The use of Delft3D for Irrigation Systems Simulations

Abstract

Irrigation systems performance and sustainability are affected by sediment deposition. Cohesive sediment (suspended load) is an important problem in irrigation canals and its behaviour is significantly different from that of non‐cohesive sediment (bed load). Most studies on sedimentation in irrigation systems deal with non‐cohesive sediment. Studies on cohesive sediments are mostly done in rivers and estuaries, but not in irrigation canals. The few existing studies on cohesive sediment in irrigation canals are limited by their use of 1D models. Therefore, in this study we test whether an existing 3D model that was designed for rivers and estuaries can be used in irrigation canals. Delft3D was identified as a suitable model. Simulations were done for different sizes and configurations of the irrigation network. After some adaptations to the model, the simulations of different scenarios provided promising results. From a hydrodynamic and morphological point of view the Delft3D model was able to realistically represent water and sediment flows in a hypothetical canal set‐up, consisting of a main canal, a branch canal and several hydraulic structures. Some challenges remain in the use of Delft3D for irrigation canals, in particular regarding wall roughness in small rectangular canals and computation times for complex systems. However, these challenges are not insurmountable and the advantages of using Delft3D are clearly shown in this paper. © 2019 John Wiley & Sons, Ltd.

Stakeholder Roles and Perspectives on Sedimentation Management in Small-Scale Irrigation Schemes in Ethiopia

“…Ethiopia experience the most serious erosion in the world [17][18][19], 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 [20], damages infrastructure, and may trigger the complete collapse of irrigation systems. Since irrigation is a major consumer of water [21,22], 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 modelling sediment transport [20,23,[32][33][34][35][36][37]. Improved operation and maintenance of the system and real and coordinated participation of concerned stakeholders are crucial in dealing with excessive sedimentation problems.…”

The Role of Gate Operation in Reducing Problems with Cohesive and Non-Cohesive Sediments in Irrigation Canals

“…So far the Delft3D model has been used primarily for rivers [23][24][25][26] and for estuaries [21,27] in 2D and/or 3D modes. The model has been used by Reference [16] for irrigation canals in both 2D and 3D. Running the model in 2D mode is to ensure better representation of the sediment processes and the large scale behavior with an acceptable simulation time period.…”

The role of gate operation in reducing problems with cohesive and non-cohesive sediments in irrigation canals

“…Most studies regarding cohesive sediment behavior have been done in rivers and estuaries [10][11][12][13][14][15]. There is a great need to study the mechanism of cohesive sediment transport in irrigation canals [16], in particular under different scenarios of gate operation.The impact of gate operation on the cohesive sediment in the Gezira Scheme in Sudan has been studied by Reference [17]. They considered two gate operation scenarios: (1) a system in which water allocation is based on water duty and the cropped area and water is given by a fixed discharge for one week.…”

“…Most studies regarding cohesive sediment behavior have been done in rivers and estuaries [10][11][12][13][14][15]. There is a great need to study the mechanism of cohesive sediment transport in irrigation canals [16], in particular under different scenarios of gate operation.…”