Journal of Irrigation and Drainage Engineering

Zero-inertia equations are more easily numerically solved than complete hydrodynamic equations. Thus, the zero-inertia equations were applied to describe the surface water flows in 2D basin irrigation. Then, finite-volume and finite-difference approaches in the spatial cell and cell interface spatially were applied to discretize the continuous and momentum components of zero-inertia equations, respectively. Meanwhile, a dual time-stepping approach was implicitly implemented to achieve unconditional stability. The Gauss–Seidel iterative method was used to solve the space–time discretized expressions of the zero-inertia equations, and an efficient numerical model for 2D basin irrigation was developed. Three field experiments were conducted to validate the developed model. The validated results show that the developed model presents good agreement between the simulated and observed data, and achieves more mass conservation than the existing model. Its high efficiency is suitable for practical engineering.

Estimation of root-zone soil moisture (RZSM) at regional scales is a critical issue in surface hydrology that could be a great help for estimating evapotranspiration, erosion, runoff, and irrigation requirements, etc. A significant number of satellites [soil moisture and ocean salinity (SMOS), special sensor microwave imager (SSM/I), advanced microwave scanning radiometer-EOS (AMSR-E), tropical rainfall measuring mission/microwave imager (TRMM/TMI), etc.] retrieve surface soil moisture (SSM) using passive microwave remote sensing. This information can be used to derive RZSM using a new mathematical filter. In particular, the recently developed soil moisture analytical relationship (SMAR) can relate the surface soil moisture to the moisture of deeper layer using a relationship derived from a soil water balance equation where infiltration is estimated based on the relative fluctuations of soil moisture in the surface soil layer. In the present paper, the SMAR model is tested on two research databases in Africa and North America [African monsoon multidisciplinary analysis (AMMA) and soil climate analysis network (SCAN), respectively], where field measurements at different depths are available. Furthermore, the TRMM/TMI Satellite is selected to retrieve the satellite SSM data of the studied regions using the land parameter retrieval model (LPRM). Both remotely sensed SSM and field measurements are used within the SMAR model to explore their ability in reproducing the RZSM and also to explore the existing difference in model parameterization moving from one dataset to the other. The SMAR model is applied using three different schemes: (1) with parameters calibrated using surface field measurements, (2) with parameters calibrated using remotely sensed SSM as input, and finally (3) using the remotely sensed SSM with the same parameters calibrated in Scheme 1. In all cases, SMAR parameters have been calibrated using a genetic algorithm optimizing the root-mean square error (RMSE) between SMAR prediction and measured RZSM. The results show that remotely sensed data may be coupled with the SMAR model to provide a good description of RZSM dynamics, but it requires a specific parameterization respect to Scheme 1. Nevertheless, it is surprising to observe that two of the four parameters of the model related to the soil texture are relatively stable moving from remote-sensed to field data.

Pipe size of pressurized irrigation networks that usually have a branched layout had been optimized by assuming a predetermined layout. Few researches have considered simultaneous layout and pipe size optimization. In this study, a hybrid approach that is a combination of pipe size optimizer and layout optimizer is adapted for simultaneous layout and pipe size optimization. Once the solutions (specific layouts) are developed, a modified version of Labye’s iterative discontinuous method (LIDM) is applied to optimize pipe sizes. After the layout optimizer rearranges, the solutions and the process continues. Two versions of a new discrete particle swarm optimization (PSO) are used as tree layout optimizer, namely, original jumping PSO (JPSO) and tree growing JPSO (TG-JPSO). In the original JPSO, a loop model network is considered first, and a spanning tree is produced by using JPSO for eliminating certain branches. Tree growing JPSO without producing a loop model directly deals with branched layout. The proposed methods are applied on three benchmark examples. The results showed that using the proposed approach leads to better solutions with a very small number of function evaluation. However, compared with the existing nonhybrid approaches, the hybrid approach takes a longer CPU time to calculate objective function because of the application of LIDM for pipe sizes optimization.

Accurate flow ratings at water-control structures are essential for water-resource management. This paper presents an approach to obtain numerically generated data using computational fluid dynamics (CFD) to complement field measurements needed to improve spillway flow-rating formulas. The procedure to generate CFD flow data described herein is based on solving Reynolds-Averaged Navier-Stokes equations using the $\kappa \text{-}\epsilon$ turbulence closure model with the free surface resolved by the volume of fluid (VOF) method. The steps for setting the computational domain, generating the mesh, selecting the boundary conditions, and choosing a convergence criteria for the simulations are discussed. The turbulence closure model and VOF method for the present application are verified with data from laboratory measurements of submerged jet flow below a gate and in a sharp open-channel bend. CFD flow data generation is validated with laboratory and field measurements for gated ogee spillways in south Florida. The results presented here demonstrate that CFD is a plausible alternative to complement data measured at prototype structures and reduced-scale models for the purpose of calibration and validation of rating formulas used for real-time flow monitoring at prototype water-control structures.

Traditionally, flow-rating formulas for hydraulic structures are calibrated and validated with data comprising field measurements of discharge, water stages, and operational settings monitored in near real time. Lack of sufficient field measurements that include all flow types and cover the full operational ranges has been a major constraint in developing reliable flow ratings for prototype hydraulic structures. A companion paper introduced a plausible method that relies on computational fluid dynamics (CFD) simulations to generate accurate flow data that complements field measurements for flow rating analysis. In this paper, a general framework for applying CFD in flow rating is proposed, which includes planning of CFD simulations, assessing CFD flow data, and improving existing flow ratings using a hybrid data set of field-measured and CFD-simulated flows. Finally, two case studies of flow rating for spillways and weirs carried out to demonstrate the proposed framework are presented. Results show that the proposed framework offers a cost-effective approach that provides robust, comprehensive flow rating formulas that yield reliable flow estimates for the operation of hydraulic structures under multiple water-resource management constraints.

Optimal sizing of exfiltration trenches for both flood control and water-quality control is investigated for conventional and partially submerged trenches. An analytic formulation is presented, showing that the minimum required trench length for flood control can be determined directly from parameters that characterize the design rainfall, catchment, trench, and porous medium surrounding the trench. It is also shown that the minimum required trench length for water-quality control can be determined directly from the design water-quality depth, exfiltration time that is credited to water-quality control, and parameters that characterize the trench and catchment. Using these analytic relationships, a six-step procedure is presented for sizing trenches that simultaneously meet both flood-control and water-quality control objectives. Implementation of the design methodology is illustrated for both conventional and partially saturated trenches.

The partitioning of crop canopy water may affect soil water distribution and this may in turn affect sprinkler irrigation application efficiency. The aim of this work was to develop a methodology to evaluate spatial and temporal soil water content distribution in the case of sprinkler irrigation application efficiency considering stemflow. Time domain reflectometry (TDR) soil moisture monitoring was carried out on eight soil water sensor locations for both center pivot and traveling big gun irrigation in different phenological and tillage cases. The two case studies were chosen because they show the two opposite limits of the methodology’s application. Two water distribution estimation methods were employed: raw measured soil moisture and model simulation of the infiltration process. The infiltration process was modeled by means of the two-dimensional (2D) Richard’s equation. The simulations were calibrated on the data measured at eight soil water sensor locations. The stemflow and surface runoff conveyed in the interrow by hilling were obtained as additional model-fitting parameters. During center pivot irrigation, 34% of the water delivered in the interrow was conveyed in the row. During traveling big gun irrigation, 88% of the water delivered in the row was conveyed in the interrow. Soil water distributions calculated from measured data overestimated irrigation application efficiency by approximately 15%. The spatial and temporal soil water content distribution obtained from simulation of the water infiltration process allowed mass balance closure in both case studies. The proposed simulation method evaluated stemflow effects on the water distribution profile, leading to accurate application efficiency calculations.

Open-channel junctions are critical design elements for many major and minor drainage infrastructures. Typical examples of these structural elements are encountered in stormwater drainage systems, urban water networks, irrigation, and natural or artificial waterways. The analysis of flow behavior and condition of those structures are of considerable use to engineers involved in the design and planning processes. However, these analyses are very challenging due to the interaction among the incoming junctional and main channel flow coupled with the functional parameters involved, such as the angle of confluence, channel width, cross-section, bed slope, flow direction, discharge, and wall roughness. Therefore, the aim of this paper is to illustrate the application of a finite volume/numerical analysis method to model stormwater flow conditions and separation zone at 45 and 90° of open-channel junctions. In general, the simulation results and analysis suggested that for a 90° junction the separation zone area and discharge ratio is indirectly proportional due to recirculating flow, low pressure, and minimum velocities near the T-junction and Y-junction’s areas. For a 45° junction, flow separation is the function of divergence angles and flow velocity. Statistical analyses were also applied using the chi-square test to verify the accuracy of the numerical model result used to investigate the dimensions of the separation zone.

The government has provided financial assistance on approximately 200 tailwater recovery systems in the state of Mississippi, and more in other states. The objective of this study was to quantify surface water capture and use within 31 tailwater recovery ditches (TWR) and on-farm storage reservoirs (OFS), so that conservation benefits could be evaluated. Water-level data were combined with system dimensions, rainfall data, and evaporation estimates to assess total gains and losses over the course of a year. Systems had a net positive balance of approximately 2,200,000 ${\mathrm{m}}^3$ (2,200 ML) of captured surface water. Losses from evaporation and infiltration were between 8.68 and $10.97\mathrm{mm}{\mathrm{d}}^{-1}$ for TWR and 4.96 to $8.40\mathrm{mm}{\mathrm{d}}^{-1}$ for OFS. The highest losses occurred in the fall for TWR due to the installation cycle, whereas they were highest in the summer for OFS, driven by evaporation. Producers irrigated with an average of 41,000 ${\mathrm{m}}^3$ (41 ML) (TWR) and 84,000 ${\mathrm{m}}^3$ (84 ML) (OFS) of surface water. Irrigation levels were generally below thresholds set by the government for sufficient use.

An analytical solution of nondimensional hydraulic energy equation is derived in cosine form for the flow in rectangular open channels considering nonhydrostatic pressure and nonuniform velocity distributions across flow depth and friction and turbulent losses. The new inverted energy equation is a single equation describing all the three roots of the nondimensional hydraulic energy equation. The energy losses due to turbulence and bed shear are also implicitly accounted. Only two roots out of the three roots are practically significant, which denote the two alternate depths and are distinguishable for subcritical and supercritical flow, respectively. These equations yield direct determination of alternate depths in a single step, avoiding an iterative procedure. The use of the new equations is illustrated through worked-out examples. The new single-term analytical inverted equations are computationally simple and useful for academicians, field engineers, and practitioners in directly solving in a single step the problems of energy-equation inversion often encountered when dealing with transitions in a channel section, and flows over a dam-spillway and under a sluice gate, with correction-factors and loss coefficients estimated or known.