Journal of Irrigation and Drainage Engineering

The semiarid climate of the majority of agricultural districts in the Mediterranean means that water is a key factor limiting production. It is therefore necessary to distribute water in the most efficient way possible and foment the sustainable use of this valuable resource. It is a difficult task to ascertain whether the use of water in an irrigation district is efficient or not, given that water as a resource cannot be considered in an isolated manner. The development of techniques for data envelopment analysis (DEA) has made it possible to evaluate, in a global manner, where the application of water is most efficient. DEA techniques consider the production process as a set of inputs which obtain a set of outputs in the form of profits. The study of efficiency as a combination of resources allows us to assess when the application of water will lead to greater profitability and hence aid water management authorities in distributing the water of their basins in an appropriate manner. In this study, the data envelopment analysis Baker, Charnes, and Cooper model is applied to all of the irrigation districts in Andalusia (Southern Spain). Using the Wilcoxon–Mann–Withney statistical test we conclude that extensive agriculture (located in the interior) and intensive agriculture (on the littoral) are difficult to compare. Although intensive agriculture with localized irrigation systems achieves the highest efficiency values, the spatial distribution of efficiencies is of great utility in detecting local inefficiencies. It is also useful in providing general guidelines as to which trends should be followed in order to obtain the greatest possible efficiency.

The Hargreaves method enables reference crop evapotranspiration $\left({\mathrm{ET}}_0\right)$ estimation in areas where meteorological information is scarce, as, for example, southern Spain. However, this method is known to produce considerable bias in this region, especially during the dry, hot summer months. An evaluation of the method is made by comparing daily estimates with those made by the more commonly recommended Penman–Monteith method at 16 meteorological stations. Computed ${\mathrm{ET}}_0$ values at the coastal stations are, on average, 0.69 mm d⁻¹ smaller than the Penman–Monteith estimates whereas at inland stations a small average overestimation of 0.13 mm d⁻¹ is shown. The adjusted Hargreaves coefficient (AHC), obtained through regression analysis, increases at the coastal stations, on average, to 0.0029, and decreases at the inland stations to 0.0022. Adjustment with the Samani method does generally not produce more accurate estimates in this region. Finally a linear relationship between the AHC and the rate of the average temperature to the average daily temperature range is proposed for the regional adjustment of the Hargreaves coefficient.

Improvements in irrigation efficiency are well documented when changing from flood to sprinkler irrigation methods; however, other impacts to the watershed associated with this change are not well known. The resulting impacts to a river basin hydrology when irrigation and conveyance methods are changed are the focus of this study. In an attempt to improve water application and conveyance efficiencies in the Salt River Basin of western Wyoming, irrigation practices were changed from flood irrigation to sprinkler irrigation beginning in the late 1960s, with completion by the mid-1970s. Based upon a water balance, flow in the Salt River increased an average of 65.62 MCM/year. Return flow timing was also impacted by the conversion to sprinkler irrigation. Flows increased 34% in May and 50% in June, while decreasing 15 and 14% in August and September. These changes may have coincided with decreases in groundwater storage. However, analysis of changes in groundwater levels with time was inconclusive. Surface water total dissolved solids (TDS) appears unaffected by the conversion in irrigation practices, while limited groundwater quality data indicate that TDS values are lower in sprinkler irrigated areas.

The hydraulic design of a lateral or a submain unit in a microirrigation system has been a problem tackled by many authors. In applications of previous analytical approaches for trickle lateral hydraulic computation, it is generally assumed that the emitter outflow along the lateral is constant. However, significant deviations from accurate numerical solutions in hydraulic analysis could be caused by this basic assumption of constant emitter outflow. Recently, some alternative analytical methods with more accurate results were developed based on the spatially variable outflow approach. In this study, seven hydraulic calculation methods were analyzed and classified for comparative purposes from points of view such as solution methods, basic assumptions, formulations used, and differences in application. A comparison test was applied to the seven design examples with the special limited design conditions of some calculation methods, such as emitter discharge exponent, to cover various combinations of irrigation parameters, varying emitter discharge exponents, and different ground slope conditions. The results were shown graphically in dimensionless form. These figures could also be used as design charts in practice.

An advanced technology cost-effective drip irrigation system design and setup on environmentally sensitive elevated steep slopes (batters) of a coal train derailment site in Central Queensland, Australia, are presented. The final profile of the coal burial site consists of six batters and associated berms with a drop in elevation of about 35 m. A small dam constructed downstream of the confluence of the two main drainage channels at the site supplied water for irrigation of the batters to aid the establishment of grass to control erosion. Water was periodically pumped from the small dam to three storage tanks using a petrol (gas) pump. Three solar pumps drew water from the storage tanks and dam to irrigate the top four batters. Contactors, pressure switches and irrigation control valves in turn shared a single solar power source between the solar pumps. Level balls (floating switches) placed in the storage tanks cut the solar power supply to the pumps when the storage tanks were nearly empty. On the whole, the irrigation system worked very well and excellent grass cover was established within 12 weeks. Given the environmental risks associated with the on-site burying of coal, and the estimated cost of about AU$11.73/m² (every 10 years) in maintenance if the railway batters are not treated, the estimated total cost of AU$4.61/m² of batter area treated with irrigation, including AU$3.08/m² in irrigation cost, is justified.

Model predictive control (MPC) is a popular control algorithm in the process control industry that is particularly suited to the automatic control of irrigation water delivery systems because it explicitly accounts for the long delay times encountered in open-channel flow. In addition, a feedforward routine is easy to implement in MPC and many of the constraints that canal operators face can be directly incorporated into the MPC scheme. The ASCE Task Committee on Canal Automation Algorithms developed a series of test cases to evaluate the performance of canal control algorithms. In this paper, simulation tests were performed on ASCE test canal 1 using a remote downstream control configuration of MPC. The MPC algorithm effectively controls ASCE test canal 1, and its performance was similar to that of other proposed controllers. When there were no minimum gate movement constraints, MPC was fairly robust because the controller performance did not significantly degrade under untuned conditions. In the presence of minimum gate movement constraints, the water levels continually oscillate around the water level setpoint. Using the configuration presented in this paper, the feedforward portion of MPC does not perform as well as other proposed feedforward routines. This underperformance is related to the simplifications made by the underlying process model and not to MPC itself.

Based on the theory of the least squares and the statistical properties of the best statistic with an unbiased estimate and minimum variance, a new method for land grading design is presented. Although it is based on least-squares theory, it does not have the cumbersome and time consuming calculations of the terms of the simultaneous equations that appear in the conventional least-squares method. In rectangular fields, the method is as accurate as the conventional least-squares method. In irregularly shaped fields the results are different but the differences are negligible. Since the developed equations can be solved by using a calculator in statistical mode and a readily available table, the proposed method has the advantage of being amenable to hand calculation.