Australia, New Zealand Encyclopedia 10. (töredék) [antikvár]

Irrigation pipes are set to lead water from the main channel in the foreground to secondary channels.IRONWOODIronwood is the name given to several species of Australian trees. Their timber is so hard and dense that some are also known as axe-breakers.The tree most commonly called ironwood. Acacia estrophiolata, grows in dry inland areas of Central Australia. It develops from a squat, rather prickly shrub into a tree of about 10m high. Its long, drooping branches and narrow grey-green leaves give it a 'weeping' appearance. The foliage is often used as drought fodder.A similar tree. Acacia excelsa, sometimes called ironwood wattle, grows on the dry western plains of NSW and Queensland. It reaches a height of about 20m, and has hard, close-grained, reddish timber.The ironwood or grey myrtle {Backhousia myrtifolia) of the tablelands of NSW has a tough, close-grained timber sometimes used for tool handles, fishing rods, mallets and wooden screws.irrigationIrrigation is the supply of water to land from reservoirs, rivers and underground sources. Irrigation enables plants to be grown and stock grazed in areas where rainfall is insuf-ficient or unrehable. Water may be released from reservoirs into man-made canals which convey it to the irrigation areas. As the water is required sluice-gates are opened into furrows (in the case of fruit trees) or irrigation bays (in the case of pastures). With rice, the crop area is totally flooded.This type of irrigation, involving the construction of diversion weirs on rivers, is expensive. For this reason it is usually government-controlled, though private individuals sometimes band together in co-operative ventures. More frequently individual farmers pump water from rivers or wells into spray lines, which are moved across the area to be irrigated.Both kinds of irrigation are used in Australia and New Zealand. In Papua New Guinea contour irrigation is the main type.AustraliaUnreliable rainfall and recurrent droughts have been constant hazards to Australian primary producers. In some regions their effects have been overcome through irrigation. There are irrigation schemes in all Australian mainland states.Despite efforts made to increase the irrigated757