ABSTRACT
The conveyance capacity of the run-of-the-river canal irrigation networks is reduced by the accumulation of sediment. In many canal network systems in general and for the Gezira Scheme in particular mechanical removal of sediment is costly. The installation of sediment ejector or excluder is often proposed as a sound alternative option. The adoption of a suitable device for sediment removal depends on the type of sediment (wash, bed, or suspended load). For the case of Gezira Scheme sediment basin at strategic locations in the canal network is recommended as possible solution due to domination of very fine sands and silts particles in the incoming sediment laden water, but it is not implemented yet, due to the large area occupied by the design basins. In this study, a simplified design procedure for settling basins using the Camp (1945) trapping efficiency criterion is developed. The adopted analytic approach assumes prevalence of velocity distribution in a uniform flow condition and uses a simplified one-dimensional equation to ensure reduced flow turbulence by determining Froude Number. The proposed procedure depends on periodical flushing of the sediment basin, and on the offer of alternative option to insert inclined plates in the basin to improve its loading rate, and to upgrade its trapping efficiency. In the model geometric configurations of the basin were identified, which can remove even the fine sediment (0.055 to 0.22 mm) from flow with high removal efficiency determined in accordance with Camp (1946). The parameter of design, operation, flushing, and diversion structures were included in a spread sheet based simplified and user interactive model. The developed model is verified by its comparison with the design of sediment basin proposed for El Golid Pump station in North Sudan. The well validated model is applied to the case of Gezira – Sudan gravity Canal network (Main, Major, and Minor canal). The results of application of scheduled flushing mode of operation proposed by the developed model revealed substantial reduction in area occupied by the basins with higher trapping efficiency. Application of the analytical design procedure for design of efficient sediment basin in earth irrigation canals supplied with sediment laden water resulted in economizing area occupied by basin system compared to current designs. Employing the concept of periodical flushing of sediment laden water resulted in reduction of basin capacity compared to end season flushing recommended by many consultants. Installation of inclined plates inside a basin in a Major Canal in the Gezira Scheme, although it reduces the flow length it results in more improvement in removal efficiency (by 95%) due to its retardation of the flow velocity and increases the retention time. It is thus, expected that these results have an important role in optimizing the design to enhance the Small Sediment removal efficiency of the settling basin.
Support the magazine and subscribe to the content
This is premium stuff. Subscribe to read the entire article.
