Canals
Canals differ from pipelines primarily in that they are visible structures, while pipelines are mostly buried. Secondly canals need to be constructed to a predetermined gradient as this influences the velocity of the liquid, and hence the flow. Pipelines on the other hand can tolerate inundations, since the enclosed environment of the pipeline allows pressure to develop, and the only real requirement for flow is that there is sufficient pressure at the start of the pipeline to overcome friction losses and elevational differences. (The other factors that have a major influence on flow in both pipes and pipelines are the cross sectional area and the roughness).
An advantage of canals is that the flow is clearly visible all along the length of the canal and it is relatively easily to measure this flow. In the event of a reduction in flow between point A and B, the water may be diverted elsewhere, and the canal inspected for cracks etc. Once these have been identified it is generally a simple matter to make the necessary repairs. It is also a simple matter to divert water out of a canal and into a furrow for purposes of flood irrigation for example. On the other hand canals are subject to evaporation losses whereas this is not the case with pipelines, but if pipelines become blocked this may present a major problem, while in the case of a canal all that is required to remove the blockages is a shovel.
Following are some examples of some small canals have been constructed/rehabilitated for use by rural farmers.
1. Rehabilitation of 7 km canal in Tongwane River Gorge
2. 1400m canal (article to follow)
3. Rehabilitation of stone masonry canal (article to follow)
An advantage of canals is that the flow is clearly visible all along the length of the canal and it is relatively easily to measure this flow. In the event of a reduction in flow between point A and B, the water may be diverted elsewhere, and the canal inspected for cracks etc. Once these have been identified it is generally a simple matter to make the necessary repairs. It is also a simple matter to divert water out of a canal and into a furrow for purposes of flood irrigation for example. On the other hand canals are subject to evaporation losses whereas this is not the case with pipelines, but if pipelines become blocked this may present a major problem, while in the case of a canal all that is required to remove the blockages is a shovel.
Following are some examples of some small canals have been constructed/rehabilitated for use by rural farmers.
1. Rehabilitation of 7 km canal in Tongwane River Gorge
2. 1400m canal (article to follow)
3. Rehabilitation of stone masonry canal (article to follow)