196 T. W. E. DAVID AND F. B. GUTHRIE. 



much water as the Darling-Murray in time of flood ? At 

 the same time it must be remembered that according to 

 Mr. H. C. Russell's 1 estimates, the Darling River at Bourke 

 discharges only about l-§-°/° of the rainfall of its catchment. 

 The Murray River, on the other hand discharges about 25°/ a 

 of its total rainfall. 



The total amount of water passing over the delta during 

 a great flood, such as that of 1857, was estimated by Mr. 

 E. O. Moriarty to be 88,000 millions of cubic feet. Mr. 

 Darley on the other hand, quotes Mr. Gordon's estimate of 

 the capacity of a reservoir necessary to contain the surplus 

 water of a heavy flood as 24,514 million cubic feet, or 

 nearly fifteen times the full capacity of Prospect Reservoir. 2 



V.— Amount, Chemical Composition and Value of the 

 Flood Water Silt. 



In order to obtain some idea of the amount and fertilizing 

 value of the silt deposited on the land during the progress 

 and subsidence of a flood, samples of flood water and silt 

 were examined, derived from the recent heavy floods in the 

 Hunter and Hawkesbury Rivers. These waters being very 

 different in character will be discussed separately. 

 (a) Hunter River Flood Water, 



Samples of the] flood water of the Hunter River were 

 obtained through the kindness of Mr. A. J. Prentice of 

 West Maitland.^The water was collected on July 12th, 

 1901, from the centre of the stream off the Belmore Bridge 



' The Source of the Underground Water in the Western Districts, 

 Journ. Eoy. Soc. N. S. Wales, 1889, pp. 57 - 63. 



3 Floods on the Hunter, By Authority, Sydney 1891, p. 2. Mr. Price 

 estimated that the proposed reservoir below Denman to hold the flood 

 waters of the Hunter and its tributary the Goulburn, should have a 

 capacity of 40,000]million cubic feet, and this of course does not allow for 

 the water contributed by the Wollouibi brook (Cock fighter), Paterson, 

 and Williams rivers, etc., so that Mr. Moriarty's estimates may not be 

 excessive. 



