398 Report S.A.A. Advancement of Science. 



more costly methods of supply ; and, further, it has been the means 

 of improving the quality of the water used for drinking purposes. 

 This source of .supply is also being utilised for the water supply of 

 small towns and villages. Avhere its importance in yielding pure sup- 

 plies of water, and thus eliminating the danger to public health from 

 water-borne disease, is being recognised. 



PRESENT POSITION. 



The present position, then, with regard to a water sujjply from 

 underground sources for the Colony is briefly this. Just beneath 

 the surface of the ground is stored a supply of water which, if utilised, 

 would be an important factor in the development of the industries 

 of the country and ensure its material prosperity ; and, further, it has 

 been proved that this water sujiply can be put on the land at a very 

 reasonable cost. As it is extremely doubtful if any other part of 

 South Africa possesses such ample supplies under the same conditions 

 of accessibility, the valuable nature of this resource is apparent, and 

 the desirability of proceeding to take achantage of it becomes obvious 

 to any one interested in the progress of this Colony. The question, 

 then, arises as to what extent this source of water supply can be made 

 use of. Unlimited it cannot be, as water is not manufactured in the 

 earth but comes from the atmosphere above, so the rainfall must ht 

 considered. 



RESERVES OF UNDERGROUND WATER. 



The distribution of the annual rainfall over the area of the 

 Colony not only varies in quantity but also in season of the year, 

 a greater part of the country enjoying summer rains, and only that 

 portion on the West and South receiving winter rains. The annual 

 quantity in the North-Western districts is small, but as it increases 

 towards the East and South considerably it is possible that the rocks 

 of the drier <listricts contain nifjre water than actually falls on the 

 ground immediately above them ; in fact, the movements of 

 underground water, as far as they are known at present, would seem 

 to indicate that water travels immense distances in the cnist of the 

 earth, descending by the faults and fissures of a formation in one 

 part of the country and ascending by other channels, in different 

 strata, in quite another region. In view of this possibility, and of the 

 fact that the rainfall, although only lo inches over a half of the 

 Colony, ranges up to 30 inches over the rest of the countrv. it would 

 not appear to be making an exaggerated estimate of the quantitv 

 which percolates into the ground and feeds the reservoirs of water 

 in the rocks if 2J, inches be taken as the average all over the Colon\ . 

 Assuming this calculation to be correct, the part of the annual rain- 

 fall which feeds the subterranean reservoirs amounts to a dailv 

 quantity of 27.715 million gallons, whereas the total quantity now- 

 daily drawn from it by all the boreholes put down up to the present 

 time is not more than 25 million gallons, so that no efforts of ours 

 need be limited by any fear that the general reserves of underground 



