lo Feb., 1911-] Irrigation. 119 



of the road space, the buckscraper uikI smoother will be found to make a 

 l)etter and cheaper job than scoops, one of the principal advantages being 

 that, with the buckscraper, the loads may be distributed at will instead 

 of dumped in a heap and smoothed afterwards as with scoops. 



The question of deciding upon the size of a head ditch must be left 

 very much to individual judgment, but it is always best to have these 

 larger than may be strictly necessary ; among other reasons, to allow for 

 siltation and growth of w-eeds. They should all be made from spoil taken 

 from inside the ditch. Taking it from outside destroys so much land, and 

 creates a hideous eyesore, besides causing resort to works of some sort to 

 pass irrigation water across the excavation. If the works are pipes thev are 

 expensive, and if of earth and the excavation or borrow pit is any size, 

 they are a nuisance to maintain and cause a good deal of additional labour. 

 Naturally, the size of the ditch is governed by the area to be supplied, 

 the time allowed for applying the water, the kind of watering required, 

 i.e., flooding or by furrows, and the class of soil. As a general idea, 

 a ditch to water an area of 20 acres should be about the dimensions shown 

 in No. j_i. 



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44. SECTION or HEAD DITCH. 



So far there has been \ery little restriction in tlie (loulburn Valley 

 irrigation areas as to time allowed for watering; but, as development pro- 

 ceeds and greater demands arise, and the value of water becomes more 

 appreciated, a schedule or roster will be prepared and more rigidly adhered 

 to. An attempt to so regulate the supply of water has been made, but has 

 so far not met with the success that later must become a sine qua non of 

 successful irrigation. The water is so regulated in most irrigation coun- 

 tries; and at Mildura, which is eminently a closer .settlement area, has 

 generally met requirements. There, the water is all raised from the River 

 Murray by pumps, and, <jf necessity, costs much more than gravitation 

 water, and the landholders find it to their own interest to assist in prevent- 

 ing any waste from imperfect distribution or other causes. There can be 

 no general law laid down as to tinit-. until experience shall have shown how 

 long particular areas take. Disturbing factors, such as variations of 

 supply in the main channel, changes in planting, rainstorms, &c., can all 

 be left to the judgment of an intelligent ganger. If an area is laid down 

 with some product such as lucerne, which is invariably watered by flooding, 

 it mav l»e finished off mon- (luickly than if it were planted with fruit 

 trees which are usuallv irrigated liy two or more furrows to each row ot 

 trees. These methods will be fully expiaiiK-d when dealing with irrigation. 

 Soils, too, vary from loose sand to still clay and the porosity of the former, 

 or rather its seepage qualities., is very much greater than tlu- latt<-r and 

 consequently the head dit( h supply is varied. 



In manv countries it is usual with irrigators to speak of a stream of 

 water as the equivalent of so many heads, the term " head " In-ing derived 

 frona old mining practice where water was nn-asured out for sluicing an<l 

 other purposes. Th<'.se heads varied even in the same country, but com- 

 mon con.sent has defined a iiead of water as i cubic foot \^.x second (usually 

 written cusec). 



