Journal of Irrigation and Drainage Engineering

Abstract

Following recommendations for replacing center pivots and center-pivot sprinkler packages can help farmers improve water application efficiency and optimize crop production. Little information exists on the frequency with which farmers are replacing center pivots and sprinkler packages. To help address this issue, this study evaluated an industry database of center pivot ($n=654$) and sprinkler package ($n=\mathrm{5,131}$) replacements in the western United States. On average, pivot systems were oldest in Montana, Idaho, and Utah, with an average age of 18, 16, and 16 years, respectively. Oregon had the lowest average pivot age (9 years). Average pivot age also varied by brand: Reinke systems were the oldest (16 years) and Valley were the youngest (11 years), on average. Across the database, 92% of the pivots were 25 years old or younger. Utah also had the oldest average sprinkler package age (10 years). Oregon and California changed sprinkler packages most frequently ($\le 4\mathrm{years}$). Sprinkler package replacement frequency varied among center-pivot manufacturers, with Valley pivots having the highest frequency of sprinkler package changes (5 years) and Zimmatic pivots having the lowest frequency (8 years). Across the database, 50% of the sprinkler packages were replaced within 2 to 5 years, and 81% were replaced within 10 years. Most farmers in the region generally follow recommendations on replacing pivots and pivot sprinkler packages, but a sizeable number of farmers do not. Therefore, an opportunity exists to improve center-pivot and sprinkler package maintenance, thereby helping to make center-pivot irrigation more water efficient and crop production more sustainable.

Practical Applications

This study contributes to industry knowledge and awareness by providing data and insights on center-pivot and sprinkler package replacement trends. The authors evaluated an industry database of center-pivot ($n=654$) and sprinkler package ($n=\mathrm{5,131}$) replacements in the western United States. Insights on the frequency of replacement can help farmers make informed decisions about when to replace their equipment, and can raise awareness on the importance of equipment maintenance. Farmers may therefore be encouraged to follow equipment maintenance recommendations and replace outdated or inefficient equipment. By so doing, farmers can irrigate more efficiently and optimize crop production, leading to improved yields and more sustainable crop production. The study revealed that equipment replacement trends vary by manufacturer. This reinforces the need for irrigators to consult with irrigation experts, manufacturers, or equipment dealers to obtain specific recommendations tailored to their specific circumstances and equipment. Irrigation equipment manufacturers and distributors can also use the study findings to improve their equipment and farmer support systems. Policy makers may use the findings in structuring and implementing farmer support programs and related policies and laws. The study, therefore, can provide insights that contribute to the nation’s goals of sustainable agricultural water use and crop production.

Abstract

The present study aimed to examine the relationship between canopy air temperature difference and vapor pressure deficit (VPD) in wheat crops under normal or nonstressfull conditions. The treatments were undertaken on five plots, having randomized block design (RBD), each maintained at different levels of soil moisture having full irrigation; no irrigation; and 10%, 30%, and 50% soil moisture. Then canopy air temperature difference was regressed against VPD to generate non-water stress and maximum water stress baselines, and the crop water stress index (CWSI) was computed using empirical approach-baseline methods at different soil moisture deficits. It was found that irrigation treatment at 30% soil moisture deficit yielded the maximum water use efficiency. The canopy air temperature difference and VPD resulted in linear relationships, and the slope ($m$) and intercept ($c$) for lower baseline of preheading and postheading stages of wheat crop were found as $m=-2.371$, $c=-1.659$; and $m=-1.8952$, $c=-2.32$, for the crop season of 2018–2019. Similarly, the non-water stress baseline equation in the season of 2019–2020 had $m=-1.7184$, $c=-2.3009$; and $m=-1.8137$, $c=-1.9176$ for preflowering and postflowering stages of wheat, respectively. The CWSI was determined by using the developed empirical equations for three irrigation schedules of different maximum allowable depletion (MAD) of available soil water (ASW). The developed CWSI may have the potential to improve irrigation scheduling of wheat in India.

Practical Applications

The study shows practical applications for enhancing wheat cultivation under varying soil moisture conditions. First, it recommends irrigating at 30% soil moisture deficit to maximize water use efficiency, aiding farmers in balancing crop yield and water conservation. Second, established relationships between canopy air temperature difference and VPD allow for the assessment of water stress. By utilizing regression equations, farmers can estimate the CWSI across soil moisture levels, guiding irrigation scheduling during critical growth stages. Third, the developed empirical equations enable real-time prediction of water stress. Monitoring the canopy air temperature difference and VPD offers insights into plant health, helping with informed decisions on irrigation and fertilization. Last, the findings are relevant for water-scarce regions like India, where tailored CWSI equations can be integrated into irrigation systems, promoting sustainable practices under a changing climate. This study may help farmers with practical tools for water-efficient wheat cultivation, fostering informed choices for sustainable agriculture, particularly in water-scarce regions.

Open-channel junctions pose a risk associated with flooding and erosion. However, despite the numerous studies concerning the channel junctions, the bed and flow field evolutions at junctions for flood conditions have yet to be investigated. To address this research gap, this paper investigates the evolutions of the bed and flow field during a flood event at a right-angled open-channel junction utilizing three-dimensional (3D) computational fluid dynamics (CFD) modeling. The transient Reynolds-averaged Navier–Stokes (RANS) equations with the renormalized group (RNG) $k–ϵ$ as the turbulence closure for the flow field, the Meyer-Peter and Muller equation for bed-load sediment transport rate, the convection–diffusion equation for the sediment concentration distribution, and the sediment continuity equation for the bed evolution are used in the numerical model. The model simulates the characteristics bed morphology at the junction with reasonable accuracy compared with the available laboratory data. Three scenarios (Scenarios 1, 2, and 3) were considered by applying the triangular flood wave at the inlet of the tributary channel, main channel, and both channels, respectively. The quasi-equilibrium deformed bed channel junction with steady inflow conditions of the validation case was considered as the initial condition for the flood flow simulations. The simulated results show that the junction bed is deformed considerably due to the significant increase in bed shear stress during a flood event. The deepest scour area gradually grows wider during the passage of the flood wave. The maximum value of the scour increased by 24.4%, 14.6%, and 31.2% in Scenarios 1, 2, and 3, respectively. The findings of the study improve the understanding of the junction hydrodynamics and bed morphological features for flood conditions.

The Himalayas are the source of several perennial rivers with significant hydropower potential. In the region, many hydropower projects are in operation, and many more are being built. Sediment transport in Himalayan rivers is high. The Alaknanda River basin (ARB) in the Indian Himalayas has a total hydropower potential of 4,081 MW. Only 871 MW of this capacity is being utilized; the remaining 3,210 MW still needs to be tapped. Comprehensive information on hydrosedimentary characteristics is required to design and develop hydropower projects. The present study assessed the spatial variation of the hydrosedimentary characteristics of the ARB. Suspended sediment samples were collected in polyethylene bottles from 19 locations in the ARB. Suspended sediment concentration (SSC), particle size distribution (PSD), shape, and mineral composition were evaluated for all the selected locations. There were minor variations in SSC for the sampling locations. The Pindar tributary was the main influence on SSC in the ARB. Most locations exhibited clay to very fine sand particles. A graphic test method indicated sediment with moderate sorting, coarse skewness, and leptokurtic distributions at most locations. Sorting tended to increase with increasing skewness. Kurtosis showed an increasing trend with skewness; it began decreasing after reaching a maximum value (1.5). No significant spatial variations in particle shape were observed in the ARB. Most of the sampling locations had sediments with high sphericity and slight elongation. No significant spatial variation of mineralogy was observed in the ARB. Numerous minerals were identified in the ARB. Quartz (68.78% to 79.93%) was the most dominant mineral. This dominance was confirmed by an elemental analysis, in which silicon (Si) and oxygen (O) were the most abundant elements (54.73% and 37.92%, respectively). Following a procedure outlined in an international standard, the mean shape and hardness factors for the ARB were estimated at 1.36 and 0.84, respectively. The maximum random uncertainty values for SSC, PSD, sphericity, and aspect ratio were found to be 1.46%, 0.37%, 0.64%, and 0.65%, respectively.