DEVELOPMENT OF THE COASTAL BELT OF SOUTH AFRICA. 215 



Note. — I inch of rainfall over the catchment area equals in 

 round figures 210 million gallons. 



Table 2 gives the total run-off for these years, and Table 3 

 gives the percentage of run-off for the wet and dry periods dur- 

 ing the same time. It will be observed that the percentage of 

 run-off is very high. The greater the rain-fall, the greater the 

 percentage of run-off. In 1917, when there was no dry period 

 during the whole year, there was nearly 40 per cent, of run-off. 



In his Annual Report for 1918 the Director of Irrigation 

 gives a table showing the run-off from the Tarka River catch- 

 ment area for the years 1914-1917, from which I have extracted 

 the information in Table 4. which shows at a glance the difference 

 m the run-off from a typical Karoo area like the Tarka River and 

 a typical coastal rain belt area like the Perie. 



Table 4. 



Run-off per Square Mile in Gallons. 



Year. Tarka River. Buffalo River. 



1914 5,517,000 293,000,000 



191 5 7,352,000 175,000,000 



1916 7,000,000 163,000,000 



1917 1 1,300,000 389,000,000 



31,169.000 1,020,000,000 



Average 7,790,000 255,000,000 



