Handbook for Irrigation of Wine Grapes in South Africa

Chapter 1

Hot semi-arid steppe Cold semi-arid steppe

Hot & dry summer (Mediterranean) Warm & dry summer (Mediterranean)

Humid subtropical with dry winter Subtropical highland with dry winter

Humit subtropical without dry season Temperate oceanic without dry season

Hot arid desert

Cold arid desert

FIGURE 1.2. Climate types for South Africa according to the Köppen-Geiger classification with average summer and winter temperatures in major cities and towns (downloaded from https://maps-southafrica.com/weather-map-south-africa).

Using the Köppen-Geiger classification can be explained by means of the following examples for Stellenbosch, Robertson and Lutzville: (i) At Stellenbosch less than 70% of the annual precipitation occurs in winter (Table 1.3). Therefore, the P threshold = (2 x mean annual temperature) + 14 = (2 x 17.3) + 14 = 48.7. Since the mean annual precipitation is more than 487 mm (= 10 x 48.7), it is not an arid climate. Given that the temperature of the hottest month is more than 10°C, and the temperature of the coldest month is between 0° and 18°C (Table 1.3), it is a temperate climate. Since precipitation in the driest summer month is less than 40 mm, and less than the precipitation in the wettest winter month divided by 3 (122.3 ÷ 3 < 40), it is regarded as a dry summer. Furthermore, the locality has a warm summer since the hottest monthly mean temperature is less than 22°C (Table 1.3), and the monthly mean

IRRIGATION OF WINE GRAPES 17