with a central clay core located northeast of Kalloni town of Lesvos Island. The dam is equipped with an Ogee Crest safety spillway which has a length of 50 m. The results show that the most unfavorable scenario of dam breach due to soil piping is the one that uses the Froelich 1995a equation. In this scenario, the maximum peak outflow from the breach is Q_peak =8225.5 m³/s and Kalloni town is inundated within 40 minutes after the breach. This time window is essential for the evacuation plan of the citizens in the case of a dam breach. Inside Kalloni town, the flood depths range from 2 to 5 m, whereas the flow velocities reach up to 6 m/s, which implies that the flood wave generated by the breach may inflict major damage to the infrastructure of Kalloni town. In Kalloni Bay, outside of the town, the flood depths reach up to 2 m and the flow velocities up to 3 m/s.

Plastic pollution is now considered a global threat. Plastics introduced into the environment remain there for dozens or even hundreds of years. They gradually break down into smaller and smaller fractions, the so-called microplastics (MPs) that enter various environmental ecosystems such as soil, water and air. It is estimated that between 19 and 23 million tonnes of plastic end up in the ocean each year, representing less than 3% of the total amount of mismanaged plastic waste. In turn, the amount of this waste that is released into the environment is ten times greater (about 30% of the total). MPs entering rivers, lakes or dam reservoirs from land may pose a threat to the living organisms inhabiting them and entire ecosystems. The breakdown of microplastics in aquatic ecosystems leads to the release of toxic chemical substances into the aquatic environment. These substances, which are components of plastics, include plasticizers, stabilizers, pigments and flame retardants. This study presents research on the potential emission of plasticizers into the aquatic environment from water and sewage installations, such as sewer pipes and accompanying elements (gaskets). The conducted research confirmed that, depending on environmental conditions, phthalate esters are leached from microplastics originating from water and sewage systems. The reaction environment temperature and incubation time significantly influenced the degree of plasticizer leaching from the polymer matrix. An additional negative aspect of microplastic degradation in the aquatic environment was the emission of greenhouse gases, such as carbon dioxide and methane. To determine the parameters that had the greatest impact on the emission levels of the analyzed contaminants from microplastics, an environmental model sensitivity analysis was conducted based on Hellwig's information capacity index analysis.

The worldwide increase in antimicrobial-resistant bacteria (ARB) presents a significant medical challenge and has emerged as one of the most critical concerns of our era. Antibiotic-resistant Klebsiella has emerged over the past few decades as a major public health threat. The prevalence of bacterial infections associated with biofilm formation is significant, accounting for approximately 65-80% of all cases. Given this scenario, this study investigates the prevalence of biofilm formation in Klebsiella isolated from surface waters and hospital wastewaters. In total, 77 samples were collected from surface waters in North Portugal, of which 33 Klebsiella (14 Klebsiella spp. and 19 K. pneumoniae strains) were isolated. Furthermore, 44 samples were collected from hospital wastewaters in Northern Portugal, of which 41 Klebsiella (25 Klebsiella spp. and 16 K. pneumoniae strains) were isolated. Biofilm production was evaluated using the microtiter plate assay. In surface waters, isolates of Klebsiella spp. and K. pneumoniae produced moderate biofilm biomass, with similar averages of biofilm formation percentages (83.1% and 86.9%, respectively). In K. pneumoniae strains, 65% (n=13) were confirmed as weak producers, 10% (n=2) were moderate, and 25% (n=5) were strong biofilm producers. Likewise, regarding Klebsiella spp., 35.7% (n=5) were weak producers, 57.1% (n=8) were moderate, and 7.1% (n=1) were strong biofilm producers. These were positive results, as the presence of biofilm-producing strains complicates infection treatment, given that antibiotics cannot eliminate the biofilm, only addressing the infection symptoms. With this, it is concluded that understanding and addressing biofilm formation is crucial for developing effective strategies for preventing and treating bacterial infections. Furthermore, detecting and controlling the spread of these and employing a One Health approach are vital for managing this problem effectively.

Climate change is a challenge for humanity. Meteorological drought is a climatic anomaly that is caused by a significant decrease in the amount of precipitation below normal averages, which affects the intakes of water supply systems and ecosystems. It can be evaluated through indices such as the Standardized Precipitation Index, Palmer Drought Severity Index, and Standardized Evaporation and Precipitation Index, among others. Hydrological droughts are a consequence of meteorological droughts and anthropogenic changes, which have a duration of about the time of concentration of the basins and can be measured through the Standardized Runoff Index. Drought indices in combination with mathematical models and models for future estimations can be used to provide tools for decision-making in general water resources management and specifically influence the establishment of operation policies for hydroelectric plants as important agents for the regulation of maximum and minimum flows in rivers. This research presents the analysis of drought indices for different regions of the world with rivers of controlled and uncontrolled flows by power plants, evaluating the incidence of droughts in the production of clean energy and water supply and their impact on ecosystems. From the current review, it has been observed that, in the dry periods evaluated in different regions of the world, the different drought indices have shown that in recent years, there has been an increase in the severity of droughts, where there has been a considerable decrease in rainfall and hydrological flows for the years evaluated, leading to greater difficulties in the impacted regions in terms of the provision and delivery of water for people, agricultural production, and the production of sustainable energies.

The use of historical information about floods is crucial for improving and reducing uncertainty in hydrological dam safety analyses. Traditionally, hydrological analyses for estimating flood frequency curves have been based on simplified hydrometeorological methods and models with limited data, leading to flood quantile estimates with great uncertainties. However, historical information such as water level marks for high-magnitude floods too old to be included in contemporary flood time series recorded at gauging stations are usually available in settlements near existing dams. Incorporating the information about such floods could improve flood quantile estimates associated with high return periods, reducing estimate uncertainties and improving hydrological dam safety analysis.

Therefore, the aim of this study entails using 2D hydrodynamic simulations to estimate flood magnitudes associated with historical floods. A given water level can be generated by a set of flood hydrographs with differing peak flows, flood volumes, and durations. Two-dimensional hydrodynamic simulations allow us to characterise the uncertainty of flood peak and hydrograph volume estimates for historical floods. Such information is incorporated in flood frequency curve estimates.

This study was carried out in the River Douro in Spain. In this area, information about historical water level marks for several floods in the past are available in the reach between the San José Dam and the city of Zamora.

This first step focuses on the calibration and validation of the hydraulic model in the current situation, which were performed using the hydrological data available. It focuses on obtaining a suitable mesh, time step, and landcover for optimal simulation.

With the validated model, simulations will be conducted on historical flood events for which flood marks are available. Given flood hydrograph shapes will be rescaled with varying peak flows and durations to determine the flood hydrographs leading to the recorded water level heights of the flood marks.

Many reservoirs employ multi-year regulation operational regimes. This raises the problem of the relationship between annual runoff and the primary runoff-forming factor (precipitation), as well as their long-term variability due to possible climatic changes.

The present study concerns the water balance of the Tsimlyansky reservoir, situated in the lower reaches of the Don River, which is subject to multi-year flow regulation. The objective of this study is to quantify the relationship between precipitation and inflow to the reservoir, expressed as annual values.

Statistical methods, including correlation analysis and data smoothing using moving averages, as well as wavelet transform filtering, were used to address the set tasks.

This study employed multi-year time series observations of precipitation and runoff to the reservoir, comprising a 56-year series for precipitation and a 142-year series for annual runoff. All series were formed as water management years (a 12 month cycle, from April to March of the following calendar year), in accordance with the water users’ requirements.

In the course of this research, the correlation coefficient between the precipitation time series and a part of the annual runoff series of corresponding duration (years 1966/67-2021/2022) was determined. The correlation coefficient was found to be equal to 0.46, with a mean square deviation of 0.13, indicating a significant relationship between annual precipitation and annual runoff to the reservoir.

The studies also revealed cyclic components in both precipitation and runoff time series with a period of approximately 12 years. Cyclic components in the time series were detected using the following two distinct methodologies: a combination of data filtering using the moving average method with calculation of autocorrelation functions of smoothed series, and filtering the data using wavelet analysis methods. The presence of such components requires the results obtained to be taken into account when modelling the long-term use of reservoir water resources.

In the present study, dam site suitability mapping was carried out for the Purna sub-basin of the upper Tapi basin. Constructing dams in strategically chosen locations is a crucial water management approach to alleviate flood risks and water scarcity. Selecting appropriate dam sites requires considering criteria such as precipitation, elevation, soil properties, slope, geomorphology, geology, lithology, stream order, distance from road, and fault tectonics. To address this complex problem, integrating Multiple Criteria Decision-Making (MCDM) techniques with Geographic Information Systems (GISs) has become increasingly prevalent. Among these techniques, the Analytic Hierarchy Process (AHP) is particularly effective for addressing water-related challenges. In this study, we developed a Dam Site Suitability Model (DSSM) by evaluating ten thematic layers: precipitation, stream order, geomorphology, geology, soil, elevation, slope, land use and land cover (LULC), and major fault tectonics. The AHP technique was employed to assign weights to these thematic layers, which were then used in an overlay analysis to create a suitability map with five classes ranging from high to low suitability. This study revealed that approximately 14% of the Purna sub-basin falls into the very high suitability category, while 27.2% is classified as highly suitable. This cost-effective approach not only simplifies the traditional method of dam site selection but also enhances decision-making accuracy. This methodology can be universally applied to identify potential dam sites, aiding flood mitigation and addressing water scarcity exacerbated by global and regional climate change. The DSSM, leveraging GIS and AHP, can significantly improve dam management and promote sustainable, environmentally responsible water resource management practices worldwide.