Underground Water in South-Eastern Bechuanaland. 257 



on the flats between Vryburg and Kuruman there are several places 

 where open water exists all the year round. Springs are not 

 uncommon, and from them in not a few places abundant, and in 

 some cases inexhaustible, supplies of water have been obtained. 



The rock is well bedded and traversed by numerous joints, which 

 have often been widened by atmospheric agencies and solution. 



This produces a condition favourable to the downward passage of 

 water ; but if the process has gone on extensively, it may lead to the 

 transference of the water to deeper levels. 



There is no evidence as yet to show whether the movement of the 

 underground water in the dolomite is considerable or rapid. This is 

 a point of the utmost importance, for the rainfall in the east is very 

 much higher than that in the west, and any transference of water 

 from east to west will increase the underground supply in the region 

 of lower rainfall. 



There is a prevalent opinion that an underground river exists 

 beneath the Kaap Plateau ; an examination of the Kuruman district 

 will probably give much information about the movements of water 

 in the dolomite. 



There are numerous layers and concretions of quartzite and chert 

 in the dolomite which may render boring operations costly and 

 laborious. 



(d) Other formations. — The Dwyka formation, although of a very 

 clayey nature, gives a fair supply of water within the town of 

 Vryburg. The water is, however, hard, and has a faintly brackish 

 flavour. 



Certain chloritic slates and phyllites associated with magnetic- 

 quartzites give excellent supplies, e.g., at Kraaipan, but it is not 

 often that advantage can be taken of these beds. 



It is clear that however water-bearing a geological formation may 

 be, there is always a limit to the amount that can be removed from 

 it ; therefore it is essential that we should consider the influences 

 that tend towards the accumulation of water underground. 



(1) Rainfall. — This is by far the most important factor, and it is 

 unfortunate that records are available for but a few stations and date 

 back for only a short period. When the great fluctuation in the 

 value of the annual rainfall is taken into account, it is clear that a 

 long series of continuous observations will be required before any- 

 thing approaching the true mean can be obtained. 



The following values are therefore only approximations : Maf eking, 

 26 inches ; Vryburg, 24 ; Groot Boetsap (on the Kaap Plateau), 23 ; 

 Campbell, 15; Griqua Town, 16; and Kimberley, 20. 



