386 PROCEEDINGS OF SECTION E. 



Friday, August 31. 



The Vice-President, Mr. G. S. Griffiths, F.R.G.S., F.G.S., of 

 Melbourne, in the Chair. 



The following paper was read : — 



1.— RIVERS OF NEW SOUTH WALES. 



By H. G. McKiNNEY, M.E., M. Inst. C.E., Engineer for Water 

 Conservation, N. S. Wales, late Engineer to the Royal Com- 

 mission on Conservation of Water, and formerly of the Irriga- 

 tion Dept., Upper India. 



The quantity of water carried by a river, and the regularity, or 

 otherwise, of its flow depend on a variety of causes and conditions. 

 Among these, the extent, elevation, and rate of slope of the catch- 

 ment area, the rainfall and climate, the natui"e of the formations 

 through or over which the stream flows, and the quantity and 

 description of the surrounding vegetation, all pi ay an important part. 

 It is evident that with such complexity of iniiuences at work the 

 quantity of water discharged by one river may be entirely 

 diflerent to that discharged by another of equal catchment area, 

 and with an equal rainfall. Hence formulae for the calcu- 

 lation of river dischages, based on extent of catchment area and 

 quantity of rainfall, are not only useless but misleading. Whilst 

 the discharge of a river throughout the entire length of channel 

 is increased by direct rainfall, and generally by surface flow and 

 underground percolation, it undergoes diminution throughout the 

 entire course owing to evaporation, to absorption by vegetation, 

 and frequently to percolation. 



If the course of a river be followed up, it will be observed that 

 the stream gradually diminishes till it becomes a mountain rivulet, 

 and it will be found on further examination that the position of 

 the source of the rivulet varies not only in different years but in 

 different seasons in the same year. These changes are generally 

 due to natural causes, and particularly to the varying conditions 

 of the rainfall ; but sometimes they are materially influenced by 

 human agency. Some interesting experiments and observations 

 on this subject were described in a paper read before the Royal 

 Society of New South Wales, on 6th June last by Mr. W. E. 

 Abbott. In the instance related by Mr. Abbott, the effect of 

 ring-barking the trees in a district timbered with Eucahjftxis was 

 to cause a permanent flow of water in several creeks which 

 formerly had run only after heavy rains. In other words the 



