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ARTESIAN WATER IN CONNECTION WITH IRRIGATION. 467 
The quantity of water used for efficient irrigation is very large, 
as, for example, in Italy the hay land gets twelve floodings each 
six inches deep during the summer six months, of which one-third 
to one-half is retained by the land, the remainder being utilized to 
similarly flood land ata lower level. The land thus gets seventy- 
two inches, and if one-third of this, viz., twenty-four inches is 
retained by the soil, this is two inches more than the fall on our 
catchment. In some other countries more is used. 
Supposing that half of the rainfall which passes into the soil 
could be made available it would only irrigate something under 
60,000 acres. If the cause of the upward pressure is as stated, 
long before this maximum was reached the bores would cease to 
be artesian. 
It seems more probable that only about one-fifth of the rainfall 
on the catchment area could be made available after allowing for 
loss by streams, evaporation, and the requirements of vegetation 
locally, and the unavoidable escape through the old channels to 
the sea, This reduces the avaz/able catchment area to forty square 
miles, giving water enough to irrigate 25,000 acres. This area 
would produce 75,000 tons of hay per annum by growing grasses 
of the largest yield, such as Timothy, taking the result as the same 
as that of Italy, viz., three tons per acre. Mr. Coglan gives the 
yield of hay in New South Wales as 1°73 tons per acre and the 
area aS 131,153 acres, so that the total crop at present is, say 
227,000 tons. Other crops could of course be raised instead, but 
hay would probably be the most valuable on the spot for conversion 
into live stock. 
Water for irrigation is not required all the year round, so that 
it would be necessary to construct reservoirs to contain and store 
it when it is not required. It is evident that no advantage can 
arise by closing down the bores either completely or partially, as 
the water would then simply find its way to the sea by the old 
channels instead of on to the land. The only possible advantage 
of closing would be that of giving other bores a chance of getting 
pressure, but this would only happen if the wells were too numer- 
