IRRIGATION IN N.S.W.

Press, Volume LVII, Issue 17224, 15 August 1921, Page 5

IRRIGATION IN N.S.W.

» LECTURE BY MR A. D. DOBSON. A leoture entitled "Irrigation in New South Wales," was givan to the Canterbury University College Engineering Society on Saturday evening by Mr A. X). Dobso.i. Th© speaker dealt chiefly with th© Mufrumbidgee Bchemo, and illustrated hia lecture with a number of lantern slides. The scheme "was intended to impound a volume of water equal in area to Sydney harbour, and to utilise it as required to • irrigate, part of the large, tract of desert land round tlie- lower reoches of the Murrumbidgee rivor. This v)aa effected by th© construction of the Burrinjuck dam, a* project which was estimated to cost £BOO,OOO, but which, owing chiefly to the use. of day labour, eventually cost 11 millions. Mr Dobson outlined the preliminary works, which were neoessary, consisting of the con-, struction of 26 miles of 2ft ga-nge railway from Koondah to th© site of the dam for the purpose of carrying materials and stoma, -n doing do he deprecated the nso of- such exceptionally light railways, as a great deal of trouble was an<i the line proved very expensive to maintain. He also remarked that the use of narrow gauges far passenger and freight service was a great mistake, as the increase s of cost, with the increase of gauge was almost negligible. The speaker then went on to deal with the dam proper, illustrating the text with some fine elides. The dam was one of the largest and finest yot constructed, «nd impoanclod a body of water which would cover 772,000 acres to a depth of one foot. The site was ideal, being located in a gorge which the river had cut through a natural wall of solid granite. The construction was of concrete bloclta cast in position, of cruciform/section, and weighing about 60 tons each. The materials, which were.placed in position by a "flying fox," included i large "plums" of granite weighing up to 10 tons. The maximum height of the dam w.is 242 ".ho length at the crest 763 ft, with « width varying from 18ft at. the cwst to Sfift at the bale. It contained about 800,00(1 ton® of concrete. From the dam the water followed the course of the river for a distance of 240 miles to the Benembed Weir, where it was diverted into the main canal, 90 miles long, from which it was subsequently (iistiibutrf. Mr Dobson then showed a number of elides illustrating the wonderful changes that had been wrought by the water. Desert that had originally grazed perhaps two snakes to the acre, had been, converted into a prosperous fruit-growing and pastoral diEtnct. In conclusion, Mr Dobson said' he thought there were vast possibilities in extending theeei schemes, remarking on -tho large population which could thus be carried fcy large areas which at present bring in no return. i In proposing a vote of thanks to the speaker, Mr Deem, spoke in Very ■ appreciative terms of the work which Mr Dob-son—-as a vice-president—had done for the _ society, and expressed -a hdpe t'hat he might for many years continue his interest. The vote of • thanke was seoonded by Mr R. A. Campbell, who had been engaged on the work in ita early stages. During jus remarks, he emphasised the fact of ibe inference between the day labour and the contract system, the cost of excavation m tba present case being nearly double t'he current rate for contract work. He also mentioned that the designer of the dam, Mr Claude V/ileon, had constructed a wooden model of the finished work to ensure that tie fitting of the blocks should be as nearly perfect aspossible. . . itMr Staveley, borough engineer ior \vnr.??.nui, who baa raen the scheme ip.-operation, spoke highly «f the results achieved. In repiy, Mr Dobson thanked his audience for their appreciation, -and declared himself just as keen to help them as ever he had been.