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Volume 15
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Water, Volume 15, Issue 12 (June-2 2023) – 165 articles

Cover Story (view full-size image): The flood scenarios of the Lagunilla case study generate an inundation envelope divided into two branches: one towards the north and the other to the south. The probability of flooding is highly influenced by the location of the breach, but, in general, the flood would be produced towards the south, with a major probability of occurrence, rather than towards the north. The flow would concentrate towards the south of the gentle hill, located at the east of the pond, with a probability above 90%, while the probability reduces to 60% towards the north, with punctual locations up to 80% at the low part of the agricultural terraces. The inundation would be less probable at the north of the hill (below 50%), with the irrigation ditch being reached in less than 40% of the failure cases. View this paper
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22 pages, 7545 KiB  
Article
The Dynamic Characteristics of a Piped Capsule Moving in a Straight Pipeline
by Xiaoni Yang, Juanjuan Ma, Yongye Li and Yonggang Li
Water 2023, 15(12), 2306; https://doi.org/10.3390/w15122306 - 20 Jun 2023
Viewed by 1350
Abstract
The hydraulic transportation of piped capsules is a new and energy-saving transportation mode, which is especially suitable for the long-distance and high-stability requirements of material transportation. In this paper, the COMSOL Multiphysics software was used to construct a mathematical model of the dynamic [...] Read more.
The hydraulic transportation of piped capsules is a new and energy-saving transportation mode, which is especially suitable for the long-distance and high-stability requirements of material transportation. In this paper, the COMSOL Multiphysics software was used to construct a mathematical model of the dynamic characteristics of a piped capsule moving in a straight pipeline, in which the boundary conditions were redeveloped, the inlet velocity distribution function was defined, and the physical experiment was carried out for verification. The dynamic characteristics were analyzed, and through the calculation of the energy consumption, the optimal piped capsule under the research conditions was obtained. The results show that the simulation results and experimental results for the piped capsule’s average moving velocity, axial velocity, and wall shear stress along the cylinder wall were basically consistent, with a maximum error of 14.22%, 2.62%, and 20.13%, respectively. With a decrease in the diameter-to-length ratio of the piped capsule, the axial velocity of the concentric annular gap flow decreased gradually. The area with a large shear stress was mainly concentrated at the front and rear ends of the cylinder wall, especially the rear area of the support feet of the piped capsule. With the increase in the diameter of the piped capsule, the wall shear stress of the capsule increased. Finally, the superior diameter-to-length ratio for the piped capsule under the research conditions was obtained and shown to be ε = 0.4. The research in this paper will provide a theoretical reference for the structural design and dynamic mechanism analysis of the piped capsule. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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22 pages, 6784 KiB  
Article
Performance Assessment of Household Water Treatment and Safe Storage in Kathmandu Valley, Nepal
by Shekhar Khanal, Shinobu Kazama, Sawangjang Benyapa and Satoshi Takizawa
Water 2023, 15(12), 2305; https://doi.org/10.3390/w15122305 - 20 Jun 2023
Cited by 3 | Viewed by 2687
Abstract
Although many households in the Kathmandu Valley rely on household water treatment and safe storage (HWTS) to obtain drinking water, the safety of treated water has not been evaluated in actual usage. Therefore, we assessed the performance and maintenance of five HWTS methods [...] Read more.
Although many households in the Kathmandu Valley rely on household water treatment and safe storage (HWTS) to obtain drinking water, the safety of treated water has not been evaluated in actual usage. Therefore, we assessed the performance and maintenance of five HWTS methods used in 101 households. The choice of HWTS methods by households was primarily influenced by the raw water source, that is, jarred water users opted for boiling and groundwater users selected reverse osmosis with ultraviolet irradiation (RO-UV). While boiling and electric dispensers (ED) did not remove inorganic contaminants (ammonia nitrogen, arsenic, and manganese), ceramic candle filters (CCF) and RO-UV reduced them moderately. The HWTS methods reduced E. coli and total coliforms (TC) by 95.8 and 84.1%, respectively, but 11.8 and 69.3% of treated water samples remained positive for these two bacteria. Combined methods (CM) and RO-UV showed an inferior TC reduction compared to the simpler HWTS methods, boiling, CCF, and ED, possibly due to difficulties with regular maintenance and storage contamination. Therefore, it is recommended to choose simpler HWTS methods that meet the requirements of the household’s water sources rather than more expensive and difficult-to-maintain methods, which should be chosen only if the raw water contains high concentrations of inorganic contaminants. Full article
(This article belongs to the Special Issue Sustainable Water Supply, Sanitation and Wastewater Systems)
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21 pages, 11269 KiB  
Article
Hydrochemical Response of Karst Groundwater to Rapid Urbanization in Xingtai, North China
by Rui Wang, Xiaohan Li, Fenggang Dai, Zhichao Cai, Wenbo He, Lulu Song and Zhoupan Jiang
Water 2023, 15(12), 2304; https://doi.org/10.3390/w15122304 - 20 Jun 2023
Viewed by 1532
Abstract
Karst groundwater is the main water source for domestic, industrial, and agricultural needs in Xingtai City, North China. The objective of this study was to comprehensively access changes in the hydrochemical characteristics and evolution of karst groundwater in response to rapid urbanization. Water [...] Read more.
Karst groundwater is the main water source for domestic, industrial, and agricultural needs in Xingtai City, North China. The objective of this study was to comprehensively access changes in the hydrochemical characteristics and evolution of karst groundwater in response to rapid urbanization. Water samples from the late 2010s and the 1970s were compared utilizing statistical analysis, hydrochemical diagrams, and inverse simulation technology. The total dissolved solids (TDS), total hardness (TH), NO3−, and Fe contents were significantly higher in the more recently obtained karst groundwater samples. Further, the dominance of HCO3-Ca-type water decreased, with new types emerging, relative to 1970s karst groundwater. Abnormal TDS, TH, SO42−, NO3−, and Cl− concentrations can be attributed to sewage discharge and fertilizer. Two groundwater discharge areas around the center of Xingtai City and Yangfan Town in the south of the study area were the most significantly affected by human activities. However, inverse modeling indicated that the dissolution of gypsum and halite, as well as cation-exchange processes, occurred in the groundwater paths during both periods. Recent increases in ion concentrations of karst groundwater in the study area have caused carbonate minerals to dissolve, resulting in a further increase of ion concentrations. The hydrochemical response and evolution of karst groundwater requires further study. Full article
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17 pages, 3364 KiB  
Article
Improved Delivery of Nanoscale Zero-Valent Iron Particles and Simplified Design Tools for Effective Aquifer Nanoremediation
by Carlo Bianco, Federico Mondino and Alessandro Casasso
Water 2023, 15(12), 2303; https://doi.org/10.3390/w15122303 - 20 Jun 2023
Cited by 1 | Viewed by 1737
Abstract
The subsurface injection of nanoscale zero-valent iron particles (nZVI) for the in situ reductive remediation of contaminated aquifers has grown over the last 25 years. However, several efforts are still being made to improve the stability and delivery of nZVI and to simplify [...] Read more.
The subsurface injection of nanoscale zero-valent iron particles (nZVI) for the in situ reductive remediation of contaminated aquifers has grown over the last 25 years. However, several efforts are still being made to improve the stability and delivery of nZVI and to simplify the procedure for site-specific injection design. In this study, the injectability and mobility of a commercial nZVI-based reactive gel was tested in a radial geometry laboratory setup. The gel proved to be highly mobile in sandy porous media, allowing for the achievement of a radius of influence (ROI) of 0.7 m with a homogeneous nZVI distribution within the domain. The experimental results therefore confirmed that nZVI permeation injection with a good radius of influence is possible in conductive formations. The software MNMs 2023 (Micro- and Nanoparticle transport, filtration, and clogging Model-Suite) was then applied to model the radial transport experiment and extrapolate results with the aim of developing a new graphical tool for simple and effective nZVI permeation injection design. For this purpose, 1800 numerical simulations were performed to build two multiparametric maps to predict the expected ROI in two typical aquifer lithologies and over a wide range of operating conditions. Full article
(This article belongs to the Special Issue Coupled Flow and Reactive Transport Processes in Subsoil)
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18 pages, 3901 KiB  
Article
LI-DWT- and PD-FC-MSPCNN-Based Small-Target Localization Method for Floating Garbage on Water Surfaces
by Ping Ai, Long Ma and Baijing Wu
Water 2023, 15(12), 2302; https://doi.org/10.3390/w15122302 - 20 Jun 2023
Cited by 1 | Viewed by 1443
Abstract
Typically, the process of visual tracking and position prediction of floating garbage on water surfaces is significantly affected by illumination, water waves, or complex backgrounds, consequently lowering the localization accuracy of small targets. Herein, we propose a small-target localization method based on the [...] Read more.
Typically, the process of visual tracking and position prediction of floating garbage on water surfaces is significantly affected by illumination, water waves, or complex backgrounds, consequently lowering the localization accuracy of small targets. Herein, we propose a small-target localization method based on the neurobiological phenomenon of lateral inhibition (LI), discrete wavelet transform (DWT), and a parameter-designed fire-controlled modified simplified pulse-coupled neural network (PD-FC-MSPCNN) to track water-floating garbage floating. First, a network simulating LI is fused with the DWT to derive a denoising preprocessing algorithm that effectively reduces the interference of image noise and enhances target edge features. Subsequently, a new PD-FC-MSPCNN network is developed to improve the image segmentation accuracy, and an adaptive fine-tuned dynamic threshold magnitude parameter V and auxiliary parameter P are newly designed, while eliminating the link strength parameter. Finally, a multiscale morphological filtering postprocessing algorithm is developed to connect the edge contour breakpoints of segmented targets, smoothen the segmentation results, and improve the localization accuracy. An effective computer vision technology approach is adopted for the accurate localization and intelligent monitoring of water-floating garbage. The experimental results demonstrate that the proposed method outperforms other methods in terms of the overall comprehensive evaluation indexes, suggesting higher accuracy and reliability. Full article
(This article belongs to the Special Issue Artificial Intelligence, Machine Learning and Digital Innovation in Water Management)
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23 pages, 8042 KiB  
Article
Characterising Rhythmic and Episodic Pulsing Behaviour in the Castleton Karst, Derbyshire (UK), Using High Resolution in-Cave Monitoring
by John Gunn and Chris Bradley
Water 2023, 15(12), 2301; https://doi.org/10.3390/w15122301 - 20 Jun 2023
Cited by 1 | Viewed by 1477
Abstract
The discharge from most karst springs exhibits a consistent and reasonably predictable response to recharge but a few exhibit short-term (‘rhythmic’) changes in flow that are commonly attributed to the geometry of feeder conduits and the action of siphons. This paper investigates water [...] Read more.
The discharge from most karst springs exhibits a consistent and reasonably predictable response to recharge but a few exhibit short-term (‘rhythmic’) changes in flow that are commonly attributed to the geometry of feeder conduits and the action of siphons. This paper investigates water flow in a karst system that exhibits rhythmic and episodic changes in discharge due to variations in flow from two phreatic conduits (Main Rising (MR) and Whirlpool Rising (WR)) that pass through Speedwell Cavern en route to the springs. Water tracing experiments indicate that the conduits receive both allogenic and autogenic recharge. Flow dynamics and conduit behaviour were investigated using high-resolution (2-min) water depth data collected from MR and WR between 2012 and 2015 (when MR was dominant) and between 2021 and 2023 (when WR was dominant). Water depths were also logged in a cave at the upstream end of a conduit draining to both MR and WR and at springs. The short-term temporal variability in water depths at both MR and WR is greater than any documented in previous studies. This is attributed to conduit bedrock geometry and changes in conduit permeability due to sediment accumulation in phreatic loops, which together influence the response to recharge. Full article
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12 pages, 3762 KiB  
Article
Analysis of the Partial Nitrification/Anammox Performance and Microbial Structure of Low C/N Wastewater by A2/O Process
by Lei Ye, Yanhao Zhou, Liangdong Tang, Sixing Chen and Xianguang Zhao
Water 2023, 15(12), 2300; https://doi.org/10.3390/w15122300 - 20 Jun 2023
Viewed by 2287
Abstract
Given the carbon limitation of low C/N wastewater, the improvement of nitrogen-removal efficiency remains a challenging task of municipal wastewater treatment plants (WWTPs) in China. In this study, a partial nitrification/anammox (PN/A) system was established to facilitate the anaerobic-anoxic-aerobic (A2/O) treatment [...] Read more.
Given the carbon limitation of low C/N wastewater, the improvement of nitrogen-removal efficiency remains a challenging task of municipal wastewater treatment plants (WWTPs) in China. In this study, a partial nitrification/anammox (PN/A) system was established to facilitate the anaerobic-anoxic-aerobic (A2/O) treatment of low C/N (C/N = 3) wastewater with insufficient carbon sources. Effects of dissolved oxygen (DO) concentration and internal reflux ratio on nitrogen-removal efficiency and pathway were investigated. Under the optimal DO (0.5–0.8 mg·L−1) and internal reflux ratio (250%), the highly efficient NH4+-N removal (97.21%) and TN removal (80.92%) were achieved based on PN/A. Moreover, the relative abundance of ammonia-oxidizing bacteria (Nitrosomonas) was 3 times higher than the abundance of nitrite-oxidizing bacteria (Nitrospira) in phase V, which was the main cause of PN in the reactor. Anaerobic ammonia-oxidizing bacteria (Candidatus Brocadia, Pirellula, and Gemmata) were also found and considered as the key microbes involved in anammox. This study reports that the A2/O process can achieve advanced nitrogen removal of low C/N wastewater based on PN/A by optimizing conventional process parameters. The outcomes of this study may provide practical engineering applications as a reference for nitrogen removal based on the A2/O process. Full article
(This article belongs to the Special Issue Water-Sludge-Nexus)
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23 pages, 14372 KiB  
Article
Phytoplankton Diversity and Co-Dependency in a Stratified Oligotrophic Ecosystem in the South Adriatic Sea
by Antonija Matek, Maja Mucko, Raffaella Casotti, Anna Chiara Trano, Eric P. Achterberg, Hrvoje Mihanović, Hrvoje Čižmek, Barbara Čolić, Vlado Cuculić and Zrinka Ljubešić
Water 2023, 15(12), 2299; https://doi.org/10.3390/w15122299 - 20 Jun 2023
Cited by 4 | Viewed by 2533
Abstract
The oligotrophy of the southern Adriatic Sea is characterized by seasonal stratification which enables nutrient supply to the euphotic layer. A set of interdisciplinary methods was used to elucidate the diversity and co-dependency of bacterio- and phytoplankton of the water column during the [...] Read more.
The oligotrophy of the southern Adriatic Sea is characterized by seasonal stratification which enables nutrient supply to the euphotic layer. A set of interdisciplinary methods was used to elucidate the diversity and co-dependency of bacterio- and phytoplankton of the water column during the stratification period of July 2021. A total of 95 taxa were determined by microscopy: 58 diatoms, 27 dinoflagellates, 6 coccolithophores, and 4 other autotrophs, which included Chlorophyceae, Chrysophyceae, and Cryptophytes. Nanophytoplankton abundances were higher in comparison to microphytoplankton. The prokaryotic plankton community as revealed by HTS was dominated by Proteobacteria (41–73%), Bacteroidota (9.5–27%), and cyanobacteria (1–10%), while the eukaryotic plankton community was composed of parasitic Syndiniales (45–80%), Ochrophyta (2–18%), Ciliophora (2–21%), Chlorophytes (2–4%), Haptophytes (1–4%), Bacillariophyta (1–13%), Pelagophyta (0.5–12%) and Chrysophyta (0.5–3%). Flow cytometry analysis has recorded Prochlorococcus and photosynthetic picoeukaryotes as more abundant in deep chlorophyll maximum (DCM), and Synechococcus and heterotrophic bacteria as most abundant in surface and thermocline layers. Surface, thermocline, and DCM layers were distinct considering community diversity, temperature, and nutrient correlations, while extreme nutrient values at the beginning of the investigating period indicated a possible nutrient flux. Nutrient and temperature were recognized as the main environmental drivers of phytoplankton and bacterioplankton community abundance. Full article
(This article belongs to the Special Issue Marine Phytoplankton Diversity)
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28 pages, 9629 KiB  
Article
Coupling Machine and Deep Learning with Explainable Artificial Intelligence for Improving Prediction of Groundwater Quality and Decision-Making in Arid Region, Saudi Arabia
by Fahad Alshehri and Atiqur Rahman
Water 2023, 15(12), 2298; https://doi.org/10.3390/w15122298 - 20 Jun 2023
Cited by 18 | Viewed by 2803
Abstract
Recently, machine learning (ML) and deep learning (DL) models based on artificial intelligence (AI) have emerged as fast and reliable tools for predicting water quality index (WQI) in various regions worldwide. In this study, we propose a novel stacking framework based on DL [...] Read more.
Recently, machine learning (ML) and deep learning (DL) models based on artificial intelligence (AI) have emerged as fast and reliable tools for predicting water quality index (WQI) in various regions worldwide. In this study, we propose a novel stacking framework based on DL models for WQI prediction, employing a convolutional neural network (CNN) model. Additionally, we introduce explainable AI (XAI) through XGBoost-based SHAP (SHapley Additive exPlanations) values to gain valuable insights that can enhance decision-making strategies in water management. Our findings demonstrate that the stacking model achieves the highest accuracy in WQI prediction (R2: 0.99, MAPE: 15.99%), outperforming the CNN model (R2: 0.90, MAPE: 58.97%). Although the CNN model shows a relatively high R2 value, other statistical measures indicate that it is actually the worst-performing model among the five tested. This discrepancy may be attributed to the limited training data available for the CNN model. Furthermore, the application of explainable AI (XAI) techniques, specifically XGBoost-based SHAP values, allows us to gain deep insights into the models and extract valuable information for water management purposes. The SHAP values and interaction plot reveal that elevated levels of total dissolved solids (TDS), zinc, and electrical conductivity (EC) are the primary drivers of poor water quality. These parameters exhibit a nonlinear relationship with the water quality index, implying that even minor increases in their concentrations can significantly impact water quality. Overall, this study presents a comprehensive and integrated approach to water management, emphasizing the need for collaborative efforts among all stakeholders to mitigate pollution levels and uphold water quality. By leveraging AI and XAI, our proposed framework not only provides a powerful tool for accurate WQI prediction but also offers deep insights into the models, enabling informed decision-making in water management strategies. Full article
(This article belongs to the Special Issue Novel Perspective for Interactions between Water and the Geology Using GRACE and Remote Sensing Data)
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19 pages, 3233 KiB  
Article
Study on the Acoustic Emission Characteristics and Failure Precursors of Water-Rich Frozen Sandstone under Different Lateral Unloading Rates
by Shuai Liu, Gengshe Yang, Hui Liu, Xihao Dong and Yanjun Shen
Water 2023, 15(12), 2297; https://doi.org/10.3390/w15122297 - 20 Jun 2023
Cited by 1 | Viewed by 1389
Abstract
The artificial freezing method is used to cross the water-rich soft rock strata in order to exploit deep coal resources. At present, studies that consider both freezing effect and unloading rate are insufficient. To study the influences of the excavation rate using the [...] Read more.
The artificial freezing method is used to cross the water-rich soft rock strata in order to exploit deep coal resources. At present, studies that consider both freezing effect and unloading rate are insufficient. To study the influences of the excavation rate using the artificial freezing method on the unloading deformation and failure of the water-rich surrounding rock, we carry out mechanical and synchronous acoustic emission (AE) tests on frozen (−10 °C) sandstone samples under different lateral unloading rates. Combined with the AE signals, the stress, strain and failure process are analysed to determine the mechanical behaviours of frozen rock samples under different lateral unloading rates. The damage difference between normal temperature rock and frozen rock during lateral unloading is studied. According to acoustic emission signals, the damage relationships among acoustic emission amplitude, energy, cumulative acoustic emission energy (CAEE), stress and strain were compared and analyzed. In this paper, acoustic emission 3D positioning system is used to monitor the fracture propagation trajectory in the process of unloading confining pressure of frozen sandstone. The results show that the peak stress of frozen sandstone during lateral unloading is about 2.5 times of that at 20 °C. More than 2 AE amplitudes per second are regarded as the precursor of failure (FP), and point FP is taken as the first level warning. The CAEE of rock samples at 20 °C and frozen rock samples shows the same change law over time, increasing slowly before the FP point and exponentially after the FP point. Peak stress increases and axial strain decreases with the increase of unloading rate of frozen rock sample. The CAEE at point FP and the peak acoustic emission energy (AEE) and the CAEE at the time of failure increase when the unloading rate of frozen rock sample increases. Principal component analysis method was used to extract key characteristic energy to obtain a clearer AEE concentration area, which was defined as second-level early warning. The research results can provide guidance for freezing shaft construction to reduce the occurrence of disasters. Full article
(This article belongs to the Topic Advances in Well and Borehole Hydraulics and Hydrogeology)
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17 pages, 2705 KiB  
Article
Effect of Autumn Irrigation on Salt Leaching under Subsurface Drainage in an Arid Irrigation District
by Jiawei Liu, Quanzhong Huang, Ze Li, Na Liu, Jinshuai Li and Guanhua Huang
Water 2023, 15(12), 2296; https://doi.org/10.3390/w15122296 - 20 Jun 2023
Cited by 4 | Viewed by 1790
Abstract
Non-growing season irrigation and farmland subsurface drainage play a crucial role in salt leaching and salinization control in arid irrigation areas. This study aimed to investigate the reduction of autumn irrigation quotas and drainage discharge while maintaining soil moisture retention and reducing soil [...] Read more.
Non-growing season irrigation and farmland subsurface drainage play a crucial role in salt leaching and salinization control in arid irrigation areas. This study aimed to investigate the reduction of autumn irrigation quotas and drainage discharge while maintaining soil moisture retention and reducing soil salinization. Field experiments were conducted with different autumn irrigation quotas (160 mm for SD1, 180 mm for SD2, and 200 mm for SD3) combined with subsurface drainage (1.5 m drain depth and 45 m spacing). A control treatment (referred to as CK) without subsurface drainage received 200 mm of irrigation. The results showed that, after 31 days of autumn irrigation, the groundwater depth in all three subsurface drainage plots stabilized to 1.5 m, with the CK being 0.2–0.3 m shallower compared to the SD plots. The mean soil water content in the 0–150 cm soil layer of the SD1, SD2, SD3, and CK after autumn irrigation was 0.36, 0.39, 0.41, and 0.42 cm3cm−3, respectively. The combination of autumn irrigation and subsurface drainage significantly reduced the soil salt content. The mean desalination rates in the root zone (0–60 cm) soil layer were 57.5%, 53.7%, 51.9%, and 45.1% for the SD3, SD2, CK, and SD1, respectively. The mean desalination rate of 60–150 cm was not significantly different between the SD2 and SD3 (p > 0.05), and both were significantly higher than that of the SD1 and CK (p < 0.05). The drainage discharge was 31, 36, and 40 mm in the SD1, SD2 and SD3, respectively. The amount of salt discharge through the drain pipe increased with increasing irrigation quota, which was 1.22 t/ha, 1.41 t/ha, and 1.50 t/ha for the SD1, SD2, and SD3, respectively. Subsurface drainage is an effective way to prevent salt accumulation in the soil, and an autumn irrigation quota of 180 mm is recommended for leaching of salinity in the Hetao Irrigation District. These findings provide valuable insights into optimizing irrigation practices and managing soil salinization in arid regions. Full article
(This article belongs to the Special Issue Coupling Effect of Water and Fertilizer on Crops in Salinized Soil)
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24 pages, 3205 KiB  
Article
Project Risks Influence on Water Supply and Sanitation Sector Financing Opportunities
by Inês Freire Machete and Rui Cunha Marques
Water 2023, 15(12), 2295; https://doi.org/10.3390/w15122295 - 20 Jun 2023
Cited by 2 | Viewed by 2798
Abstract
Private financing mobilized in the water supply and sanitation sector has not been sufficient to cover the sector’s needs. Several barriers hinder private financing leveraging, including the risk perception of water supply and sanitation projects. This study analyzed 185 water supply and sanitation [...] Read more.
Private financing mobilized in the water supply and sanitation sector has not been sufficient to cover the sector’s needs. Several barriers hinder private financing leveraging, including the risk perception of water supply and sanitation projects. This study analyzed 185 water supply and sanitation projects financed by the World Bank between 2015 and 2021 to understand how perceived project risks can influence the financing of these sectors. This study demonstrates the parallels between different types of project risks, their ratings, and the different lending instruments and amounts committed by the bank. The most prevalent risks in the analyzed WSS projects were identified, namely, fiduciary, institutional capacity for implementation and sustainability, environmental and social, and political and governance. The World Bank appears to have different levels of tolerance for the different types of risks, and this tolerance seems to vary between regions and with time. Risks seem to have different weights when financiers decide which WSS projects to finance. Global and regional risk profiles of the 185 WSS projects financed by the World Bank were developed, which can help borrowers identify risks that they can mitigate to potentially improve their ability to attract private finance for WSS projects. Full article
(This article belongs to the Special Issue Urban Water Management and Governance)
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20 pages, 3393 KiB  
Article
Modelling Crop Evapotranspiration and Water Use Efficiency of Maize Using Artificial Neural Network and Linear Regression Models in Biochar and Inorganic Fertilizer-Amended Soil under Varying Water Applications
by Oluwaseun Temitope Faloye, Ayodele Ebenezer Ajayi, Toju Babalola, Adeyinka Oluwayomi Omotehinse, Oluwafemi Ebenezer Adeyeri, Bolaji Adelanke Adabembe, Akinwale Tope Ogunrinde, Abiodun Okunola and Abayomi Fashina
Water 2023, 15(12), 2294; https://doi.org/10.3390/w15122294 - 20 Jun 2023
Cited by 4 | Viewed by 2340
Abstract
The deficit irrigation strategy is a well-known approach to optimize crop water use through the estimation of crop water use efficiency (CWUE). However, studies that comprehensively reported the prediction of crop evapotranspiration (ETc) and CWUE under deficit irrigation for improved water [...] Read more.
The deficit irrigation strategy is a well-known approach to optimize crop water use through the estimation of crop water use efficiency (CWUE). However, studies that comprehensively reported the prediction of crop evapotranspiration (ETc) and CWUE under deficit irrigation for improved water resources planning are scarce. The objective of the study is to predict seasonal ETc and CWUE of maize using multiple linear regression (MLR) and artificial neural network (ANN) models under two scenarios, i.e., (1) when only climatic parameters are considered and (2) when combining crop parameter(s) with climatic data in amended soil. Three consecutive field experimentations were carried out with biochar applied at rates of 0, 3, 6, 10 and 20 t/ha, while inorganic fertilizer was applied at rates of 0 and 300 Kg/ha, under three water regimes: 100% Full Irrigation Treatment (FIT), 80% and 60% FIT. Seasonal ETc was determined using the soil water balance method, while growth data were monitored weekly. The CWUE under each treatment was also estimated and modelled. The MLR and ANN models were developed, and their evaluations showed that the ANN model was satisfactory for the predictions of both ETc and CWUE under all soil water conditions and scenarios. However, the MLR model without crop data was poor in predicting CWUE under extreme soil water conditions (60% FIT). The coefficient of determination (R2) increased from 0.03 to 0.67, while root mean-square error (RMSE) decreased from 4.07 to 1.98 mm after the inclusion of crop data. The model evaluation suggests that using a simple model such as MLR, crop water productivity could be accurately predicted under different soil and water management conditions. Full article
(This article belongs to the Section Water, Agriculture and Aquaculture)
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16 pages, 2141 KiB  
Article
Research on the Development and Application of a Deep Learning Model for Effective Management and Response to Harmful Algal Blooms
by Jungwook Kim, Hongtae Kim, Kyunghyun Kim and Jung Min Ahn
Water 2023, 15(12), 2293; https://doi.org/10.3390/w15122293 - 19 Jun 2023
Cited by 2 | Viewed by 1935
Abstract
Harmful algal blooms (HABs) caused by harmful cyanobacteria adversely impact the water quality in aquatic ecosystems and burden socioecological systems that are based on water utilization. Currently, Korea uses the Environmental Fluid Dynamics Code-National Institute of Environmental Research (EFDC-NIER) model to predict algae [...] Read more.
Harmful algal blooms (HABs) caused by harmful cyanobacteria adversely impact the water quality in aquatic ecosystems and burden socioecological systems that are based on water utilization. Currently, Korea uses the Environmental Fluid Dynamics Code-National Institute of Environmental Research (EFDC-NIER) model to predict algae conditions and respond to algal blooms through the HAB alert system. This study aimed to establish an additional deep learning model to effectively respond to algal blooms. The prediction model is based on a deep neural network (DNN), which is a type of artificial neural network widely used for HAB prediction. By applying the synthetic minority over-sampling technique (SMOTE) to resolve the imbalance in the data, the DNN model showed improved performance during validation for predicting the number of cyanobacteria cells. The R-squared increased from 0.7 to 0.78, MAE decreased from 0.7 to 0.6, and RMSE decreased from 0.9 to 0.7, indicating an enhancement in the model’s performance. Furthermore, regarding the HAB alert levels, the R-squared increased from 0.18 to 0.79, MAE decreased from 0.2 to 0.1, and RMSE decreased from 0.3 to 0.2, indicating improved performance as well. According to the results, the constructed data-based model reasonably predicted algae conditions in the summer when algal bloom-induced damage occurs and accurately predicted the HAB alert levels for immediate decision-making. The main objective of this study was to develop a new technology for predicting and managing HABs in river environments, aiming for a sustainable future for the aquatic ecosystem. Full article
(This article belongs to the Special Issue Harmful Algae Control)
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30 pages, 18880 KiB  
Article
Fish Assemblages as Ecological Indicators in the Büyük Menderes (Great Meander) River, Turkey
by Stamatis Zogaris, Nicholas Koutsikos, Yorgos Chatzinikolaou, Saniye Cevher Őzeren, Kaan Yence, Vassiliki Vlami, Pinar Güler Kohlmeier and Gürçay Kıvanç Akyildiz
Water 2023, 15(12), 2292; https://doi.org/10.3390/w15122292 - 19 Jun 2023
Cited by 4 | Viewed by 2122
Abstract
This research describes fish assemblages and associated aquatic ecosystem degradation patterns in the Büyük Menderes River, one of Turkey’s most important Anatolian basins. Using standard electrofishing, 44 river sites were sampled throughout the basin accounting for the distribution and abundance of 20 native [...] Read more.
This research describes fish assemblages and associated aquatic ecosystem degradation patterns in the Büyük Menderes River, one of Turkey’s most important Anatolian basins. Using standard electrofishing, 44 river sites were sampled throughout the basin accounting for the distribution and abundance of 20 native and seven non-native species, totaling 13,535 fish specimens. At each sampling site, anthropogenic pressures were assessed, and information was gathered to determine the degree of human-induced degradation that may affect fish and their habitats; each site was scored on the basis of a site quality index (SQI). Using the best-available relatively less-degraded river sites, cluster analyses of the samples defined six fish assemblage river types. Further classification of all fish samples utilizing bipartite network analysis resulted in comparable assemblage groupings. The European Fish Index (EFI+) with minor adaptations was applied for assessing river ecological integrity at all sampled sites in order to explore the utility of this widely used index. The EFI+ index results correlated with scores of the SQI but provided a very narrow assessment range, thus failing to accurately and consistently assess the severity of anthropogenic degradation. We recommend a new multimetric index to be developed for the Western Anatolian Ecoregion, of which this basin is a part. The data and insights gained from this exercise may help continue fish-based indicator development for policy-relevant management and conservation in Turkey’s rivers. Full article
(This article belongs to the Special Issue Freshwater Biodiversity: Conservation and Management)
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16 pages, 2473 KiB  
Article
Sediment Fungal Communities of Constructed Wetlands Dominated by Zizania latifolia and Phragmites communis and Their Effect on Organic Pollutant Removal
by Yiting He, Zhongliang Huang, Hui Li, Jing Huang, Xiaoli Qin and Zijian Wu
Water 2023, 15(12), 2291; https://doi.org/10.3390/w15122291 - 19 Jun 2023
Cited by 1 | Viewed by 1411
Abstract
The purpose of the study was to investigate the relationship between wetland plants and fungal communities with a focus on their combined functions to remove organic pollutants. Two constructed wetland (CW) systems, covering a total area of 4.24 hm2, were established [...] Read more.
The purpose of the study was to investigate the relationship between wetland plants and fungal communities with a focus on their combined functions to remove organic pollutants. Two constructed wetland (CW) systems, covering a total area of 4.24 hm2, were established to treat the agricultural non-point source pollution using, respectively, Zizania latifolia (CW1) and Phragmites communis (CW2) as the dominant plant species. The obtained results showed that CW1 performed much better than CW2 in terms of promoting the abundance and diversity of the sediment fungal community identified by high-throughput sequencing technology. The enhanced fungal activity was shown to be one of the main factors that raised the pollutant removal rates and reduced the contents of the target pollutants (COD, TN, TP and NH4+-N) to levels below the stipulated national standards. Significant differences in abundant fungi were observed between the CW units and their inlet and outlet sampling sites, indicating that the plant species and pollutant concentrations were the key factors affecting the diversity and activity of the sediment fungal community. The findings of the study provided not only a better understanding of the plant–fungi symbiotic system but also useful information for the development of CW technology. Full article
(This article belongs to the Special Issue Microbial Remediation of Polluted Water Bodies and Degraded Water Ecosystems)
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14 pages, 3358 KiB  
Article
Adsorption-Reduction of Cr(VI) with Magnetic Fe-C-N Composites
by Xu Liu, Huilai Liu, Kangping Cui, Zhengliang Dai, Bei Wang, Rohan Weerasooriya and Xing Chen
Water 2023, 15(12), 2290; https://doi.org/10.3390/w15122290 - 19 Jun 2023
Cited by 6 | Viewed by 2133
Abstract
In this study, the iron-based carbon composite (hereafter FCN-x, x = 0, 400, 500, and 600 calcination) was synthesized by a simple high-temperature pyrolysis method using iron-containing sludge coagulant generated from wastewater treatment settling ponds in chemical plants. The FCN-x was used for [...] Read more.
In this study, the iron-based carbon composite (hereafter FCN-x, x = 0, 400, 500, and 600 calcination) was synthesized by a simple high-temperature pyrolysis method using iron-containing sludge coagulant generated from wastewater treatment settling ponds in chemical plants. The FCN-x was used for the adsorptive reduction of aqueous phase Cr(VI) effectively. The FCN-x was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and Brunauer-Emmett-Teller theory (BET). FCN-x adsorption of Cr(VI) was examined in batch experiments using CrO42− as a function of physicochemical parameters. The chemical kinetics of Cr(VI) adsorption by FCN-500 were modeled by 1st and 2nd order empirical pseudo kinetics. Based on these experiments, FCN-500 has been selected for further studies on Cr(VI) adsorptive reduction. The maximum Cr(VI) adsorption by FCN-500 was 52.63 mg/g showing the highest removal efficiency. The Cr(VI) adsorption by the FCN-500 was quantified by the Langmuir isotherm. XPS result confirmed the reduction of Cr(VI) to Cr(III) by the FCN-500. The iron-based carbon composites have high reusability and application potential in water treatment. The electroplating wastewater with 117 mg/L Cr(VI) was treated with FCN-500, and 99.93% Cr(VI) was removed within 120 min, which is lower than the national chromium emission standard of the People’s Republic of China. This work illustrates the value-added role of sludge generated from dye chemical plants to ensure environmental sustainability. Full article
(This article belongs to the Special Issue Adsorption Technology for Water and Wastewater Treatments)
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14 pages, 3311 KiB  
Article
Modeling of Distributed Control System for Network of Mineral Water Wells
by Ivan M. Pershin, Elena G. Papush, Tatyana V. Kukharova and Vladimir A. Utkin
Water 2023, 15(12), 2289; https://doi.org/10.3390/w15122289 - 19 Jun 2023
Cited by 52 | Viewed by 2287
Abstract
The article is devoted to solving the problem of designing a distributed control system for a network of production wells on the example of mineral water deposits in the Caucasus Mineral Waters region, Russia. The purpose was to determine the set of parameters [...] Read more.
The article is devoted to solving the problem of designing a distributed control system for a network of production wells on the example of mineral water deposits in the Caucasus Mineral Waters region, Russia. The purpose was to determine the set of parameters of the control system to ensure technologically effective and safe operating modes of mineral water deposits. A mathematical model of the deposit was developed taking into account the given configuration and production rate of the network of the wells. The detailed algorithm is presented for designing the control system under consideration based on the frequency concept of analysis and synthesis for distributed control systems. The experimental tests and model validation were performed at the production wells facility of “Narzan”, Kislovodsk, Russia. The results of modeling and field experiments confirmed the adequacy of the mathematical model and the effectiveness of the proposed algorithm. The authors came to the conclusion that the adapted mathematical model can be used to create a regional automated field cluster management system for monitoring, operational management and forecasting the nature of real hydrogeological processes and ensuring their stability. Full article
(This article belongs to the Special Issue Advances in Aquifer Systems Analysis: Flows, Interactions, Quality Status, and Remediation)
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22 pages, 3265 KiB  
Article
Analysis of Social Networks of Water-Use-Related Information in the Rio Mayo Irrigation District (038) in Northern Mexico: Ethnicity, Land Tenure and Land Use
by Ixtoc Marlo Rivera-Nuñez, Diana Luque Agraz, Arthur D. Murphy and Eric C. Jones
Water 2023, 15(12), 2288; https://doi.org/10.3390/w15122288 - 19 Jun 2023
Cited by 2 | Viewed by 1719
Abstract
(1) Background: In Mexico, 76% of water consumed is used for crop irrigation, and close to half of this is used in 86 irrigation districts for agroindustry throughout the nation. The present study combines a political ecology approach with social networks analysis to [...] Read more.
(1) Background: In Mexico, 76% of water consumed is used for crop irrigation, and close to half of this is used in 86 irrigation districts for agroindustry throughout the nation. The present study combines a political ecology approach with social networks analysis to identify how water-use-related information networks are structured according to the ethnicity (indigenous and non-indigenous) of the users of the Rio Mayo Irrigation District 038 (RMID) and how these networks are influenced by users’ type of land tenure and land use. (2) Methods: The study involved three stages: identification of social actors that influence water management (SAIWM); application of 118 structured interviews with users of RMID; and ethnographic fieldwork. (3) Results: Thirty SAIWM were identified. Only 11.8% of RMID users interviewed were indigenous farmers and only 5% were indigenous holders of collective landholdings. The information network metrics indicate that indigenous users have less access to information than non-indigenous users. (4) Conclusions: Ethnicity as well as land tenure and land use influence the structure of information networks and determine whether RMID users work as land-holding farmers or as hired labor. Full article
(This article belongs to the Special Issue Water Contestations: Socio-Technical Entanglements, Politics and Social Mobilisation)
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21 pages, 8161 KiB  
Article
Optimizing Rotation Forest-Based Decision Tree Algorithms for Groundwater Potential Mapping
by Wei Chen, Zhao Wang, Guirong Wang, Zixin Ning, Boxiang Lian, Shangjie Li, Paraskevas Tsangaratos, Ioanna Ilia and Weifeng Xue
Water 2023, 15(12), 2287; https://doi.org/10.3390/w15122287 - 19 Jun 2023
Cited by 3 | Viewed by 1738
Abstract
Groundwater potential mapping is an important prerequisite for evaluating the exploitation, utilization, and recharge of groundwater. The study uses BFT (best-first decision tree classifier), CART (classification and regression tree), FT (functional trees), EBF (evidential belief function) benchmark models, and RF-BFTree, RF-CART, and RF-FT [...] Read more.
Groundwater potential mapping is an important prerequisite for evaluating the exploitation, utilization, and recharge of groundwater. The study uses BFT (best-first decision tree classifier), CART (classification and regression tree), FT (functional trees), EBF (evidential belief function) benchmark models, and RF-BFTree, RF-CART, and RF-FT ensemble models to map the groundwater potential of Wuqi County, China. Firstly, select sixteen groundwater spring-related variables, such as altitude, plan curvature, profile curvature, curvature, slope angle, slope aspect, stream power index, topographic wetness index, stream sediment transport index, normalized difference vegetation index, land use, soil, lithology, distance to roads, distance to rivers, and rainfall, and make a correlation analysis of these sixteen groundwater spring-related variables. Secondly, optimize the parameters of the seven models and select the optimal parameters for groundwater modeling in Wuqi County. The predictive performance of each model was evaluated by estimating the area under the receiver operating characteristic (ROC) curve (AUC) and statistical index (accuracy, sensitivity, and specificity). The results show that the seven models have good predictive capabilities, and the ensemble model has a larger AUC value. Among them, the RF-BFT model has the highest success rate (AUC = 0.911), followed by RF-FT (0.898), RF-CART (0.894), FT (0.852), EBF (0.824), CART (0.801), and BFtree (0.784), respectively. Groundwater potential maps of these 7 models were obtained, and four different classification methods (geometric interval, natural breaks, quantile, and equal interval) were used to reclassify the obtained GPM into 5 categories: very low (VLC), low (LC), moderate (MC), high (HC), and very high (VHC). The results show that the natural breaks method has the best classification performance, and the RF-BFT model is the most reliable. The study highlights that the proposed ensemble model has more efficient and accurate performance for groundwater potential mapping. Full article
(This article belongs to the Section Hydrogeology)
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23 pages, 4587 KiB  
Article
Integration of Managed Aquifer Recharge into the Water Supply System in the Algarve Region, Portugal
by Kath Standen, Luís Costa, Rui Hugman and José Paulo Monteiro
Water 2023, 15(12), 2286; https://doi.org/10.3390/w15122286 - 19 Jun 2023
Cited by 2 | Viewed by 2843
Abstract
The Algarve region of Portugal is experiencing severe water scarcity with existing water supplies insufficient to meet demand, with limited resilience to drought. Managed aquifer recharge (MAR) can provide intermediate storage and bridge the gap between water availability and demand, with success depending [...] Read more.
The Algarve region of Portugal is experiencing severe water scarcity with existing water supplies insufficient to meet demand, with limited resilience to drought. Managed aquifer recharge (MAR) can provide intermediate storage and bridge the gap between water availability and demand, with success depending on the water available and the aquifer capacity to accept and store the water. We present the results of a regional study quantifying both these aspects to estimate the regional potential for MAR. Our results demonstrate that MAR can comprise 10% of the total water demand of the region (24 Mm3/yr) using water that is not otherwise captured, with quality that meets the requirements of the Groundwater Directive. MAR can replace 15 Mm3/yr of surface water used in the public irrigation perimeters and 9 Mm3/yr can be used to develop and maintain a strategic groundwater resource in the aquifers of the Central Algarve. Although climate change is predicted to result in an 8–13% decrease in MAR recharge, this can be addressed by incrementally increasing MAR design capacity. MAR has similar water resource benefits to the planned major infrastructure projects (desalination and River Guadiana abstraction), with reduced environmental impacts and lower costs than almost all feasible alternatives. We conclude that MAR is an important measure to increase water supply security and drought resilience in the Algarve region. Full article
(This article belongs to the Special Issue Managed Aquifer Recharge: A key to Sustainability)
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20 pages, 5456 KiB  
Article
Changes in Water and Sediment Processes in the Yellow River and Their Responses to Ecological Protection during the Last Six Decades
by Suiji Wang and Xumin Wang
Water 2023, 15(12), 2285; https://doi.org/10.3390/w15122285 - 19 Jun 2023
Cited by 6 | Viewed by 2313
Abstract
The variation of river hydrologic process can reflect the impact of not only natural factors, but also human activities. The purpose of this study is to reveal the change in the hydrologic regime of the Yellow River and its response to ecological protection. [...] Read more.
The variation of river hydrologic process can reflect the impact of not only natural factors, but also human activities. The purpose of this study is to reveal the change in the hydrologic regime of the Yellow River and its response to ecological protection. Based on the daily water and sediment observation data of representative gauging stations of the Yellow River, we analyzed the variation of the annual and monthly runoff and suspended sediment load (SSL), as well as monthly mean runoff, suspended sediment transport rate (SSTR), sediment inflow coefficient, and hydrological regime in a decadal average of the gauging stations during the period of 1960–2019. The results showed that the variation of annual runoff and SSL, as well as the monthly mean runoff and SSTR in a decadal average, had a significant decreasing trend in the 1960s–1990s, which was mainly in response to the gradual implementation of ecological protection measures such as afforestation, terrace construction, check dam construction, etc., in the basin. In 2000s and 2010s, the annual runoff increased, while the SSL increased slightly. This was a response to the implementation of new river management measures such as ensuring the ecological water demand of the lower reaches and scouring the riverbed by manually regulated water discharged from the Xiaolangdi Reservoir. At the same time, the monthly mean runoff and SSTR for the flood season (July–October) decreased remarkably while the process curve of the monthly mean discharge and sediment concentration changed from a clockwise loop to a counterclockwise loop in the river reach below the Xiaolangdi dam. This was a comprehensive response to the environmental protection measures in the Yellow River basin, in which the construction and operation of the Xiaolangdi Reservoir played a key role. This study can provide reference for river basin management. Full article
(This article belongs to the Special Issue Yellow River Basin Management under Pressure: Present State, Restoration and Protection II)
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18 pages, 1199 KiB  
Review
Wastewater Irrigation: A Promising Way for Future Sustainable Agriculture and Food Security in the United Arab Emirates
by Fatima Hasan Al Hamedi, Karthishwaran Kandhan, Yongming Liu, Maozhi Ren, Abdul Jaleel and Mohammed Abdul Muhsen Alyafei
Water 2023, 15(12), 2284; https://doi.org/10.3390/w15122284 - 19 Jun 2023
Cited by 16 | Viewed by 11103
Abstract
In the recent past, the production of wastewater from domestic and industrial sources steadily increased through population growth, urbanization, the Industrial Revolution, and economic development. In the world, 80% of wastewater consists of several harmful substances and hazardous chemicals that cause many deadly [...] Read more.
In the recent past, the production of wastewater from domestic and industrial sources steadily increased through population growth, urbanization, the Industrial Revolution, and economic development. In the world, 80% of wastewater consists of several harmful substances and hazardous chemicals that cause many deadly effects on human beings as well as ecosystems. So, the elimination of this toxic substance before discarding it into landfills is utilized as an alternative source of water which is an emerging need. Using treated wastewater for agricultural purposes is an excellent approach to rendering wastewater beneficial. As the quantity of wastewater grows, it becomes necessity to redistribute the water in a beneficial way. The rapidly increasing world population will undoubtedly increase the food demand, which directly requires more water for irrigation purposes. The rapidly increasing world population rate will undoubtedly demand an increased food production rate, which directly impacts agricultural water usage. In order to achieve sustainability in terms of agricultural water usage, alternative water resources should be explored. In this review, we tried to focus on summarizing all the leading studies in the field of wastewater utilization, the most prominent treatment methods, and a benchmarking of their technical efficiency in agriculture with special emphasis on agriculture in the marginal lands, with special emphasis on the United Arab Emirates. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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14 pages, 3276 KiB  
Article
Historical Trends and Driving Forces of River Water Quality Improvement in the Megacity Shenzhen, China
by Xiang Sun, Qingping Wu, Jiping Jiang and Kairong Lin
Water 2023, 15(12), 2283; https://doi.org/10.3390/w15122283 - 18 Jun 2023
Viewed by 2215
Abstract
The water quality of urban rivers in China has undergone significant improvement since the 13th Five-Year Plan period (2016–2020). Among these, urban rivers in Shenzhen are the most representative. Assessing historical trends and analyzing the driving forces of river water quality improvement is [...] Read more.
The water quality of urban rivers in China has undergone significant improvement since the 13th Five-Year Plan period (2016–2020). Among these, urban rivers in Shenzhen are the most representative. Assessing historical trends and analyzing the driving forces of river water quality improvement is of great importance and provides valuable insights. This study selects two typical watersheds, Maozhou River and Longgang River, to explore how water quality trends link with water control projects in Shenzhen from 2003 to 2020. The historical trends were evaluated using a recently developed index called WQI-DET, which considers DO, COD, NH3-N, TP, and anionic surfactants. Results showed that both rivers were seriously polluted before 2010 and gradually improved during the 12th Five-Year Plan period. After 2010, the water quality improved rapidly thanks to the environmental remediation of the mainstream, especially the interception project of Longgang River around 2010, and the Maozhou River interception project in 2015. The rainwater and sewage diversion renovation project mainly contributed to meeting the standards for Class IV water bodies during the 13th Five-Year Plan period. This study reveals the semi-quantitative link between comprehensive water quality improvement and pollution control engineering measures. It is a helpful review for Shenzhen and provides a useful reference for other cities. Full article
(This article belongs to the Special Issue Smart Water and the Digital Twin)
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17 pages, 4510 KiB  
Article
Macrophyte- and Macrozoobenthic-Based Assessment in Rivers: Specificity of the Response to Combined Physico-Chemical Stressors
by Emilia Varadinova, Gana Gecheva, Violeta Tyufekchieva and Tanya Milkova
Water 2023, 15(12), 2282; https://doi.org/10.3390/w15122282 - 18 Jun 2023
Cited by 1 | Viewed by 2041
Abstract
The importance of adequate biological assessments of rivers based on aquatic assemblages is essential to establish recovery measures. Macrophyte and macroinvertebrate communities react differently in time and in response strength to diverse stressors. Our hypothesis was that each group response is a result [...] Read more.
The importance of adequate biological assessments of rivers based on aquatic assemblages is essential to establish recovery measures. Macrophyte and macroinvertebrate communities react differently in time and in response strength to diverse stressors. Our hypothesis was that each group response is a result of specific and combined abiotic factors and each stressor’s impact. To address the above, both biological quality elements (BQEs) and values of the ecological quality ratio (EQR) were studied in relation to four abiotic parameters and five physico-chemical stressors. Discrepancies of more than one degree between the ecological status assessments of Bulgarian river sites determined using macrophytes and macrozoobenthos were discussed. The RDA analysis showed that altitude had a determining role in shaping the abundance of macrophyte and macrozoobenthos communities. Aquatic flora richness positively correlated with nitrogen enrichment and macroinvertebrate fauna—with altitude and biochemical oxygen demand (BOD). Nutrients and shading were most significant for the ecological status evaluation defined with both macrophytes and macrozoobenthos. Macrophyte-based EQR was related to oxygen concentration and shading, while macroinvertebrate-based EQR was better at sites with coarser substrates. Among tested stressors, mainly total nitrogen and BOD explained the lower macrophyte-based assessment at half of the studied sites. In conditions of increased nitrogen and BOD, but remaining in the range of good status, macrophytes as primary producers gave a faster and stronger response. Despite the differences in the assessment, both BQEs have higher values in conditions of lower BOD and total phosphorus. Full article
(This article belongs to the Special Issue Aquatic Ecology and Biological Invasions)
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12 pages, 4436 KiB  
Article
Decentralized Constructed Wetlands for Wastewater Treatment in Rural and Remote Areas of Semi-arid Regions
by Ibrahim Hendy, Martina Zelenakova, Katarzyna Pietrucha-Urbanik, Yasser Salama and Mohamed Abu-hashim
Water 2023, 15(12), 2281; https://doi.org/10.3390/w15122281 - 18 Jun 2023
Cited by 6 | Viewed by 2421
Abstract
Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and [...] Read more.
Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and to investigate the use of Paulownia trees in VFCWs for wastewater treatment. To compare the efficiency of the plants based on the treatment performance of the VFCWs, three units were prepared and composed of Paulownia, the commonly used Phragmites Australis, and an unplanted unit used as a control during the experimental program. The results show significant reductions in both the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) levels for both planted units, with removal ratios for COD and BOD5 of 60% to 98%, respectively. Both Paulownia and Phragmites Australis significantly reduced the levels of COD and BOD5 in the effluent, with removal percentages ranging from 57.1% to 98% for COD and 49.1% to 98% for BOD5. The control unit, without plantings, showed a lower but still significant removal percentage for both COD (from 55.1% to 96.1%) and BOD5 (from 48.3% to 97.8%). Thus, the results reveal that the efficiency of constructed wetlands can be significantly enhanced by the presence of suitable plant species, such as Paulownia and Phragmites Australis, and constructed wetlands can be a viable and cost-effective option for the treatment of wastewater in various settings, with the added benefit of using the relevant biodiversity. Full article
(This article belongs to the Special Issue Rainwater Harvesting and Treatment)
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19 pages, 7717 KiB  
Article
Full-Scale Constructed Wetlands Planted with Ornamental Species and PET as a Substitute for Filter Media for Municipal Wastewater Treatment: An Experience in a Mexican Rural Community
by Luis Carlos Sandoval Herazo, José Luis Marín-Muñiz, Alejandro Alvarado-Lassman, Florentina Zurita, Oscar Marín-Peña and Mayerlin Sandoval-Herazo
Water 2023, 15(12), 2280; https://doi.org/10.3390/w15122280 - 18 Jun 2023
Cited by 7 | Viewed by 2353
Abstract
Alternative polymer-based filter media and ornamental plants in constructed wetlands (CWs) are a relatively unexplored field. These approaches have the potential to reduce construction costs and enhance the aesthetic appearance of CWs. This study evaluated for the first time the use of ornamental [...] Read more.
Alternative polymer-based filter media and ornamental plants in constructed wetlands (CWs) are a relatively unexplored field. These approaches have the potential to reduce construction costs and enhance the aesthetic appearance of CWs. This study evaluated for the first time the use of ornamental plants as monoculture and polyculture, as well as the incorporation of polyethylene terephthalate (PET) as a filter medium in a large-scale community HC (divided into 12 cells) for the treatment of municipal wastewater. Duplicate cells were planted with monocultures of Canna hybrids, Spathiphyllum blandum, Anturium spp., and Thypa spp., while two units had mixed cultures of these plants and two control units remained without vegetation. Systems with vegetation achieved average removal efficiencies of 86.95, 81.3, 64.6, 85.2, and 52% for COD, BOD5, TSS, TP, and TN, respectively. Meanwhile, in systems without vegetation, the removal efficiencies for these pollutants were 81.33, 72.86, 43.68, 3.93, and 30.70%, respectively, indicating significant differences between vegetated and non-vegetated systems (p < 0.05). The PET-based filter medium showed effective pollutant removal, with values comparable to or surpassing those reported in existing literature. All ornamental species exhibited good development with new offspring and flower production both in monoculture and in polyculture. The use of such a filter medium and ornamental vegetation could make CWs more attractive to rural communities. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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12 pages, 2736 KiB  
Article
Identifying the Influencing Factors of Plastic Film Mulching on Improving the Yield and Water Use Efficiency of Potato in the Northwest China
by Juzhen Xu, Yanbo Wang, Yuanquan Chen, Wenqing He, Xiaojie Li and Jixiao Cui
Water 2023, 15(12), 2279; https://doi.org/10.3390/w15122279 - 18 Jun 2023
Cited by 4 | Viewed by 1812
Abstract
Potato is an important crop in the Northwest China, however, its production is constrained by water scarcity. Plastic mulching film is an efficient technical measure to alleviate potato production restrictions. Therefore, studying the response of potato yield and water use efficiency to plastic [...] Read more.
Potato is an important crop in the Northwest China, however, its production is constrained by water scarcity. Plastic mulching film is an efficient technical measure to alleviate potato production restrictions. Therefore, studying the response of potato yield and water use efficiency to plastic mulching film is of great significance. The study conducted a meta-analysis to quantify the effect of plastic film on potato yield and water use efficiency in the Northwest. The study then quantified the effects of different levels of natural conditions (mean annual precipitation, mean annual accumulated temperature ≥ 10 °C), fertilizer application (nitrogen fertilizer, phosphate fertilizer, potassium fertilizer), cultivation measures (planting density, cultivation method, mulching method), and mulching properties (mulching color, mulching thickness) through subgroups analysis. Finally, the random forest model was used to quantify the importance of factors. Plastic film mulching increased yield by 27.17% and water use efficiency by 27.16%, which had a better performance under relatively lower mean annual precipitation, low mean annual accumulated temperature ≥ 10 °C, relatively lower fertilizer application, planting density of 15,000–45,000 plants·ha−1, ridge, and black mulching. Natural conditions, fertilization measures were vital to improve productivity. The research results can provide reference for agricultural management strategies of potato cultivation using plastic film in the Northwest China and other potato-producing areas. Full article
(This article belongs to the Special Issue Impact of Climate and Socio-Economic on Irrigation Water Management and Agricultural Water Productivity)
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18 pages, 17634 KiB  
Article
Spatial or Random Cross-Validation? The Effect of Resampling Methods in Predicting Groundwater Salinity with Machine Learning in Mediterranean Region
by Panagiotis Tziachris, Melpomeni Nikou, Vassilis Aschonitis, Andreas Kallioras, Katerina Sachsamanoglou, Maria Dolores Fidelibus and Evangelos Tziritis
Water 2023, 15(12), 2278; https://doi.org/10.3390/w15122278 - 18 Jun 2023
Cited by 4 | Viewed by 2433
Abstract
Machine learning (ML) algorithms are extensively used with outstanding prediction accuracy. However, in some cases, their overfitting capabilities, along with inadvertent biases, might produce overly optimistic results. Spatial data are a special kind of data that could introduce biases to ML due to [...] Read more.
Machine learning (ML) algorithms are extensively used with outstanding prediction accuracy. However, in some cases, their overfitting capabilities, along with inadvertent biases, might produce overly optimistic results. Spatial data are a special kind of data that could introduce biases to ML due to their intrinsic spatial autocorrelation. To address this issue, a special resampling method has emerged called spatial cross-validation (SCV). The purpose of this study was to evaluate the performance of SCV compared with conventional random cross-validation (CCV) used in most ML studies. Multiple ML models were created with CCV and SCV to predict groundwater electrical conductivity (EC) with data (A) from Rhodope, Greece, in the summer of 2020; (B) from the same area but at a different time (summer 2019); and (C) from a new area (the Salento peninsula, Italy). The results showed that the SCV provides ML models with superior generalization capabilities and, hence, better prediction results in new unknown data. The SCV seems to be able to capture the spatial patterns in the data while also reducing the over-optimism bias that is often associated with CCV methods. Based on the results, SCV could be applied with ML in studies that use spatial data. Full article
(This article belongs to the Special Issue Advances on the Dynamics of Groundwater Salinization)
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23 pages, 4472 KiB  
Article
Multi-Tier Validation of a Macroscale Nitrogen Model for Groundwater Management in Watersheds Using Data from Different Monitoring Networks
by Tim Wolters, Georg Berthold, Ralf Kunkel, Björn Tetzlaff, Axel Thomas, Michael Zacharias and Frank Wendland
Water 2023, 15(12), 2277; https://doi.org/10.3390/w15122277 - 17 Jun 2023
Viewed by 1587
Abstract
For the Hessian river basins, an area-differentiated modeling of the nitrogen input to the groundwater and surface waters was carried out for six diffuse input pathways and six point source input pathways on the basis of the geodata available at the state level. [...] Read more.
For the Hessian river basins, an area-differentiated modeling of the nitrogen input to the groundwater and surface waters was carried out for six diffuse input pathways and six point source input pathways on the basis of the geodata available at the state level. In this context, extensive plausibility checks of the model results were carried out using the data from several official monitoring networks at the state level. These include the comparison of modeled runoff components and input pathways for nitrogen using the data from the network of discharge monitoring stations. For the validation of the modeled nitrate concentrations in the leachate, the data from groundwater monitoring wells for controlling the chemical status of groundwater were used. The validation of the modeled nitrate inputs to the groundwater and denitrification in the groundwater was carried out using the data from a special monitoring network of groundwater monitoring wells that include N2/Ar measurements. The data from the Surface Water Quality Monitoring Network were used to verify the plausibility of the modeled total N inputs to the surface waters from diffuse sources and from point sources. All of the model results evaluated by the plausibility checks prove that the nitrate pollution situation in Hesse is adequately represented by the model. This is a prerequisite for accepting the model results at the state level as a basis for developing and implementing regionally appropriate mitigation measures. The Hessian State Agency for Nature Conservation, Environment and Geology uses the model results in the broader context of the work on implementing the EU Water Framework Directive and the EU Nitrate Directive. Full article
(This article belongs to the Special Issue Assessment of Groundwater Quality and Monitoring of Flow and Pollution Transport)
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