Journal of Irrigation and Drainage Engineering

This study reexamines flow over a sharp-crested weir using computational fluid dynamics (CFD) to identify the optimal operating range under which the weir functions with accuracy as a free-flowing measurement device. A numerical parametric study was conducted for two separate channel and weir geometries under a range of flow rates resulting in different $h/P$ values, where $h$ is the elevation head over the weir crest, and $P$ is the weir height. Analysis of velocity and pressure profiles over the weir revealed three distinct flow regimes: a high acceleration regime, an ideal operating regime, and a weir-inundated regime that may lead to submerged flow. The high acceleration regime correlates to flows with $h/P<0.6$, and the weir-inundated regime occurred when $h/P>2.0$. The ideal operating regime was found to occur in the range $0.6<h/P<2.0$, where flow rate estimates using measurements of $h$ are enhanced. These results are also consistent when considering how the discharge coefficient for the weir rating equation changes with $h/P$ and highlight the need for caution in using empirical discharge coefficients over a broad range of $h/P$ values.

Agricultural fertilization and irrigation are closely related to the problems of agricultural yield, product quality, and environmental pollution. Precision fertilization and irrigation is an effective method to solve this problem. In order to precisely control plant fertilization and irrigation, a monitoring system is designed and implemented using open-source software, loose communication structure, industrial control computer (IPC), programmable logic controller (PLC), and control and monitoring devices. The control command management subsystem of the system’s upper computer is built using GoWin IPC, cloud server, mobile devices, and 4G wireless network. Each application running in the upper computer is developed using open-source software such as PostgreSQL, Smobiler, etc. The fertilization and irrigation monitoring subsystem of the lower computer was built using HollySys PLC model LE5107L and different sensors for various data parameters as control units. The system allows real-time remote monitoring and control of agricultural precision fertilization and irrigation through mobile applications, with an average communication delay of 1.45 s between the upper and lower units, and less than 3 s overall, allowing for long-term stable communication. The current system can adapt to the variable environment in the field and has been operating stably in the field for 2 months. This paper provides a convenient system construction solution for field farmland where network wiring is not possible, and it has low construction and maintenance costs, reliable operation, and a flexible structure for agricultural applications.

Stormwater quality has become an increasingly important issue in agricultural, urban, and construction sectors. Soil, nutrient, and pollutant discharge caused during rainfall events is one of the greatest sources of stormwater quality degradation. Enhanced stormwater treatment mechanisms are needed to economically and efficiently remove suspended pollutants in runoff. In this research, the performance of electrocoagulation (EC) combined with lamella settlers (LS) was investigated. EC is a highly effective and proven water-treatment technology that uses an electrochemical anode corrosion process to destabilize and remove contaminants and that has been shown to have widespread applications for treating a variety of wastes. LSs have been shown to enhance soil-particle capture by increasing the surface area and reducing the settling distance. This research demonstrated that the combination of EC and LS can enhance the sedimentation process while simultaneously decreasing the required detention time and size of traditional sediment control practices (i.e., detention basins, sediment basins). Combining EC with a LS is a novel approach for treating suspended particles in stormwater. In this project, bench-scale experiments were conducted using EC as pretreatment upstream of a LS reactor. Synthetic silica filler at concentrations of $500\mathrm{mg}/\mathrm{L}$, $\mathrm{1,000}\mathrm{mg}/\mathrm{L}$, and $\mathrm{5,000}\mathrm{mg}/\mathrm{L}$ were used to evaluate treatment efficiency at 0.5-h, 1.0-h, and 1.5-h residence times. Collected data, including turbidity, total suspended solids, and particle size distribution, were used to statistically characterize the system’s sediment removal performance. Through a series of experiments and statistical analyses of the results, an optimized EC+LS reactor with 1.27-cm (0.5-in.) LS plate spacing and 1.5-h residence time reduced turbidity by up to 98% and total suspended solids by 99% in effluent when compared with a base case reactor with a 31.8 cm (12.5 in.) settling distance (no LS plates installed) and 0.5-h residence time without EC pretreatment. In addition, particle size distribution analyses resulted in a decrease in the ${\mathrm{D}}_{90}$ value by 84%, indicating that the optimized reactor was effective in capturing larger-diameter soil particles. To validate the laboratory results with synthetic sediment-laden influent, stormwater samples were collected from a construction site and treated through the optimized system, resulting in a turbidity reduction of 50% and TSS reduction of 69%.

Application of numerical flood models in hydraulic engineering, loss and risk analysis, and urban policy making has increased significantly in recent years. While those models are widely being used, verification of underlying solvers and quality control (QC) of flood inundation results are still scarce among the hydraulic engineering community. This paper provides comprehensive verification methods/tools to fill this gap of knowledge. In this paper, the implementation of different code/solution verification procedures to build confidence in flood models was presented. The model verification approaches covered in this study includes: method of exact solution (MES), method of manufactured solution (MMS), Richardson extrapolation (RE), and the grid convergence index (GCI). Three test cases (steady subcritical flow, smooth transcritical flow, and dam-break shock formation) were used during the analyses to uncover all possible error/limitations in a shallow-water-wave solver. The asymptotic regime of convergence was used to select appropriate discretization sizes. The results from the MES and MMS indicate matched values for the observed and formal order of accuracy. For most of the discretization sizes, the observed order of accuracy indicates better performance for the water depth values than for the velocities. Although formal order of convergence is not achieved in some cases, the solution verification results show acceptable convergence behavior in the error norms as the grid resolution is refined. The RE and the GCI were successfully implemented for generating reference solutions and estimating the numerical uncertainty upper and lower bounds. Overall, this study provides a complete framework with essential set of tests to fully build a confidence in a flood model (1D or 2D) before applying it to solve real-world problems.

A model-based approach to control system design is developed for regulating the discharge flows at the outlets of a pipeline network supplied by an irrigation channel. The open channel is also controlled automatically to regulate the supply-point water level. The hydraulic pressure at the source of the network is therefore dynamic when flow load varies. Regulation of the piped discharge flows is achieved by adjusting outlet control valves on the basis of the specified flow demand and sensor measurements. A blend of feedforward and feedback control is proposed. The steady-state behaviour of a nonlinear distributed-parameter model of the network is used to determine the feedforward control action. The feedback control action is used to compensate for modeling error. The design of the feedback controller is based on a frequency-domain transfer function model of the system dynamics, and classical loop-shaping ideas. This model is obtained via the admittance matrix of linearized network equations. The synthesis of both centralized and decentralized feedback controller configurations is considered. Simulations that involve a nonlinear distributed-parameter model of the network dynamics are used to illustrate controller performance.

Correct soil water content measurement is important for various environmental and agricultural applications. The aim of this study was to evaluate the performance of two commercially available dielectric sensors, the SM150T (Delta-T Devices) and TRIME-Pico 32 (IMKO). We evaluated the manufacturer’s calibration functions and the two-point calibration function recommended by Delta-T Devices. The coefficients of the two-point calibration showed a statistically significant dependence on clay content. Because the soils tested contained a wide range of clay contents, a clay content correction function was developed. Soil-specific calibration functions were also developed. In general, measurement errors were the largest when the manufacturer’s calibration was used, but were smaller for the SM150T [root mean square error (RMSE) of 0.011 to $0.051{\mathrm{m}}^3{\mathrm{m}}^{-3}$] compared to the TRIME-Pico 32 (RMSE of 0.030 to $0.060{\mathrm{m}}^3{\mathrm{m}}^{-3}$). The errors decreased after applying the clay content correction function for TRIME-Pico 32. For both sensor types, the two-point calibration reduced the errors, and the soil-specific calibration yielded the lowest error rates.

Smart irrigation is one application of digital agriculture that can be used to achieve improved crop yields while saving water and energy. Many variations of smart irrigation can be applied, but there is no consensus among the scientific community as to which method is the best practice. The objective of this research was to evaluate two smart irrigation methods: a soil moisture–based method using sensors and an evapotranspiration- (ET-) based technique. The selected crop was sweet corn. Growth variables (biomass, yield, harvest index, and water productivity) were compared for each of the two methods. Three irrigation regimes were applied for each method: 60%, 90%, and 120% of crop evapotranspiration (${\mathrm{ET}}_{\mathrm{c}}$) for the ET-based method, and 25%, 30%, and 35% of the total soil moisture for the soil moisture–based method. Corn sap flow was measured in response to the three treatments in the soil moisture–based experiment to measure transpiration. The results showed that the ET-based method is easier to implement with less infrastructure, and it can result in similar yields compared to the soil moisture–based method. Although the fresh yield was 16% higher using the soil moisture–based method, grain yield can be sustained with the ET-based method using 8% less water. Selection of an appropriate irrigation scheduling method should be based on marketable yield: keeping the soil water content near field capacity will result in a higher fresh yield but will not translate into more dry matter. If grain yield is the target, the ET-based method is less expensive and more farmer friendly, but care should be taken to properly estimate irrigation losses to avoid underirrigation. An evaporative stress index (determined using sap flow measurements) of 70% will cause a 22% reduction in fresh sweet corn yield but only a 7% reduction in grain yield. Transpiration peaked when the soil moisture was above 85% of the available water (i.e., at 38% in the calcareous clay soil of the experiment).

This study was carried out to determine the effect of deficit irrigation applications on yield and quality criteria in 20-year-old grapefruit (Citrus paradisi Macf. cv. Star Ruby), irrigated by subsurface drip irrigation method in Batı Akdeniz Agricultural Research Institute between 2018 and 2019. In the research, full irrigation ${\mathrm{I}}_1$ (100%) and deficit irrigation ${\mathrm{I}}_2$ (67%), ${\mathrm{I}}_3$ (33%) treatments were tested. Considering the 2-year averages, irrigation water amounts of the ${\mathrm{I}}_1$, ${\mathrm{I}}_2$, and ${\mathrm{I}}_3$ irrigation levels were 597.9, 407.6, and 217.2 mm, respectively. Evapotranspiration (ET) values were 708.8 mm for ${\mathrm{I}}_1$, 566.3 mm for ${\mathrm{I}}_2$, and 406.3 mm for ${\mathrm{I}}_3$. Total yield was determined as $48.03\mathrm{t}{\mathrm{ha}}^{-1}$ for ${\mathrm{I}}_1$, $41.90\mathrm{t}{\mathrm{ha}}^{-1}$ for ${\mathrm{I}}_2$, and $36.57\mathrm{t}{\mathrm{ha}}^{-1}$ for ${\mathrm{I}}_3$. Fruit weight, fruit width, fruit length, skin thickness, juice yield, and pH decreased in accordance with the water stress imposed. However, the amount of water-soluble dry matter, titratable acidity, total dry matter amount, total flavonoid, total phenol, antioxidant, and ascorbic acid amounts increased when the irrigation level decreased. Although there were no statistical differences between sucrose, glucose, and fructose amounts, the amount of sucrose, glucose, and fructose increased as the irrigation water level decreased in general. The maximum net income was obtained from ${\mathrm{I}}_1$ treatment followed by ${\mathrm{I}}_2$ and ${\mathrm{I}}_3$ irrigation treatments. According to these results, if the subsurface drip irrigation method is used, grapefruit should be irrigated to bring the soil water content to the field capacity, when 30% of the available moisture in the soil is consumed.

A transition is typically required in irrigation canals, laboratory flumes and many other waterways. The warped type transition (WTT) is the preferred link structure between a small rectangular and relatively large trapezoidal channel section. However, the best method of determining the WTT geometry still requires evaluation. This paper provides an analytical function for the three-dimensional (3D) WTT geometry. This was achieved by solving a Dirichlet problem for Laplace’s equation. The boundary conditions in the problem were chosen based on guidelines and recommendations from earlier studies of transitions. Solving the problem analytically yields a harmonic function. The geometry given by this function guarantees a streamlined rectangular-trapezoidal link and avoids sharp corners. The streamlined transition would work to reduce flow separation and head loss. This paper contributes to the development of a new method for fabricating WTT with precision and repeatability. The harmonic function can generate geometrical data as essential input for laboratory-scale and field-scale WTTs and can aid in the construction of a three-dimensional model for use in computational fluid dynamic models.