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| A method for evaluating the economic benefit of sediment control in irrigation systems |
| The report describes how to determine the economic benefits of introducing sediment control structures at schemes where desilting costs are unacceptably large, or where sedimentation reduces the areas that can be easily irrigated An application of the procedure on an irrigation system in the Philippines is described. |
| Background Maintenance budgets in many run of river irrigation schemes are dominated by the costs of removing sediment from canals. The problem results from the limited sediment transporting capacity of most canal networks, and occurs when water is diverted from rivers carrying high sediment loads. Sediment deposition results in rising canal bed levels, reduced canal capacities, and problems in supplying the required amounts of water to some or all parts of the irrigated area. These problems can be reduced or eliminated by constructing sediment control structures. Such structures reduce the quantities of sediment entering irrigation systems by excluding sediment at river intakes, or extracting it from canal flows. Subsequent reductions in the amount of desilting required, lower the costs of sediment removal. Improvements in the reliability of water supply to downstream parts of irrigation systems enable the irrigated area to be maintained. The report |
productive
potential due to sedimentation. "With project" costs are calculated
on the basis that sustaining an acceptable irrigation service to the scheduled
area, and reducing desilting costs are primary objectives.
The second section of the report describes a verification of the evaluation procedure at the Agno River Irrigation System in the Philippines. Sediment control facilities consisting of a vortex tube sediment extractor and low level sluicing gates were constructed at the head of the main canal. Actual performance was then monitored and results compared with predictions made from use of the evaluation procedure. The report concludes that low cost sediment control structures, such as the one studied, will pay for themselves in a few years through reductions in desilting costs. Contributors Intended users |
| Available at: http://www.dfid-kar-water.net/w5outputs.html For a CD ROM or a hard copy contact: International Development Group, HR Wallingford Ltd, Howbery Park, Oxon, OX10 8BA, UK Tel: +44 (0) 1491 835381, Fax: +44 (0) 1491 826352, E-mail: w5outputs@hrwallingford.co.uk |
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