Journal of Irrigation and Drainage Engineering

The piano key weir is a unique new geometric type that can have a linear (rectangular or trapezoidal) or arc (trapezoidal) layout. Depending on the flow hydraulics and the bed type, different shapes of scour holes can form downstream of these weirs. Two types of piano key weirs—rectangular, and trapezoidal with an arced plan—were built to investigate the sediment transport patterns. The bed material comprised sand ($d_{50}=1.25\mathrm{mm}$) and gravel ($d_{50}=8.9\mathrm{mm}$). The results revealed that the scour hole dimensions and bed topography patterns depend on hydraulic conditions, crest geometry, and bed material gradation. Analysis of the data suggested that local scour depths behind a piano key weir with a rectangular crest might be as much as 12% larger than those for other configurations in sand or gravel.

The incorporation of a reliability analysis in the design of hydraulic structures can provide insights into management strategies that may consider potential failure modes, uncertainties, and corresponding risks. This study evaluates the reliability of water supply channels (applicable to channels in design or existing) using the reliability theory based upon field observations, specifically two failure modes observed in channels in the Maragheh-Bonab plain of Iran. Failure Mode 1 occurs when the main channel cannot pass the design flow. Failure Mode 2 occurs when the intake from the main channel is not responsive to the design flow. The formulation established the performance function based on the safety margin and load/resistance, where the mean-value first-order second-moment method approximated the mean and variance of the performance functions. The formulation was implemented in the water supply channels of the Maragheh-Bonab plain, northwest of Iran. The results of Mode 1 confirmed high reliability values in most channels, which compliments economic optimization efforts. A conclusion from this study highlights a safety issue is that although the channels are conservatively designed, the Failure mode 2 can still occur where water overflows the main channel. This study also provides a practical guide for the design or analysis of canals by providing reliability curves as a function of the distance between the regulator gate and the intake channel. These curves can assist with locating or relocating intake channels and show an inverse relation between reliability and the distance.

Abstract

The alarming water scarcity in Gujarat state justifies the adoption of water-efficient technologies like drip irrigation. Effective transfer and implementation of banana cultivation practices with improved irrigation system as a water-saving device is important as banana is a water-intensive crop. The study aims to assess the economic impact of drip irrigation as well as break down the income difference between drip and conventional irrigation technologies in banana cultivation. Primary data were collected from 120 banana growers each practicing drip and conventional methods of irrigation. The results of economic analysis revealed that the average total cost ($₹2.94(10{)}^{\wedge }5/\mathrm{ha}$) under the drip method was found to be less than the total cost under the conventional irrigation method ($₹3.28(10{)}^{\wedge }5/\mathrm{h}$ a) despite higher initial capital investment on the drip system. The benefit-cost ratio was higher on drip-irrigated farms ($1:2.60$) as compared to nondrip farms ($1:1.91$). The output decomposition model revealed that adopters of drip irrigation technology produced 17.26% higher income, implying the income of banana growers practicing drip irrigation would be higher even if they used the same mean level of inputs as farmers practicing conventional methods of irrigation. Moreover, drip irrigation technology alone contributed 24.02% increase in income, while the overall contribution of change in input levels was found to be negative to the tune of $-6.76\%$. This calls for intensive extension efforts through appropriate institutional support systems for rapid upscaling of the technology.

Practical Applications

This paper aimed at working out the cost and returns involved in the production of bananas under drip and conventional irrigation methods. The study revealed that drip irrigation technology, apart from saving water and enhancing water use efficiency, was found to be an essential tool in achieving the goal of doubling farmers’ income in South Gujarat. Moreover, drip irrigation technology significantly reduced the cost of cultivation and resulted in higher yields, thereby assuring remunerative returns to the farmers in the region. Considering the rapid decline in irrigation water availability and low water use efficiency of conventional irrigation methods, awareness needs to be created about the benefits of investment in drip irrigation as one of the most economically viable, resource efficient, and environmentally adaptable methods of irrigation.

Abstract

This research evaluated several methods to help reduce pivot ruts or wheel tracks on pivots. On-farm trials were established at nine site-years with corn (Zea mays L.), alfalfa (Medicago sativa L.) and wheat (Triticum aestivum L.) during 2020–2022 in Utah and Idaho. The eight-boom design (i.e., Advantage booms) had mostly positive crop responses but did not reduce wheel track depth. The part circle (PC) method provided much shallower tracks at one site, but it also lowered crop yield. At other sites there were minimal effects to yield and quality with the PC method, but the early-season, shallow wheel tracks did not usually last through the heaviest time of irrigating. The low energy precision application (LEPA) method was the most reliable method for maintaining crop yield and quality, while improving wheel tracks. The single boom method often maintained crop quality, but it also often reduced yield, and did not improve wheel tracks compared with the nontreated controls. The polyacrylamide had few effects on crop yield and quality, or wheel track depth. There was no approach in the study that maintained yield and reduced pivot track depth compared with no treatment in every scenario, but the LEPA method displayed the greatest potential for uniformly irrigating the area near the wheel track to maintain crop yield and quality, while minimizing water entering the track, to help reduce burdensome pivot ruts. Thus, LEPA may be one of the most effective sprinkler modifications for reducing pivot tracks and adequately irrigating the area around the track.

Practical Applications

This research evaluated how several sprinkler modifications and a soil conditioner help reduce pivot ruts or wheel tracks on pivot irrigation systems. On-farm research trials were established at six fields with corn, alfalfa, and wheat during 2020–2022 in Utah and Idaho. The eight-boom sprinkler modification had mostly positive crop responses but did not reduce wheel track depth. The part circle (PC) sprinkler method sometimes reduced wheel rut depth but came at the expense of lost crop production. The low energy precision application (LEPA) sprinkler method was the most reliable method for maintaining crop yield and quality, while improving wheel tracks. The single boom method often reduced yield and did not improve wheel tracks compared with the nontreated tracks. The polyacrylamide soil conditioner had few effects on crop yield and quality, or wheel track depth. There was no approach in the study that maintained yield and reduced pivot track depth compared with no treatment in every scenario, but the LEPA method displayed the greatest potential for uniformly irrigating the area near the wheel track and maintaining crop yield and quality. Thus, LEPA may be one of the most effective tools for reducing pivot tracks and adequately irrigating the area around the track.

Abstract

The effect of discrete movement of center-pivot towers on water distribution uniformity is a phenomenon difficult to demonstrate in the field; thus, in this paper, the dependence of uniformity of water application on the movement of the towers was investigated. To accomplish this, global navigation satellite system (GNSS) receivers were installed on three center-pivot towers to track their location during system operation. The data obtained were modeled by a computer program developed in Visual Basic for Applications, in an Excel software spreadsheet. Analysis of the temporal behavior of water depths due to the movement of each tower was described by Fourier series analysis. The results showed that towers closer to the center of irrigated circle presented longer stopping times, shorter movement times, and lower speeds, which together resulted in greater variability in applied water depth. Irrigation uniformity was affected by the misalignment angle between center-pivot spans, with uniformity being greater with smaller misalignment angles. Misalignment angles below 2° are not recommended because they result in very short cycle times (time in motion), which can cause the alignment sensors in the towers closer to the pivot point to fail, and therefore prevent movement. Finally, the amplitude of water depths as a function of tower movement increased when the misalignment angle increased. With the Fourier series analysis, regarding the interval between dominant peaks, it is possible to verify the influence of the equipment stoppage time on the water application cycles of each tower, and consequently on the overall uniformity.

Practical Applications

The evaluation of misalignment angle effect on irrigation uniformity allowed us to verify why its value is currently about 5° and, in addition, it shows that it is not necessary to minimize it closer to zero (straight alignment) with the use of more complex technologies, considering that 5° angle already results in values of irrigation uniformity greater than 90%. On the other hand, the novel and successful use of time series to describe the center-pivot movement can be an important tool to be implemented on software to more realistic simulation of center-pivot irrigation.