THE SURPLUS WATERS OF THE ZAMBEZI [To the Editor of
the SPECTATOR.]
Sin,—Last year the Government of the Union of South Africa sent an expedition up the Zambezi river from the Victoria Falls, to investigate the possibilities of diverting the flood water of that river and sonic of its tributaries to the south- wards into the basins of Lake Ngami and the Makarikari.
It had been propounded by Professor Schwarz that it would be possible to fill all this low country from the surplus water, of the Zambezi and so by producing a huge sheet of water, where at present there exists mostly desert, to increase the humidity of the atmosphere and thus to some extent increase the rainfall over the adjoining territory, where an average annual rainfall of only a very few inches above the present would be of great benefit.
The question is fully discussed in a very interesting report on the " Kalahari Reconnaissance " issued at Pretoria by the Union Government. The conclusion is there arrived at that although all the low-lying country could be converted into a sheet of water it would have little effect on the rainfall on the adjoining land of Bechuanaland and Rhodesia, and the Transvaal further to the eastwards.
. Several suitable sites were located and examined on the Zambezi where a dam or weir might be built, and the extra- ordinary. fact was discovered that a dam built on one of these sites to a height of some seventy feet would in all probability stop the flow of the river, except in a year of very exceptional rainfall, which might occur at rare intervals. In other words the huge volume of water carried by the Zambezi river would never be sufficient to fill the dam, as the loss from seepage and evaporation over the expanse of country would more than equal the supply of water brought into it. Nowhere else in the world, I think, do such conditions obtain with a river anywhere approaching the size of the Zambezi.—I am, Sir, &c.,
Shamva, Southern Rhodesia. J. M. MOUBRAY.
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