The Effects of Three Furrow Shapes on Water Advance Characteristics, Application Efficiency, Deep Percolation and Tail Water Run-off
Abstract
Furrow irrigation is considered to be inefficient when compared to most pressurized irrigation systems. The objective of this research was to determine if different furrow shapes have different impacts on water management practices such as application efficiency, deep percolation ratio and tail water runoff. Three furrow shapes, a triangular (V-shaped), rectangular (R) and trapezoidal (Tp) shaped were evaluated and the results were compared with output from SIRMOD II. The parameters calculated from field data were not very different from those determined by the model. This indicated that the model predicted the volume balance of the field data with reasonable accuracy. It was observed that the time of advance was shorter for the triangular shaped furrow and much longer for the rectangular shaped furrow. Performance efficiency parameters were good for the trapezoidal and triangular shaped furrows and very poor for the rectangular furrow. Tail water ratio (TWR) was much higher in the triangular furrow and lower in the rectangular furrow. Where there was no deep percolation ratio, the model failed to return a reasonable value.
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Introduction
Furrow irrigation is probably the oldest and most widely used method for applying irrigation water to many field crops and vegetables worldwide (Childs et al., 1993; Walker and Skogerboe, 1989; Nie et al., 2018, Dlamini, 2020). Lima et al. (2014) observed that surface irrigation systems still remain the most used irrigation system worldwide mainly due to their energy saving capacity and ease of operation but they show low performance level as a consequence to the general design and inadequate management. This observation was also made by Lamaddalena et al. (2021). According to Spencer et al. (2019) the two primary factors causing inefficiencies in furrow irrigation are deep percolation losses and tail water runoff and are the two major constraints in furrow irrigation practices. Eldeiry et al. (2005) although measured various parameters including furrow geometry, in their study they concluded that the length of the furrow and its inlet inflow are the main factors affecting application efficiency. They observed that when using longer furrow lengths the irrigation system was less sensitive to variations in furrow inflow, furrow shape, field slope, and roughness. However, where longer furrow lengths are not possible, the application of water should be carefully controlled to maintain high efficiencies. In free ending furrow irrigation, the recession phase was very fast in the entire field compared to the advance. Thus, the time of advance becomes the main contributor to the water application in the furrow. Haddad and Bouhadef (2012) studied the impact of geometric shape of farming grooves on sediment transport and found that there were variations among the shapes.
The results of Schwankl et al. (2000) indicated that variability of furrow physical characteristics, in decreasing order of their relative impact on furrow irrigation performance was: furrow inflow rate, infiltration, geometry, and roughness. The infiltration characteristics (Dlamini, 2021) also plays an important role in understanding the movement of water along the furrow, with furrow shape (Eldeiry et al. 2005) being a critical parameter for determining the advance time. The application efficiency (AE) and distribution uniformity (DU) are the main indicators to evaluate the overall performance of any surface irrigation event (Lamaddalena et al. 2021). Holzapfel et al. (2010) noted that efficient irrigation practices that minimize deep percolation will therefore minimize leaching of contaminants.
Conclusion
From the results of the study, it could be concluded that the parameters calculated from field data were not very different from those determined by the SIRMOD II model. This indicated that the model predicted the volume balance of the field data with reasonable accuracy. It was also observed that the time of advance was shorter for the triangular shaped furrow and much longer for the rectangular shaped furrow. Performance efficiency parameters were good for the trapezoidal and triangular shaped furrows and very poor for the rectangular furrow. The tail water ratio (TWR) was much higher in the triangular furrow and lower in the rectangular furrow. Where there was no deep percolation ratio, the model failed to return a reasonable value.