- Title
- Quantifying the water savings benefit of water hyacinth (Eichhornia crassipes) control in the Vaalharts Irrigation Scheme
- Creator
- Arp, Reinhardt
- ThesisAdvisor
- Fraser, Gavin
- ThesisAdvisor
- Hill, Martin
- Date
- 2016
- Type
- Thesis
- Type
- Masters
- Type
- MEcon
- Identifier
- http://hdl.handle.net/10962/409
- Identifier
- vital:19956
- Description
- Global fresh water resources are under increasing pressure from an ever-growing population and global economic development, highlighting the need for sustainable water management. Effective sustainable management must also control any additional factors that may aggravate the water scarcity problem. Invasive alien plants present such an aggravating threat, and pose a particular problem for water scarce countries in particular. South Africa is not immune to this global phenomenon, with plant invasions estimated to carry an annual loss of R5.8 billion in water provisioning services. Given the country’s semi-arid climate, and relative water scarcity, the threat presented by invasive plants needs to managed effectively for the sustainability of the countries already scarce fresh water resources. One species in particular, water hyacinth (Eichhornia crassipes), is regarded as one of the most destructive aquatic weeds in the world. The threat presented by this weed is of particular concern for economically productive water resources, such as irrigation water. Through high levels of evapotranspiration, water hyacinth leads to substantial water losses that could otherwise have been used more productively, thereby creating an externality on irrigation fed agriculture. An economic valuation of irrigation water and the loss thereof from water hyacinth, is a step towards improved water management and alien plant control. This will provide policy makers, stakeholders and irrigation managers with the relevant information they need to improve sustainability, allocate scarce resources more efficiently and enhance the returns to water. This thesis provides such an evaluation of the benefits of water hyacinth control, using the Vaalharts Irrigation Scheme as a case study. The benefit of water hyacinth control programmes are essentially ‘avoided costs’ of no control. The study quantified the water saving benefits of water hyacinth control for the Vaalharts Irrigation Scheme at Warrenton Weir on the Vaal River, South Africa. Three evapotranspiration to evaporation (ET:EW) ratios at three levels of invasion (100; 50 and 25% cover) were used to estimate the net annual water loss at Warrenton Weir. A Residual Value Method was employed to estimate the average production value of irrigation water, to serve as a proxy for the value of water lost via evapotranspiration by water hyacinth. The average production value of irrigation water for the Vaalharts was estimated to be R300/m3, which translated into an annual benefit of between R500 million and R9 billion. However, due to various limitations associated with the valuation method, the inflationary bias of estimating the average value of water and the unlikelihood of ET:EW ratios being larger than 1.4 in reality, it was suggested that R500 million was the more realistic value of the benefit of control. Despite being a conservative estimation, the benefit still equated to a quarter of the annual production value of the irrigation scheme, suggesting the water hyacinth could potentially reduce the productivity of the scheme by as much as 25% in the event of a scarcity of water on the scheme. The results of this research highlight the need for invasive plant control, especially where invasions affect economically productive water resources. Therefore, it is recommended that alien plant control policy prioritise invasions of this nature, as they present significant costs to the economy yet carry substantial benefits.
- Format
- 163 leaves, pdf
- Publisher
- Rhodes University, Faculty of Commerce, Economics and Economic History
- Language
- English
- Rights
- Arp, Reinhardt
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