PRESIDENTIAL ADORESS— SECTION A. I() 



and will be, in q^reat demand, it will well repay landowners to 

 i)lant trees on land which is unsuitable for cultivation in other 

 respects. The time required for trees to matuie for provuhno 

 timber for industrial purposes will ran^e, accordinj^ to locality 

 and rainfall, from 8 to 15 years. The cost of planting, clearing, 

 supervising during growth, cutting down and preparing for the 

 n.arket will be about £10 per acre, whereas the value when ready 

 for felling will be in the neighbourhood of £30 per acre. Many 

 farmers are unaware of the value of timber trees, and it is 

 suggested that the Government Forest Department should, circu- 

 late information with reference to this matter to all farmers 

 within the Union. Apart from the monetary return for the 

 trees, the fact of there being large plantations all over the catch- 

 ment will tend to increase the rainfall to some extent, but the 

 principal advantages will be obtained owing to the dry weather 

 flow- of the river being increased and the maximum flood dis- 

 charge being less. This is a very important matter, for within 

 the last few years the Vaal River has been absolutely dry at 

 certain places between Parys and its junr*^ion with the Orange 

 River. 



Rainfall Records on the Vaal River Catchment Area. 



A table (B) is appended, which shows the rainfall at various 

 places within the Vaal River catchment area. As, however, the 

 records have not been observed in many cases over a sufficiently 

 long period to give correct averages, the number of years has 

 been stated in the third column of the table. The reference 

 numbers in the first column locate the position of the rainfall 

 station on Plate 2. 



A summary of the averages of each particular catchment is 

 also given in table (C), and the reference letters are shown on 

 tne map. 



It will be observed that the rainfall varies very consider- 

 ably over the Vaal River catchment area- For instance, the 

 Riet River area has a rainfall of only 13.58 inches, as compared 

 with 31.8 inches for the Wilge River. These rainfalls are for 

 fairly large areas, and individual rain gauges will register falls 

 from about 10 inches in the lower portion of the catchment to 

 45 or 50 inches at the sources of the Vaal. A fall of 14 inches 

 has been recorded within a period of 24 hours at Krugersdorp, 

 and 3 to 4 inches have been recorded, in an hour on several 

 occasions in the Transvaal. 



The rainfall records at Joubert Park, Johannesburg, for the 

 years 1902-1919 inclusive is shown on Plate 5. 



