Letters to the Editor (Water Wheel May/June 2011)

Abstract

Empty for a reason I refer to the article on Beer­ vlei Dam in the January/Feb­ ruary 2011 issue of The Water Wheel as well as the letter from CL Marechal (Pr Eng) on the same topic in the March/April 2011 edition. Mention was made in the original article that the main purpose of the project was that of flood attenuation for the lower Gamtoos Valley. In order to achieve this objective the reservoir of the Beervlei Dam needs to be empty at the start of the flood in order to store as much of the flood water as possible. The Karoo sediments in the area contain a lot of salts and it has been found that lengthy storage of water results in high water salinity. The mode of opera­ tion is that any floodwater is used as quickly as possible Letters to the Editor Upfront by the downstream irrigators and the reservoir is thus kept empty for flood absorption purposes. A similar flood attenuation dam has been built upstream of the town of Ladysmith (KwaZulu­Natal) and this dam has a large uncontrolled outlet in its base to ensure emptying after a flood.

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