Comparative engineering costing and implications of commercial and smallholder irrigator design for projects

[摘要] ENGLISH ABSTRACT: In the study, six irrigation schemes based in the Eastern Cape have beenconsidered and evaluated, according to two levels of supply (LOS) of irrigationwater. The two levels of supply are that of a commercial irrigator and that of asmallholder irrigator. The irrigation infrastructure for each of the six schemeswas designed, and the associated costs determined, for each level of supply.The primary objective of the study is to determine the impact of infrastructurecosts and irrigation areas on the target user, either the commercial or thesmallholder irrigator. This is related directly to the assumption that lower watervolumes are used by the smallholder irrigator.The study addresses the impact of different designs on the amount of waterused, land utilised and resultant costs of the infrastructure.The initial capital costs and the on-going operational and maintenance costs(O&M) for each level of supply for each of the schemes have been calculated.The evaluation of the two LOS has shown that the capital cost for thecommercial LOS is approximately 18 % higher than for the smallholder LOSand the O&M costs 6 % to 36 % higher.The schemes that were investigated can be grouped into five general schemetypes. The first type is gravity schemes, which need rehabilitation, while the bulksupply is in place with no augmentation or rehabilitation required. The second ispumped scheme which is in need of rehabilitation, while the bulk supply is inplace with no augmentation or rehabilitation required. The third type includesrun-of-river schemes where water is abstracted and pumped directly to thelands. The fourth type includes run-of-river schemes where water is abstractedand pumped to storage. The fifth type is the gravity scheme where the bulksupply needs to be installed as part of the scheme. These types are thengrouped and can be used to give guidance on the anticipated costs dependanton the scheme type and the required level of service. A further objective of the research is to determine the impact on the smallholderirrigators who find themselves on a commercial LOS system. This can be eitheron a scheme that has already been designed, or on a new system.The evaluation of the commercial under-utilised LOS and the smallholder LOShas shown that the commercial capital cost is 18 % higher and the O&M costs5 % to 29 % higher.The study further aligns the estimated costs with the farmer typology providing abroader understanding of the design to be adopted for different levels of supply.This provides the linkage between farmer types, the design to be implementedand the anticipated costs thereof.

[发布机构] Stellenbosch University