Abstract The anticlogging performance and clogging law of a single-wing labyrinth drip irrigation emitter were analyzed through hydraulic performance tests. On this basis, numerical calculation was carried out using computational fluid dynamics (CFD) technology, and the flow channel structure was improved. The results showed that there is a large flow dead zone in the flow channel structure of traditional single-wing labyrinth emitters, and the proportion of the low-flow-velocity area reaches 54.39% of the total trapezoidal flow channel area. The flow dead zone area of the improved bidirectional flow channel structure emitter is significantly reduced, and the proportion of the low flow velocity area is only 12.41% of the total flow channel area. Compared with the traditional single-wing labyrinth trapezoidal flow channel emitter, the proportion of the low flow velocity area decreased by 41.98%. Through optimizing the flow channel structure of the irrigation emitter, the average velocity within the flow channel increased by 110.2%, and the average concentration of particulate matter at the outlet increased by 77.7%. Compared with the traditional single-wing labyrinth flow channel structure, the bidirectional flow channel structure has a better sediment discharge capacity and anticlogging performance, and the concentration of particles at the outlet is significantly increased.
Abstract In response to increasing water scarcity affecting rice production worldwide, this study presents a field case study evaluating the feasibility of cultivating rice under aerobic soil conditions using surface drip irrigation. The experiment was conducted on a commercial farm in Veneto, northeastern Italy, during the 2021 growing season, where traditional flood irrigation was compared with drip irrigation on two adjacent clay soil plots of approximately 5,000 m 2 each. Three dripline spacings (1.0, 1.25, and 1.5 m) were tested to assess their influence on soil wetting patterns and crop performance. The potential effect of irrigation water oxygenation, achieved by air injection through Venturi ejectors, was also evaluated. In addition to irrigation water consumption, four main crop parameters were measured: number of grains per panicle, plant height at the tillering stage, 1,000-seed weight, and grain yield at harvest. Results showed a yield reduction of approximately 40% in the drip-irrigated plot compared with flood irrigation, mainly due to increased weed competition. However, estimates based on yield components suggest that the potential yield reduction attributable to the irrigation method itself may be closer to 10%. Drip irrigation reduced water consumption by approximately 50% compared with the submerged system. The introduction of air into the irrigation water increased root system density, suggesting potential improvements in water and nutrient uptake efficiency. Although these findings highlight the potential of drip irrigation as a water-saving alternative for rice cultivation under the conditions examined, further research is required to address agronomic constraints and optimize system management.
The drip irrigation layout and dripper flow rate impact the soil water and salt distribution, leading to uneven growth in the middle and side rows of cotton within a mulched drip irrigation system. Consequently, it is crucial to analyze how these factors influence soil water, salt distribution, and cotton growth. This study examined three drip tape layouts (L1: in the middle of a narrow row; L2: drip tapes in the middle and on both sides of a narrow row; L3: on the left side of the narrow row) and three dripper flow rates (Q1: 2.4 L/h, Q2: 3.2 L/h, Q3: 3.6 L/h). The findings indicated that the Q2L2 combination provided the best soil water and salt distribution in the 0-60 cm root zone, with a 41.68% increase in water content, a 38.49% increase in soil water storage, and a 50.42% reduction in relative salinity compared to other treatments. Plant height, stem diameter, and leaf area index under Q2L2 were significantly higher than the other treatments (p<0.05), dry matter accumulation peaked during the flowering and boll stage, with the highest proportion in the bolls, and cotton yield (7,228.31 kg/ha) and water use efficiency [15.27 kg/(ha & centerdot;mm)] were also the highest. A structural equation model revealed that drip irrigation layout and dripper flow rate indirectly influenced cotton growth and yield by regulating the soil water and salt environment. Using the entropy weight and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) models, we assessed four indices: relative change in soil salinity, water use efficiency, dry matter accumulation, and cotton yield. The Q2L2 treatment had the highest evaluation index, with a closeness coefficient of 0.89, making it closest to the positive ideal solution and showing significantly better overall benefits than other combinations. The results of this study can be used to optimize drip irrigation configurations and provide a theoretical basis for improving the yield and water use efficiency of drip-irrigated cotton.
The Soil and Water Assessment Tool (SWAT) is a widely recognized model for evaluating hydrological impacts and supporting water resource management under the lens of climate change. With growing concerns around water scarcity and climate variability in India, the SWAT model has emerged as a vital tool to assess future water availability scenarios. This review examines 110 SWAT-based studies conducted between 2013 and 2023 focusing on Indian condition. They were focused on the implications of climate change on India's water resources. Findings reveal that 90% of these studies reported satisfactory performance metrics; the curve number (CN2) was identified as the most sensitive parameter in 50% of the cases. Despite its utility, the model's application to extreme weather events such as storms and droughts is underrepresented. Many studies integrated climate projections into SWAT using methods such as delta change and quantile mapping with less significance in scenario studies. This review also identifies gaps related to extreme events and suggests pathways for enhancing the reliability of SWAT model in the context of increasing climate uncertainty in India.
Short-crested trapezoidal-sectioned weirs fitted with vertical lift gates are extensively used as river diversion structures in the Indian subcontinent. While the downstream slopes of the weir are known to influence the discharge coefficient, the present work investigates the increase in discharge capacity of the structure with the addition of a semicylindrical lip upstream of the gate. The lip helps straighten the streamlines at the gate opening, as confirmed from flume experiments, supplemented by numerical simulations carried out with the computational fluid dynamics (CFD) software package ANSYS-Fluent. The addition of a semicylindrical lip, even with a small radius, improves the discharge coefficient (Cd) by up to 28%-36% compared to the sharp-edged gate. A steeper downstream slope of the weir accelerates the flow, further increasing the coefficient under free and submerged flow conditions, although at the cost of a lower pressure over the weir crest. Compared with a flat bed, a weir with a 1V:2H downstream slope increases the Cd by approximately 13%-16% under free-flow and 48%-56% under submerged-flow conditions for a semicylindrical lipped gate. The modular limit increases significantly with the addition of a lip, indicating that submergence occurs at higher tailwater levels, whereas a milder downstream slope further delays weir submergence. For a given discharge under free-flow, a sharp-edged gate exhibits 65%-70% higher energy dissipation and a longer downstream roller than a semicylindrical lipped gate. Pressure dips at weir-crest edges also show significant variations with both weir slope and lip diameter.
The Piano Key Weir (PKW) has emerged as an effective solution for enhancing the discharge capacity of spillways, particularly in low-head dams. This study presents an experimental investigation comparing two Type A PKW models that differ solely in the geometry of their outlet keys: linear (L-PKW) and curvilinear ogee (CL-PKW). Laboratory tests were conducted under free-flow conditions, and H/P ratios (where H is the upstream head above the crest and P is the weir height) between 0.17 and 0.63 were analyzed in detail. The results suggest that CL-PKW shows improved discharge efficiency relative to L-PKW, with observed increases ranging from 12.4% to 18.1% across the tested conditions. The curvilinear ogee outlet key, derived from the Waterways Experiment Station (WES) standard spillway profile and fabricated as a smooth, curved slab, reduces nappe interference and flow separation, contributing to a higher discharge coefficient. A novel empirical equation was developed using 90 data points, including results from the present study and previous literature, to predict the discharge coefficient of Type A PKWs with both outlet key types. Comparative analysis with existing equations indicates that the proposed equation provides predictive accuracy comparable to, and in some cases slightly better than, established formulations, with 88% and 100% of data points falling within 9% and 12% absolute error bounds, respectively. The proposed equation also exhibited lower root mean squared error (RMSE) and mean absolute percentage error (MAPE) values, indicating a predictive performance that is comparable to, and in some cases modestly better than, existing empirical equations for different outlet geometries and flow conditions. By addressing the overlooked influence of outlet key geometry, this study fills a critical research gap and introduces a versatile tool for discharge prediction. The findings offer practical guidance for hydraulic engineers in the design and optimization of PKWs for spillway improvements and dam safety upgrades.
To explore the effect of irrigation water containing organic impurities on the clogging performance of nonpressure screen filters, this study employed a multiobjective optimization method that considers both initial flow and water quality. Filter cake porosity, pressure drop, and thickness were chosen as evaluation indicators. Predictive models for each indicator were developed using the response surface methodology (RSM) to analyze their variation patterns and quantify the contribution rates of the influencing factors. A subjective-objective integrated weighting approach combined with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was then applied to the Pareto optimal solutions, enabling a comprehensive performance evaluation and optimization of the clogging behavior. The results indicate that filter cake porosity peaks (exceeding 0.9) at an organic matter content of 0.35-0.45. The pressure drop increases significantly with higher flow, rising by more than 30% as the flow increases from 120 to 160 m(3)& centerdot;h(-1). Meanwhile, filter cake thickness shows an approximately linear increase with both flow rate and impurity concentration, nearly doubling at 160 m(3)& centerdot;h(-1) compared with that at 120 m(3)& centerdot;h(-1). The sand to organic matter ratio is the primary controlling factor for porosity (contribution rate: 2.183) and thickness (contribution rate: 2.909), while the initial flow predominantly governs pressure drop (contribution rate: 1.417). Using the combined weighting method, the weights of each evaluation indicator for filter cake clogging performance were determined as follows: filter cake pressure drop (50.579%) > filter cake porosity (35.811%) > filter cake thickness (13.610%). For irrigation water sources with a high concentration of impurities, a medium-low flow is recommended for nonpressure screen filters to optimize the balance between system energy consumption and impurity removal capacity. These results provide decision-making references for the application of nonpressure screen filters.
Increasing traffic demand necessitates constructing new bridges adjacent to existing ones, resulting in eccentrically arranged piers. Preventing excessive scour to avoid bridge failures is crucial by managing potential interference among piers. Limited research has addressed these specific bridge arrangements, highlighting the need for further investigation. In this study, experiments were conducted varying eccentricity (e) and flow intensities to evaluate their influence on the temporal scour depth (ds) and identify conditions that minimize scour. Single-pier experiments were also performed to assess scour severity with rear pier positioning. Dimensional analysis revealed that flow shallowness, flow intensity, Froude number, time, and e are the key parameters influencing ds. The postexperiment analysis focused on scour geometry and bed morphology. The lowest ds for the front pier occurred when e equals 2.12h, whereas the rear pier experienced 25% more ds. Conversely, the minimum ds for the rear pier occurred when e equals 1.2h, with the front pier showing a 14% lower ds. Overall, the minimum ds for the safest bridge pier design was identified at e equals 2.1h for the selected hydraulic conditions. Furthermore, multilinear regression analysis using integrative data from literature and this study provided a superior equation for estimating ds compared with multi-nonlinear and all literature equations. This research aids in selecting geometric parameters, particularly eccentric spacing, to reduce scour, ensuring safe and cost-effective bridge pier construction.
The flow uniformity within an orifice group is crucial for the irrigation performance of porous microsprinkling hoses. This study investigated the hydraulic performance of microsprinkling hoses with a single-row oblique circular orifice arrangement by systematically evaluating five structural parameters, i.e., folded diameter (DN), orifice diameter (d), number of orifices per group (n), orifice inclination angle (alpha), and edge distance (s '), using an orthogonal array design (25 configurations) under multiple operating pressures. Group flow rate, within-group flow uniformity, and the pressure change across the orifice group (Delta p) were quantified to assess the relative importance of operating pressure and geometric parameters within the investigated domain. The results show that operating pressure increases group flow rate, whereas its influence on within-group uniformity and Delta p is negligible compared with the geometric parameters within the tested pressure range. Among the structural parameters, d and n are the key factors governing group flow rate, DN and d dominate within-group flow uniformity, and n and DN dominate Delta p. The highest within-group flow uniformity among the tested levels was obtained at DN=50 mm, d=1.5 mm, n=11, alpha=60 degrees, and s '=2 mm, while the smallest Delta p among the tested levels occurred at DN=50 mm, d=0.8 mm, n=8, alpha=30 degrees, and s '=8 mm. These findings provide an experimentally grounded, multimetric basis for parameter selection and design screening of similar microsprinkling hoses within the investigated parameter levels and operating pressures.
Water scarcity is an escalating threat to global agriculture, especially in semi-arid regions. Precision irrigation, guided by crop water stress indicators, is critical for sustainable water resource management. This study evaluates the potential of artificial neural networks (ANNs) for predicting the crop water stress index (CWSI) in wheat using canopy temperature and meteorological data. Field experiments were conducted in Uttarakhand, India, across multiple irrigation treatments. Two ANN models were developed: Model 1 was trained separately for key phenological stages [crop development (Stage 2) and reproductive (Stage 3)], while Model 2 (designated the whole-season model) was trained on combined data from the entire physiologically stable crop period (Stages 2 and 3: crop development and reproductive phases). Results show that Model 1 outperformed Model 2, with higher accuracy in Stage 3 (R=0.935) and Stage 2 (R=0.903), compared to Model 2 (R=0.805). Experimental treatments [T1 (well-watered) through T6 (maximum stress)] were maintained consistently across all analyses. These findings emphasize the importance of growth-stage-specific modeling in capturing crop physiological responses for more precise irrigation scheduling. This study supports the integration of machine learning into crop water management strategies for improved agricultural sustainability.
Local scour is the primary cause of failure in bridge piers and abutments. This study synthesizes two decades of experimental and analytical studies on twin piers in a tandem configuration. It identifies the hydrodynamic features influencing scour evolution, including horseshoe vortices, wake interactions, and flow acceleration-deceleration patterns. Empirical and semiempirical models are evaluated, emphasizing the role of pier spacing, alignment, approach flow velocity, and sediment properties. Comparative analyses reveal maximum scour depth at the upstream (u/s) pier under wake-concentrated flow and reduced scour at the downstream (d/s) piers due to vortex sheltering. Results highlight the need for spacing-optimized design criteria and recent advances in temporal scour equations and computational fluid dynamics (CFD) validations. The inadequacy of single-pier equations for twin-pier systems is demonstrated, necessitating arrangement-specific models. Although the spacing ratio (s/b) is widely adopted in existing models, sensitivity analysis reveals that flow velocity ratio (V/Vc) and time ratio (t/T) (for t
Tilting weirs are widely used to regulate water levels in open channel irrigation systems and can also provide flow measurement capability that helps optimize irrigation efficiency and ensure equitable water distribution. This case study demonstrates adaptation of lab-based tilting weir ratings to field settings, where flow behavior is more complex. We compile and analyze an extensive data set derived from independent studies of five structures within three canal systems, featuring both lined and unlined channels with discharge ranging from 0.35 to 15 m3/s (12 to 530 ft3/s). Results indicate that lab-based rating equations can be calibrated to account for site-specific variations (channel roughness, flow separation, etc.) using a field correction factor, KF, applied to the discharge coefficient in the rating equation. The average KF value across the seven data sets was 0.92, an 8% reduction from the laboratory. The case study demonstrates that tilting weirs can serve multiple purposes in the field, offering both stage regulation and discharge measurement with mean absolute percentage errors of approximately +/- 6.2%. Guidelines are given for optimizing tilting weir performance within engineered canals and additional research needs are identified for addressing complex natural channels.
