Journal of Irrigation and Drainage Engineering

The aim of this article is to determine with real data to what extent the hypotheses on which Clément’s first formula is based are fulfilled, and to compare the results of applying this formula. To this end the flow demand in the peak period was studied in two distribution networks with different irrigation methods and crops located in the Ebro River basin (northeast Spain). The calibration procedure for this formula proposed by the Centre Technique du Génie Rural des Eaux et des Forets (CTGREF) in 1977 was also analyzed. The result was that most of the hypotheses were not fulfilled. Furthermore, the discharge distributions obtained in the period of study did not correspond to a normal distribution. However, comparing the real accumulated probability curve and that calculated by Clément’s formula, it was found that the differences between the two curves for probabilities greater than 90% (a wide range of application of the formula) were lower than 9.4%. The reason for this result was found. It was shown also, that the CTGREF adjustment procedure did not provide substantial improvement in the estimation of flows because the aim of the fit was to achieve a normal distribution rather than an accumulated distribution function.

The level-furrow irrigation system consists of furrowing a level basin. In level furrows, irrigation proceeds just like in level basins: the field is flooded from one point and water spreads to irrigate each furrow. Several writers have reported that this irrigation system has the potential to conserve water as compared to level-basin irrigation. However, no comparative studies on the performance of both irrigation systems are available, and the simulation of level furrows has not been attempted. In this work, two field experiments are reported. Both of them were performed in the same soil and in the same conditions. In the first experiment, infiltration was estimated for a series of furrow irrigation discharges and for a level basin. In the second experiment, a level furrow irrigation event was evaluated. A simulated level basin irrigation event in the level furrow experimental field required six times more time and water to complete advance. Infiltration equations including the irrigation discharge or the wetted perimeter as independent variables were proposed for the experimental furrow conditions. Application of a furrow simulation model to the level–furrow experiment resulted in an underestimation of the time of advance. To overcome this problem, a simulation model for level furrows was developed and is presented in a companion paper. The reported field experiments were used to validate the model, which was applied (in a companion paper) to explore adequate conditions for level furrow irrigation performance.

In a companion paper, experimental evidence was elaborated to confirm that in particular circumstances the performance of level-furrow irrigation can exceed that of level-basin irrigation. The application of a single furrow simulation model to an irrigation event in a level-furrow field resulted in large estimation errors. To overcome them, the development and validation of a numerical model of level-furrow irrigation is reported in this work. The model is based on the interconnection of a number of one-dimensional channels. The individual channels are connected using confluence or bifurcation points. Furrow infiltration is modelled through a Kostiakov infiltration equation including the furrow discharge as an independent variable. The proposed model is validated using the experimental level furrow evaluation presented in the companion paper. Finally, the model is applied to explore the conditions in which level furrow irrigation can outperform level basin irrigation. The proposed model stands as a valuable tool in the design and management of level furrow irrigation systems.

Despite its widespread use in agricultural systems, the Venturi-type ejector presents lower efficiency than that obtained by conventional jet pumps. In this study, low-cost ejectors built from PVC T-junctions, with geometry similar to that of the conventional jet pumps, were developed and evaluated experimentally. The tests were carried out on ejectors with nominal diameters of 25 and 32 mm with area ratios of 0.25, 0.35, and 0.53. For each diameter, a Venturi-type ejector with an area ratio of 0.35 was also employed. The ejectors developed in this research presented efficiency between double and triple of that of the Venturi type, with a maximum of 30.5% being reached with the ejector of 25 mm and area ratio of 0.35. The head-loss coefficients for each component of the ejectors were evaluated by fitting a one-dimensional model. The results showed that the low-cost ejectors developed here presented an operation comparable to that of conventional jet pumps and had a better benefit/cost ratio than the Venturi-type ejectors.

A field water balance model is developed for rainfed rice in medium land (a rice field with intermittent ponding and drying phase is characterized as medium land) in eastern India with provision of supplemental irrigation from an on-farm reservoir. The model inputs consist of soil, crop, and daily climatic data. By developing a computer program in Visual Basic 6.0, the model simulates various water-balance parameters such as actual evapotranspiration, percolation, seepage, supplemental irrigation, surface runoff, and ponding depth in the field on a daily basis. Physically based saturated and unsaturated flow processes are incorporated into the model to simulate the aforesaid model parameters that occur during wet and dry periods. The model parameters are validated with the observed data of the experimental field. The Z-test was used to look for significant differences between the observed and simulated values of the parameters. The model hypothesis is found to be acceptable at a 5% level of significance for simulating the actual evapotranspiration and ponding depth and at the 1% level of significance for simulating percolation.

A methodology for parameter estimation for the Muskingum model of streamflow routing is developed. The methodology minimizes the outflow prediction errors subject to the satisfaction of the streamflow-routing equations for all time stages in the routing process. The routing equations incorporate the Muskingum channel storage models. An algorithm is developed for parameter estimation that iteratively solves the governing equations to identify the Muskingum model parameters.

In the early days of the Reclamation Service, the criteria for irrigability of lands generally consisted of two elements: (1) is water available? and (2) can we get the water to the land? Within a few years, many of the early projects were experiencing reduced agricultural productivity and reduced ability to repay construction loans because the soils were becoming waterlogged and saline. By 1915, construction of subsurface drainage facilities had been initiated on several projects. However, at the time, subsurface drainage was more of an art than a science. Much of the world’s experience with agricultural drainage had been gained in humid areas which were quite different from arid areas. With no standards and limited knowledge of ground water movement, these early drainage efforts met with varying degrees of success. This paper summarizes the development of scientific methods to ensure successful application of drainage in a sustainable irrigated agriculture. Reclamation has introduced these methods to solve irrigated drainage problems at the international level. This paper will address the international experience, and how the same design and construction methods and procedures are now being used to design corrective drainage facilities for dams and other major structures and to support environmental enhancement programs.

The effect of stone and vegetative covers was evaluated for soil and water conservation in a waterway on alfisols. Experiments were conducted on a hydraulic tilting flume under simulated flow (93 and 40 ${\mathrm{cm}}^2 s^{-1})$ and slope (0.1, 1.0, 3.0, and 5.0%) conditions. The depth of soil was maintained at 0.35 m over a perforated bed to facilitate deep drainage. A comparative study of bare soil, stone cover (50%), and vegetative cover (50%) is made to evaluate soil loss, deep drainage, Manning’s roughness coefficient, and the Froude number. The study has revealed that stone cover is more effective than vegetative cover at lower discharge in reducing the flow velocity, and thereby soil erosion. Deep drainage has been reduced from lower to higher discharge for all the slopes with cover measures, including bare soil. It is found that cover measures are necessary beyond 3% slope in order to prevent rill erosion in alfisols.

Two mathematical models for parameter estimation in closed-loop, open-channel flow networks are presented. The parameter estimation models seek to determine the parameter values that would reproduce an observed flow profile in the channel network. The governing equations for gradually varied flow in channel networks are the optimization models’ constraints. The projected augmented Lagrangian method is used to solve the optimization models. Performance of these two optimization models is evaluated for a given closed-loop network configuration. Results establish the potential of the developed models for use in real-life flow scenarios.

Analytical solutions exist for the seepage discharge from polygonal and nonpolygonal canal sections underlain by a drainage layer at a hydraulically infinite depth. These solutions lead to underestimation of the seepage discharge if a drainage layer occurs at a shallow depth. This paper presents solutions for seepage discharge from circular and exponential sections overlying a shallow drainage layer. The discharge has been calculated by a finite-difference-based numerical solution of the differential governing the seepage flow. The phreatic boundaries of the flow domain were described in terms of two parameters that were estimated by a minimization process. Such seepage computations were performed for a large number of independent dimensionless variables of the section geometry. Subjecting the computed seepage to regression analyses, explicit equations for seepage discharge loss have been obtained. Using these seepage loss equations, the design variables for minimum seepage loss have been obtained. The use of the design equations has been illustrated by design examples.