IRRIGATION • Agriculture is the dominant economic activity in the Murray-Darling Basin. Further, the Basin is Australia's most important agricultural region, accounting for just over 41 per cent of the nation's gross value of agricultural production.
Irrigation involves a variety of irrigation methods and equipment. They can be summarised as follows: • flood, some with laser land forming, especially for pastures and rice production; • furrows, the predominant method for horticultural and field crops, and, particularly in the older schemes, for vines and tree crops; • sprinklers: various types of overhead sprinkler systems, depending on the crops; particularly for tree crops and vines, but also include centre pivot systems used for growing fodder crops, lucerne, vegetables, etc.; systems can be fixed or portable, though the latter can involve considerable labour input; increasing use of under-tree and micro-sprinklers resulting in much greater water use efficiencies; • trickle/drip hoses: even more efficient, due to much more direct application of water; and • sub-surface drip systems.
Figure 1 Major areas of irrigation and irrigated crops and pastures in the MDB Major irrigation Areas Irrigated crops and pastures x 5,000 hectares Irrigated crops and pastures x22 hectares.
SCALE • There are 14,743 farms with irrigated crops and/or pastures, which is 28.5 per cent of the total number of farms in the Basin, and 47.2 per cent of all Australian farms with irrigation. Not surprisingly, irrigation dominates water use in the Basin - over 95 per cent according to the latest study (MDBMC 1995) - and in Australia - some 70 per cent of all water used in Australia is used by irrigation in the MDB
An historical overview • The initial establishment of irrigation in the Murray-Darling Basin can be seen as a response of settlers from the well watered lands of Europe to the dry and unpredictable environment of Australia. In particular, it was a desire to overcome the variability of the Australian climate; it was seen as a means of providing protection from some of its harsh features; it provided a form of security. It was also regarded as an endeavour to make the 'deserts' green (Powell 1993).
ECONOMY • The Basin has been termed Australia's agricultural heartland, its 'food basket', but it is much more than that, as its agricultural output makes a major contribution to the national economy. Agriculture provides the raw materials for most of the MDB's manufacturing activity, as well as many processing companies beyond the Basin
Budget stuff • For the Basin as a whole, the gross value of agricultural production in 1991-92 was estimated as $8,555,983,514, 41.04 per cent of the Australian total of $20,848,019,725**. • the 1991 Census indicated an average figure for the Basin of over 16 per cent of the workforce directly engaged in agriculture,
Rice • Except for a small quantity grown in Queensland and the Northern Territory, all of the Australian rice crop is grown in the MDB*****. In the MDB, rice is grown on 1,288 farms, with a total area of 109,186 hectares, 95.8 per cent of the Australian total of 114,000 hectares, producing 928,533 tonnes, 97.0 per cent of the Australian total of 957,000 tonnes. The crop was was valued at $176.0 million, 96.1 per cent of the national total of $183.1 million.
THE PROBLEM WITH RICE • there are resource constraints, not only in terms of the availability of irrigation water, but also because of the environmental consequences of the large quantities of water and flood irrigation methods that are used. Up to half of the water that percolates down to groundwater from irrigated areas in southern NSW comes from rice production. This represents some 200,000 ML of water every year, worth over $2m. Not only is this water wasted, it is an undesirable addition to already high watertables.
Irrigation Controversy In comparison with many other countries, Australia has long had a low rate of return on its investment in irrigation largely due to the fact that the bulk of the irrigation water used in the southern Basin supports mixed farming and low-value commodities. This situation is complicated by the fact that a number of the commodities produced are also inefficient users of water . For example, while fruit, vegetables and dairying are among the most efficient, rice and grazing are the most inefficient, with cotton in between .
Table 3 Water required to make $100 profit (source: adapted from Hall et al. 1994)
Table 1 Major land degradation problems in the Murray-Darling Basin • wind erosion • water erosion, including gullying, rill and sheet erosion, • mass movement of hill slopes • dryland salinity • irrigation-induced salinity • soil surface scalding • Waterlogging • soil acidity • soil structure decline • soil fertility decline or nutrient loss • vegetation decline and degradation, such as weed infestation and lack tree regeneration • loss of flora and fauna and hence of biodiversity • Source: MDBMC 1987.
Figure 1 Aspects of land degradation in the MDB (source: Land Assessment a Policy Unit, CRCSLM; Spencer et al. 1996; Noble 1997) Murray darling basin Woody weed effected area Acidic soil at surface Acidic throughout Alkaline soil 400mm rainfall
BILIOGRAPHY • http://kids.mdbc.gov.au/encyclopedia/irrigation