Commercial plantations of introduced tree species provide most of the timber and fibre requirements of South Africa. However, not much is known about how much water is used for commercial forestry, how the water use varies among genera and regions, and how water used for commercial forestry compares with other competing land uses. The CGA, funded by the Water Research Commission of South Africa, is undertaking to describe, analyse and interpret location-specific differences in water use between and within the primary commercial forestry tree genera at specific locations in South Africa.
The first phase of this project is to identify and develop of a geodatabase the primary areas of commercial forestry in South Africa, including delineating compartment borders, and determining compartment age and genus. The figure below shows an initial output for this – the commercial forestry near Garcia overlaid on Landsat-8 imagery before (A1) and after (A2) preprocessing i.e. atmospheric correction and pansharpening. In order to automatically determine the age of the plantations, over 120 Landsat images spanning the last 20 years have been preprocessed in such a manner.
The second phase of the project, targeted for 2021, will be to quantify consumptive water use of individual forest compartments, validate these against historical in situ measurements and analyse and interpret spatial and temporal differences in water use.