Journal of Irrigation and Drainage Engineering

This paper presents a combined simulation-optimization model for simulating reservoir operations without any detailed operation rules; it features the integration of a nonlinear, multiple-objective function and a heuristic search method, the Shuffled Complex Evolution method, developed at the University of Arizona. The model is applied to optimal water allocations from both Balan Reservoir and Seomjingang Dam in South Korea, an irrigation reservoir and a multipurpose, multioutlet reservoir, respectively, that primarily supply irrigation water. In the case of the optimal operation of Balan Reservoir, the simulation results show that the optimal release patterns are similar to those of historical operations because the demands for irrigation water are accurately predicted and guide optimal reservoir operations. In addition, the model is successfully applied to establishing a long-term reservoir operation plan. As for the optimal operation of Seomjingang Dam, the reservoir operations are affected by the target water stages, and the model provides reasonable results, irrespective of inflow conditions. Moreover, the model is employed to create a new operation rule that is necessary to adapt to changes in the circumstances related to water management. Consequently, it is concluded that the model is useful for assessing reservoirs’ irrigation water supply capacities when establishing operation plans and providing feasible alternatives for new operation rules, and it could be applied to real-time reservoir operations.

Increasing concern for groundwater pollution with nitrate (${\mathrm{NO}}_3^{–}$) has motivated the use of solute-transport studies to explore and predict the transport behavior of ${\mathrm{NO}}_3^{–}$. The main objective of this study was to examine the effect of pore-water velocity on nonequilibrium solute-transport parameters in variably saturated homogeneous and layered soil columns. A second objective was to evaluate the effect of solute concentration on nonequilibrium solute-transport parameters in layered soil columns. The study was conducted in 10-cm long columns repacked with air-dried and sieved (Number 10 sieve) sand and loam soils. A 0.1 M calcium nitrate and calcium chloride [${\mathrm{CaCl}}_2+\mathrm{Ca}({\mathrm{NO}}_3{)}_2$] solution was applied to the columns at $-0.30\mathrm{kPa}$ suction to generate ${\mathrm{Cl}}^{–}$ and ${\mathrm{NO}}_3^{–}$ breakthrough curves. The CXTFIT program was used to determine the two-region model parameters. Additional experiments were conducted with repacked layered soil columns downscaled from existing soil profile at New Mexico State University experimental station. Layered soil-column experiments were conducted for two solute concentrations of 0.05 and 0.1 M under near-water-saturated conditions. The dispersion coefficient ($D$), volumetric mobile water content (${\theta }_m$), and retardation factor ($R$) for both anions increased with increasing pore-water velocity, but the mass-exchange coefficient ($\omega$) was inconsistent in both homogeneous and layered soil columns. Layered soil-column experiments conducted with a solute concentration of 0.1 M had greater $R$ values than those conducted with 0.05 M solution. The ${\mathrm{NO}}_3^{–}$ and ${\mathrm{Cl}}^{–}$ exhibited similar transport behavior through homogeneous and layered soil columns under variably water-saturated conditions and displayed the potential of predicting ${\mathrm{NO}}_3^{–}$ movement from easily measured ${\mathrm{Cl}}^{–}$ data.

A labyrinth weir provides an effective way to increase weir crest length without an associated increase in structure width. Labyrinth side weirs have important advantages compared to conventional side weirs in term of discharge capacity, length of the channel opening, and nappe height over the weir. A different equation is needed for each number of cycles to determine the discharge coefficient of labyrinth side weir. Unlike labyrinth spillways, one or two cycles are mostly sufficient for the labyrinth side weirs to accommodate the required discharge. This study examines the hydraulic characteristics of trapezoidal labyrinth side weirs with two cycles in a subcritical situation and the effect on discharge capacity of using single or multiple cycles in side weirs with the same length openings and crest lengths. The results show that a side weir with one cycle has slightly greater discharge coefficient. In addition, the variation of the discharge capacity was investigated for both one-cycle and two-cycle side weirs with the same opening length in the main channel. The results show that the relationship obtained for a one-cycle side weir is not suitable for multiple-cycle side weirs if dimensionless weir length $L/B=0.5$. Consequently, the relationships for the De Marchi coefficient of discharge in a subcritical flow for trapezoidal labyrinth side weirs were introduced as functions of dimensionless variables. The empirically obtained equations for discharge coefficient agree considerably with the experimental data.

Recently, supervisory control and data acquisition (SCADA) systems have become widely used in agricultural applications, particularly in conjunction with irrigation management systems that require calculated applications of water. The objective of this study is to present a new SCADA platform for the regulated deficit irrigation management of almond trees. This new platform implements a wireless architecture that ensures error-free communication among the irrigation system components with no need to maintain cables. The implemented SCADA application performs the following irrigation-related tasks: (1) based on the edaphoclimatic data from the parcel to be treated, an estimation of the crop water requirements, including the values required for drip irrigation scheduling, is computed; and (2) using the calculations from the previous step, the different components of the irrigation system, such as the electrovalves, pump system, variable frequency drive, and pressure alarms are placed under either automatic control or the control of manual activating actuators. The proposed platform was installed in a parcel of almond trees located at Fuente Alamo de Murcia, Spain, with half of the parcel configured with regulated deficit irrigation and the other half configured with conventional irrigation. The results demonstrate the benefits of using this new platform, as well as a method for reducing water consumption through the use of regulated deficit irrigation.

A methodology for incorporating site-specific landscape characteristics into vegetated stream buffer design has been developed. This methodology consists of calculations within a geographic information system format, and applies a sequential accumulation of the contribution of individual pixels of buffer width to overall performance. A demonstration of the application of the methodology to a watershed expecting development is presented here and implications for decision making are discussed. Information layers derived from landscape data layers and used in buffer-performance calculations are displayed. Specific calculations performed in the demonstration are buffer delineation, with implications related to the potential impact of variable versus fixed width buffers, to the impact of assumptions with respect to the type of sediment needing to be settled out, and to the need to mandate wider buffer widths adjacent to lower order streams. Sediment-trapping efficiency calculations can be used to set performance standards and assess the viability of certain criteria in terms of areas potentially available for buffers. The reduction in peak discharges of storm-water runoff (through some combination of infiltration and detention) is becoming a surrogate water-quality parameter for non-point-source pollution in recent total maximum daily load determinations. Infiltration-volume estimation can be used in assessing the feasibility of such a surrogate approach.

Circular-crested weirs are overflow structures with a reasonably high discharge coefficient, compared with that of sharp- and broad-crested weirs. In this study, combining the potential flow around a circular cylinder and the free vortex flow, to determine the discharge coefficient and velocity distribution simulated flow over circular-crested weirs. Both the potential flow around a fixed-circular cylinder and the free vortex flow independently consider a symmetrical flow field. However, in realized conditions, the inertia force induces deviation of the flow streamlines over the circular cylinder. Therefore, a more comprehensive theory is essential to simulate the asymmetry of the flow streamlines properly. For this purpose, in the present study, both the mentioned theories were combined to simulate the flow around the circular-crested weirs using the potential flow past a circular cylinder with circulation. The analytical results were calibrated and compared with the experimental data of former investigations. Results indicate that the suggested semi-analytical model can predict the discharge coefficient and velocity distribution satisfactorily for the relative crest curvature ($H_1/R_b$) up to 7. In addition, results of the sensitivity analysis demonstrated that $H_1/R_b$ is the most prominent parameter influencing the discharge coefficient of circular-crested weirs.

This paper proposes and evaluates a number of drainage water mixing projects in canals applying QUAL2K, which is a river and stream water quality model recommended by the United States Environmental Protection Agency (U.S. EPA). Mitigation measures and precautions were suggested fur use as guidelines for environmentally safe application. The results showed that QUAL2K proved to be an effective tool in the comparative evaluation of potential water quality improvement programs, particularly on the salinity and water quality parameters that address agriculture practices. Simulation results showed that most selected water quality parameters for most of the considered projects complied with the standards of Egyptian law. Moreover, electrical conductivity (EC) predictions were found within the permissible limit with the recommended fit crops. The reduction in drain discharge reduces pollutant loads entering Temsah Lake and might help save the flora and fauna to support recreation activities.

Water-saving strategies aimed at improving water use efficiency need to be applied in agriculture today to ensure sustainable use of scarce water resources. This article presents results of a 2-year study done at Washington State University’s Irrigated Agriculture Research and Extension Center (IAREC) to determine the effect of various water stress levels applied at various times during the growth period to the yield quantity, quality, and production costs of drip-irrigated native spearmint (Mentha spicata L.). The field experiment included four irrigation levels (40, 54, 80, and 100% of ETc) and four stress timings: T1(the irrigation levels were applied throughout the growing season), T2, T3, and T4 where the irrigation levels were applied 21, 14, and 7 days before harvest, respectively. Hay yields decreased with increasing water stress; mean annual hay yield ranged from $47.2\mathrm{Mg}/\mathrm{ha}$ under the driest treatment (40% irrigation level at timing T1) to $61.2\mathrm{Mg}/\mathrm{ha}$ under 100% irrigation level. Mean annual oil yields ranged between 108 and $147\mathrm{kg}/\mathrm{ha}$ among treatments. Fully irrigated plots gave average oil yields of $127\mathrm{kg}/\mathrm{ha}$. Deficit irrigation thus has potential to give similar or even higher oil yields than those from fully irrigated plots. Water stress did not significantly affect oil quality. The oil concentration (kg of oil per kg of hay) increased with water stress; mean oil concentrations ranged from 0.22% under 100% irrigation level to 0.31% under the driest treatment. Water use efficiency (oil yield per unit volume of water consumed) also increased with increasing water stress, ranging from $0.009\mathrm{kg}/{\mathrm{m}}^3$ under 100% irrigation level to $0.026\mathrm{kg}/{\mathrm{m}}^3$ under the driest treatment. Costs of production savings were 2.9, 6.6, and 8.6% per hectare for the 80, 54, and 40% of ETc, respectively, when compared to the full irrigation scenario. Results show that up to 60% irrigation deficit in native spearmint, no matter its timing, can save water, improve water use efficiency, and reduce costs of production while maintaining oil yields and quality similar to those from fully irrigated plants.

This work presents a critical analysis of submerged flow over rectangular weirs of finite crest length. For finite crest length weirs, because the existing data sets are not extensive, new experiments for these weirs with sharp-edged and rounded crest were conducted. Based on these data, a diagram is developed to show the variation of the normalized tailwater depth with $h_o/L$ where $h_o$ is the free flow head and $L$ is the length of the crest, to predict the onset of submergence or the modular limit. Water surface profiles of flow over weirs of finite crest length with square-edge and rounded crests were plotted to study the formation of waves in modular and submerged conditions. Characteristics length scales such as wave length and amplitude at the modularity limit and the location of the first trough downstream of the weir were measured to generalize surface profiles at different flow discharges. An empirical equation for the discharge reduction factor was also formulated. This equation has two exponents with different values for several classes of finite crest length weirs with either square edged or rounded crest.