Study Area

Maize yield forecasts were developed across various climatic regions of South Africa, where these regions were represented by selected Quaternary Catchments (QC). A QC is the smallest (fourth level) catchment subdivision used in general water resources planning in South Africa, and may be considered to be a relatively homogeneous natural response unit. The QCs, which generally range in area from 100 to 600 km2, also represent a convenient scale for generating crop yield forecasts, as associated databases of climate and soil information to facilitate the production of the forecasts, are available at this scale. Fifteen QCs were selected for consideration in the study, these catchments being in poverty stricken former "homeland" regions where small-scale/ subsistence farming is practiced and where household food security is lacking. The location of the QCs within South Africa is shown in Fig. 21.1.

The QCs represent a range in rainfall regimes and allow the yield forecasting methodology to be tested under a variety of conditions. Mean annual precipitation in the catchments varies from 330 mm to 910 mm, with the wetter areas being in the east and the drier areas in the west. The 15 selected catchments fall within the summer rainfall region of the country in areas where it is climatically feasible to grow maize (Schulze 2003).

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