n South African Journal of Economic and Management Sciences - An economic case for drainage for sustainable irrigation : case studies in the lower Vaal and Riet catchments : environmental and ecological economics

Volume 10, Issue 4
  • ISSN : 1015-8812
  • E-ISSN: 2222-3436



Where evaporation exceeds precipitation salinisation is inevitable. This paper presents a multidisciplinary framework of the dynamic interactions between the hydrology, bio-physical and economics of irrigated agriculture in a semi arid area. Status quo drainage and cropping situations are compared to a scenario of increased drainage and leaching and subsequent higher value crops. Stochastically generated hydrology data fitted to a salinisation:yield production function is inputted in a crop enterprise budget (CEB) simulation model.

Results show losses due to salinisation of up to R6 962/ha, which exceed the direct costs of installing drainage to control salinisation. Although feasible, farmers at this stage of degradation often do not have the financial ability to repay the loans. Where losses do not exceed the financial costs of drainage, soils are further degrading, higher value crops cannot be planted and potential benefits are lost to society, motivating a green box grant. A macro-economic analysis reveals that the potential benefits to society of drainage can repay the total cost of all necessary drainage in a short period of time.

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