the Riverland, the principal method of irrigation is the highlift
type where a main pumping station on the bank of the river lifts
water to heights of 30 metres or more. From here distribution was
generally, until recently, through a system of open channels (usually
concrete lined) and with sloping sides. The main channels were
between 3 and 6 metres wide, with systems of smaller branch channels
leading off them. In some of the new settlements, low pressure
pipelines were used instead of open channels, or in combination with
them. In the older areas the open channels are being progressively
replaced with pipe mains.
open channels are in use, water is supplied on an "on order"
basis once a week throughout the irrigation season. In winter the
frequency is reduced to fortnightly or monthly, depending on the
requirements of the irrigation area involved.
is admitted to blocks (usually 4 -12 ha in size) by sluice gates from
where it is used for furrow irrigation or run to a pumping sump
and/or tanks and be used for spray irrigation. With the pipe main
system there is much greater flexibility and water is supplied more
to the requirements of the individual irrigator, once again subject
to ordering in advance. Piped mains also lend themselves to low flow
irrigation system, which are potentially very important in reducing
the quantity of water applied and are reducing the amount of saline
drainage effluent, they also lessen the damage done by salinity.
the reclaimed swamp areas, the irrigation method is different as the
'swamps' are in most cases below normal river level which is
regulated by the Barrages. Embankments keep the river from flooding the
swamps and when an irrigation is required sluice gates in the
embankments are opened. The size of holdings in the reclaimed swamp
area varies but the average is about 2 ha. The main land use is