38 PRESIDENTIAL ADDRESS SECTIO,\ A. 



reasonable, if larg-e irrigable areas are available within a reason- 

 able distance from a dam site. 



Irrigation Act No. 8 of 191 2. 



According to the Irrigation Act No. 8 of 191 2, the water 

 of a public stream is subject to use for primary, secondary, and 

 tertiary purposes. 



(A). Primary use is for water used by stock and for domestic 



purposes. 

 (Bi). Secondary use is for irrigation. 

 (C). Tertiary use is for mechanical or industrial purposes. 



The development of power will, therefore, come under 

 tertiary use ; but the water is subject to a reasonable secondary 

 use for lower riparian owners. 



In storing water for tertiary purposes provision must, there- 

 fore, be made for the protection o'f lower riparian owners, and 

 the Water Court will fix the ''normal flow" of the stream. 

 This i'. in practice, usually based upon the dry weather flow 

 during the months of May, June, July, August, September and 

 October, but it does not follow that such a ]>erio(l is or will be 

 taken as the basis. 



Tn the case of the Rand Water Board's i\.ct, the average 

 flow per day, taken over a period of 10 years for the months 

 May to October (inclusive), was taken as the basis, and although 

 thf actual figure was only 167 cusecs, the normal flow at the 

 bp.rrage site was fixed at 250 cusecs. 



Monthly Discharge of the Vaal River. 



It will be observed, by referring to Table " E," which 

 gives the average monthly flow of the Vaal River at Vereeniging 

 over a period of 13 years, that the greatest average monthlv flow 

 is in January, with 22,507 million cubic feet, while the lowest 

 average monthly flow is in June, with 556 million cubic feet. 

 During October, 1903, the registered quantity at the Vereeniging 

 weir for the month was only 145 million cubic feet. The lowest 

 recorded daily flow at the Vereeniging weir has been 4 cusecs ; 

 but the Vaal River, below Parys. has stopped running for several 

 weeks together during a very dry season. It therefore follows that 

 either auxiliary steam or oil plant, or storage in reservoirs, must 

 be provided where hydro-electric schemes are installed to cover 

 the period of low flow. In the circumstances, the best financial 

 results 7vin be obtained by a joint pozwr and irrigation project, 

 for it is out of the cjuestion to erect auxiliary plant for developing 

 power during the dry season, owing to the high capital cost of 

 two separate plants. 



Development of Water Power from the .Vaal River. 

 The provisiou of cheap motive power is one of the principal 

 factors in the industrial progress of any country. The usuat 



