SECTIONAL TRANSACTIONS.— E. 345 



mates by means of interpolation. Area in the Western Karroo, which mu.st bo 

 -called desert according to Koppen, or classified under the driest type of arid climate 

 according to Hirth. Comparison with other dry regions. 



3. Distribution of population in the Western Karroo. Small direct influence of 

 rainfall. Comparison of density-figures with those for the Kalahari, the American 

 Plateau States, and the dry regions of Australia. 



4. Economic conditions and the human and natural factors by which they are 

 determined. No mining ; no industries ; types of farming. Geology. Relief. 

 Nature of Vegetation. River-system. Underground water. Historical influences. 

 Character of population. Transport. Markets. 



5. Conclusions. Reasons why the Western Karroo cannot be called a desert in 

 the geographical sense of the word. 



Mr. R. J. Van Reenen. — Utilisation of Available Water Supplies in 

 South Africa. 



This paper treats mainly of conditions within the boundaries of the Union of 

 South Africa and the mandated territory of South-West Africa. 



The sub-continent consists of a moderately humid coastal belt, surrounding a 

 high-lying plateau on which the rainfall, usually considerably smaller than on the 

 marginal area, diminishes from east to west. 



The purposes for which water is used fall broadly into the following classes : — 



(i) Domestic, 

 (ii) Agricultural and stock farming. 



(iii) Fishing. 



(iv) Power producing. 

 (v) Industrial, and 



(vi) Transport. 

 While all these uses are interesting and of importance to society, the use of water 

 in maintaining life, that is in agriculture and stock farming, is of prime importance 

 and of the most interest to the Association. 



The country is divided into winter- and summer-rainfall zones. The raising of 

 crops in the former is possible on a much smaller annual rainfall than in the latter. 

 Where the rainfall is insufficient agriculture is possible only under irrigation. The 

 ultimate extent of irrigation in South Africa is definitely limited both by the rainfall 

 and the low percentage run-oS. Owing to the nature of the incidence of the rainfall 

 large storage works are necessary. Omng to the nature of the country such storage 

 works are costly. 



The water reaching the rivers and water-courses is but a small proportion (about 

 6i per cent.) of the total water falling on the country in the form of rain. The efficient 

 utilisation of the remainder (93J per cent.) is of far greater economical importance to 

 the country. To render the use of that water more beneficial, improvement in the 

 methods of dryland farming and, what is perhaps economically even more important, 

 improvement in the practice of grazing, is needed. 



The problem of increasing the pastoral products of the country has up to the 

 present been almost entirely a problem of jackal extermination, and the most 

 successful weapons yet devised for the combating of the jackal are fencing and bore- 

 holes. 



Underground water for drinking purposes can be obtained by means of wells or 

 relatively shallow bore-holes, without great difficulty. But little artesian water has 

 been developed. 



Dew ponds do not provide a feasible method of supplying water for the greater 

 part of the sub-continent. In South-West Africa underground dykes or ' grund- 

 schwelle ' are employed with great success in obtaining water from the beds of inter- 

 mittent streams. 



Legal and financial phases of the matter are beyond the scope of this paper. 



Thursday, July 25. 



Dr. Marion Newbigin. — The Mediterranean Climatic Type : its World 

 Distribution and the Human Response. 

 The paper includes a comparative survey of the five world regions in which the 

 Mediterranean type of climate occurs in typical form. It is pointed out that of these 



