Effect of Gate Selection on the Non-Cohesive Sedimentation in Irrigation Schemes

Abstract

In order to cover the crop water requirements, flow control structures such as gates and weirs are used to transfer the desired amount of water from the canals to the field canals. This paper examines the impact of gate operation and the selection of gates on the deposition of non-cohesive sediment. The Delft3D model is used to simulate the effects of different scenarios regarding gate operation and the location of the gate that is opened. The model results showed that the gate selection affects not only hydraulic parameters but also morphological parameters. It was found that opening the gates closer to the offtake resulted in less sediment deposition at the entrance of the branch canal when compared to opening the gates further away. Gate selection can be used as a tool in sediment management. By alternating the opening of different gates sediments that are already deposited after opening one gate can be eroded when another gate is operated, thus minimizing the additional cost of sediment removal. The use of Delft3D proved beneficial as the selection of different gates leads to asymmetric sediment deposition patterns which would be missed when using a 1D model.

Sediment Influx and Its Drivers in Farmers’ Managed Irrigation Schemes in Ethiopia

“…A lack of resources for operation and maintenance aggravates problems of excessive sedimentation [17], as the physical infrastructure of many schemes is deteriorated. In farmer-led schemes, farmers apply tacit knowledge to temporarily reduce the quantity of sediment entering their irrigation schemes, for example, by delaying water abstraction when river sediment loads are particularly heavy [16] and diverting surface runoff to prevent it from entering the canal (Figure 1).…”

Challenges and prospects to reduce sedimentation in small-scale irrigation schemes in the Great Rift Valley Basin, Ethiopia

“…Although topography is a key factor in the location of irrigation system intake structures, the distance from the intake to the field plots is crucial in determining the quantity of sediment that enters the canal (de Sousa et al, 2019;Theol et al, 2020a). The greater the distance from the intake to the field plots, the greater the observed sediment deposition in the schemes.…”

“…Ethiopia experience the most serious erosion in the world (Erkossa et al, 2015;Gelagay and Minale, 2016;Haregeweyn et al, 2017), one of the most significant adverse environmental problem in developing countries. Excessive sedimentation in irrigation systems gradually blocks the flow of irrigation water, causes water stress and unfair distribution (Theol et al, 2019a), damages infrastructure, and may trigger the complete collapse of irrigation systems. Since irrigation is a major consumer of water (He et al, 2018;Li et al, 2019), the loss of water due to damage to infrastructure by excessive sedimentation results in a decline in water availability and increased competition among different water uses and users.…”

“…Despite the foremost role of local norms, values, and knowledge, as well as institutions and stakeholders, in managing excessive sedimentation in irrigation schemes, few studies address these aspects directly. Most research rather investigates sediment transport, focusing essentially on understanding sedimentation processes and modeling sediment transport (Depeweg and Mendez, 2007;Depeweg and Méndez, 2002;Depeweg et al, 2016;Munir, 2011;Osman, 2015;Paudel, 2010;Theol et al, 2019a;Timilsina, 2005). Improved operation and maintenance of the system and real and coordinated participation of concerned stakeholders are crucial in dealing with excessive sedimentation problems.…”

“…A lack of resources for operation and maintenance aggravates problems of excessive sedimentation (Theol et al, 2020a), as the physical infrastructure of many schemes is deteriorated. In farmer-led schemes, farmers apply tacit knowledge to temporarily reduce the quantity of sediment entering their irrigation schemes, for example, by delaying water abstraction when river sediment loads are particularly heavy and diverting surface runoff to prevent it from entering the canal (Figure 4.1).…”