Abstract
Five-minute rainfall data measured at different stations in the KwaZulu-Natal Drakensberg are presented and although the data are limited this paper is the first to analyse individual rainfall events in the area. The occurrence of rain days in the Drakensberg shows strong seasonality with most rain recorded during the summer months. Although the number of rain days as well as the number of rainfall events increases with an increase in altitude, the mean daily rainfall and mean rainfall generated from individual events is less on the escarpment than in the foothills. All stations show a high percentage of rain days with single rainfall events as well as a high proportion of rainfall received from events generating more than 10 mm, but the escarpment station receives less rainfall from these events than the stations in the foothills. It is known that rainfall in the Drakensberg is mostly generated from thunderstorms, and data presented here indicate that rainfall predominately occurs in the late afternoon / early evening when sufficient cooling has possibly taken place for condensation and cloud formation to occur.
Highlights
Declared a Trans-Frontier National Park, the Drakens berg is part of the main escarpment of Southern Africa, which extends as a passive margin around the sub-continent and reaches above 3 000 m on the watershed border between KwaZulu-Natal and Lesotho
Even though daily rainfall and mean rainfall from individual events are less on the escarpment, the number of rain days as well as the number of rainfall events increases with altitude
All stations show a high percentage of rain days recording single rainfall events and these events contribute between 61 and 81% of the total daily rainfall
Summary
Declared a Trans-Frontier National Park, the Drakens berg is part of the main escarpment of Southern Africa, which extends as a passive margin around the sub-continent and reaches above 3 000 m on the watershed border between KwaZulu-Natal and Lesotho. Glenisla recorded the highest rainfall per day of 62.4 mm, while RNNP, Sani Pass and the Outpost measured maximum daily rainfall of 59.8 mm, 55.6 mm and 44.4 mm respectively. Natal National Park (RNNP) measured 1 559.4 mm of rainfall event as a storm when total rainfall exceeds 12.5 mm, maximum from December 2001 to April 2003 in 166 rain days, while Sani 5 min intensity exceeds 25 mm·h–1 and the event is isolated by TABLE 1 Daily rainfall characteristics measured at the recording stations in the KZN Drakensberg. Sani Pass measured 231 rainfall events during the recording period, while Injisuthi Outpost, RNNP and Glenisla measured 223, 205 and 161 respectively (Table 2). Sani Pass and RNNP have the highest number of days (5) measuring three rainfall events, while the Outpost only measured three discreet rainfall events on 3 d and Glenisla did not record a single day with three rainfall events. Rainfall events at Sani Pass with rainfall above 10 mm only generate 47 % of the total rainfall
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