DISCUSSIONS 



Session I. 

 CLIMATE AND PHYSICAL ENVIRONMENT 



Chairman Dr Edward Hindle, F.R.S. 



In the discussion that followed the first session, Professor J.A. Prescott, 

 F.R.S. said that there was no nomadism in Australia, but that cattle moved to new 

 green areas after each thunderstorm. There were no fences in Northern Australia 

 to restrict their movements, and permanent water- holes were kept as a final re- 

 serve: Canning stock routes had been used only once since their establishment and 

 were difficult to maintain. The scattered nature and local distribution of rainstorms 

 had long been recognized by pastoralists engaged in cattle rearing on the tropical 

 margins of the Australian deserts, and played a part in determining the size of 'pad- 

 docks'. Cattle moved towards more favoured areas during the dry season and would 

 be stopped by fences. 



Considerable experience had been gained in Australia on the use of water for 

 irrigation, stock and domestic purposes. In the neighbourhood of Adelaide water 

 containing 800 parts per million total salts was regularly used for irrigation and was 

 supplemented by 20 inches of rain falling in winter. Probably the longest record of 

 the satisfactory use of such water for irrigation came from Siwa Oasis where waters 

 containing 2,000 parts per million of salt had been in use. An extraordinarily effi- 

 cient drainage system had made possible an unusually permanent irrigated agricul- 

 ture. In Southern Australia the search for underground waters was of lively interest 

 to the Department of Mines and Geological Survey. The existence of overlying 

 saline ground waters was frequently observed, and attempts were made to avoid 

 mixing these with fresh water from lower levels. 



Asked whether water could be de-salinized chemically, Professor F. W, Shot- 

 ton replied that the operation was costly, required skilled supervision and was 

 therefore not practicable, but Dr H. Boyko said that methods were being investigated 

 at Harvard and the Weizman Institute. Another speaker pointed out that in hot cli- 

 mates saline drinking water was desirable, and Dr N. Wright enquired about the ade- 

 quacy of geological knowledge. Professor Shotton agreed that such knowledge was 

 still inadequate and that the details were largely unknown. Although the quality of 

 underground water could not be determined in advance, geophysical methods could 

 increase the proportion of productive borings. Dr C. B. Uilliams asked about the 

 wells at Fuca, and Professor Shotton answered that there had been two native wells 

 there. 



Mr J. Tosic said that a distinction must be drawn between 'free* and 'bound' 

 water in the analysis of desert soil samples, and Mr H. Green pointed out that irri- 

 gation was associated with a stable system of agriculture but that there were transi- 

 tional stages leading to nomadism. The flood waters of the Nile did not follow pre- 

 cisely the same course each year. The inland deltas of the Gask and Barak rivers 

 in the Anglo- Egyptian Sudan and Wadi Bana at Aden each year received violent 



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