THE IRRIGATION AGE. 



VOL. X. 



CHICAGO, JULY, 1896. 



NO. 1 



Bound 



Periodical 



IRRIGATION TRUSTS IN VICTORIA/ 



CHAPTER II. NATIONAL WORKS- 

 MAY 17 BY FRED CAMPBELL, C. E. - ^ *t> 



IT has been stated in the preceding paper 

 that when a scheme for establishing a 

 trust or trusts came before Parliament, 

 certain portions of the proposed works, on 

 the recommendation of the Minister for 

 Water Supply and his technical advisers, 

 could be denominated " national works;" 

 these would then be constructed at the 

 cost of the State. It is now proposed to 

 describe these works. 



In comprehensiveness of design, in mag- 

 nitude of works and in area of irrigated 

 land commanded, the Goulburn Weir 

 comes easily first. The Goulburn, a trib- 

 utary of the Murray, is the largest of the 

 Vict9rian rivers, and takes its source in 

 high mountainous country, some of the 

 peaks reaching an altitude of 5,000 and 

 6,000 feet. The area of its watershed 

 above the weir is 3,940 square miles, and 

 as the bed rock, a dense, close-jointed 

 schist, lies near the surface over a 

 large extent of the watershed, the propor- 

 tion of total rainfall discharged into the 

 river is large. The river basin below the 

 weir comprises a further area of 2,500 

 square miles, and is composed of alluvial 

 plains of deltaic origin. The weir is con- 

 structed just above where the country 

 changes to alluvial flats from low ranges, 

 and it was to provide a steady water sup- 

 ply to the rich deltaic flats during summer 

 droughts that induced the state to under- 

 take this large work. From careful ob- 

 servations of rainfall and river gaugings 

 carried out over a period of nine years, it 

 has been ascertained that the proportion 

 of total rainfall over the catchment area, 



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passing the site of the weir, varied between 

 18 per cent and 37 per cent, the average 

 having been 29 per cent. 



Various reports from the Department of 

 Water Supply were presented to Parlia- 

 ment, on the construction of a storage 

 basin and regulating weir on the Goulburn 

 river, and finally, in 1886, Parliament 

 authorized its construction. By the mid- 

 dle of the following year a contract had 

 been let and work commenced. 



DESCRIPTION OF THE WORKS. 



The rock, forming the foundation of the 

 weir and extending under the bed of the 

 river and up both banks at a small depth 

 below the surface, is a soft shale of the 

 upper silurian formation. Its structure is 

 alternating beds of sandstone, slate and 

 pipeclay, standing on edge almost verti- 

 cally. The weir is 695 feet in length, ex- 

 clusive of the space occupied by channel 

 regulators a further length of 230 feet 

 and the summer level of the river is raised 

 by it about 45 feet. 



The main part of the structure is of con- 

 crete masonry, composed of broken stone, 

 clean washed gravel, sharp sand and Port- 

 land cement. It is backed by granite 

 steps for its full height and notched into 

 that below. While the superstructure was 

 in progress, the water was carried by six 

 tunnels left in the lower portion, each of 

 forty-four square feet section area. These 

 were permanently closed by heavy cast-iron 

 gates, when the upper works had been 

 completed. During the course of the 

 works a heavy flood totally submerged 

 them, but without doing any damage. 



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