Water, Volume 15, Issue 21 (November-1 2023) – 164 articles

Cutoff walls are widely used to limit seepage, piping, and the uplift under hydraulic structures. Therefore, this study focused on a numerical investigation of the hydraulic performance of cutoff walls beneath hydraulic structures during both static and dynamic conditions, considering location and inclination angle influences. The results confirmed that placing the cutoff wall at the upstream heel was more effective in reducing uplift pressure compared to other placements during static conditions. The inclination angles for the different placements of the cutoff wall had a significant impact on the total uplift pressure, exit hydraulic gradient, and seepage discharge during both static and dynamic states. The earthquakes had a noticeable effect on uplift pressure, seepage discharge, and exit hydraulic gradient. During static conditions, the inclination angle of 90° was the most effective angle for decreasing seepage discharge, irrespective of the cutoff wall position. During an earthquake, the seepage discharge values were high regardless of the inclination angle. In the case of placing a cutoff wall at the upstream heel, the maximum seepage discharge value occurred at an inclination angle of 45°. This study provided insights into the behavior of cutoff walls under different conditions and can inform the design and construction of such structures for effective seepage control. The experimental feed-forward neural network (FFNN) was also successfully built. According to the following criteria (uplift pressure, seepage, and exit hydraulic gradient), the hydraulic performance of cutoff walls beneath hydraulic structures under static conditions can be examined. The FFNN can make predictions with root mean square errors (RMSE) of 0.0697, 0.0021, and 0.0059, respectively, and R² values of 1.00, 0.9994, and 0.9997. Full article

The dam-break water flow is a complex fluid motion, showing strong nonlinearity and stochasticity. In order to better study the characteristics of the dam burst flood, the smooth particle hydrodynamics (SPH) method was chosen to establish a two-dimensional classical dam-burst model, and the flow velocity distribution graph was obtained by calculation and compared with the experimental results in the literature, and the fitting degree of the two was obtained to be 88.4%, which verifies the validity of the model. On this basis, according to the principle of dam failure, the two failure modes of equal-interval gradual failure and progressive gradual failure were simulated, and the water body characteristics such as water flow velocity, energy, pressure, etc., were analyzed based on the different working conditions of the two modes to obtain the characteristics of gradual dam-failure water flow under the two kinds of numerical models. The simulation results show that, compared with the instantaneous dam failure mode, (1) the flow rate of the dam-failure stream reaching the downstream slows down in the gradual dam-failure mode; (2) the depth development of the breach extends downward in layers and stages over time, and the overall duration of the breach is prolonged; (3) the destructive power of the dam-failure flood is weakened as the number of segments increases. The results of the study show that, compared with the instant dam-failure mode, the calculation results of the breach development considering the progressive gradual dam-failure mode are more in line with the theoretical solution and closer to the actual process of dam failure, which can provide ideas and references for advancing the numerical study of dam failure. Full article

Chemically modified bioadsorbents were prepared using sawdust (Aspidosperma polyneuron) functionalized with urea at different concentrations (BC-1M, BC-3M, and BC-6M) to evaluate their adsorption capacity by the methylene blue method. Fourier transform spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) were employed to characterize the surface morphology of the biomaterials. The best adsorption capacity was obtained using the biocarbon modified with urea 6M (BC-6M), displaying a methylene blue index of 12.4 mg/g with a zero-charge point (pHpzc) at 5.5, suggesting the potential application of this chemically modified bioadsorbent for the removal of cationic contaminants in aqueous media. Full article

Permeable concrete is a class of materials that has long been tested and implemented to control water pollution. Its application in low-impact development practices has proved its efficiency in mitigating some of the impacts of urbanization on the environment, including urban heat islands, attenuation of flashfloods, and reduction of transportation-related noise. Additionally, several research efforts have been directed at the dissemination of these materials for controlling pollution via their use as permeable reactive barriers, as well as their use in the treatment of waste water and water purification. This work is focused on the potential use of these materials as permeable reactive barriers to remediate ground water and treat acid mine drainage. In this respect, advances in material selection and their proportions in the mix design of conventional and innovative permeable concrete are presented. An overview of the available characterization techniques to evaluate the rheology of the paste, hydraulic, mechanical, durability, and pollutant removal performances of the hardened material are presented and their features are summarized. An overview of permeable reactive barrier technology is provided, recent research on the application of permeable concrete technology is analyzed, and gaps and recommendations for future research directions in this field are identified. The optimization of the mix design of permeable reactive concrete barriers is recommended to be directed in a way that balances the performance measures and the durability of the barrier over its service life. As these materials are proposed to control water pollution, there is a need to ensure that this practice has minimal environmental impacts on the affected environment. This can be achieved by considering the analysis of the alkaline plume attenuation in the downstream environment. Full article

Arsenic (As) is a prominent carcinogen component produced via both geogenic and anthropogenic processes, posing serious risks to human health. This study aimed to investigate the potential of hydrochar prepared from red macroalgae for removing As from synthetic wastewater. The hydrochar was produced through 5 h hydrothermal carbonization (HTC) treatment at 200 °C, and then, chemically activated with ferric chloride hexahydrate (FeCl₃·6H₂O). SEM analysis revealed a permeable structure of hydrochar, while FTIR analysis detected the occurrence of several functional groups at the hydrochar interface. EDS analysis showed an increase in carbon concentration after FeCl₃·6H₂O activation. Hydrochar was then tested in batch experiments to investigate its As removal efficiency, with ICP-MS used to determine the levels of As after the adsorption process. The results showed that As removal efficiency increased with increasing initial As concentration from 50 to 250 mg/L, and the highest As removal efficiency was 84.75% at a pH of 6, initial concentration of 0.25 mg/L, and adsorbent dose of 1000 mg at 120 min. The Langmuir isotherm model supported the occurrence of homogeneous adsorption over the surface of hydrochar, while the pseudo-second-order model confirmed the chemisorptive nature of the process. Full article

The relationship between the soil surface temperature and groundwater level is complex and influenced by various factors. As the soil surface temperature increases, water evaporates quickly from the soil, which can lead to a decrease in the groundwater level. In this study, we analyzed the impact of soil surface temperature on changes in the groundwater level in the Bukhara region of Uzbekistan using data from 1991 to 2020. The Bukhara region experiences regular water shortages, increased soil salinization, and inefficient energy in lift-irrigated areas, which is a typical constellation of challenges to the water–energy–food–environment (WEFE) nexus. The soil surface temperature data were collected from the Hydrometeorological Service Agency, whereas groundwater level data were obtained from the database of the Amelioration Expedition under the Amu-Bukhara Basin Irrigation Systems Authority. We used linear regression analysis and Analysis of Variance (ANOVA) tests to establish the significance of the relationship between the soil surface temperature and groundwater level, as well as the impact of the location of the groundwater level measurements. The results indicate that the model was a good fit to the data, and both the intercept and the soil surface temperature were significant factors that affected groundwater level. The results further suggest that the strength of the relationship between solar radiation and soil surface temperature is very high, with a correlation coefficient of 0.840. This means that when solar radiation increases, soil surface temperature also tends to increase. The analysis also showed that 53.5% of the changes in groundwater level were observed by the regression model, indicating a moderately correlated relationship between the groundwater level and soil surface temperature. Finally, higher solar radiation leads to higher soil surface temperature and higher evapotranspiration rates, which can lead to a decrease in groundwater level. As a result, we observe that the soil surface temperature determines changes in the groundwater level in the study region. Full article

Chlorophyll a (Chla) is a crucial pigment in phytoplankton, playing a vital role in determining phytoplankton biomass and water nutrient status. However, in optically complex water bodies, Chla concentration is no longer the primary factor influencing remote sensing spectral reflectance signals, leading to significant errors in traditional Chla concentration estimation methods. With advancements in in situ measurements, synchronized satellite data, and computer technology, machine learning algorithms have become popular in Chla concentration retrieval. Nevertheless, when using machine learning methods to estimate Chla concentration, abrupt changes in Chla values can disrupt the spatiotemporal smoothness of the retrieval results. Therefore, this study proposes a two-stage approach to enhance the accuracy of Chla concentration estimation in optically complex water bodies. In the first stage, a one-dimensional convolutional neural network (1D CNN) is employed for precise Chla retrieval, and in the second stage, the regression layer of the 1DCNN is replaced with support vector regression (SVR). The research findings are as follows: (1) In the first stage, the performance metrics (R², RMSE, RMLSE, Bias, MAE) of the 1D CNN outperform state-of-the-art algorithms (OCI, SVR, RFR) on the test dataset. (2) After the second stage, the performance further improves, with the metrics achieving values of 0.892, 11.243, 0.052, 1.056, and 1.444, respectively. (3) In mid- to high-latitude regions, the inversion performance of 1D CNN\SVR is superior to other algorithms, exhibiting richer details and higher noise tolerance in nearshore areas. (4) 1D CNN\SVR demonstrates high inversion capabilities in water bodies with medium-to-high nutrient levels. Full article

Chemical fertilizer loss during agricultural production is an important factor leading to the eutrophication of lakes and reservoirs. As fertilizer technology has become more widespread, it has become necessary to explore the ecological compensation mechanism in areas with important ecological functions to further reduce chemical fertilizer application. Among these, farmers’ preferences for chemical fertilizer reduction are one of the most important issues. Based on the survey data of 142 farmers surrounding Poyang Lake, this paper studies the farmers’ willingness to accept (WTA) the attributes of a chemical fertilizer reduction scheme using the choice experiment method. The results are as follows: (1) The farmers’ WTA value for each additional year of the program was 63.75 CNY/ha/year, the WTA value for every 10 percent increase in the proportion of participating land area was 73.875 CNY/ha/year, and the WTA value for every 10 percent reduction in the fertilizer application was 413.505 CNY/ha/year. (2) The household support burden, the proportion of non-agricultural income, and farmers’ understanding of the importance of wetlands significantly affect farmers’ WTA value. (3) The interviewed farmers can be divided into four different types: farm type, farm-oriented hybrid type, off-farm-oriented hybrid type, and off-farm workers, each with different preferences for fertilizer reduction schemes. Full article

Pharmaceuticals and Personal Care Products (PPCPs) constitute a group of compounds that are challenging to break down and potentially pose risks to both ecosystems and human health when they accumulate in water bodies. This study established and operated small-scale constructed wetland–microbial fuel cells (CW-MFCs) continuously for 60 days, maintaining a hydraulic retention time (HRT) of 3 days. The research aimed to assess the treatment efficiency of wastewater containing Ibuprofen (IBP) and Diclofenac (DCF) using different co-substrates (glucose, sucrose, and sodium acetate) and to analyze the impact of these co-substrates on the composition of bacterial communities within the CW-MFC. After 60 days of operation, CW-MFC achieved removal rates of 89.29% for IBP and 84.10% for DCF. The elimination of IBP was primarily dependent on co-metabolic degradation processes occurring in both the anode and cathode, while DCF removal relied on anodic co-metabolism. Additionally, various co-substrates have an influence on the bacterial community diversity of the anode and cathodes. The possible bacterial groups involved in PPCP degradation were identified. In summary, Glu was identified as a more suitable co-substrate for CW-MFC in the removal of IBP and DCF, while SA as a co-substrate favored the induction and enrichment of EAB in the anodes. These findings offer valuable insights into the potential of CW-MFC for mitigating emerging contaminants. Full article

Meteorological drought is a continuous spatiotemporal phenomenon that poses a serious threat to water resource security. Dynamic evolution and multivariable frequency analysis of meteorological drought are important for effective drought mitigation and risk management. Therefore, this study aims to analyze meteorological drought events in northwestern China between 1960 and 2018 based on the standardized precipitation evapotranspiration index (SPEI) through a three-dimensional identification method. This study investigates the meteorological drought dynamic evolution on different time and space scales and evaluates the frequency analysis considering the spatiotemporal variability based on Copula. The results show that SPEI presents an upward trend in Northwestern China. A trend towards increased humidity is observed in arid regions, contrasted by a trend towards aridification in semi-arid and semi-humid areas, indicating that the spatial distribution of drought in the study area tends towards homogenization. The possibility of high-intensity drought events occurring in the same area was relatively low, whereas low-intensity drought events were frequent. Additionally, this study analyzes the dynamic migration process of individual drought events from a three-dimensional perspective. Neglecting any one drought variable could significantly underestimate the occurring probability of severe drought events. Therefore, a multivariable frequency analysis considering the spatiotemporal variability plays a crucial role in the formulation of drought prevention and mitigation strategies, as well as drought forecasting. Full article

The problem of shoaling on coastal structures is the result of an event that occurs as part of the natural cycle. In cases where shoaling cannot be detected or prevented, various economic and operational problems may arise and may cause disruptions. In this study, the complex coastal dynamic impact of shoaling on three sequential fishery coastal structures located within the borders of Rize province in the Eastern Black Sea region of Türkiye was examined in terms of bathymetric changes and sediment transport under the influence of the incident wave climate. The effects of these structures on each other were also investigated. With this aim, bathymetric measurements were carried out to examine the impact of waves on seabed erosion and deposition. A serious shoaling problem was identified at one of the harbor launches under investigation, where approximately 13,200 m³ of deposition occurs annually in a relatively small harbor launch area. Such physical problems are thought to be the result of shoaling, the selection of sites that are not viable for fishery-related coastal structures, or the wrong positioning of the breakwater. Full article

As a coastal city with rapid urbanization and high-intensity human activities, Shenzhen, China has carried out a series of comprehensive treatments for water pollution control and ecological restoration in recent years. However, the restoration effect is mainly reflected in the improvement of water quality and riparian landscape, and there is still a big gap in reaching the river’s ecological restoration goals. Therefore, it is necessary to make a full investigation and evaluation of river aquatic systems that focuses on the restoration of aquatic communities and ecosystem health. We surveyed forty-seven sampling sites in nine basins to investigate water quality and aquatic organisms (algae and macroinvertebrates) during the low-water period in 2019. Under the guidance of the EU Water Framework Directive (WFD), the urban river ecosystem health assessment system, with a total of twenty indicators from six criteria layers, was established. We addressed the bioremediation objectives in this system and aquatic organism indicators as high-weight characteristic indicators. The results showed that the degradation of the river ecosystem in Shenzhen is serious, which is mainly reflected in the simple structure of the aquatic biological community and the low biodiversity. Only one “healthy” sample site, accounting for 2% of the total sampling sites; six sites of “sub-health” level, accounting for 13%; twenty-four “poor” sample points, accounting for 51%; sixteen “extremely poor” sample points, accounting for 34%. From the perspective of spatial distribution, the river ecological status of Daya Bay Basin and Dapeng Bay Basin is good, which is at the level of “health” to “sub-health”; the Guanlan River Basin, Maozhou River Basin, Shenzhen River Basin, Shenzhen Bay Basin, Pingshan River Basin, and most of the Longgang River Basin are of “poor to extremely poor” grade; the Pearl Estuary basin is of “extremely poor” grade. This assessment system can be used as an effective tool to monitor the ecological health status, especially the enhancement of biodiversity and ecosystem function of rivers. Moreover, it could provide important decision-making guidance for river management affected by high-intensity human activities. Full article

Bromate is a potentially carcinogenic disinfection by-product of potential concern in desalinated waters, where bromide derived from seawater can be converted to bromate by the oxidising species used for disinfection. Historically, it has been difficult to maintain complete adherence to national standards of no more than 10 ppb for bromate at all locations served with desalinated seawater by the Saline Water Conversion Corporation (SWCC) in the Kingdom of Saudi Arabia. In this full-scale study, the addition of 100–200 ppb of ammonia to the produced water of a Multi-Stage Flash Desalination plant effectively controlled the formation of bromate in the transmission system supplying inland centres in the Makkah Province of the Kingdom of Saudi Arabia (Arafa, Taif) on a time scale sufficient for the distribution of water to the consumer, even when the bromide content of the produced water was artificially enhanced (up to 132 ppb) via the addition of seawater. Full article

Technologies used in municipal wastewater treatment plants (WWTPs) allow the recovery of energy and valuable elements (phosphorus, nitrogen, and organic carbon) for the soil. This article presents, in schematic form, the carbon, nitrogen, and phosphorus cycling in a WWTP with a load of 70,000 Population Equivalent and develops a spreadsheet to estimate their recovery. Biogas generation enables the recovery of 1126 Mg of organic carbon per year and the generation of 12.6 GWh of energy. The most rational form of organic waste recycling is the production of compost with fertilizing parameters, but efforts should be made to reduce iron compounds in its composition. It has been estimated that compost production provides the recovery of 30% of carbon, 98% of phosphorus, and 18% of nitrogen from the streams of these elements entering the WWTP. The possibility of partially replacing the iron coagulants used to precipitate phosphorus with waste magnesium salt is presented, leading to the precipitation of struvite, which is well absorbed by plants. The article presents the advantages of combining sewage treatment with organic waste management in WWTPs. The developed spreadsheet allows for the control of energy recovery through the quantitative selection of organic waste for fermentation. Full article

To clarify the soil nutrient status and identify the safety risks of heavy metals in Camellia oleifera planting regions, the integrated soil fertility status was assessed using the improved Nemero composite index method, weighted average method, and coefficient of variation (CV) method, and the impact of heavy metals in the soil on human health was evaluated with a health risk assessment model using the Qianyu C. oleifera planting base in Yuping County, Guizhou Province, as the study object. The results showed the following: (1) The soil pH levels were 4.12–6.17, with CV values of 0.04–0.66, and no significant differences were observed among the plots. The soil was rich in organic matter, alkali-hydrolyzed nitrogen, and available phosphorus, with a high total potassium content, total phosphorus content, and rapidly available potassium, indicating a high level of comprehensive soil fertility. (2) The total carcinogenic risk (CR) index of the arsenic (As), cadmium (Cd), and chromium (Cr) in the soil was 1.92 × 10⁻⁷, and among these elements, the CR index of the As was the highest (1.3–8.0 × 10⁻⁷), but all were below the highest acceptable level (10⁻⁶) recommended by the United States Environmental Protection Agency (USEPA). (3) The redundancy analysis (RDA) between the soil fertility and trace elements revealed that the soil organic matter content was positively correlated with the contents of lead (Pb), manganese (Mn), and Cr and negatively correlated with the contents of zinc (Zn), iron (Fe), Cd, mercury (Hg), As, and copper (Cu). The soil pH was positively correlated with the contents of Cr, Fe, and Cu and negatively correlated with the contents of Mn, Pb, Zn, Cd, Hg, and As. In the study area, the soil was slightly acidic with overall high fertility without any CR. The quality of the C. oleifera was degraded by soil acidification, but the slightly acidic soil facilitated the absorption of trace elements by C. oleifera. Soil acidification could be relieved by taking appropriate measures, such as the addition of biochar or CaCO₃. This study determined the soil fertility of the Qianyu C. oleifera planting base and assessed the health risk of heavy metals in the soil, providing a theoretical reference for enhancing C. oleifera quality, preventing the excessive accumulation of soil heavy metals, and improving the soil in this planting base. Full article

The western plain of the Nansihu Lake Basin (NLB) is an important agricultural economic zone in Shandong Province, where there is a high content of fluoride in soils. Studying the content and influencing factors of fluoride in soils is of great significance for the maintenance of regional eco-logical security and human health. This study takes the farmland soils in the west of NLB as the research focus and uses a method based on GIS and geostatistics to quantitatively analyze the spatial variation characteristics of soil total fluoride and water-soluble fluoride contents to draw a map showing their spatial distribution. The effects on the spatial distribution of soil total fluoride and water-soluble fluoride were analyzed from the aspects of geomorphological type, soil parent material (stratigraphic lithology), crop type, and groundwater fluoride concentration, among others, and the correlation between groundwater and soil fluoride contents was also analyzed. Our study results in the following findings: (1) The average content of total fluoride in topsoil in the study area is 652.8 mg/kg, the national background value is exceeded in 99.5% of the sampling sites, and the background value of Shandong Province is exceeded in 98.7% of the sampling sites. The average water-soluble fluoride is 15.2 mg/kg and exceeds 5.0 mg/kg in 94.3% of the sampling sites. Topsoils have high values of total fluoride and water-soluble fluoride. (2) The total fluoride and water-soluble fluoride in topsoils exhibit moderate spatial variability, indicating that their spatial distribution is the result of structural factors such as soil parent materials and man-made random factors such as fluorinated fertilizers. (3) In the 2 m vertical profile of shallow soils, total fluoride and water-soluble fluoride increase with the increase in soil viscosity, and the water-soluble fluoride has the characteristics of surface aggregation due to the influence of soil adsorption. Because fluoride ions as ligands are easily adsorbed and form fluoride complexes with other ions such as aluminum ions, the water-soluble fluoride shows the characteristics of surface aggregation and fractionation. (4) The analysis of influencing factors reveals that the lithology of Quaternary strata, geomorpho-logical types, and planting crop types have significant effects on the distribution of the total fluoride and water-soluble fluoride in the topsoils, and the distribution of the groundwater soluble fluoride in the topsoils is not related to that in groundwater. Our study provides data and technical support for improving both the soil environmental quality and water quality of the eastern route of the South-to-North Water Transfer Project, thus helping to promote the sustainable development of the social economy and ecological environment in the NLB. Full article

Accurate forecasting of the tail water level (TWL) is of great importance for the safe and economic operation of hydropower stations. The prediction accuracy is significantly influenced by the backwater effect of downstream tributaries and the operation of adjacent hydropower stations, but the explicit quantification method of the backwater effect is lacking. In this study, a deep-learning-model-based forecasting method for TWL predictions under the backwater effect is developed and applied in the Xiangjiaba (XJB) hydropower station, which is influenced by the backwater effect of downstream tributaries, including the Hengjiang River (HJR) and the Minjiang River (MJR). Firstly, the random forest algorithm was used to analyze the influence of HJR and MJR flows with different lag times on the TWL prediction error of the XJB hydropower station. The results show that the time lags of the backwater effect of HJR and MJR run offs on the TWL of the XJB are 5~7 h and 1~2 h, respectively. Then, the run off thresholds of the HJR and MJR for impacting the TWL of the XJB station are obtained through scenario comparison, and the results show that the run off thresholds of the HJR and the MJR are 700 m³/s and 7000 m³/s, respectively. Finally, based on the analysis of the time lag and the threshold of the backwater effect, a deep learning model (LSTM)-based TWL forecasting method is established and applied to predict the TWL of the XJB station. The results show that the forecasting model has a good predictive performance, with 98.22% of absolute errors less than 20 cm. The mean absolute error over the validation dataset is 5.27 cm, and the maximum absolute error is 63.35 cm. Compared with the LSTM-based prediction model without considering the backwater effect, the mean absolute error decreased by 31%, and the maximum absolute error decreased by 71%. Full article

Freshwater is fundamental for all aspects of human well-being and sustainable development. The supply of freshwater resource largely depends on the natural water cycle, leading to extremely unequal distribution over the world. This uneven distribution and increasing freshwater demand results in spatial and temporal physical freshwater shortage. By discussing the limitations of desalination techniques and the shortcomings of existing pathways for freshwater transfer including water transfer projects, bottled water market, and virtual water trade, we suggest that international freshwater trade as an additional pathway is necessary. The analysis of the cost structure of freshwater production and transportation and the hypothetical examples between potential exporting and importing countries show the feasibility of international freshwater trade. The establishment of a global freshwater market is confronted with six challenges, namely, natural sustainability, ecological safety, opinions of stakeholders, market access mechanism, pricing mechanism, and infrastructure system. We conclude that a global freshwater market is expected to make contributions to achieving SDG 6 by mitigating spatial and temporal freshwater scarcity and by resolving transboundary freshwater conflicts and managing local freshwater consumptions. Full article

The optimization of dam operations to transform them into multi-objective facilities constitutes a challenge for both hydrology, hydrogeology, and hydropower generation. However, the use of the optimal algorithm for such transformation is critically important. Additionally, the literature has highlighted that dams might negatively influence the recharge of groundwater. Within this study, we provide an overview of the available algorithms for the optimization of dam operations. Additionally, an overview focusing on hydropower generation in Greece illustrates the high potential of the Mediterranean region for hydropower generation and the application of MAR. The water quality of the reservoirs is also highlighted as a critical parameter. Within this study, we present indices for water quality monitoring in dam reservoirs, while the most prevailing index is the SRDD. This study constitutes a guide for researchers in choosing the optimal tools for the optimization of dam operations and the water quality monitoring of reservoirs. The present study suggests a meta-heuristic optimization methodology using the harmony search algorithm. The model uses a geometric model of the reservoir and calculates the level–supply curve. Furthermore, a multi-criteria optimization model was developed with two objective functions: the maximum power output from the hydroelectric power plant turbines and the optimal groundwater recharge. The model with appropriate parameter modifications can be applied to any small dam as it is a decision- and policy-making methodology, independent of local conditions. A further step is the application of these approaches dealing with field data and the numerical modeling of case studies. The interdisciplinary approach of this study links deferent aspect and scientific perceptions, providing a comprehensive guide to optimal water resource management and environmental sustainability. Full article

Speed governing control is significant in ensuring the stable operation of pumped storage units. In this study, a state-space equation mathematical model of the pumped storage governing system considering the complex hydraulic pipeline structure of the pumped storage plant is proposed to describe the system’s dynamic behaviors under small disturbance conditions. Considering the frequent operating condition transitions and the complicated nonlinear dynamic characteristics of the pumped storage units, the fractional-order PID (FOPID) scheme that possesses a higher degree of control freedom than the traditional PID scheme is discussed in detail. To optimize the control parameters of the unit governor, an improved gravitational search algorithm (IGSA) that combines the basic searching mechanisms of the gravitational search algorithm and chaotic search, elastic sphere boundary treatment, and elite guidance strategy is developed. Comparative studies have been carried out under frequency and load disturbance conditions. Simulation results indicate that the control performance of FOPID is better than that of PID under diverse operating conditions and the proposed IGSA has satisfactory parameter optimization capability. Full article

In the context of global climate change, the frequency of watershed flooding events resulting from extreme rainfall has significantly increased. Especially at river or lake confluences, the presence of backwater effects greatly amplifies the flood risk. To investigate the influence of backwater effects on the hydraulic characteristics of rivers and lakes, this study focuses on the Dongping Lake in China. An enhanced two-dimensional hydrodynamic model was employed to simulate and analyze three different degrees of backwater effects. The results indicate that, compared to the working conditions without the backwater effect, the highest lake water level increased by 1.0 m and 0.1 m under severe and moderate backwater effect conditions, respectively. The total outflow flood volume decreased by 30.1% and 2.3%, respectively. The demolition time for the Jinshan Dam needs to be advanced by 12.5 h and 10.0 h, respectively, and the inundation area in the western region expanded by 2.73% and 0.32%. Additionally, the average inundation depth increased by 0.93 m and 0.08 m, respectively. These results provide valuable data support for the safe operation of Dongping Lake, the formulation of flood defense strategies, and, likewise, offer valuable insights into the risk management of flood events in other rivers and lakes with backwater effects. Full article

In this work, raw rice husk biochar (RRHB) was investigated for its potential as a valuable industrial byproduct for the decontamination of water using rhodamine B (RB) as a model pollutant. Specific functional chemical groups that were identified in the structure of the biochar using Fourier transform infrared (FTIR) spectra were determined to be responsible for the interaction between the biochar and the pollutant, explaining the sorption process. The interaction between the pollutant and biochar was also explained by the porosity of the sorbent, as demonstrated by scanning electron microscopy (SEM), and the specific surface area (Brunauer–Emmett–Teller analysis, BET). The ionic charge of the biochar structure was determined based on the point of zero charge (pH_PCZ). The best kinetic fit for the sorption of the dye on/in the biochar was obtained with the nonlinear pseudo-second-order and Elovich models. The nonlinear Freundlich isotherm had the best fit to the experimental data, and it was determined that the maximum sorption capacity was ~40 mg g⁻¹. The thermodynamic parameters indicated that the sorption of the RB on/in the RRHB was spontaneous. Overall, RRHB was demonstrated to be a potential biosorbent for cationic dyes such as RB. Finally, it is possible to recover the biosorbent, aggregating value to the byproduct and showing it to be an excellent option for use in water purification filters. Full article

In drinking water catchments, exploiting ecosystem services provided by stream buffers has the potential to complement conventional engineering solutions such as water treatment and reduce the overall public health risks to consumers. These stream buffers interrupt the movement of contaminants and sediments from non-point source sources, such as agricultural land, to surface waters. Effectively managing stream buffers can be challenging due to the complexity and diversity of factors that can directly and indirectly impact efficacy. This study uses System Theoretic Process Analysis (STPA) and Early Warning Signal Analysis based on STPA (EWaSAP) methodology to systematically examine the sociotechnical structures for managing stream buffers in surface water catchments using a theoretical scenario representative of typical surface water supplies. The combination of STPA and EWaSAP provides a practical approach for developing requirements for stream buffers in drinking water catchments, focusing on hazard assessment and management measures. The evaluation considers the complex management arrangements for land uses within catchment areas. The performance and effectiveness of these actions can be tracked through the selected sensors and early warning measures. As a practical matter, this approach would help specify requirements for catchment management and drinking water source protection that can be systematically integrated into relevant management strategies. Full article

The flow pattern of the forebay of the pumping station has a considerable effect on the operating efficiency and stability of the pump unit. A good forebay flow pattern can enable the pump unit to improve efficiency and operating conditions. This study takes a large pumping station as the research object and considers two rectification schemes, namely, a single bottom sill and a “bottom sill + diversion pier”. Without rectification facilities under different start-up schemes, the forebay flow pattern after the addition of rectification facilities is calculated, and the influence of single and combined rectification facilities is analyzed. Results show large-scale undesirable flow structures such as backflow and vortex in the forebay of the original design that without rectification facilities and uneven flow distribution occurs in the operating unit. The addition of a bottom sill in the forebay can control the central water beam from the water diversion pipe. The flow is divided to spread to both sides of the forebay and can be rectified twice after installing the diversion piers. The combined rectifier facility of “bottom sill + diversion pier” is beneficial to disperse incoming flow and make the flow distribution of each unit more uniform. The backflow and vortex inside the forepond are basically eliminated, and the flow state of the forepond is significantly improved. Full article

The purpose of this research was to determine the natural factors that contribute to maintaining the standard quality of fresh drinking groundwater in areas with high strontium content. Hazard index values for the consumption of water containing strontium were also calculated to assess the overall non-carcinogenic health risk from combined ingestion and dermal exposure. The results showed that the groundwater with strontium concentrations exceeding the maximum permissible concentrations had an increased correlation of strontium concentrations with total dissolved solids and celestite and gypsum saturation indices. A decrease in calcium content was recorded with a simultaneous increase in the concentration of magnesium and strontium. Reducing conditions in the aquifer were also favorable for the conservation of these waters. In waters of standard quality, all these factors did not appear, which indicates their formation in sediments with discretely located small inclusions of celestite and gypsum. These waters were characterized by a calcium bicarbonate composition, low total dissolved solids (TDS), and oxidizing conditions. Elevated radiocarbon contents indicate their relatively young age. In general, it was found that children in the study area are most vulnerable to risks. Fifty percent of wells supply drinking water that is unsafe for consumption. The water from about a third of the wells studied is dangerous for adults. Full article

Raised-field agricultural systems have received attention from scholars involved in the analysis of prehistoric agricultural intensification in the New World. This paper discusses the function of raised fields associated with the Tiwanaku society (500–1100 CE) located on the southern rim of Lake Titicaca in Bolivia. The overnight internal heat storage capacity of Tiwanaku raised-field berms located at the high-altitude (~3810 masl) Bolivian altiplano is analyzed through ANSYS (version 4.2B) finite difference methods to provide an understanding of ancient agricultural engineers’ knowledge regarding how to protect crops from nightly subzero freezing temperatures and water saturation. The present analysis concludes that enhanced berm heat storage capacity derived from solar radiation into multi-layered moist berm agricultural soils, together with radiative heating of berm-surrounding swale water (swale water depth determined from excavation into the groundwater aquifer), was an essential Tiwanaku design element of raised-field agriculture to protect crops from freezing damage during both wet and dry seasons. This paper reports the ANSYS temperature distribution results derived from a raised-field berm swale computer model of ancient excavated raised fields in the form of a 24 h heat input and cooling cycle, which indicates the presence of an internal berm heat storage effect designed to protect crops from freezing damage. The calculations performed use specific hydrological and climatological conditions characteristic of the littoral and near-shore environment of Lake Titicaca. The use of the ANSYS finite element code to investigate the source of internal berm heat storage protecting crops from freezing temperatures, compared to the field test results from experimental use of reconstructed ancient, raised fields, provides an understanding of the technologies developed by Tiwanaku agricultural engineers to increase raised-field agricultural production. Full article

During the cofferdam construction of the toe reinforcement project at the Qiantang River Estuary, the scouring of the riverbed at the groin head often led to the collapse of geotube groins due to strong tidal currents. Based on field experience, employing a combination of clay and geotubes proved to be a more effective solution to this problem. This study adopted a flume model experiment to investigate the scouring and deposition around geotube groins and mixed clay–geotube groins. The results indicated that the influence of tidal surges on geomorphic changes surrounding the groins was more pronounced during spring tides than during neap tides. Under the same flow conditions, the scour depth at the head of the geotube groin was notably deeper than that of the mixed clay–geotube groin. Additionally, sediment silting behind the mixed clay–geotube groin was significantly greater than that behind the geotube groin. The clay component of the mixed clay–geotube groin served to mitigate the head scour, enhancing the overall structural stability to a certain extent. The geotube groin, with its surrounding scour pits expanding over time, experienced increasing tensile strain. This resulted in the rupture of the geotextile material, the loss of internal sand and, ultimately, groin collapse. It was found that mixed clay–geotube groins were better suited for cofferdam construction in strong tidal estuaries compared to geotube groin alternatives. Full article

Methods for downstream river flow prediction can be categorized into physics-based and empirical approaches. Although based on well-studied physical relationships, physics-based models rely on numerous hydrologic variables characteristic of the specific river system that can be costly to acquire. Moreover, simulation is often computationally intensive. Conversely, empirical models require less information about the system being modeled and can capture a system’s interactions based on a smaller set of observed data. This article introduces two empirical methods to predict downstream hydraulic variables based on observed stream data: a linear programming (LP) model, and a convolutional neural network (CNN). We apply both empirical models within the Colorado River system to a site located on the Green River, downstream of the Yampa River confluence and Flaming Gorge Dam, and compare it to the physics-based model Streamflow Synthesis and Reservoir Regulation (SSARR) currently used by federal agencies. Results show that both proposed models significantly outperform the SSARR model. Moreover, the CNN model outperforms the LP model for hourly predictions whereas both perform similarly for daily predictions. Although less accurate than the CNN model at finer temporal resolution, the LP model is ideal for linear water scheduling tools. Full article

Flooding has become one of the most dangerous and expensive disasters due to urbanization and climate change. Tools for assessing flood impact are required to support the shift of flood mitigation management from post-disaster recovery and reconstruction to community-driven pre-disaster warning and preparation. This study aims to develop an integrated approach to spatially assess the economic and social losses and ecological gain and identify the geographical factors of locations with high impacts of floods in Brisbane using the datasets collected from both the 2011 and 2022 flood events. Water depth, inundated area, land cover, ecosystem service value, mortality, and morbidity were considered to assess flood impacts. It is found that downstream (above 23,500 m from the upper stream) riverside communities (within 800 m of the river) with low altitudes (below 15 m) are more likely to experience significant flood damage. Flood impacts have bell-shaped developments with elevation and direct distance to the upstream river source and an exponential decline with distances to the river. These findings have implications for formulating future urban land use and community-tailored mitigation strategies, particularly for flood warning and preparation. Full article

This study proposes a numerical model for depth-averaged Reynolds equations (shallow-water equations) to investigate a dam-break problem, based upon a two-dimensional (2D) second-order upwind cell-centre finite volume method. The transportation terms were modelled using a modified approximate HLLC Riemann solver with the first-order accuracy. The proposed 2D model was assessed and validated through experimental data and analytical solutions for several dam-break cases on a wet and dry bed. The results showed that the error values of the model are lower than those of existing numerical methods at different points. Our findings also revealed that the dimensionless error parameters decrease as the wave propagates downstream. In general, the new model can model the dam-break problem and captures the shock wave superbly. Full article