IRRIGATION METHODS

In 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.

Where 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.

Water 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.

In 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 dairying.