Water

19 pages, 3689 KiB

Open AccessArticle

Evaluation of a Desalination System Combining Photovoltaic and Membrane Technology: A Case Study on the Benefit Analysis of an Apple Orchard

by Yang Yang, Zhilin Sun and Chaoqun Zhai

Water 2024, 16(16), 2306; https://doi.org/10.3390/w16162306 (registering DOI) - 16 Aug 2024

Abstract

Water shortage is one of the main issues affecting agricultural development in many regions, and the problem of crop yield reduction caused by the salinisation of irrigation water has become increasingly prominent. Xinjiang is a major agricultural development province in China, with mostly [...] Read more.

Water shortage is one of the main issues affecting agricultural development in many regions, and the problem of crop yield reduction caused by the salinisation of irrigation water has become increasingly prominent. Xinjiang is a major agricultural development province in China, with mostly remote agricultural land and an unstable electricity supply. We have introduced a combination of photovoltaic and reverse osmosis technology in the local Aksu region, using wastewater for irrigation to improve returns. In order to verify the feasibility of two schemes, we evaluated the benefits of the apple orchard after irrigation with desalinated water. The result shows that the net present value of the orchard has become 2.4 times that of the initial. It not only used secondary wastewater resources in the drainage canal, but also changed the trend of apple orchard profits declining year by year. The influence of various factors on the income of the orchard has obviously reduced, and the possibility of investment profit is greatly improved. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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17 pages, 4057 KiB

Open AccessArticle

Sewage Vertical Infiltration Introduced Polygenic Multipollutants into Groundwater

by Yihan Dong, Yifan Han, Xu Han, Yaoxuan Chen and Yuanzheng Zhai

Water 2024, 16(16), 2305; https://doi.org/10.3390/w16162305 (registering DOI) - 16 Aug 2024

Abstract

With the increasing environmental impacts of human activities, the problem of polygenic multipollutants in groundwater has attracted the attention of researchers. Identifying the hydrobiogeochemical characteristics of the surface sewage that replenishes groundwater is crucial to addressing this problem. The input of polygenic multipollutants [...] Read more.

With the increasing environmental impacts of human activities, the problem of polygenic multipollutants in groundwater has attracted the attention of researchers. Identifying the hydrobiogeochemical characteristics of the surface sewage that replenishes groundwater is crucial to addressing this problem. The input of polygenic multipollutants into groundwater leads to not only the mechanical superposition of pollutants but also the formation of secondary pollutant types. The evolution of polygenic multipollutants is influenced by aquifer characteristics, carbon sources, microbial abundance, etc. Therefore, this study took a sewage leakage point in Northwest China as the research object, carried out a controlled laboratory experiment on the impact of sewage discharge on groundwater, and, combined with long-term field monitoring results, determined the main hydrobiogeochemical processes of polygenic multipollutants and their secondary pollutants. The results showed that the redox environment and the gradient change in pH were identified as the most critical controlling factors. In oxidative groundwater during the early stage of vertical infiltration, sewage carries a substantial amount of NH₄⁺, which is oxidized to form the secondary pollutant NO₃⁻. As O₂ is consumed, the reduction intensifies, and secondary pollutants NO₃⁻, Mn (IV), and Fe(III) minerals are successively reduced. Compared with the natural conditions of rainwater vertical infiltration, the reaction rates and intensities of various reactions significantly increase during sewage vertical infiltration. However, there is a notable difference in the groundwater pH between sewage and rainwater vertical infiltration. In O₂ and secondary pollutant NO₃⁻ reduction, a large amount of CO₂ is rapidly generated. Excessive CO₂ dissolves to produce a substantial amount of H⁺, promoting the acidic dissolution of Mn (II) minerals and generation of Mn²⁺. Sewage provides a higher carbon load, enhancing Mn (II) acidic dissolution and stimulating the activity of dissimilatory nitrate reduction to ammonium, which exhibits a higher contribution to NO₃⁻ reduction. This results in a portion of NO₃⁻ converted from NH₄⁺ being reduced back to NH₄⁺ and retained in the groundwater, reducing the denitrification’s capacity to remove secondary NO₃⁻. This has important implications for pollution management and groundwater remediation, particularly monitored natural attenuation. Full article

(This article belongs to the Special Issue China Water Forum 2024)

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30 pages, 11884 KiB

Open AccessArticle

Mechanisms of Thick-Hard Roof and Thin Aquifer Zone Floor Destruction and the Evolution Law of Water Inrush

by Min Cao, Shangxian Yin, Shuqian Li and Xu Wang

Water 2024, 16(16), 2304; https://doi.org/10.3390/w16162304 - 15 Aug 2024

Viewed by 235

Abstract

The collapse of thick-hard roofs after coal has been extracted is not a consequential process in all cases. Rather, it happens due to the augmentation of high stress conducted at depth, followed by a wider range of damage as the floor cracks. The [...] Read more.

The collapse of thick-hard roofs after coal has been extracted is not a consequential process in all cases. Rather, it happens due to the augmentation of high stress conducted at depth, followed by a wider range of damage as the floor cracks. The extent and spread of the cracks in the floor indicate the intensity of the collapse, and the mine will be submerged by the high-pressure water of the coal ash. Therefore, it is particularly important to study the mechanism of the combined effect of high stress on the roof and confined aquifer on the deformation and failure of the coal seam mining floor. This study analyzes and compares the impact of thick-hard magmatic rocks on the destruction of thin floor rock layers in coal seams. Plastic theory calculations are used to determine the plastic zone yield length of floor destruction under hard roof conditions, and the location and height of the maximum floor destruction depth are solved. An empirical formula and BP neural network are used to establish a prediction model for floor destruction. The results of the model’s prediction of the depth of floor failure were compared with the measured values, with an absolute error of 2.13 m and a residual of 10.3%, which was closer to the true values. The accuracy of the theoretical model and prediction model is verified using numerical simulation and on-site in situ measurements. Based on this, the deformation and destruction forms of the floor under pressure and the water inrush mechanism are summarized for mining under the condition of a thick-hard roof. Thus, the floor is subjected to high vertical stress, accompanied by significant disturbances generated during coal seam mining, resulting in intense working face pressures. The floor near the working face coal wall will experience severe compression and shear deformation and slide towards the goaf. The floor in the goaf is relieved of high vertical stress, and horizontal stress compression will result in shear failure, leading to floor heave and further increasing the height of the floor destruction zone. After the mining of the working face, the goaf will undergo two stages of re-supporting and post-mining compaction. During the re-supporting stage, the floor rock undergoes a transition from high-stress to low-stress conditions, and the instantaneous stress relief will cause plastic deformation and failure in the coal seam floor. The combined action of primary floor fractures and secondary fractures formed during mining can easily create effective water channels. These can connect to the aquifer or water-conducting structures, making them highly dangerous. The main modes of floor water inrush under the condition of a thick-hard roof are as follows: the high-stress mode, inducing a floor destruction zone connected to the water riser zone; the mining damage mode, connecting to water-conducting faults; the mining damage mode, connecting to water collapse columns; and the coupled water inrush mode, between the mining damage zone and the highly pressurized water floor. Full article

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14 pages, 6570 KiB

Open AccessArticle

Dewaterability Enhancement of Anaerobic Sludge Using Polymeric Aluminum Chloride and Polyoxyethylene Alkyl Ether Surfactants

by Eunhye Song, Eunju Kim, Gyeong Woo Kim, Cheol Jin Jeong, Wonbae Lee and Seong Kuk Han

Water 2024, 16(16), 2303; https://doi.org/10.3390/w16162303 - 15 Aug 2024

Viewed by 223

Abstract

The use of coagulants, such as ferric chloride hexahydrate, in wastewater treatment processes is known to induce pipe corrosion and to contribute to the discoloration of treated water. This study explores alternative approaches to sludge dewatering by evaluating the effectiveness of polymeric aluminum [...] Read more.

The use of coagulants, such as ferric chloride hexahydrate, in wastewater treatment processes is known to induce pipe corrosion and to contribute to the discoloration of treated water. This study explores alternative approaches to sludge dewatering by evaluating the effectiveness of polymeric aluminum chloride (PAC) as a coagulant and polyoxyethylene alkyl ether (POAE) as a surfactant. The impacts of coagulation/flocculation were assessed using time to filtration (TTF) and a pressure filter press. The effects of certain coagulant and surfactant dosages were studied. The inputs were in the range of 105–1750 mg/L for PAC and 28–152 mg/L for POAE, which were determined based on zeta potential (ZP) measurements. The optimal concentrations were 876 mg/L for PAC and 114 mg/L for POAE, resulting in a TTF of less than 1 min. Moreover, the effect of pH on anaerobic sludge dewaterability was investigated. At a low pH below 8, the ZP reached the maximum value, and a higher pH resulted in a reduction in ZP. Under low-pH adjustments, it was observed that the dewatering performance of the POAE surfactant improved more significantly than that of the PAC coagulant. In addition, the effect of pressure was analyzed using a pressure filter under conditions favoring POAE, with relatively lower dosages and greater cost-effectiveness. In order to evaluate the solubility of organic matter under pressurized conditions, the filtrate’s removal efficiency, chemical oxygen demand (COD), and total phosphorus (TP) were investigated. Solubilization did not occur at an increased pressure of around 10 bars. The findings presented in this study provide technical assistance for sludge treatment. Full article

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16 pages, 3069 KiB

Open AccessArticle

Source-Oriented Health Risks and Distribution of BTEXS in Urban Shallow Lake Sediment: Application of the Positive Matrix Factorization Model

by Ivana Trajković, Milica Sentić, Jelena Vesković, Milica Lučić, Andrijana Miletić and Antonije Onjia

Water 2024, 16(16), 2302; https://doi.org/10.3390/w16162302 - 15 Aug 2024

Viewed by 259

Abstract

The degradation of sediments in urban environments worldwide is driven by population growth, urbanization, and industrialization, highlighting the need for thorough quality assessment and management strategies. As a result of these anthropogenic activities, benzene, toluene, ethylbenzene, xylenes, and styrene (BTEXS) are persistently released [...] Read more.

The degradation of sediments in urban environments worldwide is driven by population growth, urbanization, and industrialization, highlighting the need for thorough quality assessment and management strategies. As a result of these anthropogenic activities, benzene, toluene, ethylbenzene, xylenes, and styrene (BTEXS) are persistently released into the environment, polluting sediment. This study employed self-organizing maps (SOMs), positive matrix factorization (PMF), and Monte Carlo simulation of source-oriented health risks to comprehensively investigate sediment in an urban shallow lake in a mid-sized city in central Serbia. The results indicated a mean ∑BTEXS concentration of 225 µg/kg, with toluene as the dominant congener, followed by m,p-xylene, benzene, ethylbenzene, o-xylene, and styrene. Three contamination sources were identified: waste solvents and plastic waste due to intensive recreational activities, and vehicle exhaust from heavy traffic surrounding the lake. Both non-carcinogenic and carcinogenic health risks were below the permissible limits. However, children were more susceptible to health risks. Benzene from vehicle exhaust is the most responsible for non-carcinogenic and carcinogenic health risks in both population groups. The results of this study can help researchers to find a suitable perspective on the dynamics and impacts of BTEXS in lake sediments. Full article

(This article belongs to the Special Issue Fate, Transport, Removal and Modeling of Pollutants in Water)

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22 pages, 5820 KiB

Open AccessReview

Solutions Based on Nature to Face Water Stress: Lessons from the Past and Present

by Daniel O. Suman, Manuela Morais and Carlos Hiroo Saito

Water 2024, 16(16), 2301; https://doi.org/10.3390/w16162301 - 15 Aug 2024

Viewed by 304

Abstract

Nature-based solutions (NbS) to water scarcity, environmental degradation, climate change, and biodiversity losses are enjoying increasing implementation throughout the world. This manuscript reviews three case studies from Brazil, Panama, and Portugal that illustrate NbS and searches for commonalities that may assist their usefulness [...] Read more.

Nature-based solutions (NbS) to water scarcity, environmental degradation, climate change, and biodiversity losses are enjoying increasing implementation throughout the world. This manuscript reviews three case studies from Brazil, Panama, and Portugal that illustrate NbS and searches for commonalities that may assist their usefulness in new sites. The Tijuca Forest in Rio de Janeiro is a remarkable story of centuries of forest management and restoration that initially aimed at providing water security for the capital of the country during the XIX Century while it was still a monarchy. Today, it is recognized as a UNESCO World Heritage Site. The Panama Canal Watershed produces water for canal operations, electricity generation, and drinking water for half the country’s population. Traditional water mills and weirs near streams in the Alentejo Region, Portugal, have largely been abandoned due to the damming of the Guadiana River. Yet today, weirs are increasingly recognized for their important contribution to water provisioning in this dry region. All have a primary goal related to water provisioning, yet their ecosystem benefits are multiple. The cases offer important lessons for adaptation to climate change, cultural benefits from traditional human activities, and concerns about social equity. Full article

(This article belongs to the Special Issue Coastal and Marine Governance and Protection)

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17 pages, 3602 KiB

Open AccessArticle

Understanding Two Decades of Turbidity Dynamics in a Coral Triangle Hotspot: The Berau Coastal Shelf

by Faruq Khadami, Ayi Tarya, Ivonne Milichristi Radjawane, Totok Suprijo, Karina Aprilia Sujatmiko, Iwan Pramesti Anwar, Muhamad Faqih Hidayatullah and Muhamad Fauzan Rizky Adisty Erlangga

Water 2024, 16(16), 2300; https://doi.org/10.3390/w16162300 - 15 Aug 2024

Viewed by 251

Abstract

Turbidity serves as a crucial indicator of coastal water health and productivity. Twenty years of remote sensing data (2003–2022) from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite were used to analyze the spatial and temporal variations in turbidity, as measured by total [...] Read more.

Turbidity serves as a crucial indicator of coastal water health and productivity. Twenty years of remote sensing data (2003–2022) from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite were used to analyze the spatial and temporal variations in turbidity, as measured by total suspended matter (TSM), in the Berau Coastal Shelf (BCS), East Kalimantan, Indonesia. The BCS encompasses the estuary of the Berau River and is an integral part of the Coral Triangle, renowned for its rich marine and coastal habitats, including coral reefs, mangroves, and seagrasses. The aim of this research is to comprehend the seasonal and interannual patterns of turbidity and their associations with met-ocean parameters, such as wind, rainfall, and climate variations like the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The research findings indicate that the seasonal spatial pattern of turbidity is strongly influenced by monsoon winds, while its temporal patterns are closely related to river discharge and rainfall. The ENSO and IOD climate cycles exert an influence on the interannual turbidity variations, with turbidity values decreasing during La Niña and negative IOD events and conversely increasing during El Niño and positive IOD events. Furthermore, the elevated turbidity during negative IOD and La Niña coincides with rising temperatures, potentially acting as a compound stressor on marine habitats. These findings significantly enhance our understanding of turbidity dynamics in the BCS, thereby supporting the management of marine and coastal ecosystems in the face of changing climatic and environmental conditions. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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15 pages, 5792 KiB

Open AccessArticle

Cobalt-Based MOF Material Activates Persulfate to Degrade Residual Ciprofloxacin

by Yiting Luo and Rongkui Su

Water 2024, 16(16), 2299; https://doi.org/10.3390/w16162299 - 15 Aug 2024

Viewed by 196

Abstract

Antibiotic residues in water environments have garnered widespread attention. Metal-organic frameworks (MOFs) have found extensive applications in water purification. This study investigates the use of a cobalt-based MOF material, zeolitic imidazolate framework-67(ZIF-67)(Co), for activating persulfate (PMS) to remove residual antibiotic ciprofloxacin (CIP) from [...] Read more.

Antibiotic residues in water environments have garnered widespread attention. Metal-organic frameworks (MOFs) have found extensive applications in water purification. This study investigates the use of a cobalt-based MOF material, zeolitic imidazolate framework-67(ZIF-67)(Co), for activating persulfate (PMS) to remove residual antibiotic ciprofloxacin (CIP) from aqueous environments. The main findings are as follows: ZIF-67(Co) exhibits insignificant adsorption capacity for CIP, and PMS alone does not degrade CIP effectively. However, ZIF-67(Co)-activated PMS demonstrates the efficient degradation of CIP, following pseudo-second-order reaction kinetics. Under optimal conditions of the catalyst dosage (15 mg) and PMS concentration (1.0 mM), the removal efficiency reaches 88% after 60 min. Comparative analysis of CIP degradation at different initial pH levels shows that the highest efficiency is reached under mildly acidic conditions, with an 86% removal rate achieved within 60 min under these conditions. Investigation into the impact of various inorganic anions on the ZIF-67(Co)-catalyzed PMS degradation of CIP reveals significant inhibition by chloride ions (

{Cl}^{-}

), whereas nitrate (

{NO}_{3}^{-}

) and sulfate (

{SO}_{4}^{2 -}

) ions have minor effects on the degradation efficiency. The system demonstrates a consistent performance across different water matrices, highlighting ZIF-67(Co)/PMS as effective for ciprofloxacin removal in environmental waters. This study provides technical support for the efficient removal of antibiotic residues. Full article

(This article belongs to the Special Issue Biomass Carbon Materials in Wastewater Treatment and Resource Utilization)

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14 pages, 3470 KiB

Open AccessArticle

A Novel Screening Method of Surfactants for Promoting the Static Imbibition of Shale

by Zhaokai Hou, Yuan Yuan, Jingyu Qu, Ye Chen, Shihui Sun and Ying He

Water 2024, 16(16), 2298; https://doi.org/10.3390/w16162298 - 15 Aug 2024

Viewed by 233

Abstract

Following hydraulic fracturing operations within shale reservoirs, there frequently exists a considerable volume of residual oil that remains encapsulated within the matrix, thereby impeding the singular shale well’s productivity from attaining projected yields. In pursuit of augmenting the recovery efficiency of shale oil, [...] Read more.

Following hydraulic fracturing operations within shale reservoirs, there frequently exists a considerable volume of residual oil that remains encapsulated within the matrix, thereby impeding the singular shale well’s productivity from attaining projected yields. In pursuit of augmenting the recovery efficiency of shale oil, the industry has widely adopted a post-fracture shut-in strategy within shale oil wells. This methodology is predicated on the aspiration to escalate both the production output and the recovery factor of the oil well by leveraging the imbibition and displacement mechanisms of the fracturing fluid throughout the shut-in interval. There are many kinds of surfactants, and how to select surfactants suitable for shale reservoirs from these many surfactants has become a key issue in improving shale reservoir recovery. In this study, a new surfactant screening method for improving imbibition recovery in shale reservoirs is proposed. An interfacial tension test, contact angle test, and anti-adsorption test are carried out for the collected surfactant products, and the interfacial tension, contact angle, and anti-adsorption are gradually used as indicators. The type of surfactant is initially screened. On this basis, the static imbibition experiment of shale is made to determine the type and concentration of surfactants suitable for shale oil development. The results show that the surfactants screened by this method have the characteristics of decreasing oil–water interfacial tension, varying rock wettability, and strong anti-adsorption, which can effectively improve imbibition efficiency. The study results herein can provide technical support for optimizing shale oil surfactants and provide a new idea for improving oil exploitation in low-permeability reservoirs. Full article

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13 pages, 1141 KiB

Open AccessArticle

Multi-Objective Planting Structure Optimisation in an Irrigation Area Using a Grey Wolf Optimisation Algorithm

by Li Wu, Junfeng Tian, Yanli Liu, Yong Wang and Peixin Zhang

Water 2024, 16(16), 2297; https://doi.org/10.3390/w16162297 - 14 Aug 2024

Viewed by 311

Abstract

To improve agricultural production efficiency, increase farmers’ income, and promote sustainable development, we established a multi-objective optimisation model for crop planting structure in an irrigation area using the grey wolf optimisation (GWO) algorithm to comprehensively consider the resource, economic, and social objectives associated [...] Read more.

To improve agricultural production efficiency, increase farmers’ income, and promote sustainable development, we established a multi-objective optimisation model for crop planting structure in an irrigation area using the grey wolf optimisation (GWO) algorithm to comprehensively consider the resource, economic, and social objectives associated with agriculture. This model was subsequently applied to obtain the optimal planting structure in the southern bank of the Xiaolangdi Reservoir irrigation area in Henan Province, China. The planting areas of wheat, corn, autumn miscellaneous, and economic crops are 30,417; 25,050; 7157; and 1789 hm², respectively. The irrigation water is 8292.66 × 10⁴ m³, output value of crops is 105,721.37 × 10⁴ CNY, and crop yield is 34,280.31 × 10⁴ kg. Different solutions are used to solve the model to evaluate the results, and the order degree entropy method is used to evaluate and compare the results of multiple solutions. The optimisation scheme obtained with this model is consistent with the evaluation results of the cooperative game optimisation scheme, and the relative order degree entropy is 0.136, which is better than that in other schemes. Thus, the optimisation scheme of crop planting structure obtained via GWO comprehensively considers irrigation water consumption, economic benefits, and crop yield, which ensures coordinated development of resource, economic, and social systems and is conducive to promoting the benign development of the whole irrigation area system. Full article

(This article belongs to the Section Water Use and Scarcity)

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14 pages, 3684 KiB

Open AccessArticle

Effects of Stocking Density of Filter-Feeding Fishes on Water Quality and Bacterial Community in Rice–Crayfish Polyculture System

by Yuanyuan Zhang, Liangjie Zhao, Jiaoyang Duan, Yongtao Tang and Jun Lv

Water 2024, 16(16), 2296; https://doi.org/10.3390/w16162296 - 14 Aug 2024

Viewed by 274

Abstract

To evaluate the effects of filter-feeding fishes on water quality and bacterial community in the rice–crayfish coculture system, four different stocking densities of bighead carp (0, 500, 1000, 1500 ind./200 m²) were set up in rice–crayfish coculture systems. Water samples in [...] Read more.

To evaluate the effects of filter-feeding fishes on water quality and bacterial community in the rice–crayfish coculture system, four different stocking densities of bighead carp (0, 500, 1000, 1500 ind./200 m²) were set up in rice–crayfish coculture systems. Water samples in the systems were collected biweekly to detect dissolved oxygen (DO), temperature (T), potential of Hydrogen (pH), ammonia nitrogen (NH₄⁺-N), nitrite nitrogen (NO₂⁻-N), nitrate nitrogen (NO₃⁻-N), total nitrogen (TN), total phosphorus (TP), and Chlorophyll-a (Chl-a); the bacterial community in the water was analyzed simultaneously, then the correlation between water quality and microorganisms were studied. The results showed that concentrations of TN, TP, NO₂⁻-N, and NH₄⁺-N decreased while DO and NO₃⁻-N increased along with the breeding process. NO₂⁻-N, NO₃⁻-N, TN, and NH₄⁺-N were important environmental factors affecting the bacterial community structure in water (p < 0.05). Bighead carp stocking had an impact on the diversity, richness, and evenness of the bacterial communities in the systems. The dominant bacteria in the four different carp density groups were Proteobacteria, Actinomycetes, Bacteroidetes, and Cyanobacteria. Bighead carp increased the abundance of Bacteroidea but reduced that of Actinomycetes, Cyanobacteria, and Proteobacteria. The introduction of bighead carp promoted the conversion of nitrogen and phosphorus, reducing the risk of cyanobacterial blooms. Group 1000 ind./200 m² exhibited the best effect on the removal of nitrogen and phosphorus from the water body. Full article

(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)

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26 pages, 4621 KiB

Open AccessArticle

Recasting Klamath Dam Removal as Eco-Cultural Revitalization and Restorative Justice through Karuk Tribal Leadership

by Sibyl Diver, John R. Oberholzer Dent, Daniel Sarna-Wojcicki, Ron Reed and Cole Dill-De Sa

Water 2024, 16(16), 2295; https://doi.org/10.3390/w16162295 - 14 Aug 2024

Viewed by 331

Abstract

Moving from an era of dam building to dam removal brings additional perspectives to indigenous water governance and hydrosocial relations in the Klamath River Basin (US). This collaborative research initiative with the Karuk Tribe builds greater understanding of the sociocultural impacts of Klamath [...] Read more.

Moving from an era of dam building to dam removal brings additional perspectives to indigenous water governance and hydrosocial relations in the Klamath River Basin (US). This collaborative research initiative with the Karuk Tribe builds greater understanding of the sociocultural impacts of Klamath dam removal and river restoration through Karuk knowledge. Addressing a knowledge gap around the social dimensions of dam removal, we held focus groups and interviews with Karuk cultural practitioners, tribal leaders, and tribal youth in the six-month period leading up to demolition. Extending beyond a focus on infrastructure removal or single-species restoration, we consider how Indigenous environmental relations and cosmologies are embedded in dam removal and river restoration. Specifically, Karuk knowledge shifts the significance of dam removal by elucidating deeply interconnected ecological, cultural, and ceremonial relations that are co-constituted with the Klamath watershed, thereby recasting dam removal as a holistic eco-cultural revitalization initiative. This reconfigures dam removal goals to include improving community health and well-being, enhancing spiritual elements of river restoration, responding to colonial legacies, and engaging tribal youth. In the Klamath case, restorative justice becomes possible through Karuk participation in river restoration to facilitate the revitalization of reciprocal relations held between Karuk people and the Klamath River—including Karuk eco-cultural and ceremonial practices for restoring balance in the world. Full article

(This article belongs to the Special Issue Water Contestations: Socio-Technical Entanglements, Politics and Social Mobilisation)

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16 pages, 3045 KiB

Open AccessArticle

Efficient Phosphate Adsorption from Groundwater by Mn-FeOOHs

by Mengxue Li, Guanghui Sun, Ziyang Chu, Jing Wang and Yu Qiu

Water 2024, 16(16), 2294; https://doi.org/10.3390/w16162294 - 14 Aug 2024

Viewed by 227

Abstract

Manganese co-precipitated with goethite (Mn-FeOOH) is ubiquitous within (sub-)surface environments, which are considered one of the most important sinks for phosphorus pollution management. Accordingly, various mole ratios of Mn-FeOOHs are synthesized and characterized by XRD, FE-SEM, FTIR, BET, XPS, hysteresis loop, acid–base titration [...] Read more.

Manganese co-precipitated with goethite (Mn-FeOOH) is ubiquitous within (sub-)surface environments, which are considered one of the most important sinks for phosphorus pollution management. Accordingly, various mole ratios of Mn-FeOOHs are synthesized and characterized by XRD, FE-SEM, FTIR, BET, XPS, hysteresis loop, acid–base titration and zero potential. According to XRD and FESEM images, the substitution of Mn causes subtle alterations in the microstructure and crystal structure of goethite, and the morphology of Mn-FeOOHs is transformed from needle-shaped goethite to a short-rod-shaped rough surface with increasing Mn substitution. Based on the analysis of BET and acid–base titration, the substitution of Mn into goethite significantly improved the surface area, pore volume, surface properties and active sites of goethite, thereby establishing a theoretical basis for effective subsequent adsorption. Batch experiment results show that the removal rate of phosphate decreases with the increasing solution pH, indicating that acidic groundwater conditions are more conducive to the removal of phosphate. In addition, the adsorption of phosphate on Mn-FeOOHs is independent of ionic strength, indicating that the inner-sphere surface complexation predominated their adsorption behaviors. The isotherm experiment results showed that Mn-G15 exhibits the strongest adsorption capacity for phosphate at pH 5.5 and T = 318 K, with a maximum adsorption capacity of 87.18 mg/g. These findings highlighted the effect of Mn content on the fixation of phosphate onto Mn-FeOOHs from (sub-)surface environments in pollution management. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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17 pages, 6701 KiB

Open AccessArticle

Reflections on How to Reach the “30 by 30” Target: Identification of and Suggestions on Global Priority Marine Areas for Protection

by Chang Zhao, Yuejing Ge and Miaozhuang Zheng

Water 2024, 16(16), 2293; https://doi.org/10.3390/w16162293 - 14 Aug 2024

Viewed by 309

Abstract

The establishment of marine protected areas (MPAs) is an important method to ensure marine protection. To protect and conserve global marine biodiversity, with the adoption of the “Kunming-Montreal Global Biodiversity Framework” during the 15th meeting of the Conference of the Parties of Convention [...] Read more.

The establishment of marine protected areas (MPAs) is an important method to ensure marine protection. To protect and conserve global marine biodiversity, with the adoption of the “Kunming-Montreal Global Biodiversity Framework” during the 15th meeting of the Conference of the Parties of Convention on Biodiversity (CBD) in December 2022, the establishment of an effectively managed MPA network by 2030 and the protection of 30% of the world’s oceans will be common goals for all countries party to the CBD over the next decade. Based on the distribution of over 150 types of marine species, habitats, ecosystems, and abiotic elements, ArcGIS10.5 and Zonation are used in this study to calculate the marine protection priority levels of coastal, nearshore, open ocean, and deep ocean trench areas, and a plan to reach the “30 by 30” targets is proposed. The suggestions for scientifically identifying and managing MPAs are as follows: first, improve MPA planning and establish a well-connected MPA network in national jurisdictions, then conduct scientific marine investigations to obtain background data on MPA establishment and delimitation. Full article

(This article belongs to the Special Issue Coastal and Marine Governance and Protection)

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17 pages, 7217 KiB

Open AccessArticle

Damage Inflicted by Extreme Drought on Poyang Lake Delta Wetland and the Establishment of Countermeasures

by Yang Xia, Yue Liu, Zhichao Wang, Zhiwen Huang, Wensun You, Qiuqin Wu, Sufen Zhou and Jun Zou

Water 2024, 16(16), 2292; https://doi.org/10.3390/w16162292 - 14 Aug 2024

Viewed by 248

Abstract

Due to the joint influence of climate change and human activities, the hydrological rhythm of Poyang Lake has changed in recent years, leading to an increasingly severe drought problem during autumn and winter in this region. Notably, the extreme drought that occurred in [...] Read more.

Due to the joint influence of climate change and human activities, the hydrological rhythm of Poyang Lake has changed in recent years, leading to an increasingly severe drought problem during autumn and winter in this region. Notably, the extreme drought that occurred in 2022 had profound impacts on shipping, water supply and the ecological environment of the wetlands in the Poyang Lake Delta, sparking widespread concern. Based on the historical hydrometeorological data of Poyang Lake, we used statistical models (such as Chow test, correlation analysis, etc.) to analyze the cause of the extreme drought in the Poyang Lake Delta from the perspectives of natural factors and human activity. Through correlation analysis, we found that the water level, discharge, and drought duration of the Poyang Lake Delta were all significantly affected by climate change, particularly rainfall in the Poyang Lake basin. Furthermore, combining the results of Chow test and correlation analysis, we also found that the operation of the Three Gorges Reservoir had a notable impact on the water level of the Poyang Lake Delta. Based on remote sensing images, ecological and environmental sampling monitoring, the damage inflicted by the extreme drought event on the Poyang Lake Delta was analyzed. The results show that the inundated area of the delta wetlands in the extreme-drought year (2022) decreased by 45.75% compared with that in a normal year (2017). In addition, the ecological environment of the wetlands deteriorated significantly. The water quality parameters (TN, TP, NH₄⁺-N) increased by 50.2%, 240% and 64.7%, respectively. The concentrations of TN and TP were 3.8 mg/L and 0.17 mg/L, respectively, while the context values in the delta were 1.2 mg/L and 0.075 mg/L. The density and biomass of algae increased by 87.2% and 557.9%, respectively. In contrast, the density and biomass of benthos decreased by 59.9% and 78.5%, respectively. The control strategy for the Poyang Lake Delta under extreme drought was studied through an experiment on the operation of hydraulic controllers. The results show that under extreme drought conditions, the newly built hydraulic controllers could raise the water level of the delta from 9.1 ± 0.7 m to 14.2 ± 1.8 m, thus effectively solving the water cut-off problem in the four branches of the delta. Furthermore, by adjusting the distributive ratio of the main, north, middle and south branches of the delta to 50%, 4%, 24% and 22% through newly built hydraulic controllers, the water area can be increased by 56%. Full article

(This article belongs to the Special Issue Statistical Modelling of Hydrological Extremes: Floods and Droughts)

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18 pages, 3957 KiB

Open AccessArticle

Predicting Arsenic Contamination in Groundwater: A Comparative Analysis of Machine Learning Models in Coastal Floodplains and Inland Basins

by Zhenjie Zhao, Amit Kumar and Hongyan Wang

Water 2024, 16(16), 2291; https://doi.org/10.3390/w16162291 - 14 Aug 2024

Viewed by 278

Abstract

Arsenic (As) contamination in groundwater represents a major global health threat, potentially impacting billions of individuals. Elevated As concentrations are found in river floodplains across south and southeast Asia, as well as in the inland basins of China, despite varying sedimentological and hydrogeochemical [...] Read more.

Arsenic (As) contamination in groundwater represents a major global health threat, potentially impacting billions of individuals. Elevated As concentrations are found in river floodplains across south and southeast Asia, as well as in the inland basins of China, despite varying sedimentological and hydrogeochemical conditions. The specific mechanisms responsible for these high As levels remain poorly understood, complicating efforts to predict and manage the contamination. Applying hydro-chemical, geological, and soil parameters as explanatory variables, this study employs multiple linear regression (MLIR) and random forest regression (RFR) models to estimate groundwater As concentrations in these regions. Additionally, random forest classification (RFC) and multivariate logistic regression (MLOR) models are applied to predict the probability of As levels exceeding 10 μg/L in the Hetao Basin (China) and Bangladesh. Model validation reveals that RFR explains 80% and 70% of spatial variability of As concentration in the Hetao Basin and Bangladesh, respectively, outperforming MLIR, which accounts for only 35% and 32%. Similarly, RFC outperforms MLOR in predicting high As probability, achieving correct classification rates of 98.70% (Hetao Basin) and 98.25% (Bangladesh) on training datasets, and 82.76% (Hetao Basin) and 91.20% (Bangladesh) on validation datasets. The performance of the MLOR model on the validation set yields accuracy rates of 81.60% and 72.18%, respectively. In the Hetao Basin, Ca²⁺, redox potential (Eh), Fe, pH, SO₄²⁻, and Cl⁻ are key predictors of As contamination, while in Bangladesh, soil organic carbon (SOC), pH, and SO₄²⁻ are significant predictors. This study underscores the potential of random forest (RF) models as robust tools for predicting groundwater As contamination. Full article

(This article belongs to the Topic Human Impact on Groundwater Environment)

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17 pages, 2434 KiB

Open AccessArticle

Treatment of Domestic Wastewater in Colombia Using Constructed Wetlands with Canna Hybrids and Oil Palm Fruit Endocarp

by Alexi Jose Peralta Vega, Vicente Vergara Flórez, Oscar Marín-Peña, Sandra G. García-Aburto and Luis Carlos Sandoval Herazo

Water 2024, 16(16), 2290; https://doi.org/10.3390/w16162290 - 14 Aug 2024

Viewed by 312

Abstract

Untreated domestic wastewater from rural areas poses significant risks to ecosystems and human health. Constructed wetlands (CWs) are a viable alternative for this wastewater treatment, enhancing nitrogen removal using substrates as carbon sources. This process is particularly beneficial for wastewater with low carbon-to-nitrogen [...] Read more.

Untreated domestic wastewater from rural areas poses significant risks to ecosystems and human health. Constructed wetlands (CWs) are a viable alternative for this wastewater treatment, enhancing nitrogen removal using substrates as carbon sources. This process is particularly beneficial for wastewater with low carbon-to-nitrogen (C/N) ratios, making the treated water suitable for agricultural irrigation. In this study, a Horizontal Subsurface Flow CW (HSF-CW) was evaluated using Canna hybrids and a mixed substrate of gravel and endocarp from oil palm fruit (EOP) as a carbon source to leverage its abundance in the region. It was also determined that the effluent complies with the permissible limits set by Resolution 1207 of 2014 from the Colombian Ministry of Environment and Sustainable Development, which establishes environmental standards for wastewater treatment to ensure environmental protection and enable safe reuse in agricultural irrigation. The key parameters analyzed included organic contaminants, heavy metals, nutrients, and microbiological indicators. Removal efficiencies of up to 91%, 94%, 98%, 52%, 73%, 78%, and 75% were achieved for BOD, TSS, total phosphorus, nitrates, nitrites, ammonium, and total nitrogen, respectively, demonstrating the CW’s strong performance in contaminant removal and meeting most standards for agricultural irrigation. Although the carbon source was not highly efficient, the overall system performance supports its viability for improving water quality and promoting sustainable agricultural practices in rural areas. Full article

(This article belongs to the Special Issue Constructed Wetlands and Wastewater Treatment for the Improvement of Environmental Quality)

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22 pages, 5903 KiB

Open AccessArticle

A Study on the Construction and Evaluation of the Water Resource Reutilization System for Farmland Diversion and Drainage

by Qiuyi Ge, Chengli Zhu, Jizhou Hu, Genxiang Feng, Xing Huang and Xue Cheng

Water 2024, 16(16), 2289; https://doi.org/10.3390/w16162289 - 14 Aug 2024

Viewed by 333

Abstract

Water is an essential resource for both rural and agricultural areas; it can be wisely distributed and used in the field to protect daily life, production, the natural environment, and the safety and stability of regional drainage and flood control systems. Our research [...] Read more.

Water is an essential resource for both rural and agricultural areas; it can be wisely distributed and used in the field to protect daily life, production, the natural environment, and the safety and stability of regional drainage and flood control systems. Our research selected a typical plains rural river network area with agriculture as the main industry to investigate the most effective method of farmland diversion and drainage. We comprehensively planned and transformed the water system flow, water conservation engineering, and the ecological environment in the irrigation area through the reutilization system. The reutilization system’s operation and scheduling design is implemented for four specific periods: the water replenishment cycle, agricultural irrigation, agricultural drainage and the rainy period of the flood season. The research period ranges from 2020 to 2023 after the completion of the system. We used monitoring, the recording of hydraulic equipment parameters and data collection to evaluate the balance of water supply and demand in the study area. At the same time, we have tracked and evaluated the four aspects of water quality enhancement, water conservation and flood control, and agricultural irrigation. The results show that the total agricultural water consumption decreased by 2.9%, and the amount of water saved increased by 9.6%. The current segment creates the rivers’ embankment standards. With a 92% irrigation guarantee rate, the current section forms and the embankment standards of the rivers satisfy the design storage volume and the flood level of one in twenty years. The water quality of all the rivers in the area has decreased by 5~10% compared to the average concentration prior to establishment. This study verifies the comprehensive effect and the suitability of the system by comparing the before and after effects, and provides a scientific basis for the method of efficient recycling and utilization of water resources in the rural plains river network area; we also propose the guidance of increasing the digital twin control and long-term operation mechanism to ensure the long-term stable operation of the technology. Full article

(This article belongs to the Section Ecohydrology)

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18 pages, 6982 KiB

Open AccessArticle

Groundwater Quality Assessment at East El Minia Middle Eocene Carbonate Aquifer: Water Quality Index (WQI) and Health Risk Assessment (HRA)

by Abdel-Aziz A. Abdel-Aziz, Alaa Mostafa, Salman A. Salman, Ramadan S. A. Mohamed, Moustafa Gamal Snousy, Mohamed S. Ahmed, Mariacrocetta Sambito and Esam Ismail

Water 2024, 16(16), 2288; https://doi.org/10.3390/w16162288 - 14 Aug 2024

Viewed by 487

Abstract

Around the world, groundwater supply is critical for vital needs such as drinking and irrigation. This work investigates groundwater in the carbonate aquifer of the Middle Miocene in the east El Minia area, Egypt. In this regard, thirty-two groundwater samples were collected. The [...] Read more.

Around the world, groundwater supply is critical for vital needs such as drinking and irrigation. This work investigates groundwater in the carbonate aquifer of the Middle Miocene in the east El Minia area, Egypt. In this regard, thirty-two groundwater samples were collected. The water samples were analyzed for Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, SO₄²⁻, NO₃⁻, CO₂⁻, HCO₃⁻, Fe, Mn, Cd, As, Cr, Cu, and Pb. Groundwater has been evaluated using two methods, which are water quality index (WQI) and health risk assessment (HRA). The predominant groundwater is soft water, and the samples range in salinity from fresh to slightly salty. The groundwater mostly falls into the alkaline water type. All the groundwater samples under study are deemed low quality for human consumption due to water contamination. Fe, Mn, Cd, Cu, and Pb have high HQnc values, which can result in non-carcinogenic health issues in adults, while Mn, Cu, and Pb can give rise to non-carcinogenic health issues in children. Full article

(This article belongs to the Special Issue Managing Water Resources Sustainably)

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16 pages, 4169 KiB

Open AccessArticle

Assessing the Impact of Anthropogenically Modified Land Uses on Wetland Health: Case of Witbank Dam Catchment in South Africa

by Sylvester Mpandeli, Stanley Liphadzi, Chengetanai Mabhaudhi, Tafadzwanashe Mabhaudhi and Luxon Nhamo

Water 2024, 16(16), 2287; https://doi.org/10.3390/w16162287 - 13 Aug 2024

Viewed by 513

Abstract

Wetlands are critical ecological infrastructures that improve water quality, serve as habitat for fish and other aquatic life, accumulate floodwaters, and maintain surface water flow during dry periods. However, the health of wetlands has been compromised by anthropogenic activities that affect the constant [...] Read more.

Wetlands are critical ecological infrastructures that improve water quality, serve as habitat for fish and other aquatic life, accumulate floodwaters, and maintain surface water flow during dry periods. However, the health of wetlands has been compromised by anthropogenic activities that affect the constant supply of ecosystem services. This study assessed the impact of anthropogenically modified land use on wetland health in the Witbank Dam Catchment in South Africa, whose land use has been severely modified for agriculture and mining purposes. The study developed a model linking surface runoff generated in the catchment with land use and wetland typology to comprehend diffuse pollution from pollution-source land uses. Runoff data and related wetland spatial information were processed and analysed in a Geographic Information System (GIS) to estimate pollutants (agricultural nutrients and acid mine drainage) from runoff detained and released by wetlands. The analysis facilitated the assessment of the value of wetlands in enhancing water quality, as well as human and environmental health. The runoff volume from pollution-source land uses (urban areas, farmlands, and mining) was used to evaluate annual pollution levels. Wetland types are ranked according to their efficiency levels to filter pollutants. The assumption is that the difference between filtered and unfiltered runoff is the quantity of polluted runoff water discharged into the river system. The analysis has shown that 85% of polluted runoff generated in the catchment ends up in the river system. An important observation is that although wetlands have a substantial ability to absorb excess pollutants, they have finite boundaries. Once they reach their full holding capacity, they can no longer absorb any further pollutants. The excess is discharged into the river system, risking human and environmental health. This explains why the Limpopo River is heavily polluted resulting in the death of fish, crocodiles and other aquatic life. Full article

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18 pages, 8874 KiB

Open AccessArticle

Groundwater Level Prediction for Landslides Using an Improved TANK Model Based on Big Data

by Yufeng Zheng, Dong Huang, Xiaoyi Fan and Lili Shi

Water 2024, 16(16), 2286; https://doi.org/10.3390/w16162286 - 13 Aug 2024

Viewed by 399

Abstract

Geological conditions and rainfall intensity are two primary factors that can induce changes in groundwater level, which are one of the major triggering causes of geological disasters, such as collapse, landslides, and debris flow. In view of this, an improved TANK model is [...] Read more.

Geological conditions and rainfall intensity are two primary factors that can induce changes in groundwater level, which are one of the major triggering causes of geological disasters, such as collapse, landslides, and debris flow. In view of this, an improved TANK model is developed based on the influence of rainfall intensity, terrain, and geological conditions on the groundwater level in order to effectively predict the groundwater level evolution of rainfall landslides. A trapezoidal structure is used instead of the traditional rectangular structure to define the nonlinear change in a water level section to accurately estimate the storage of groundwater in rainfall landslides. Furthermore, big data are used to extract effective features from large-scale monitoring data. Here, we build prediction models to accurately predict changes in groundwater levels. Monitoring data of the Taziping landslide are taken as the reference for the study. The simulation results of the traditional TANK model and the improved TANK model are compared with the actual monitoring data, which proves that the improved TANK model can effectively simulate the changing trend in the groundwater level with rainfall. The study can provide a reliable basis for predicting and evaluating the change in the groundwater state in rainfall-type landslides. Full article

(This article belongs to the Special Issue Assessment of the Rainfall-Induced Landslide Distribution)

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17 pages, 9091 KiB

Open AccessArticle

Machine Learning Enhanced by Feature Engineering for Estimating Snow Water Equivalent

by Milan Čistý, Michal Danko, Silvia Kohnová, Barbora Považanová and Andrej Trizna

Water 2024, 16(16), 2285; https://doi.org/10.3390/w16162285 - 13 Aug 2024

Viewed by 369

Abstract

This study compares the calculation of snow water equivalent (SWE) using machine learning algorithms with the conventional degree-day method. The study uses machine learning techniques such as LASSO, Random Forest, Support Vector Machines, and CatBoost. It proposes an innovative use of feature engineering [...] Read more.

This study compares the calculation of snow water equivalent (SWE) using machine learning algorithms with the conventional degree-day method. The study uses machine learning techniques such as LASSO, Random Forest, Support Vector Machines, and CatBoost. It proposes an innovative use of feature engineering (FE) to improve the accuracy and robustness of SWE predictions by machine learning intended for interpolation, extrapolation, or imputation of missing data. The performance of machine learning approaches is evaluated against the traditional degree-day method for predicting SWE. The study emphasizes and demonstrates gains when modeling is enhanced by transforming basic, raw data through feature engineering. The results, verified in a case study from the mountainous region of Slovakia, suggest that machine learning, particularly CatBoost with feature engineering, shows better results in SWE estimation in comparison with the degree-day method, although the authors present a refined application of the degree-day method by utilizing genetic algorithms. Nevertheless, the study finds that the degree-day method achieved accuracy with a Nash–Sutcliffe coefficient of efficiency NSE = 0.59, while the CatBoost technique enhanced with the proposed FE achieved an accuracy NSE = 0.86. The results of this research contribute to refining snow hydrology modeling and optimizing SWE prediction for improved decision-making in snow-dominated regions. Full article

(This article belongs to the Section Hydrology)

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16 pages, 3735 KiB

Open AccessArticle

Material Activity in Debris Flow Watersheds Pre- and Post-Strong Earthquake: A Case Study from the Wenchuan Earthquake Epicenter

by Yu Yang, Ming Chen, Yinghua Cai, Chenxiao Tang, Wenli Huang and Chenhao Xia

Water 2024, 16(16), 2284; https://doi.org/10.3390/w16162284 - 13 Aug 2024

Viewed by 369

Abstract

The 2008 Wenchuan earthquake released vast quantities of loose material, significantly influencing post-earthquake material dynamics, particularly through recurrent debris flow disasters that posed long-term threats to the earthquake-affected area. To explore the transport and involvement of loose materials in debris flow events within [...] Read more.

The 2008 Wenchuan earthquake released vast quantities of loose material, significantly influencing post-earthquake material dynamics, particularly through recurrent debris flow disasters that posed long-term threats to the earthquake-affected area. To explore the transport and involvement of loose materials in debris flow events within earthquake-affected basins, this study focuses on a representative area near the Wenchuan epicenter, creating a multi-temporal database of active landslides and channel materials pre- and post-earthquake, quantitatively assessing material transport and source replenishment in debris flow basins, and categorizing debris flows based on channel material activity, post-earthquake historical activity, and sustainability of activity. This study revealed that pre-earthquake material activity was concentrated in the watershed’s upper regions, while post-earthquake materials were progressively transported from the central to the lower regions, with many small co-seismic landslides ceasing activity. The supply area ratio from active landslides capable of recharging debris flows, i.e., those connected to channels, consistently remained at approximately 72%, with the peak area of channel material activity comprising approximately 2.5% of the total watershed area. Channel material activity areas serve as valuable indicators for hazard assessment in regions lacking historical debris flow data, with the watershed area predominantly determining the sustainability of post-earthquake debris flow activity. Full article

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28 pages, 9121 KiB

Open AccessArticle

Flood Hazard and Risk Assessment of Flash Floods for Petra Catchment Area Using Hydrological and Analytical Hierarchy (AHP) Modeling

by Mustafa Al Kuisi, Naheel Al Azzam, Tasneem Hyarat and Ibrahim Farhan

Water 2024, 16(16), 2283; https://doi.org/10.3390/w16162283 - 13 Aug 2024

Viewed by 462

Abstract

Floods are a widespread natural disaster that occur in most areas of the world, except for the polar regions. To minimize the damage caused by floods, effective management strategies and policies must be implemented. Petra and Wadi Musa areas are prone to floods, [...] Read more.

Floods are a widespread natural disaster that occur in most areas of the world, except for the polar regions. To minimize the damage caused by floods, effective management strategies and policies must be implemented. Petra and Wadi Musa areas are prone to floods, which happen every 2–3 years and result in significant harm to both lives and properties. To address this issue, a composite hazard and vulnerability index is commonly utilized to evaluate flood risk and guide policy formation for flood risk reduction. These tools are efficient and cost-effective in generating accurate results. Accordingly, the present study aims to determine the morphological and hydrometeorological parameters that affect flash floods in Petra catchment area and to identify high-risk zones using GIS, hydrological, and analytical hierarchy (AHP) modeling. Nine factors, including Elevation (E), Landuse/Landcover LULC, Slope (S), Drainage density (DD), Flood Control Points (FCP) and Rainfall intensity (RI), which make up the six risk indices, and Population Density (PD), Cropland (C), and Transportation (Tr), which make up the three vulnerability indices, were evaluated both individually and in combination using AHP in ArcGIS 10.8.2 software. These parameters were classified as hazard and vulnerability indicators, and a final flood map was generated. The map indicated that approximately 37% of the total area in Petra catchment is at high or very high risk of flooding, necessitating significant attention from governmental agencies and decision-makers for flood risk mitigation. The AHP method proposed in this study is an accurate tool for flood mapping that can be easily applied to other regions in Jordan to manage and prevent flood hazards. Full article

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47 pages, 26197 KiB

Open AccessReview

Review of Subsurface Dam Technology Based on Japan’s Experience in the Ryukyu Arc

by Imaizumi Masayuki

Water 2024, 16(16), 2282; https://doi.org/10.3390/w16162282 - 13 Aug 2024

Viewed by 299

Abstract

Based on the success of an irrigation project that utilized two subsurface dams as water sources on Miyako Island, ten additional subsurface dams have now been completed. The technologies that have made the giant subterranean dam possible are the integrated storage model for [...] Read more.

Based on the success of an irrigation project that utilized two subsurface dams as water sources on Miyako Island, ten additional subsurface dams have now been completed. The technologies that have made the giant subterranean dam possible are the integrated storage model for creating water utilization plans and the Soil Mixed Wall method for constructing cut-off walls. Although it might be tempting to assume that all subsurface dams in the Ryukyu limestone region were built under identical topographical and geological conditions, the reality is quite different. Each dam faced unique geological and construction challenges that engineers skillfully overcame during the building process. The purpose of this paper is to introduce information on the planning and construction technology of agricultural subsurface dams in the Ryukyu Arc, which has not been reported in English so far, and to clarify the characteristics of agricultural subsurface dams in the Ryukyu Arc. There is a strong correlation between the gross reservoir capacity and the active capacity of large-scale subsurface dams. Eleven percent of the construction cost was the cost of design and investigation. The water price is the same as or slightly higher than that of surface dams. Full article

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21 pages, 6293 KiB

Open AccessStudy Protocol

Flocculants for the High-Concentration Activated Sludge Method and the Effectiveness of Urban Wastewater Treatment

by Benfu Luo, Haixin He, Yujing Yan, Yin Wang, Xi Yang, Yuhang Liu, Jiaran Xu and Weiheng Huang

Water 2024, 16(16), 2281; https://doi.org/10.3390/w16162281 - 13 Aug 2024

Viewed by 350

Abstract

In this paper, the three inorganic flocculants polymeric chloride PAC, FeCl₃, and Al₂(SO₄)₃ and two organic flocculants anionic polyacrylamide APAM and cationic polyacrylamide CPAM were screened to determine the most efficient flocculants and the optimal dosage, [...] Read more.

In this paper, the three inorganic flocculants polymeric chloride PAC, FeCl₃, and Al₂(SO₄)₃ and two organic flocculants anionic polyacrylamide APAM and cationic polyacrylamide CPAM were screened to determine the most efficient flocculants and the optimal dosage, optimizing the flocculation operating conditions through the orthogonal test and then proving the experimental effect according to a comparison study of the high-concentration method and the traditional activated sludge method. The results show that the addition of CPAM achieves the best flocculation for high-concentration activated sludge suspension, and that the sludge interface descent rate, sludge volume index, and sludge settling ratio are better than those of other flocculants. The orthogonal test was used on the sludge volume index to perform evaluations and analyses: mixing section mixing intensity > Flocculation Stage 1 section mixing intensity > Flocculation Stage 2 section mixing intensity > mixing section residence time > flocculation section hydraulic residence time. In the comparison test, the settling performance of the high-concentration method was higher than that of the traditional activated sludge method. In terms of pollutant removal, the removal rates of COD, ammonia nitrogen, and total nitrogen of the traditional activated sludge method were 90.85%, 95.74%, and 71.6%, respectively. The average removal rates of COD, ammonia nitrogen, and total nitrogen of high-concentration activated sludge method were 92.24%, 97.28%, and 80.97%—higher than that of the traditional activated sludge method. Full article

(This article belongs to the Special Issue Advanced Technologies in Water Treatment)

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21 pages, 3575 KiB

Open AccessArticle

Research on Foundation Scouring for Offshore Wind Turbines in the Vast Yangjiang Sea Area

by Weiping Wang, Yonggang Cao, Cansheng Zeng, Shizhi Liao, Yizhan Chen, Changjian Liu, Xiangyi Li and Shihao Luo

Water 2024, 16(16), 2280; https://doi.org/10.3390/w16162280 - 13 Aug 2024

Viewed by 284

Abstract

Based on field hydro-meteorological observations and sediment sampling data, this study analyzes sediment transport under normal conditions in the Fanshi offshore wind farm project area in Yangjiang, China. It was found that sediment transport in the engineering sea area is relatively stable, and [...] Read more.

Based on field hydro-meteorological observations and sediment sampling data, this study analyzes sediment transport under normal conditions in the Fanshi offshore wind farm project area in Yangjiang, China. It was found that sediment transport in the engineering sea area is relatively stable, and seabed sediments are not easily mobilized. By building a tidal current–sediment mathematical model, the impact of wind farm construction on the erosion and deposition environment in the surrounding sea areas was studied. It was found that areas with significant accumulation are mainly located near the pile foundations of wind turbines. Furthermore, considering ocean dynamics, geological conditions, and wave–current interactions, different local erosion empirical formulas were used to calculate local erosion depth and range. The results show that Han Haiqian’s formula and the HEC-18 formula, which consider wave velocity, are very close and more suitable for the actual conditions of this project. As turbine pile diameters increase, local scour depths and ranges also increase. This study preliminarily analyzes the basic scour characteristics of deep-sea wind turbines off the western coast of Guangdong Province, offering important design parameters for the construction of this project, and also providing a systematic and scientific method for studying local scour at turbine pile foundations. This has great reference value for deep-sea wind farm construction projects. Full article

(This article belongs to the Section Oceans and Coastal Zones)

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22 pages, 11318 KiB

Open AccessArticle

Extreme Rainfall Events Triggered Loess Collapses and Landslides in Chencang District, Shanxi, China, during June–October 2021

by Chang Zhou, Zhao Xia, Debin Chen, Leqian Miao, Shenghua Hu, Jingjing Yuan, Wei Huang, Li Liu, Dong Ai, Huiyuan Xu and Chunjin Xiao

Water 2024, 16(16), 2279; https://doi.org/10.3390/w16162279 - 13 Aug 2024

Viewed by 353

Abstract

In recent years, the increasing frequency of extreme weather events has exacerbated the severity of geological disasters. Therefore, it is important to understand the mechanisms of geological disasters under extreme rainfall conditions. From June to October 2021, Baoji City, Shanxi Province, China, experienced [...] Read more.

In recent years, the increasing frequency of extreme weather events has exacerbated the severity of geological disasters. Therefore, it is important to understand the mechanisms of geological disasters under extreme rainfall conditions. From June to October 2021, Baoji City, Shanxi Province, China, experienced some extreme and continuous heavy rainfalls, which triggered more than 30 geological disasters. Those geo-disasters threatened the lives of 831 people and the safety of 195 houses. The field investigations found that most of these geological disasters were devastating collapses that occurred in the loess layer, primarily due to the cave dwelling construction. The shear strength, montmorillonite content, disintegration degree, and plasticity index of two typical loesses, namely the Sanmen Formation stiff clay and the Hipparion red clay, were analyzed, and their water sensitivities were evaluated. The failure mechanisms of the landslides, ground fissures, and collapses were analyzed and most of them were controlled by the cave dwelling construction and the strong water sensitivity of the loess. This study provides data for understanding shallow geological disasters induced by extreme rainfall in the loess area, which are more threatening than large geological disasters. We proposed an intensity–duration (I–D) rainfall threshold as I = 90 D^−0.92, which relates the rainfall intensity (I) to the rainfall event duration (D). The empirical threshold provides some useful information for the early warning of collapses or landslides in similar geological settings in the loess area. Full article

(This article belongs to the Special Issue Approaches to Water-induced Landslide Hazard Risk Forecasting and Assessment)

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17 pages, 1346 KiB

Open AccessArticle

Targeting Macrophytes: Optimizing Vegetation Density to Enhance Water Quality within Constructed Wetlands

by Austin Johnathon McBrady and Walter Den

Water 2024, 16(16), 2278; https://doi.org/10.3390/w16162278 - 13 Aug 2024

Viewed by 327

Abstract

This study of constructed wetland design investigated relationships between macrophyte species selection and planting density for water quality improvement. A lab-scale wetland was compared against a pilot-scale wetland in San Antonio, Texas, at Mitchell Lake to measure differences in effluent water quality improvement [...] Read more.

This study of constructed wetland design investigated relationships between macrophyte species selection and planting density for water quality improvement. A lab-scale wetland was compared against a pilot-scale wetland in San Antonio, Texas, at Mitchell Lake to measure differences in effluent water quality improvement using three native macrophyte species. Using a novel, two-phase method, a targeting macrophyte was identified from among Olney’s bulrush (Schoenoplectus americanus), hardstem bulrush (Schoenoplectus acutus), and California bulrush (Schoenoplectus californicus), based on its marked capability for improving water quality factors, then it was planted in varied majority densities to compare differences in treatment effectiveness. The results showed that the planting density with 50% giant bulrush, 25% Olney’s bulrush, and 25% hardstem improved conductivity removal by 34% and increased dissolved oxygen by 3713% as compared to the Mitchell Lake pilot-scale results. The 70% and 90% majority density plantings (giant bulrush) were not shown to be as effective for the tested parameters, indicating diminishing returns as the vegetation density increasingly becomes a monoculture within the system. The results of this study showed that this complementary approach to wetland design displayed significant improvement in certain treatment parameters than the evenly planted species distribution of the pilot study. These findings demonstrate that the constructed wetland design can be optimized by selecting and planting macrophytes based on their effectiveness in targeting site-specific water quality concerns by capitalizing on their individual traits within complex wetland systems. Full article

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16 pages, 5424 KiB

Open AccessArticle

Distinct Diazotrophic Communities in Water and Sediment of the Sub-Lakes in Poyang Lake, China

by Qiang Wu, Zhigang Zhu, Longlingfeng Liu, Yin Qin, Yufang Jiang, Jinfu Liu, Wenxiang Zou, Fei Wang and Yuwei Chen

Water 2024, 16(16), 2277; https://doi.org/10.3390/w16162277 - 13 Aug 2024

Viewed by 379

Abstract

The sub-lakes of Poyang Lake have significant ecological value. To date, the diazotrophs in sub-lakes are unknown. Moreover, no study has simultaneously focused on diazotrophic communities in the water and sediment in natural freshwater ecosystems. In this study, we investigated the diazotrophic alpha [...] Read more.

The sub-lakes of Poyang Lake have significant ecological value. To date, the diazotrophs in sub-lakes are unknown. Moreover, no study has simultaneously focused on diazotrophic communities in the water and sediment in natural freshwater ecosystems. In this study, we investigated the diazotrophic alpha diversity, structure, abundance, molecular ecological network, and community assembly mechanism in the water and sediment of sub-lakes using Illumina MiSeq sequencing and a quantitative polymerase chain reaction assay. The results showed that the sediment had a greater diversity of diazotrophs than the water. Proteobacteria and Spirochaetes were the dominant diazotrophic phyla in the water, whereas Proteobacteria was the dominant diazotrophic phylum in the sediment. There were significant differences in the composition of diazotrophic communities between the water and sediment. The sediment had a more complex co-occurrence network of diazotrophs than the water. Deterministic processes dominate the community assembly of diazotrophs in both the water and sediment of the sub-lakes, and the relative role of deterministic processes was stronger for sediment than water. Our study is the first to reveal the differences in the diazotrophic communities between the water and sediment in natural freshwater ecosystems and provides the fundamental scientific datasets for understanding the nitrogen fixation process in sub-lakes. Full article

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Water, Volume 16, Issue 16 (August-2 2024) – 92 articles

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