Search Results (92)

Introduction: Artificial infrastructure interrupts river longitudinal connectivity, preventing the free flow of water, matter, energy, and organisms through the system, altering the habitat and impacting freshwater biodiversity. Freshwater fishes are especially sensitive to this threat, since they are constrained to the limits of the river network. Transversal obstacles, such as dams and weirs, hinder their movements upstream and downstream and fragment populations. Longitudinal connectivity can be simply measured as the proportion of connected river length in a basin. However, other indices have been suggested more recently, measuring connectivity as the proportion of connected elements of interest (e.g., populations of a species) in a river basin. Objective: The aim of this work was to study (1) the degree of connectivity of native freshwater fish species populations in eleven Spanish river basins and (2) the impact of artificial river fragmentation in these basins on population connectivity. Methodology: Fish populations’ location and size were estimated through sampling presence data, and completed using the predicted occurrence of each species in a river basin, calculated through Species Distribution Models (SDMs). To estimate the degree of connectivity between populations of each species, the Population Connectivity Index (PCI) was calculated under two scenarios: the “current” scenario, considering all the artificial obstacles fragmenting the river network and their specific passabilities, and the “natural” scenario, considering that all the artificial obstacles in the river network were completely passable. Results: Native freshwater fish populations are severely fragmented in Spanish rivers, with a mean current PCI of 9.8% across species and river basins. The impact of artificial fragmentation is high, causing a mean decrease in PCI of 52 percentage points across species and river basins. Moreover, although the impact of artificial river fragmentation is high in all river basins, it is important to point out that there are significant differences between river basins attributed to their size and the specific traits of the ichthyofauna inhabiting them. Conclusions: The degree of connectivity in a river basin varies depending on the elements of interest considered. Therefore, incorporating ichthyofauna into the decision-making process is essential to improve the effectiveness of river restoration actions. Full article

Introduction: The Guadiana basin harbours one of the most threatened freshwater fish faunas in Europe, concentrating a high number of Iberian endemisms and species of high conservation interest. Among these, the Iberian minnowcarp (Anaecypris hispanica) and the Iberian Arched-Mouth Nase (Iberochondrostoma lemmingii) stand out as threatened species whose populations are in serious decline. Methodology: In March 2023, an obsolete river barrier, the Galaches weir, was removed from the Odeleite River (Guadiana basin), releasing an 8 km lotic stretch previously inaccessible to downstream fish fauna. This study aimed to evaluate the effects of weir removal on the composition and structure of the fish community, using a Before-After design with fish sampling conducted before (2022) and after (2024) weir removal. Fish sampling took place in early summer by means of electrofishing in two 150 m long river sites, one upstream and one downstream of the weir. Results: Before removal, both upstream and downstream sites were dominated by native leuciscids (A. hispanica, I. lemmingii, Squalius pyrenaicus, and Pseudochondrostoma willkommii) and cyprinids (Luciobarbus spp.), with non-natives Lepomis gibbosus and Australoheros facetus occurring in lower abundance. After removal, native species remained clearly dominant at both sites, while A. facetus was no longer detected and L. gibbosus did not increase in abundance, suggesting that barrier removal did not favour the spread of non-native fish. Species size–structure revealed the presence of multiple size classes, possibly supporting a regular recruitment of key native taxa: A. hispanica occurred almost exclusively with total lengths of 4 to 6 cm, whereas I. lemmingii and other native leuciscids displayed broader size ranges, spanning juveniles to adults, consistent with sustained reproduction and growth in the restored river stretch. Conclusions: These findings support the hypothesis that weir removal has improved the sustainability of native fish populations such as A. hispanica by improving habitat connectivity and increasing recruitment. The results highlight the importance of weir removal for the conservation of threatened species in Mediterranean river systems. Full article

Introduction: The upper Arlanza River (Duero Basin, Burgos, Spain) hosts a genetically distinct local lineage of brown trout (Salmo trutta fario), the “Arlanza strain”, largely free from hatchery-derived introgression, alongside other native cyprinids of conservation concern, including the Iberian chub (Achondrostoma arcasii, Vulnerable—IUCN). The river also supports the Iberian desman (Galemys pyrenaicus, Endangered—IUCN) and Eurasian otter (Lutra lutra). Despite these values, the study reach presents multiple transverse obstacles limiting longitudinal connectivity and degraded riparian cover in critical sections due to livestock erosion, compromising habitat quality for all species. Objective: This study aimed to design engineering interventions to improve fluvial and riparian habitat in a 4 km reach of the upper Arlanza River, restoring longitudinal connectivity and thermal refuge availability while strictly preserving the genetic integrity of the native Arlanza trout strain. Methodology: The reach was characterised through electrofishing surveys, riparian quality assessment (modified RQI index), hydraulic refuge evaluation (IR index), and hydrological analysis based on a 30-year flow record. Brown trout population dynamics were modelled using dimP 1.0 software, with a comparative analysis between upstream (Quintanar de la Sierra village) and downstream (Vilviestre del Pinar village) sampling points to identify connectivity bottlenecks. Engineering works were scheduled to avoid reproductive periods of all target species. Results: The upstream population showed a rejuvenated age structure (density: ~1.40 ind/m; mean length: 12.0 cm), consistent with good spawning conditions but limited growth capacity due to cold temperatures and low summer flows. The downstream point exhibited a severely reduced population (~0.10 ind/m), indicating marked loss of connectivity and habitat degradation. Priority intervention zones were identified in the Camping and lower Prado Mayor sub-reaches. Proposed measures included weir notching to restore fish passage, livestock watering points to reduce bank erosion, and riparian restoration by planting native species (Populus tremula, Betula alba, Salix spp.) protected with fences. Conclusions: Restoring longitudinal connectivity and riparian cover in the upper Arlanza River are essential to protect the genetically valuable Arlanza trout strain, the endangered G. pyrenaicus, and other native fish species, providing a transferable framework for headwater fluvial restoration that jointly addresses biodiversity conservation and genetic resource protection. Full article

Introduction: Sediment flushing is widely used to recover storage capacity and maintain outlet functionality in Mediterranean reservoirs, but it can also generate short downstream pulses of suspended sediment, oxygen depletion, and ammonia that may threaten fish and fish habitats. Despite this, operation-specific environmental criteria explicitly oriented to reducing acute fish risk during flushing remain poorly defined. Objective: This study aimed to develop and validate a practical operational protocol for sediment flushing in southern Spain, with emphasis on reducing acute downstream risk to fish through field-applicable thresholds, decision rules, and stop criteria. We also evaluated whether water density could serve as a rapid surrogate for total suspended matter (TSM) during operations. Methodology: The protocol was applied to 14 flushing events conducted at seven reservoirs and weirs in Andalusia, southern Spain. Monitoring included upstream and downstream stations, pre-operation baseline surveys, 15-minute measurements during flushing, and post-operation recovery checks. Operational control was based on pre-alert and alert thresholds for dissolved oxygen, ammonium/ammonia, conductivity, suspended matter, and a density-based surrogate for TSM. Protocol validation considered operational safety during flushing, the relationship between field density and laboratory-measured TSM, and before–after multivariate changes in downstream environmental conditions. Results: Threshold exceedances occurred in 5 of the 14 events, comprising 4 pre-alerts and 1 alert. Pre-alerts were mainly driven by ammonium/ammonia or dissolved oxygen, and exceedance durations were generally short (30–120 min). The only alert-level event combined severe oxygen depletion with high sediment concentrations and triggered suspension of the operation, showing the usefulness of the stop rule. Density was significantly related to laboratory TSM in all reservoirs retained for calibration (R² = 0.365–0.934), supporting its use as a rapid field proxy when calibrated at the reservoir scale. Before–after multivariate analysis detected no consistent overall downstream shift, although event-level responses were heterogeneous. Conclusions: The protocol proved operationally feasible as a science-based framework for managing sediment flushing while reducing acute risk to downstream fish in Mediterranean reservoirs. Its combination of fish-relevant thresholds, real-time monitoring, site-specific density calibration, and explicit stop rules can support safer operations, improve transparency, and strengthen environmental permitting. Full article

Compact low-pressure emitters (LPEs) can improve the affordability of drip irrigation, but they must also demonstrate clog resistance for long-term reliability and adoption. Recent research on LPEs has focused on their hydraulic modeling and characterization, but few studies have evaluated or improved their clog resistance. To address this gap, we present a design theory for clog-resistant LPEs and characterize their performance in the lab and field. We focused on the emitters’ weir (or ‘overflow groove’ or ‘channel’), a micrometer-scale internal hydraulic passage, traditionally having a rectangular cross-section. In LPEs, the weir must be shallow to generate the hydraulic resistance required for low-pressure operation, thereby increasing the risk of particulate-jamming-based clogging. A hydraulic model of weirs with arbitrary cross-sections was used to estimate that trapezoidal profiles could be 33–41% deeper than hydraulically equivalent rectangular ones, suggesting that the trade-off between clog resistance and hydraulic performance in LPEs could be navigated through weir cross-section design. To practically validate this proposition, two compact LPEs with trapezoidal weirs (1 and 2 L/h nominal discharge) were designed and tested in the lab and field. Lab results indicated compatibility with 125 μm (1 L/h) and 177 μm (2 L/h) mesh filters that are typical for these flow rates, providing a basis for field testing the LPEs against commercial emitters. After field tests with these filters, the LPEs held 90–94% of their initial discharge and demonstrated irrigation reliability that was statistically on par with or better than some commercial emitters, despite having 15–65% lower operating pressure. The findings of this work demonstrate the practical viability of compact LPEs for affordable drip irrigation and provide a design framework for their continued development. Full article

The structural integrity of hydraulic structures is frequently weakened by local scour processes downstream of weirs. This study investigates the relationship between hydraulic parameters and erosion patterns to improve the predictability of bed deformation. The research methodology integrates detailed field measurements from the Radomka River in Piaseczno with laboratory experiments using a 1:30 physical scale model of the existing weir. Bed shear stress demonstrated the strongest correlation with maximum scour depth (r ≈ 0.93; RMSE ≈ 0.0032), as it directly represents the tangential force acting on sediment particles at the bed surface, which controls their entrainment, transport capacity, and ultimately the intensity of local scour development, whereas near-bed velocity showed weak and non-significant dependence (r ≈ 0.26; ${\rho }_s$ ≈ −0.11). This weak dependence reflects the dominance of turbulence-induced velocity fluctuations and localized vortical structures in the near-bed region, which obscure the relationship between mean velocity and sediment mobilization. The relationships between mean velocity, Froude number, and scour depth were moderate (r ≈ 0.63–0.73) and showed nonlinear characteristics, confirmed by HSIC values up to 9.1 × 10⁻³, due to the complex interaction between flow structures and evolving bed morphology. This nonlinearity results from the interaction between turbulent flow structures, jet-induced vortices, and the dynamically evolving bed morphology, combined with the threshold-controlled and nonlinear response of sediment transport to hydraulic forcing. Among all tested parameters, bed shear stress ranked as the dominant predictor of scour depth, outperforming velocity-based indicators. These findings imply that including bed shear stress parameters significantly improves hydraulic structure safety assessments. This study based on 11 experimental runs concludes that a combined field and laboratory approach provides a robust framework for river engineering. Finally, an improved understanding of erosion mechanisms, as presented in this work, enhances the prediction of local scour development and supports the design of more resilient hydraulic infrastructure. Full article

In sediment-laden irrigation channels, sediment deposition upstream of hydraulic measuring structures can degrade hydraulic performance, reduce measurement reliability, and increase maintenance demand. To clarify the effects of structural optimization on sediment transport and siltation resistance, physical model experiments were conducted on an airfoil weir-orifice facility under different discharges, structural angles, and sediment concentrations. The analysis focused on sediment deposition patterns, longitudinal water surface profiles, sediment concentration, suspended sediment transport rate, cross-sectional velocity distribution, vertical velocity gradient, and Froude number. The results showed that the optimized configuration produced a flatter and more uniform upstream bed morphology, and the average deposition thickness decreased from 4.83 cm to 4.31 cm, corresponding to a reduction of 10.58%. Under all tested conditions, the optimized configuration reduced upstream backwater, increased local flow velocity, and shifted the hydraulic jump closer to the facility outlet. Sediment concentration and suspended sediment transport rate were consistently higher after optimization, indicating enhanced sediment carrying capacity. In addition, the optimized configuration increased the vertical velocity gradient and Froude number, while all cases remained within the subcritical-flow regime. These findings demonstrate that structural optimization can simultaneously improve hydraulic regulation and siltation resistance, and provide an experimental basis for the application of streamlined hydraulic measuring structures in sediment-laden irrigation channels. Full article

To investigate the evolution of impermeability and pore structure in concrete under long-term service, systematic tests were conducted on submerged concrete from dam sections with over 75 years of service. Results show that the surface water permeation resistance index of concrete in the downstream section of the main dam is only 9.19 × 10⁻⁹, significantly lower than that of concrete from the upstream of the main dam (UMD), downstream of the main dam (DMD), upstream of the auxiliary dam (UAD), and upstream of the weir (UW). Moreover, its impermeability improves noticeably within the 0–100 mm depth range. Mercury intrusion porosimetry revealed that the median pore diameter, average pore diameter, pore content, and porosity in this region reach 306.7 nm, 55.4 nm, 35.64%, and 3.961 mm, respectively—all markedly higher than in other dam sections. Combined XRD and SEM/EDS analyses indicate that crystallization pressure from saline solutions in the coastal environment, together with long-term carbonation, leads to structural loosening and increased porosity in the downstream concrete of the main dam, ultimately degrading its impermeability performance. Full article

The Extra-Long Weir Construction method for deep foundation pit construction is crucial for urban underground development. However, as excavation projects become deeper and more complex, construction safety risks increase markedly. Existing monitoring technologies and numerical simulation models face persistent challenges: high uncertainty in risk occurrence, complex environmental interactions, and difficulties in extracting effective warning signals from multi-source data. To address these challenges, this study establishes a systematic risk evaluation framework comprising 6 primary and 29 secondary indicators through Fault Tree Analysis and develops a novel DL-MSD (Deep Learning and Multi-Source Data Prediction) model integrating CNN, ResUnit, and LSTM networks for spatiotemporal sequence analysis and multi-source data fusion. Validated using 6524 samples from the Jinji Lake Tunnel project, the model employs single-factor prediction for hazard source tracing and multi-factor fusion for comprehensive risk assessment. Results demonstrate exceptional performance: 90.2% average accuracy for single-factor warnings and 77.1% for multi-factor fusion, with, critically, all severe warnings (Level I risks) identified with zero omissions. Comparative analysis with T-S fuzzy neural networks, EWT-NARX, and Random Forest confirmed superior accuracy and computational efficiency. An integrated platform incorporating BIM and IoT technologies enables automated monitoring, intelligent prediction, and adaptive control. This study establishes a data-driven intelligent early warning framework that significantly improves prediction accuracy, timeliness, and reliability in deep foundation pit construction, marking a paradigm shift from reactive response to proactive prevention. The findings provide theoretical and methodological support for safety management in ultra-deep excavation projects, offering reliable decision-making evidence for enhancing construction safety and risk management. Full article

(1) Background: In the context of rapid urbanization and climate change, Chinese traditional villages are facing severe challenges such as deterioration of hydrological environment, weakened social resilience, and degradation of cultural heritage. (2) Methods: This paper took Baoyan Village in Zhenjiang City, Jiangsu Province as the research object and constructs a research framework of “assessment of historical hydrological resilience–diagnosis of current problems–construction of enhancement strategies”, aiming to explore the paths and driving mechanisms for enhancing the resilience of traditional villages. The spatio-temporal evolution of historical hydrological resilience in Baoyan Village was quantitatively evaluated by establishing a three-dimensional resilience index system of “ecological governance–social adaptation–cultural continuity”, combined with the Analytic Hierarchy Process (AHP) and GIS spatial overlay technology. (3) Results: The study found that ① The hydrological resilience zoning of Baoyan Village presented spatial differentiation characteristics of “core vulnerability-marginal resilience”, and the high-risk area was concentrated in the cultural building density area along the old Tongji River in the historical town area, indicating that this area requires key flood protection and resilience construction; ② this paper constructed a composite evaluation system of “Ecological Governance–cultural inheritance–social adaptation”, and the total score after evaluation was 0.67, indicating that the overall HHRI of Baoyan Village has declined. Specifically, the scores for Ecological Governance Resilience and Cultural Heritage Resilience were 0.48 and 0.46, respectively, reflecting a significant decrease compared to historical scenarios. Conversely, the score for Social Adaptation Resilience was recorded at 1.05, suggesting an improvement in this dimension. This enhancement can be attributed to advancements in water infrastructure and increased levels of community organizational support, which have bolstered the village’s capacity to withstand flooding events. ③ The integrity of weir fields, the transmission of traditional disaster prevention knowledge, and the stability of natural river channels are the main factors hindering the improvement of resilience systems. (4) Conclusions: Based on the assessment results, this study proposed the resilience enhancement path of “ecological space reconstruction-traditional water management wisdom activation–cultural resilience empowerment” for this case, and constructed a four-pronged driving mechanism consisting of government guidance, community participation, technology empowerment, and industrial synergy for implementation. Practice has shown that through specific strategies such as restoring the weir and field system, constructing sponge village units, and developing the rain and flood cultural experience industry, the key obstacle factors of the village can be effectively addressed, and the goals of flood safety and cultural inheritance can be achieved in a coordinated manner. This case provides an empirical reference that combines historical wisdom with modern technology for understanding the evolution of human–water relationships and the enhancement of resilience in traditional villages, and its research framework and methods are also of reference value for similar villages. Full article

Microfluidics enables precise manipulation of scarce Traditional Chinese Medicine (TCM) samples while accelerating analysis and enhancing sensitivity. Device-level structures explain these gains: staggered herringbone and serpentine mixers overcome low-Reynolds-number constraints to shorten diffusion distances and reduce incubation time; flow-focusing or T-junction droplet generators create one-droplet–one-reaction compartments that suppress cross-talk and support high-throughput screening; “Christmas-tree” gradient generators deliver quantitative dosing landscapes for mechanism-aware assays; micropillar/weir arrays and nanostructured capture surfaces raise surface-to-volume ratios and probe density, improving capture efficiency and limits of detection; porous-membrane, perfused organ-on-a-chip architectures recreate apical–basolateral transport and physiological shear, enabling metabolism-aware pharmacology and predictive toxicology; wax-patterned paper microfluidics (µPADs) use capillary networks for instrument-free metering in field settings; and lab-on-a-disc radial channels/valves exploit centrifugal pumping for parallelised workflows. Framed by key performance indicators—sensitivity (LOD/LOQ), reliability/reproducibility, time-to-result, throughput, sample volume, and sustainability/cost—this review synthesises how such structures translate into value across TCM quality/safety control, toxicology, pharmacology, screening, and delivery. Emphasis on structure–function relationships clarifies where microfluidics most effectively closes gaps between chemical fingerprints and biological potency and indicates practical routes for standardisation and deployment. Full article

A rigorous rate-based absorption model integrated with an improved thermodynamic framework was developed to simulate natural gas desulfurization using TMS–MDEA (Tetramethylene Sulfone–Methyldiethanolamine) aqueous solutions. The model was validated against 50 sets of industrial and experimental data, achieving R² values above 0.98 and average deviations within 5%. The model was formulated for steady-state operation of a trayed absorber integrated with flash and packed-bed regeneration and applicable over industrially relevant ranges (absorber pressure 3–6.4 MPa; gas–liquid ratio 350–720; flash pressure 0.3–0.6 MPa; packing height ≥ 3 m). The results indicate that H₂S can be removed almost completely (>99.9%); CO₂ and COS achieve 70–85% and 75–83% removal, respectively; and CH₃SH removal exceeds 90% under typical conditions. Parametric analysis revealed that higher tray numbers, weir heights, and pressures enhance absorption efficiency, whereas hydrocarbon solubility increases with carbon number and is strongly affected by pressure and the gas–liquid ratio. In the desorption section, flash regeneration efficiently strips light hydrocarbons, with decreasing desorption efficiency from CH₄ to C₆H₁₄. This study provides quantitative insights into the coupled absorption–desorption process and offers practical guidance for process design, solvent selection, and energy-efficient operation in natural gas purification. Full article

The Free Water Knock Out (FWKO) vessel is a critical device in the oil sands treatment process, responsible for separating water, oil, and gas. This study investigates the gas–oil interface within the FWKO and analyzes the flow characteristics of the unresolved mixture near the interface. To enhance the separation efficiency by increasing the residence time of the mixture, a concave-shaped weir was introduced. Numerical simulations were conducted using ANSYS Fluent 2023 R1, applying the Volume of Fluid (VOF) model to capture the multiphase flow behavior. Optimization was performed using a genetic algorithm, and the optimal weir curvature with a minor radius of 0.017333 m and a major radius of 0.19032 m yielded the highest separation efficiency. The model incorporating the optimized weir demonstrated a 1.26% improvement in separation efficiency compared to the reference model, and a 2.13% improvement over the baseline model without curvature. These findings confirm that applying curvature to the traditionally flat weir can achieve higher separation efficiency. Moreover, improving separation efficiency through such a simple geometric modification demonstrates significant economic effectiveness. Full article

Anthropogenic barriers fragment Portuguese rivers, threatening endemic freshwater fish communities. This study compiled national inventories and peer-reviewed research (2002–2024) to quantify fishway implementation, evolution and typology, while evaluating fish performance from published research. One hundred fishways built between 1950 and 2024 were recorded, half of which were constructed after the implementation of the Water Framework Directive in Portugal (29 Dec 2005), tripling the annual construction rate. Fishways were found to be associated mainly with weirs (46%) and small hydropower plants (44%), with typology being dominated by the pool-type design (67%), nature-like facilities (18%), fish locks and combined systems (6% each), fish lifts (2%) and a single eel pass. Forty scientific contributions addressed fishway effectiveness; three-quarters dealt with pool-type facilities, while 12.5% and 10% focused on nature-like fishways and lifts, respectively. Experimental and field studies highlighted species-specific hydraulic preferences, the benefits of vertical slot and multislot configurations, and the potential of retrofitting fishways with macro-rugosities (i.e., fixed structural elements placed on the bottom) to improve non-salmonid fish passage. However, low attraction efficiency, limited multi-season monitoring and risks of aiding invasive species remain a concern. Research needs are proposed, including the refinement of species-specific hydrodynamic criteria, and the development of standardized efficiency metrics and of selective passage solutions, to advance fishway performance under Mediterranean hydrological constraints. Full article

Sediment buildup in storage tanks over extended operation periods may compromise their efficiency. To prevent pollutant deposition in storage tanks and enhance their hydraulic self-cleaning efficiency, this study addressed the unique structural configuration of lateral flow in storage tanks. Conducting numerical simulations to investigate the hydraulic characteristics within storage tanks, an integrated approach combining physical experiments and response surface methodology (RSM) was employed to optimize flow distribution. Key findings reveal that tangential and normal velocity differences lead to flow distribution nonuniformity, exacerbated by increased inflow Froude number (F_r) and reduced relative weir height (h_i). Based on the flow-splitting mechanism, an optimized “combined raised baffle” was proposed. Through single-factor experiments, Plackett–Burman (PB) screening, and RSM experiments, the optimal combination for maximal flow uniformity was determined as h₁ = 1.27, h₂ = 1.23, and h₃ = 1.24, achieving an 87.18% improvement in Q_y compared to the initial design. After optimization, the incoming flow pattern of the inlet channel of the storage pond was improved, and the difference between tangential and normal flow velocity in the flow field was significantly reduced. This research provides a novel approach and methodological paradigm for optimizing storage tanks and other hydraulic structures, demonstrating significant academic and engineering value. Full article