2l6 DEVELOPMENT OF THE COASTAL BELT OF SOUTH AFRICA. 



It will thus be seen that the run-off from the Buffalo River 

 catchment area per square mile is over 30 times as great as the 

 run-off from the Tarka River catchment area, and this may be 

 taken as a general indication of the proportion of run-oft' per 

 square mile, from what I term the rain belt of South Africa, as 

 compared with the dry interior. 



The overflow level of the dam at the Perie is about 1,800 

 feet above sea level. This may be taken roughly as the average 

 bottom elevation of the rain belt ; as a matter of fact, in this 

 district, it probably extends as low as 1,500 feet, and in some 

 parts of the coastal belt as low as 1,000 feet above sea level. But 

 roughly speaking, the contour levels of the rain belt may be taken 

 as lying, roughly, between 4,000 and 2,000 feet above sea level. 

 Most of the water which falls on this rain belt rushes away to 

 the sea, doing very little service to the country, but often doing 

 considerable harm by eroding the steep surfaces. Yet it has 

 great potential value, if properly controlled, so as to become 

 useful to man, a value which can well rival the diamonds and 

 gold of this country. Its potential value is threefold. First, 

 as a source of power; secondly, as a source of irrigation; and, 

 thirdly, as an abundant source of pure water supply for domestic 

 purposes, at a sufficient elevation to supply by gravitation large 

 urban populations along the coast lands. 



In dealing with either water for irrigation or power purposes, 

 it is justifiable to base your calculations on the average flow. 

 However, in dealing with domestic water supply, the minimum 

 possible flow must be taken, as a town cannot go without water 

 for a single day. On the other hand, if power-users or irrigators 

 have to be restricted once in five or six years, it is not a very 

 serious matter, and in the case of water used for irrigation, any 

 shortage of water due to a severe drought is probably compen- 

 sated by increased prices received for the produce. 



Power. 



It will be seen from Table 2 that the average measured run-off 

 from the Buffalo catchment area above the Kingwilliamstown 

 reservoir is 3,816 million gallons per annum. If this were all 

 stored, and allowing 500 million gallons for loss by evaporation, 

 etc., it would leave 3,300 million gallons per annum to be utilised, 

 or an average in round figures of 9 million gallons per diem. 

 This, in passing from the Perie to the sea, would fall 1,800 feet; 

 but as the distance between the Perie and the sea is about 50 

 miles, and the fall is more or less uniform, it could not be used 

 in one large power station, but would have to be used in a series 

 of mills every two or three miles down the river, in a similar 

 manner to that in which most of the rivers in England are 

 harnessed, to drive small grinding mills, etc., the tail water of 

 the one mill practically coming out at the level of the head water 

 of the weir below. Anyone acquainted with the West Midlands 



