WATER CONSERVATION, IRRIGATION AND DRAINAGE IN N.S.W. 225 



the formation of outflow channels, with the ultimate prospect of 

 the complete disappearance of the river and the dispersal of its 

 waters in numberless small channels or in marshes. If such a 

 river be fed to any considerable extent by melting snow, there 

 will be natural irrigation on a more or less extensive scale at the 

 most suitable period of the year. It is to such a concurrence of 

 conditions that the inundation canals on the lower parts of the 

 rivers of the Punjab owe their great value ; and somewhat similar 

 conditions operate to the great benefit of large areas of country 

 on the borders of Afghanistan and Persia. 



General conditions in New South Wales, — In considering the 

 conditions of New South Wales with reference to the general 

 principles stated above, we find at the outset that it possesses 

 practically only one range of mountains which ensures the pro- 

 vision of water in sufficient quantities for irrigation on even a 

 moderately large scale. This is the Dividing Range, which extends 

 through the State approximately parallel to the coast line at a 

 mean distance inland of about seventy miles. As the summit of 

 this range varies generally from 3,000 to 5,000 feet above sea 

 level, it is obvious that there must be a rapid rate of fall and 

 consequently a high velocity in the coastal rivers. Notwith- 

 standing the resistance of the sea water, a large proportion of the 

 silt is carried into the ocean where its deposit to form deltas at 

 the mouths of the rivers is effectually prevented by the coastal 

 currents. Hence we find that our coastal rivers have no deltas 

 in the ordinary sense of the term ; though on the lower parts of 

 their courses there are considerable areas of river deposit. These 

 areas of alluvial land are more or less interspersed with marshes 

 and lagoons, and, owing to the more violent and spasmodic action 

 under which the deposits took place, they lack the regularity in 

 slope and outline which is a general characteristic of the alluvial 

 plains in the Central and Western Divisions of the State. Hence 

 even if the conditions of the climate necessitated or warranted 

 extensive irrigation works on the coastal rivers, the physical con- 

 ditions are unfavourable. Fortunately the rainfall is fairly 



O— Dec. 4, 1901. 



