The Sheep-Fluke. 



13 



much less tluke. The management of water is, however, such a complex 

 subject, that it requires to be treated under a variety of heads, such as 

 drainage, watersheds, dams, swamps, &c. 



Dams. 



There are many objections to dams as ordinarily constructed for sheep 

 in Australia, and some of these objections arise on account of the presence 

 of fluke. The water of any dam to which flukey sheep are given free 

 access will soon contain the free-swimming embryos of the fluke. Sheep- 

 dung containing the live eggs of fluke readily finds its way into the water, 

 and the eggs then soon hatch. It is in this way that the water first becomes 

 contaminated ; all the other stages in the history of the fluke follow on 

 naturally enough. So far as dams are concerned, the spread of fluke could 

 be practically prevented by keeping the water free of dung. Now this is a 

 matter to which no attention is paid, largely, I presume, because it is con- 

 sidered not to be feasible. 



Let us see. 



Few realise from how small an area of land a large dam or tank can be filled. 

 Suppose the dimensions of the water basin of a dam be 2 x 25 x 25 yards — 

 in other words, suppose the 

 capacity of the dam be about 

 1,000 (to be exact, 1,250) 

 cubic yards. If the annual 

 rainfall be 24; inches, the rain 

 that falls on an area 125 yards 

 square would fill such a tank 

 eight times full in one year. 

 Or, to suppose a moi'e com- 

 mon size, let the tank be 12 

 yards square and 6 feet deep, 

 and thus contain about 300 

 cubic yards ; then, with the 

 same rainfall, the rain that 

 falls on an area 60 yards 

 square would fill the tank 

 eight times in a year. 



It is, of course, impossible 

 to conserve all the water that 

 falls on a given area of land, 

 because a large part of it soaks 

 in and is lost, so far as con- 

 servation is concerned, yet it 

 is possible to collect a much 

 larger portion of it than is 

 commonly supposed, and that 



by a very inexpensive method— namely, the use of ploughed races or gutters. 

 Again, it is needless to say, the proportion of water that can be collected from 

 that which falls depends in a large measure on the nature of the rains ; heavy 

 showers producing much surface water, while drizzling rains almost wholly 

 soak into the soil, leaving very little to drain into dams and tanks. 



The arrangement of races that would drain a small watershed depends on 

 the slope of the land, but in general will be somewhat as in Pig. 10, where 

 c, c, c, are ploughed races leading to the tank, a. These may be single or 

 double furrow, preferably the latter in most soils. They are made by 



Fig. 10. — Diagram showing arrangement of water-shed, 

 races, tank, and trough such that a pure water supply 

 is assured. The water-shed is fenced off by the fence 

 hbbb. The races / / keep the ordinary drainage of 

 the paddock from contaminating the water-slied. The 

 ploughed races ccc empty into the tank o, from which 

 the water is siphoned through the pipe d to the 

 trough e e. 



