Art. III. — Irrigation and Water Supply in tlie 

 Australian Colonies. 



By Newtox E. Jennings, M. Inst. C.E., F.R.I.B.A. 



[Read April 12, 1888.] 



The want of water in many parts of these Colonies for 

 irrigation, as well as for the working of mines, the supply 

 of stock, and domestic purposes is generally acknowledged, 

 it is consequent]}' unnecessary to use any arguments to 

 prove this 



The rainftill, so fai- as the records show, at least in Victoria, 

 is enough to provide a sufficient supply for all purposes if 

 ])roperly distributed ; but being intermittent, and the supply 

 from the various creeks, channels and rivers being variable, it 

 cannot be relied on without the aid of some artificial means. 

 Various plans have been proposed, such as the construction 

 of dams or anicuts in rivers or streams to raise the water to 

 channels for distribution ; the supply of these channels by 

 pumping and sinking wells. In the first case, the dams 

 interfere with navigation, and in most natural watercourses 

 the level of water varies so much, that in order to take off 

 water at the driest seasons, the bed of the channel must 

 be so low that the water level in it, for a considerable 

 distance, will be below the level of the country, and a great 

 deal of the water must be lifted, or else what is frequently 

 the best and most pi'ofitable land, viz., that near the river, 

 is left without irrigation, and any expenditure on lifting 

 water where it can be avoided diminishes the profits of the 

 cultivator, and thus renders the land less capable of bearing 

 the cost of works necessaiy to bring it under irrigation, 

 besides also employing labour which could be profitably 

 utilised elsewhere. Water taken off from the natural 

 channels while in flood also contains a very large quantity 

 of silt, and as the rapidity of the flow is retarded in the 

 channels, both because a very rapid flow would injure the 

 banks, and because the inclination of the bed of the canal 

 is reduced as low as possible in order to keep the level of 

 the water above the level of the country as far as possible, 

 the silt isdej^osited in the channels, thus causing considerable 

 expense for clearing them. There is always also a tendency 



