Water

In this study, we examine, identify, and discuss fossil remains of large branchiopod crustaceans collected from six sites across the Beringian region (north-eastern Asia and north-western North America). Eggs and mandibles from Anostraca and Notostraca, as well as a notostracan telson fragment and a possible notostracan second maxilla, were collected from both paleosediment samples and also from large mammal hair. The remains of large branchiopods and other species that are limited to seasonally astatic aquatic habitats (temporary wetlands) could be useful indicator organisms of paleoecological conditions. Different recent large branchiopod species have very different ecological preferences, with each species limited to specific geochemical component tolerance ranges regarding various salinity, cation, and gypsum concentrations. Our purpose is to bring the potential usefulness of these common fossil organisms to the attention of paleoecologists. Full article

The aim of the study was to screen the waste wood biomass of 10 wood species as biosorbents for synthetic dye Congo Red (CR) removal from water and to single out the most efficient species for further batch biosorption experiments. Euroamerican poplar (EP), the most efficient species achieving 71.8% CR removal and biosorption capacity of 3.3 mg g⁻¹, was characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). Different factors affecting the biosorption process were investigated: initial biosorbent concentration (1–10 g dm⁻³), contact time (5–360 min), initial CR concentration (10–100 mg dm⁻³), and the initial pH (pH = 4–9). The results showed that CR removal efficiency increased with the increase of biosorbent concentration and contact time. Increase of initial CR concentration led to an increase of the biosorption capacity, but also a decrease of CR removal efficiency. The highest CR removal efficiency was achieved at pH = 4, while at pH = 9 a significant decrease was noticed. The percentage of CR removal from synthetic wastewater was 18.6% higher than from model CR solution. The Langmuir model fitted well the biosorption data, with the maximum biosorption capacity of 8 mg g⁻¹. The kinetics data were found to conform to the pseudo-second-order kinetics model. Full article

One of the most crucial discussions within water resource management is the debate between those who defend the concept of economic efficiency and those who privilege notions of social equity. This tension is located at the core of binary categories that currently constitute the public debate within comparative water law and policy. These categories are commodity/human right, private property/common property, free-market/state regulation, and market value/community value. This paper explores this tension by studying how neoclassical economics understands efficiency and tracing its rise as a key hegemonic principle for water resource management. I also present equity as a conceptual opposition to efficiency and describe its institutionalization through the human-right-to-water frame. A problematization of both the equity approach and the human-right-to-water frame follows. Finally, I propose a political ecology approach to better understand the tension between efficiency and equity and offer recommendations for informing the water research agenda on efficiency/equity. Full article

The understanding of hydro systems is of great importance in monitoring quantitative and qualitative changes in water resources. The Essaouira region at the edge of the Moroccan Atlantic Ocean is subject to a semi-arid climate. The decrease in rainfall as a result of climate change and the increase in the exploitation of surface and groundwater have disrupted the stability of these resources and threaten the socio-economic and environmental balance in the area under investigation. Climate scenarios estimate that precipitation will decrease by 10–20% while warming increases by 3 °C over the next 30 years. The physico-chemical parameters studied show that the evolution of the pH and temperature of the groundwater remained stable with a neutral (pH ≈ 7) and a hypothermal character (T < 30 °C). For the electrical conductivity, it showed an increasing trend from 2017 to 2020. A hydrochemical approach showed that the groundwater mineralization was controlled by the dissolution of evaporites and carbonates, by cation exchange processes, and by seawater contamination. A groundwater assessment for drinking use was made by comparing the concentrations of the chemical elements with the standards set by the World Health Organization. The results obtained show that the groundwater from the aquifers studied requires treatment before being consumed, in particular for Cl⁻ and SO₄²⁻. Furthermore, the groundwater quality for irrigation was evaluated based on the parameters Na% and Sodium Adsorption Ratio (SAR). The results showed that the groundwater was adequate for agricultural purposes, especially for the plants that adapt to high salinity. The monitoring of surface water by processing the satellite images via the calculation of the normalized difference water index (NDWI) showed an increase in water surface areas in the region following the commissioning of two large dams (Zerrar and Igouzoullene). Despite the installation of these hydraulic structures, a drop of 4.85 km² in water surface area was observed beyond 2016. This situation requires intervention in order to preserve this vital resource. Full article

Activities to ensure and maintain water quality in drinking water networks, including flushing, are presented after standardized hydrant sampling combined with a stainless-steel low pressure–high flow rate (NDHF) filter and a 100 µm mesh size was used to separate pipe inhabitants. A databank of more than 1000 hydrant samples in European lowland areas was developed and used to analyze the diversity and abundance of macroinvertebrates in drinking water networks. Load classes for water louse (Asellus aquaticus) and oligochaetes are given with three evaluation classes: normal colonization, increased colonization, and mass development. The response of Asellus aquaticus in drinking water networks to environmental conditions are presented as are their growth and reproduction, promotion of a third generation by climate change effects, food limitations, and the composition and stability of their feces. Finally, the health risks posed by dead water lice and water lice feces with bacterial regrowth and the promotion of microbe development on house filters are analyzed. Full article

Pool-type fishways have been increasingly tested to improve fish passage performance and minimize migration delays. Designing cost-effective fishways is essential for a trade-off between water uses and successful longitudinal connectivity restoration. The multislot fishway (MSF) concept, which operates with 30–50% lower discharge than a vertical slot fishway (VSF), was recently developed. This study assessed and compared the entrance performance (entrance time; entry efficiency) and transit times of two cyprinids for VSFs and MSFs. Four configurations, with the same structural characteristics (slope; water depth; head drop; pool width and depth), operating with different discharges (Q), were tested (VSF 1: Q = 112 L·s⁻¹; VSF 2: Q = 80 L·s⁻¹; MSF 1: Q = 58 L·s⁻¹; MSF 2: Q = 37 L·s⁻¹). Hydrodynamics characterization was performed using a numerical model. Results showed that entry efficiency was higher in MSFs than in VSFs, while entrance time and transit time were overall lower. Numerical modelling revealed that velocities were around 30% lower in MSFs, and turbulence could reach a difference of around 70% in Reynolds shear stress and 50% in turbulent kinetic energy. Overall, MSFs can be considered as a cost-effective fishway solution that can balance the trade-offs between divergent interests in water uses. Full article

Colored dissolved organic matter (CDOM) is an important part of aquatic ecosystems and plays a key role in the biogeochemical cycle. In this study, CDOM absorption spectrum curves and water quality parameters from 30 sampling sites in the wetlands of Poyang Lake, Jiangxi Province, China, were collected in October 2016. The optical absorption characteristics and spatial distribution of CDOM, the correlation between the absorption coefficient of CDOM at a wavelength of 355 nm (a_g(355)), and the concentration of dissolved organic carbon (DOC) were analyzed. Spectral characteristic parameters—namely, E₂/E₃ (the ratio of the CDOM absorption coefficient at a wavelength of 250 nm to the CDOM absorption coefficient at a wavelength of 365 nm), SUVA₂₅₄ (the ratio of the CDOM absorption coefficient at a wavelength of 254 nm to the DOC concentration), and spectral slopes—were used to infer the composition and sources of CDOM in the Poyang Lake wetlands. The results showed the following: (1) the CDOM absorption spectrum of water of the Poyang Lake wetlands presented significant spatial variation, showing a trend of south > west > north > east; (2) there was a strong linear correlation between the CDOM absorption coefficient and the DOC concentration in the water of the Poyang Lake wetlands (a_g(355) = 1.075DOC–0.659 (r² = 0.723, p < 0.001, n = 30)); (3) the analysis of the spectral characteristic parameters E₂/E₃, SUVA₂₅₄, and spectral slopes showed that the CDOM in the Poyang Lake wetlands has relatively high aromaticity and molecular weight, which were shown to be mainly affected by terrestrial inputs. The results showed that the molecular weight and aromaticity of CDOM were higher in the south of the lake than in other parts. Full article

Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a very low environmental impact due to their negligible effect on solid transport. Among them, kinetic turbines with vertical axis are very inexpensive and have almost zero impact on fish and local fauna. In application to tidal waves and sea waves, where vertically averaged velocities have alternate direction, a Savonius rotor also has the advantage of being productive during the whole time cycle. In this work, the effect of an upstream deflector system mounted upstream of a twisted Savonius rotor inside a channel has been investigated through numerical simulations and experimental tests. Numerical simulations were carried on using the ANSYS FLUENT 17.0 software. Based on this numerical study, it is shown that the proposed deflector system has improved the power coefficient of the Savonius rotor by 14%. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas. Full article

For reservoir basins, complex underlying surface conditions, short flood confluence times, and concentrated water volumes make inflow flood forecasting difficult and cause forecast accuracies to be low. Conventional flood forecasting models can no longer meet the required forecast accuracy values for flood control operations. To give full play to the role of reservoirs in flood control and to maximize the use of reservoir flood resources, high-precision inflow flood forecasting is urgently needed as a support mechanism. In this study, the Baipenzhu Reservoir in Guangdong Province was selected as the study case, and an inflow flood forecast scheme was designed for the reservoir by a physically based distributed hydrological model, the Liuxihe model. The results show that the Liuxihe model has strong applicability for flood forecasting in the studied reservoir basin and that the simulation results are very accurate. This study also found that the use of different Digital Elevation Model (DEM) data sources has a certain impact on the structure of the Liuxihe model, but the constructed models can both simulate the inflow flood process of the Baipenzhu Reservoir well. At the same time, the Liuxihe model can reflect the spatial variation in rainfall well, and using the Particle swarm optimization (PSO) algorithm to optimize the initial model parameters can greatly reduce the uncertainty of the model forecasts. According to China’s hydrological information forecast standards, the Liuxihe model forecast schemes constructed by the two data sources are rated as Grade A and can be used for real-time flood forecasting in the Baipenzhu Reservoir basin. Full article

Spatio-temporal distribution and leachability of some trace elements (TE) were investigated in sediments of the Xiangjiang River, tributary of the Yangtze River. Based on data collected during 2015–2017, a literature review and geoaccumulation indexes, the pollution level was the highest for Cd, Sb and Hg (I_geo > 3). Over the period reviewed, the TE contamination level displayed almost no temporal variation but an obvious spatial distribution. The most upstream contamination hotspot (Cd > Cr > As, Cu, Pb, Zn > Hg, Sb) was the Songbai section. This hotspot did not spread further downstream. The second hotspot identified was the Zhuzhou–Xiangtan section, impacted by Cd > Hg, Pb, Zn > Cu, with the Zhuzhou area being particularly highly impacted by Pb and Zn. A 30-day leaching experimental protocol under aerobic and anaerobic conditions was carried out to access TE mobility. Low percentages of TE released were calculated, showing that the TE fate mostly depends on the stability of bearing phases under specific physicochemical and microbial conditions. In this case, the studied sediments can be an important sink for these TE. However, some environmental issues have to be considered as some leachate concentrations of contaminants (As, Cr, Cu and U) released into water exceed freshwater aquatic life criteria. Full article

Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow landslides and deep slip surface of terraces induced by extreme rainfall in loess hill and gully area, we conducted a laboratory model test of a terrace under artificial rainfall and used the Swedish arc strip method. The research results are as follows. The mechanism of shallow landslides in terraces is rill erosion accelerating rainfall infiltration, suspending the slope, and increasing its bulk density. The destruction process of shallow landslides can be roughly divided into six processes, and the earth volume of the landslide is 0.24m³. The mechanism of the deep sliding surface in terraces occurs under the combined action of water erosion and gravity erosion. The soil moisture content increases, which decreases the anti-sliding moment and increases the sliding moment, and the safety factor becomes less than the allowable limit for terraces. The deep sliding deformation area of the terrace was 0 ~ 1.0 m below the slope surface, slip surface radius was 1.43 m, the slip surface angle was 92^°, and the deep sliding surface began to form earlier than terraced shallow landslides. The displacement of the characteristic points increased from the slope top, to the slope center, and to the slope foot, with maximum displacements of 40.3, 15.5, and 6.0 mm, respectively. Full article

Structural resilience describes urban drainage systems’ (UDSs) ability to minimize the frequency and magnitude of failure due to common structural issues such as pipe clogging and cracking or pump failure. Structural resilience is often neglected in the design of UDSs. The current literature supports structural decentralization as a way to introduce structural resilience into UDSs. Although there are promising methods in the literature for generating and optimizing decentralized separate stormwater collection systems, incorporating hydraulic simulations in unsteady flow, these approaches sometimes require high computational effort, especially for flat areas. This may hamper their integration into ordinary commercially designed UDS software due to their predominantly scientific purposes. As a response, this paper introduces simplified cost and structural resilience indices that can be used as heuristic parameters for optimizing the UDS layout. These indices only use graph connectivity information, which is computationally much less expensive than hydraulic simulation. The use of simplified objective functions significantly simplifies the feasible search space and reduces blind searches by optimization. To demonstrate the application and advantages of the proposed model, a real case study in the southwest city of Ahvaz, Iran was explored. The proposed framework was proven to be promising for reducing the computational effort and for delivering realistic cost-wise and resilient UDSs. Full article

This study presents an integrated modeling system for the evaluation of the quantity and quality of water resources of coastal agricultural watersheds. The modeling system consists of coupled and interrelated models, including (i) a surface hydrology model (UTHBAL), (ii) a groundwater hydrology model (MODFLOW), (iii) a crop growth/nitrate leaching model (REPIC, an R-ArcGIS-based EPIC model), (iv) a groundwater contaminant transport model (MT3DMS), and (v) a groundwater seawater intrusion model (SEAWAT). The efficacy of the modeling system to simulate the quantity and quality of water resources has been applied to the Almyros basin in Thessaly, Greece. It is a coastal agricultural basin with irrigated and intensified agriculture facing serious groundwater problems, such as groundwater depletion, nitrate pollution, and seawater intrusion. Irrigation demands were estimated for the main crops cultivated in the area, based on precipitation and temperature from regional weather stations. The models have been calibrated and validated against time-series of observed crop yields, groundwater table observations, and observed concentrations of nitrates and chlorides. The results indicate that the modeling system simulates the water resources quantity and quality with increased accuracy. The proposed modeling system could be used as a tool for the simulation of water resources management and climate change scenarios. Full article

Worldwide, consumption of resources such as water, energy and food continues to rise exponentially despite environmental and climatic change related challenges. Centralized sewerage systems continue to be implemented worldwide despite being very water and energy intensive, and although this is not always the best option for regions facing water scarcity. Deploying the Water-Energy-Food (WEF) Nexus approach, particularly through alternative technology options that can support decentralized water reclamation with integrated resource recovery, can enable resource conservation and more effective management of the WEF security Nexus for local governments with limited capacities. However, a certain pattern of “business as usual” infrastructure development and investment linked to infrastructure shaming continuously reinforces implementation of centralized sewerage systems, thereby hampering deployment of alternative technology options. This study uses two typical case study towns, Shaxi in China and Leh in India, to describe this pattern. The study finds that alternative technology approaches were in place in both towns. Yet after international consulting companies got involved, centralized sewerage systems were implemented despite limited water availability and large segments of the population not having flush toilets. This study discusses management of the WEF security Nexus implications thereof in the context of cities worldwide and a systemic socio-technical transition to a circular economy. Full article

Excess sludge reduction has been a research hotspot for a long time. Ultrasonic treatment of excess sludge was an efficient and green pretreatment method, and also can be combined with the addition of oxidants. To improve the effect of ultrasound treatment on sludge destruction, hydrogen peroxide (H₂O₂) was added to examine the combined results in the current study. The effects of the ultrasound/hydrogen peroxide system on the release of sludge organic matter during the destruction process were studied. Single-factor experiments were carried out to determine the optimal operating conditions. With the initial pH of 11.0, H₂O₂ concentration of 0.5 mmol/L, initial sludge concentration of 17 g/L, and 15 min ultrasonic treatment, the maximum soluble chemical oxygen demand (ΔSCOD) in the sludge supernatant after destruction was achieved at 3662.78 ± 239.21 mg/L, with a disintegration degree of 28.61 ± 2.14%, sludge reduction rate of 19.47 ± 0.82%, and the change of mixture sludge concentration (ΔMLSS) of 3.31 ± 0.06 g/L. Meanwhile, the release of nitrogen and phosphorus were greatly improved. Under the optimal conditions, the release of total nitrogen (TN), ammonia nitrogen (NH₃-N) and total phosphorus (TP) were 282.30 ± 24.06 mg/L, 25.68 ± 2.09 mg/L, and 105.69 ± 7.84 mg/L, respectively. The current work had provided solid evidence showing the addition of hydrogen peroxide can effectively strengthen the treatment effects of ultrasound on sludge destruction. Full article

The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams and groupings of dams and the geographies of their impacts. Specifically, we examined the 3S (Sesan, Sekong Srepok) river system in northeastern Cambodia, the Central Highlands of Vietnam, and southern Laos; the Khone Falls area in southern Laos; the lower Mun River Basin in northeastern Thailand; and the upper Mekong River in Yunnan Province, China, northeastern Myanmar, northern Laos, and northern Thailand. Evidence shows that these dams and groupings of dams are affecting fish migrations, river hydrology, and sediment transfers. Such changes are negatively impacting riparian communities up to 1000 km away. Because many communities depend on the river and its resources for their food and livelihood, changes to the river have impacted, and will continue to negatively impact, food and economic security. While social and environmental impact assessments have been carried out for these projects, greater consideration of the scale and cumulative impacts of dams is necessary. Full article

Microplastics have been documented in aquatic and terrestrial ecosystems throughout the world. However, few studies have investigated microplastics in freshwater fish diets. In this study, water samples and three trophic levels of a freshwater food web were investigated for microplastic presence: amphipods (Gammarus lacustris), Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri), and lake trout (Salvelinus namaycush). Microplastics and other anthropogenic materials were documented in water samples, amphipods, and fish, then confirmed using FTIR (Fourier-transform infrared) and Raman spectroscopy. Our findings confirmed the presence of microplastics and other anthropogenic materials in three trophic levels of a freshwater food web in a high-elevation lake in a national park, which corroborates recent studies implicating the global distribution of microplastics. This study further illustrates the need for global action regarding the appropriate manufacturing, use, and disposal of plastics to minimize the effects of plastics on the environment. Full article

Chromium (Cr) in water bodies is considered as a major environmental issue around the world. In the present study, aqueous Cr(VI) adsorption onto rice husk was studied as a function of various environmental parameters. Equilibrium time was achieved in 2 h and maximum Cr(VI) adsorption was 78.6% at pH 5.2 and 120 mg L⁻¹ initial Cr(VI) concentration. In isotherm experiments, the maximum sorption was observed as 379.63 mg g⁻¹. Among four isotherm models, Dubinin–Radushkevich and Langmuir models showed the best fitting to the adsorption data, suggesting physical and monolayer adsorption to be the dominant mechanism. The kinetic modeling showed that a pseudo-second order model was suitable to describe kinetic equilibrium data, suggesting a fast adsorption rate of Cr(VI). The results of FTIR spectroscopy indicated that mainly –OH and C–H contributed to Cr(VI) adsorption onto rice husk. This paper provided evidence that rice husk could be a cost-effective, environment-friendly and efficient adsorptive material for Cr(VI) removal from wastewater due to its high adsorption capacity. Full article

The presence of pharmaceutical compounds in the whole environment is a growing concern. These compounds might be present in the effluents of wastewater treatment plants and, hence, irrigation with treated sewage may be a source of groundwater pollution. The volcanic aquifer that lies NE of Gran Canaria (Spain) was studied to address the relationship of the occurrence of pharmaceutical compounds and a golf course that has been irrigated with regenerated water since 1973. Of the 14 analyzed groundwater samples, five wells were chosen to perform annual monitoring. Irrigation water and soil leachate were also evaluated. The target analytes were atenolol, metamizole, fluoxetine, ibuprofen, nicotine, permethrin, caffeine, and their metabolite paraxanthine. The environmental risk is limited as the concentrations of the pharmaceuticals measured in the sampled wells were always below 60 ng·L⁻¹ (lower than the detected caffeine and nicotine concentrations). Wide variations for the same wells were measured among sampling campaigns, and also among the different wells. The study points to the importance of sample conservation during transport and the need to perform analyses immediately, or to follow an in-situ extraction procedure to carry concentrated samples under better conditions. Full article