TRENDS IN RAINFALL TOTAL AND VARIABILITY (1970–2000) ALONG THE KWAZULU-NATAL DRAKENSBERG FOOTHILLS

Abstract

ABSTRACT South Africa's most valuable source of water is the eastern escarpment region of the KwaZulu-Natal Drakensberg and Lesotho highlands. These upper catchments supply much of KwaZulu-Natal, feed the Vaal River in the interior through two inter-basin transfer schemes and are important conservation areas. Analysis of rainfall and rainfall variability trends can thus contribute to a better understanding and management of the area and yet no recent studies have investigated these aspects. This study assesses the 1970–2000 rainfall period using 13 stations to the east of the escarpment in KwaZulu-Natal and presents a spatial perspective on annual rainfall totals and intra- and inter-annual variability. Altitude and distance from the escarpment eastward are found to influence total annual rainfall with an increase of 41.5 mm per 100m in altitude between approximately 1100m and 2100m a.s.l., and a corresponding decrease of 54 mm for every 10 km eastward from the escarpment. Neither inter- nor intra-annual rainfall variability is influenced directly by altitude or the relation to the escarpment. Latitudinal position is found to have no significant affect on station totals but variability increases from south to north in the Drakensberg, possibly related to the greater seasonal contribution by frontal rains in the south, or more variable annual storm activity in the north.