South African Workshop Presentations
Two Visibility Workshops have been held on the 28 – 30 January 2010 and 2-4 March 2011 and a Partner & Training Workshop on the 15 – 22 March 2013.
2.1 Abstracts of South African Workshop (January 2010)
2.1.5 Jatropha curcas: Assessing the potential water resource impacts of large-scale production in South Africa
Presenter:
Mark Gush
CSIR
In response to rising oil prices and the quest for alternative, economically viable and environmentally sustainable forms of energy, plant species with bio-energy potential such as Jatropha curcas have been proposed for large-scale planting and bio-fuel production. However, extremely limited data is available on the potential environmental impacts (specifically water-use) of J. curcas. Accurate estimates of water-use are fundamental to gaining a good understanding of the hydrological impacts of a specific plant species or vegetation type; especially should it be planted extensively.
In response to the proposed introduction of J. curcas to South Africa, field experiments were conducted to investigate its likely water-use impacts relative to other forms of vegetative land use. As no existing water-use data could be found for this species worldwide, sap flow (water-use) in J. curcas trees was measured continuously for a 17-month period at various sites in eastern South Africa. These consisted of young (4-year old) trees at a relatively wet site and mature (12-year old) trees at a dry site. Sap flow rates varied according to tree age, season, prevailing meteorological conditions, and soil moisture levels. Peak sap flow rates occurred during the warm wet summer months, but due to the deciduous nature of the species, water-use was negligible during winter.
Additional total evaporation (Et) measurements were also conducted for a year above a J. curcas trial near Pietermaritzburg, and confirmed the low water-use rates. Results from these measurements were combined with modelling exercises in an attempt to evaluate water resource impacts over a wider scale. It was concluded that the J. curcas trees studied were conservative in their water use, and were unlikely to transpire more water than indigenous vegetation types. However, it was also concluded that a holistic view of other potential environmental impacts as well as socio-economic considerations (e.g. food security and the relationship between water-use and production) were also important considerations.
