Journal of Irrigation and Drainage Engineering

Flumes for indirect discharge measurements are widespread and are characterized by a particular shape of the cross section area with various degrees of convergence and subsequent divergence. The flume named Samani, Magallanez, Baiamonte, Ferro (SMBF) is a simple and inexpensive instrument and its channel contraction is obtained by applying two semicylinders to the walls of a rectangular cross section. At first, in this paper a new stage-discharge equation for the SMBF flume is theoretically deduced. Then, this equation is experimentally calibrated using the laboratory measurements from the literature for different values of the contraction ratio. Finally the field measurements carried out at Sparacia experimental area (Sicily, South Italy) by a SMBF flume inserted into a horizontal flume and characterized by a contraction ratio equal to 0.5, are used for testing both the new stage-discharge relationship and the one originally proposed in the literature.

The hydrology of synthetic turf field (STF) drainage systems is poorly understood, which complicates their design. Field data are collected and used to parameterize computer models simulating the hydrology of a synthetic turf sport field. A model was employed to simulate infiltration through the synthetic turf, into the subsoil matrix, and free drainage into the perforated underdrains. The output from that model was routed using another model to simulate flow through the subsurface pipe drainage network to the system outfall. The drainage model was calibrated with actual hydraulic parameters obtained from field substrate material measurements, observed rainfall hyetographs, and measured discharge hydrographs for several storm events. Output from the calibrated STF drainage model closely matched the observed outlet hydrograph. Model output was then applied to investigate whether the classic rational formula was an appropriate tool for predicting peak flows from synthetic turf fields. It was determined that a single unique $C$ factor in the rational framework could not adequately account for the more complex rainfall-runoff response of the synthetic turf drainage system. The implications of this new hydrologic model of STF performance are discussed.

Droplet dynamics simulations are key to predicting sprinkler irrigation precipitation patterns. This paper includes derivations of equations describing droplet motion through a steady, uniform horizontal airflow (wind). The assumptions on which sprinkler irrigation droplet dynamics is based are stated, and the limitations they entail are highlighted. The motion of droplets is treated as an impulsively started accelerated motion of rigid spheres, originating at the sprinkler nozzle with known initial conditions, and involving no interactions between themselves. The following steps are used in the derivation of pertinent equations. First, the forces that the ambient air exerts on a water droplet undergoing a steady or accelerated rectilinear relative motion are defined, and their significance in the context of sprinkler irrigation droplet dynamics is discussed, based on which relevant equations are derived. This is followed by a discussion on the dynamics of accelerated motion of a water droplet through a quiescent ambient air. Then, the more general case of the dynamics of the motion of a droplet undergoing unsteady three-dimensional curvilinear motion under wind is discussed, the major forces acting on a droplet are defined, the type of droplet motion they produce is described, and pertinent equations are derived. An important feature of these equations, distinct from earlier approaches, is the manner in which the effect of wind on droplet motion is taken into account. The wind-induced aerodynamic forces, acting on a droplet, are differentiated into tangential and normal drag. The normal drag is shown to be responsible for the curvilinear droplet motion produced by wind, an important component of the wind drift effects on droplet motion. Wind effects on the tangential drag force, on the other hand, are shown to be represented in terms of the damping or amplification effects that wind introduces to the attenuation of the droplet absolute velocity compared with an equivalent no-wind condition. A companion paper presents a numerical solution for the droplet dynamics equations presented here and results of model evaluation.

A system of equations, with strong physical basis, was derived for sprinkler irrigation droplet dynamics in the companion paper. Numerical solution of these equations and model evaluation is discussed in this paper. With the aim of enhancing computational efficiency and robustness, the droplet dynamics equations were scaled using four characteristic variables: characteristic time, length, velocity, and density. The characteristic time, length, and velocity are derived based on consideration of the motion of a droplet falling freely, starting from rest, through a quiescent ambient air, to an eventual steady-state condition. The characteristic density was set to the density of water at standard conditions. The dimensionless system of equations was then solved numerically with a fourth-fifth order pair Runge-Kutta method capable of local error estimation and time-step size control. The numerical model was first evaluated through successful comparisons with simplified solutions derived based on more limiting assumptions. Computations were then made for more realistic scenarios of droplet motion, considering the interactive effects of wind velocity, droplet diameter, and nozzle angular setting. The simulated patterns of droplet motion concur with expectations stemming from physical and intuitive reasoning.

The timely completion of complex dam-construction projects is a challenging proposition, both in developing and developed countries. Delays are frequent in such projects and impose costly burdens on regional and national economies. One of the main reasons for the delay in those projects is caused by ignoring the uncertainty inherent in the completion of the tasks that arise in dam construction. Project managers often use the critical path method to schedule those activities. A key limitation of this method is that the completion times for activities near the critical path are frequently assessed inaccurately. This paper evaluates the uncertainty of scheduling the tasks associated with the construction of dams, and relies on the Gelal earthfill dam and Khersan 3 concrete dam projects for illustration purposes. An evaluation method based on Monte Carlo simulation and risk management indices is herein proposed. The results of this study are intended to assist project managers and decision-makers in scheduling of construction activities and minimizing associated costs. Results indicate that the probabilities of completing the aforementioned earth and concrete dams on schedule are 65 and 50%, respectively. Moreover, the results demonstrate the importance that the completion times of individual project activities has on overall timely project completion.

The Muskingum routing method involves the calculation of the storage volume in river reaches. The accurate calculation of the storage volume is difficult to achieve with the nonlinear Muskingum model (NMM). This paper couples the storage moving average (SMA) with NMM to produce a Muskingum storage moving average model (MUSSMAM), which has improved the accuracy of storage volume and output hydrograph calculation over the NMM. The parameters of the NMM and the weighting coefficients in the SMA are treated as dimensionless parameters in the combined MUSSMAM formulation. A hybrid method that merges the generalized reduced gradient (GRG) solver with an evolutionary (EV) solver is employed to obtain the best combination of parameter values of the MUSSMAM. The sum of the squared deviation (SSQ) between observed and routed inflows is the objective function optimized with the hybrid GRG-EV solver. The proposed MUSSMAM is tested with experimental, real, and multimodal hydrograph-routing problems. These results demonstrate that MUSSMAM reduces the SSQ by 2, 10, and 29 percent compared to the NMM in experimental, real, and multimodal problems, respectively.

The core of salinity problems starts from the fact that irrigation waters contain some amount of dissolved salts. Soil moisture salinity is dependent on soil type, climate, water use, and irrigation. The root water-uptake pattern for paddies is studied for saline as well as nonsaline conditions in the present study using a nonlinear root water uptake model. Field crop experiments are carried out using irrigation water with two different levels of salinity (4 and $6.25\mathrm{dS}/\mathrm{m}$) and fresh water. The effect of salinity on soil moisture uptake is studied by two approaches, i.e., effect on crop coefficient and effect on hydraulic conductivity. Based upon the experimental observations for low-saline ($4\mathrm{dS}/\mathrm{m}$), high-saline ($6.25\mathrm{dS}/\mathrm{m}$), and freshwater conditions, an exponential form of an equation is established for the hydraulic conductivity. The results obtained for soil moisture depletion in the crop root zone show significant improvement in prediction of soil moisture uptake for saline cases with the use of the obtained nonlinearity parameter.

Side weirs are used to divert the flow from a main channel to a desired environmental area. These basic hydraulic elements are commonly preferred in drainage and irrigation systems of surface water. Many studies have been conducted to determine the outflow discharge of side weirs. De Marchi’s approach, which assumes constant specific energy along the side weir, can be applied to describe the surface equation and therefore the discharge coefficient. However, the use of this approach is not easy in experimental and theoretical studies. This study presents a new semianalytical approach that determines the discharge capacity of rectangular side weirs. The findings of this new method are consistent with numerical and experimental results.

In this research work, a hybrid approach of integrating a support vector machine (SVM) with firefly algorithm (FFA) is proposed to predict daily dewpoint temperature ($T_{\text{dew}}$). The main aim of employing FFA is to identify the optimal SVM parameters and provide the possibility of enhancing the SVM’s capability. The weather data sets including 10 years of measured-daily average air temperature ($T_{\text{avg}}$), relative humidity ($R_h$), atmospheric pressure ($P$), and $T_{\text{dew}}$ for an Iranian city have been utilized. Seven different sets of parameters with one, two, and three of the considered parameters serve as inputs to establish seven models. The capability of the SVM-FFA method is compared against SVM, artificial neural network (ANN), and genetic programming (GP) to demonstrate its efficiency and viability. It is found that further precision is achieved for Model 7 established based on all approaches utilizing three inputs of $T_{\text{avg}}$, $R_h$, and $P$. The obtained results clearly indicate that the SVM-FFA method, by providing very favorable predictions, outperforms other examined techniques. In fact, hybridizing the SVM with FFA can be particularly promising as it favorably enhances the SVM’s accuracy. For the SVM-FFA Model 7, as the best model, the mean absolute bias error, root mean square error, and correlation coefficient obtained are equal to 0.6863°C, 0.8959°C, and 0.9849, respectively. While for the SVM Model 7, ranked in the next place, the attained values are 0.8810°C, 1.1487°C, and 0.9760, respectively. In summary, the SVM-FFA is indeed effective to predict daily $T_{\text{dew}}$ with greater precision and reliability.

Physical and mathematical models widely used in hydraulic engineering are not always effective in practice. Numerical methods such as the adaptive neuro fuzzy inference system (ANFIS) can be quite useful for estimating the key parameters, especially for complex and multivariate mathematical models. The aim of this study is to determine the discharge coefficients of labyrinth side weirs with two cycles using an experiment setup and ANFIS. Estimation of the discharge efficiency of the side weir has been achieved by using 285 laboratory data sets. The results of ANFIS functions and multiple nonlinear regression (MNLR) analysis were compared with experimental results. It is shown that two ANFIS functions, trimf and gbellmf, give the best estimations, and therefore this technique can be used effectively in practice.

An experimental analysis of a vertical drop shaft with a sharp-edged horizontal intake section and a coaxial venting pipe is undertaken to obtain design criteria given the limited attention provided by literature. Three different flow regimes are observed, namely weir flow and pressurized flow for extreme discharges and transitional flow for intermediate discharges. Particular attention is paid to transitional flow, which is a periodical regime consisting of an alternate switch from weir to pressurized flow, with water heads ranging between a maximum and a minimum. For transitional flow a detailed characterization of water surface oscillations is provided, and nondimensional equations are given describing mean water head, oscillation amplitude and frequency as functions of pipe Froude number and dimensionless plunged length of the coaxial pipe. Also, a region of existence is provided in terms of pipe Froude number and different wave types are identified. For weir flow, a nondimensional head-discharge relation is provided by analogy with overfalls.