Heavy Daily Rainfall Characteristics over the Eastern Botswana

Oliver Moses

Keywords

Modelling, Environmental systems, Simulation, Water resource management, Heavy daily rainfall intensity

Abstract

Heavy or extreme daily rainfall can result in increased storm water runoff or flooding. This can lead to transportation of more contaminants into drinking water resources, overloading of storm water and wastewater systems which might force additional funds to be sought to augment management facilities, and can also pose design challenges on structures such as dams. Rainfall records have been used to assess the characteristics of heavy daily rainfall in terms of its intensity and the number of days with these events over the eastern Botswana. This is crucial in addressing increased storm water runoff or flooding concerns. All the stations that have been selected for analysis experienced heavy daily rainfall of at least 50 mm. The highest heavy daily rainfall events across the stations ranged between 125 and 171 mm. Three of the seven stations had increasing trends in the intensity of their heavy daily rainfall, two had decreasing trends, while the other two did not show a clear direction of the trend. The Mann Kendall test indicated that only one of the seven stations had a statistically significant trend at the standard 5% significance level. On annual basis, the highest number of days with heavy daily rainfall events at the stations was 5.

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