Irrigation

Introduction

This content is currently under review. Statistics date from 1990.

For Australia as a whole, the area of crops and pastures irrigated, 2,069,344 hectares, is a minute proportion (0.4 per cent) of the total area of land in agricultural holdings, 465,953,718 hectares. It is only 11.7 per cent of the total area of crops and pastures.* However, the value of irrigated production is out of all proportion to the area of land involved. One source has estimated that irrigation accounts for between 25 and 30 per cent of Australia's gross value of agricultural output (Cape 1997). This puts the figure at up to approximately $7.2 billion. On top of this, there is an estimated four-fold multiplier beyond the farm gate.

What proportion of these Australian totals can be attributed to the MDB? In the absence of comprehensive data, it is possible to do no more than provide estimates of irrigated production and its value in the Murray-Darling Basin.** Of the 249 statistical areas used in this study of the Basin, only 22 have no recorded irrigated land (and more than a third of these are entirely urban). However, for the vast majority of the remaining 227 statistical areas, the figures are very small - in terms of numbers of irrigators, areas of crops and pastures irrigated, and as a proportion of the total area. In other words, most of the MDB is devoted to pastoral and dryland farming, a rural landscape that is very similar to that of much of the rest of Australia. At the same time, there are many parts of the Basin where, in every respect, irrigation dominates the landscape, the economy and the society. It is these areas that provide the basis for the strong association of irrigation with the Basin. In between such areas and the dryland regions, however, there are many areas where irrigation is undertaken, but where it is by no means such a dominant feature of the landscape.

Overall, the MDB dominates irrigation in Australia. The total area of crops and pastures irrigated in the MDB is 1,472,241 hectares. This is 71.1 per cent of the total area of irrigated crops and pastures in Australia (2,069,344 hectares), 18.7 per cent of the total area of crops, pastures and grasses, and 1.7 per cent of the total area in farms (Figure 1).

Figure 1 Major areas of irrigation and irrigated crops and pastures in the MDB

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 (see Water Use).

* Note that unless stated otherwise, the statistical data are for 1991-92, as in the Agriculture page.

** For example, irrigation data compiled by the Australian Bureau of Statistics (ABS) are for areas of crops and pastures irrigated rather than the area of land irrigated, and not all data are collected. Data relating to irrigated agriculture are available from a number of other sources, but none are entirely satisfactory and there is often little agreement between them. This page makes use of ABS statistics, primarily for some consistency between the states, together with data from state agencies and other organisations.

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).

The history of irrigation in the MDB is very largely the history of irrigation in Australia, a history that has yet to be fully told (Hallows & Thompson nd; Powell 1989 and 1991). Certainly, the main events and the key people are associated with the Murray-Darling Basin. The earliest developments were by individual farmers in numerous locations in all of the original colonies, such as on a number of the Victorian tributaries of the Murray and along the Murray itself in South Australia. Together with some early attempts at group or collective schemes, they provided indications of what might be possible with irrigation. Out of these came the support of the colonial governments for the establishment of irrigation as a means of encouraging people to settle in inland Australia. For example, irrigation in the Kerang-Pyramid Hill-Swan Hill and Shepparton-Tongala areas, most of what is now known as the Goulburn-Murray Irrigation District, dates from the 1880s (McCoy 1988). Of particular note was the role of the South Australian and Victorian governments in supporting the Chaffey brothers in founding the Renmark and Mildura irrigation settlements in 1887. Alfred Deakin played a key role in bringing these two Canadians from California to Australia. The South Australian government also established a number of communal village settlements along the Murray in 1894, of which Lyrup is the sole survivor.

In the early years of this century, the establishment of irrigation schemes played an important role in the initiation of closer settlement policies to populate Australia and especially the inland. The emphasis on increasing population in large part explains the small property sizes and the emphasis on intensive horticulture in almost all of the government-established schemes. One of the largest was the Murrumbidgee Irrigation Area (MIA) in New South Wales, where initial developments took place between 1906 and 1913, with water supplied by the Burrinjuck Reservoir, the first major reservoir built for irrigation. Communities and associated irrigation schemes were established at many other locations, including Nyah and Tresco in Victoria.

After World War I, a number of soldier settlement schemes were established, such as Berri, Cadell, Cobdogla, Ral Ral and Waikerie in South Australia. Many of these were expansions of small earlier developments, which also included Kingston and Moorook (Smith & Watkins 1993).

In Victoria, in the period following World War I, Elwood Mead, another North American, played an important part in the expansion of irrigation, though he was unsuccessful in getting the State Government to agree to the charges for irrigation water being sufficient to cover all the costs involved, including the capital ones. Another noted personality was Sir Ronald East, Chairman of the State Rivers and Water Supply Commission, 1936-64, who was responsible for much of Victoria's irrigation development, as well as being involved in the Snowy Mountains scheme.

After World War II, further War Service Land Settlement Schemes were established, as at Cooltong, Loveday and Loxton in South Australia, and Robinvale in Victoria. These involved both federal and state governments. Other developments included the Coleambally Irrigation Area, to the south of the MIA, developed between 1956 and 1969. These government schemes were followed from the late 1950s by other group irrigation schemes of a private nature, such as Golden Heights and Sunlands near Waikerie in South Australia, as well as at other locations in South Australia and elsewhere.

The continued expansion of irrigation since the late 1960s has been largely due to individual irrigation, farmers pumping their own water directly from rivers, other waterways, and underground sources. This has occurred in all parts of the Basin, but its impact has been particularly evident along the Darling and its tributaries in northern NSW and southern Queensland, areas that previously had seen little irrigation development.

Irrigation today in the MDB

Any attempt to provide a comprehensive account of irrigation in the whole of the MDB today would be both lengthy and repetitive. The following is an illustrative account, based essentially on the form of administration or operation of irrigation, with examples drawn from various parts of the Basin. Particular attention is given to the group irrigation schemes established and operated by both government agencies and private organisations (Table 1).

Government established and operated schemes

Schemes established and run by state government agencies have long been the dominant component of the irrigation industry. The following accounts provide more detailed consideration of some of them.

St George Irrigation Area, Queensland

The St George Irrigation Area is located on the Balonne River, near the town of St George (Anon. nda). The scheme dates from the mid-1950s. The completion of the Jack Taylor Weir provided a water supply for St. George and made possible the irrigation of some 2,700 hectares. The completion of the Beardmore Dam in 1972, together with the Moolabah and Buckinbah Weirs on the Thuraggi Watercourse, made possible the expansion of the irrigation scheme. Within the Irrigation Area, there is a total of 9,470 hectares of irrigable land. Downstream of the Beardmore Dam, on what is regarded as the Regulated Section of the Balonne River, irrigation allocations have been granted to 80 landholders. Cotton is the main commodity, others include cereals, oilseeds and fodder crops.

Loxton

Loxton is one of a number of irrigation areas in the South Australian Riverland and the New South Wales and Victorian Sunraysia districts of the Mallee Zone of the Murray Valley. The Murray flows through the Zone in a relatively deep valley, which means that water has to be lifted from the river by pumping rather than being available by gravity flow. This partly explains the emphasis in these irrigation areas on higher value horticultural crops. Loxton was established by the Commonwealth Government between 1948 and 1955 as a War Service Land Settlement Scheme. Along with the Cooltong Division of the Chaffey Irrigation Area (near Renmark), it was the first to use overhead sprinklers. These made the schemes possible, as they were located on "high land" sandy mallee soils, well above the level of the River Murray.

The South Australian Lower Murray

Along the lower reaches of the Murray in South Australia, are schemes unique in the context of MDB irrigation, where a number of former swamp and wetland areas have been drained. The first area, some 1,300 hectares near Wellington, was reclaimed in 1881, the work being carried out by Sir W.F.D. Jervois, who was then Governor of the Colony of South Australia. The remaining areas were reclaimed between 1904 and 1929 and now cover over 5,000 hectares (Smith & Watkins 1993) (Figure 1). Being below the level of the River, they are flood irrigated and mainly used for pasture and fodder production. They support a major part of the South Australian dairy industry, particularly for the supply of fresh milk to Adelaide.

There is some high-level intensive irrigation of fruit and vegetables, similar to that in the Riverland, adjoining a number of the reclaimed lands, particularly at Mypolonga.

Government established and now privately-operated schemes

In New South Wales, Victoria and South Australia, the state governments have moved out of the operation (and in some cases the ownership) of most of the irrigation schemes.

Murrumbidgee Irrigation Schemes, New South Wales

Along the Murrumbidgee River, initial investigations into irrigation were undertaken in the 1890s and they were further stimulated by the devastating drought that extended over a number of years around the turn of the century. In 1906, NSW State Government legislation made possible the acquisition of land for farms and the establishment of associated towns, the construction of the Berembed Weir on the Murrumbidgee River and the main and subsidiary supply channels, and the construction of the Burrinjuck Dam. Berembed Weir and 130 kilometres of the Main Canal were completed in 1911. Burrinjuck Dam was completed in 1929 (modifications were carried out between 1939 and 1956 as well as in 1995-96). There were 677 farms in the MIA by 1914. The Main Canal, 160 kilometres long, was completed in 1924. The Murrumbidgee Irrigation Area and Districts (MIA&D) consist of two irrigation areas, Yanco around Leeton, and Mirrool, around Griffith, and the Districts of Benerembah, Tabbita and Wah Wah (Figure 2 and Table 1). Rice, horticultural crops, cattle, poultry and eggs are the main commodities produced.

It is estimated that up to 80 per cent of the MIA is affected by shallow watertables, with up to 5 per cent of the area having gone out of production because of waterlogging and salinity.

The completion of the Blowering Dam in 1968, as part of the Snowy Mountains Hydro-Electric Scheme, made possible a significant increase in irrigation in the Murrumbidgee Valley, including the Coleambally Irrigation Area (CIA), which was established to the south of the MIA between 1956 and 1969, water being diverted from the Murrumbidgee at the Gogeldrie Weir (completed 1959). Rice and fat lambs are the main commodities produced.

The MIA&D are now operated by Murrumbidgee Irrigation and the CIA by Coleambally Irrigation.

The Riverine Plains of New South Wales and Victoria

The Riverine Plains of southern New South Wales and northern Victoria are the location of the most extensive areas of irrigated land in the MDB, covering over 800,000 hectares (though by no means all of this land is irrigated in any one year) (Hallows & Thompson nd, 45-51, 69-71). They are watered primarily by the Murray, the water being diverted by the Yarrawonga Weir (through the Mulwala and Yarrawonga Channels), and, for parts of northern Victoria, the Goulburn Weir on the Goulburn River (Figure 2).

Figure 2 Irrigation areas on the Riverine Plain of southern New South Wales and northern Victoria

Much of the development in both New South Wales and Victoria occurred between the two World Wars. In Victoria, there was considerable expansion of irrigation following the enlargement of the Eildon Reservoir on the Goulburn River in 1955 and the completion of other water storages and supply systems. While much of the Riverine Plains are ideal for irrigation in terms of their generally flat terrain and uniform slopes, there are large areas of clay soils of low permeability and poor structure which are not suitable for most crops. For example, nearly 90 per cent of the Kerang Irrigation Area has heavy clay soils.

Close to half of the irrigated land is under pastures, which together with other fodder crops, support dairying, fat lambs, beef cattle and sheep production. Dairying is particularly important, especially in northern Victoria, as in the Cohuna and Shepparton districts. The main crops are rice, in the Deniliquin and Wakool areas of New South Wales, and fruit, grapes and vegetables in the Shepparton and Cobram districts. The latter two account for some 80 per cent of Australia's deciduous canning fruit (peaches, pears and apricots). Other crops include oilseeds and grain legumes.

The irrigation areas in northern Victoria are operated by Goulburn-Murray Water.

Murray Irrigation

The Berriquin, Deniboota, Denimein and Wakool Irrigation Districts (Figure 2), formerly owned and operated by the NSW Government, were privatised in 1995. Irrigation water and drainage services are now provided by Murray Irrigation Limited, a private company in which each of the region's irrigators is a shareholder, shares being allocated on the basis of water entitlements. Serving a total area of 950,000 hectares with 2,200 irrigation farm holdings, it is the largest privately owned irrigation and drainage company in Australia. The region produces half of the Basin's rice crop and a wide range of other agricultural commodities.

Privately established and operated schemes

The privately operated irrigation schemes range from the long-established Renmark and Mildura Irrigation Trusts to a number of schemes of varying sizes, most of which date from the 1960s. Many of them are located along the South Australian section of the River Murray (Table 1).

Renmark Irrigation Trust

As indicated earlier, Renmark was established by the Chaffey Brothers in 1887, while they were having difficulties with the Victorian Government in getting Mildura started. Financial difficulties resulted in the operations being transferred to the Renmark Irrigation Trust in 1893. It was Australia's first irrigation settlement, established initially on the low-lying river flats that were ideally suited to furrow and flood irrigation. Along with the Mildura Irrigation Trust, it is the oldest of the privately operated irrigation schemes. There are now some 4,700 hectares of irrigated horticultural crops and pastures.

Golden Heights, Sunlands and Ramco Heights, near Waikerie

Golden Heights, Sunlands and Ramco Heights are three of a number of such schemes along the South Australian portion of the Murray, others including Sherwood, Media, Swan Reach and Greenways (Nildottie) (Figure 1). Established on the undulating mallee sand dune country, well above the level of the River Murray, they were made possible by overhead sprinkler irrigation systems, first introduced in the Loxton and Loveday Irrigation Areas. Initially developed between 1958 and the early 1960s, the schemes near Waikerie were sparked by the devastating floods of 1956. The areas now cover over 1,200 hectares. The other schemes each cover between 200 and 500 hectares. They produce primarily horticultural crops, particularly citrus and stone fruits.

Individual operations

Apart from the group schemes, there are large numbers of farmers throughout the Basin who pump their own water directly from rivers, other waterways and underground sources. Many of the operations are relatively small, but some are very large, especially those associated with cotton growing, with on-farm storages as large as many reservoirs. This is particularly true of the more recent irrigation developments in the northern part of the Basin.

One such area is the Condamine Valley in the Queensland portion of the MDB. The Upper Condamine Irrigation Project covers a 196 kilometre stretch of the Condamine River and the North Branch Condamine Diversion downstream from Warwick (Anon. ndb). Water supplies are regulated by the Leslie Dam, completed in 1965 and enlarged in 1986. A number of weirs provide further regulation along the river. There are some 93 farms taking water from surface sources and 186 using groundwater, to irrigate 9,000 and 14,000 hectares respectively (1992-93 data). In 1992-93, waterharvesting (taking water from flood flows and storing it in on-farm reservoirs) was used on 59 farms to irrigate a further 3,000 hectares. The main crop is cotton, others including sorghum, oilseeds, cereals and lucerne. A major reason for the enlargement of the Leslie Dam was to reduce over-consumption of groundwater (evident in significant lowering of the regional watertable) and to overcome restrictions on supply from surface sources.

There are individual irrigators pumping from almost all of the Basin's rivers, such as the Kiewa, Lachlan and Upper Darling. They are also found along the Murray. In the Riverland district, there are over 450 individual irrigators, while in the Sunraysia district (from the South Australian border to Nyah in Victoria) there are nearly 900. Many of these farmers are producing horticultural crops, including the use of centre pivot systems to grow vegetables and fodder crops, as on the Narrung Peninsula (between Lake Albert and the Coorong).

Irrigation methods

The irrigation of crops and pastures is undertaken in many different ways. It can be the primary source of water, with the crops more or less totally dependent on irrigation. Irrigation can also be regarded as supplementary, providing moisture at critical periods of plant growth and/or as a means of coping with the vagaries of seasonal rainfall.

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.

Other things being equal, flood and furrow methods are relatively inefficient, both in terms of application and crop water use. The area irrigated in this way is declining in real figures and as a proportion of the total area with the adoption of newer and more efficient methods. Because of the considerable capital investment, irrigation methods and equipment cannot be easily changed, except perhaps in replacing flood or furrow irrigation with more sophisticated systems. The available data on the use of the various irrigation methods are limited and problematic. South Australian data indicate that furrow methods predominate in the older areas, while sprinkler systems are found in the more recently established schemes (Smith & Watkins 1993). It can also be noted that, in South Australia, overhead sprinklers are now showing some decline after their rapid expansion in the 1960s, at least in part due to rising water salinity levels. In the Sunraysia irrigation districts, 70 per cent of farms still use furrow irrigation, a situation that is at least in part due to the dominance of grapes for dried vine fruits.

Whilst there is no doubt that the newer systems generally result in more efficient water use, a word of caution is necessary. A South Australian study indicated that efficiency of water use was not directly related to method used, but depended much more on the management skills of the irrigator (Cole 1985, 20). This has been confirmed by more recent studies in the Riverland and Sunraysia districts, which, among other things, indicated that, with current irrigation practices, pressurised systems may not be more efficient than flood irrigation (SIMPET 1995).

Major crops grown and commodities produced under irrigation

As indicated in the introduction to this page, the total area of crops and pastures irrigated in the MDB in 1991-92 was 1,472,241 hectares, which was 18.7 per cent of the total area of crops, pastures and grasses and 1.7 per cent of the total farm area. There were 14,743 farms with irrigated crops and/or pastures, which was 28.5 per cent of the total number of farms in the Basin. At the Statistical Division level, the highest proportions of farms with irrigation were Goulburn (55.7 per cent of all farms), Murray (53.6 per cent), Murray Lands (51.6 per cent), Loddon-Campaspe (48.3 per cent), and Mallee (46.8 per cent). In terms of irrigated crops and pastures as a percentage of total land in farms, the highest figures were in Goulburn (15.8 per cent), Loddon-Campaspe (12.0 per cent), Murray (4.3 per cent), and Murrumbidgee (4.2 per cent). For irrigated crops and pastures as a percentage of total crops, pastures and grasses, the highest figures were Murray (70.6 per cent),* Loddon-Campaspe (61.1 per cent), the ACT (36.0 per cent), and Murrumbidgee (30.3 per cent). These statistical divisions include the major irrigation schemes and areas of intensive irrigated agriculture, where commodities produced under irrigation provide the bulk of farm income.

There are major difficulties with data relating to irrigation in Australia. Most of the figures presented in the early parts of this page are taken from state agencies and relate to areas of land within state and privately run irrigation areas. Australian Bureau of Statistics (ABS) data relate to areas of crops and pastures irrigated, not to the area of land. Thus, if two crops are grown with irrigation on a given unit of land in a year (double cropping), the area of land is counted twice. There is also double counting where there is inter-cropping, for example, two crops being grown on the unit of land at the same time. This means that there are no accurate data on the area of land or the area of crops and pastures grown with irrigation. To complicate the situation still further, the collection of data relating to irrigated agriculture has not, until recently, been consistent across all states. For example, for Queensland, there were separate data for irrigated and dryland cotton, but not for New South Wales, while data were not available for grapevines grown under irrigation in Queensland. As a result, it is only possible to make estimates of the contribution of irrigated agriculture to total agriculture, in terms of the area of land involved, the production of particular commodities, and the value of production. One source has suggested that "nationwide, more than 90 per cent of the cotton crop, all the rice and tobacco crops, about 70 per cent of vegetables and grapes, 50 per cent of the fruit crops and about 10 per cent of pasture crops are grown under irrigation" (Anon. 1993). However, these figures do not accord with those compiled by the Australian Irrigation Council (Table 2) or what can be gleaned from ABS data.

It is not possible to obtain a figure for the value of irrigated agricultural production in the MDB from the ABS data. Further, given the limitations outlined above, no rigorous attempt has been made to estimate such a figure. Meyer (1992, 1) stated that the value of irrigated agriculture in Australia as a whole was more than $4.6 billion in 1988-89, and that this was 25 per cent of the total value of Australian agricultural production. At a conference on irrigation in the MDB held at Griffith in 1992, the value of irrigated production was put at $3.3 billion.

Using the data available from the ABS for 1991-92, it is possible to provide some indicators of the use of irrigation for the production of particular commodities or groups of commodities, over and above the total area of crops and pastures irrigated.

The total area of irrigated fruit growing (including nuts, but excluding grapes) is 38,856 hectares, 73.1 per cent of the total Australian area of 53,133 hectares (Figure 3).

Figure 3 Locations of irrigated fruit and grapevines in the MDB

Irrigated fruit growing is found on 2,732 farms in the MDB, 64.5 per cent of the Australian total of 4,239 farms. Irrigated grapevines total 30,492 hectares, 69.0 per cent of the Australian total of 44,208 hectares**. They are grown on 2,819 farms, 80.0 per cent of the Australian total of 3,525 farms. In the MDB, 75.7 per cent of the total area of grapevines is irrigated, with 77.0 per cent of the total number of farms growing grapes using irrigation.

In the MDB, 23,511 hectares of vegetables are grown under irrigation, 25.4 per cent of the Australian total of 92,502 hectares, on 1,106 farms, 21.2 per cent of the Australian total of 5,205 vegetable growers using irrigation (Figure 4). The irrigated area of vegetables in the MDB is 79.2 per cent of the total area, with the farms using irrigation being 72.7 per cent of the total number growing vegetables.

Figure 4 Locations of irrigated vegetables in the MDB

Most of the irrigated fruit, grapes and vegetables are to be found on the typical intensive horticultural properties in the irrigation areas along the Murray and Murrumbidgee valleys, such as in the Goulburn Valley, Sunraysia and Riverland districts. However, although these commodities are the ones that are typically identified with irrigation in the MDB, it is important to realise that they account for only 92,859 hectares, no more than 6.3 per cent of the Basin's total area of irrigated crops and pastures.

Only a relatively small proportion of the total cereal crop in the MDB, 4.7 per cent, is grown under irrigation. The area is 248,840 hectares, 90.6 per cent of the Australian total of 274,791 (Figure 5). This is 16.9 per cent of the total area of irrigated crops and pastures in the Basin. Irrigated cereals are produced on 2,827 farms, which is 75.7 per cent of the total Australian number of 3,782 farms with irrigated cereals, but only 12.9 per cent of the farms producing cereals in the Basin. Of the total area of irrigated cereals, rice accounted for 109,186 hectares or 43.9 per cent. Among the other irrigated cereals are wheat and maize.

Figure 5 Locations of irrigated cereal crops in the MDB

There are 862,155 hectares of irrigated pastures in the MDB, 79.8 per cent of the total Australian area of 1,080,583 hectares (Figure 1). This is 58.6 per cent of the total area of irrigated crops and pastures in the Basin. Such pastures are present on 8,584 farms in the MDB, 56.6 per cent of the total number of 15,165 farms with irrigated pastures.

In addition to the fruit, grapevines, vegetables, cereals and pastures detailed above, there are an additional 266,053 hectares of irrigated crops not elsewhere counted (NEC) (Figure 6).

Figure 6 Locations of irrigated pastures in the MDB

This is 74.8 per cent of the total Australian area in this category of 355,717 hectares***. Irrigated crops NEC accounted for 18.1 per cent of the total area of irrigated crops and pastures in the Basin. On the assumption that 80 per cent of the cotton crop is irrigated, a figure of 212,842 hectares and about 14.5 per cent of the total area of irrigated crops and pastures, then 80 per cent of the irrigated crops NEC category is accounted for by cotton, a conclusion that is supported by the largest areas in this category being in the Northern, North Western, Darling Downs, and South West Statistical Divisions.

* The data indicated a figure of 106.2 per cent for the Goulburn Statistical Division, i.e. the recorded area of irrigated crops and pastures was greater than the total area of crops and pastures.

** It should be noted that data on irrigated fruit and grapevines are not collected in Queensland, Tasmania and the Northern Territory.

*** For Australia as a whole, adding the six groups together, pastures, fruit, grapevines, vegetables, cereals and crops NEC, gives a total irrigated area of 1,900,934 hectares, which leaves 168,410 hectares unaccounted for. Another problem detected when compiling this page was a figure of 28,900 hectares for irrigated crops NEC on two farms in the Bathurst SLA. This figure is greater than the total area of land in farms in the Bathurst SLA of 22,497 hectares, let alone the total area of crops and pastures in the SLA of 2,2447 hectares. The ABS AgStats Small Area Agricultural Data volume states that given the size of the data set and its processing, "there are innumerable possibilities for error".

A controversial activity: the benefits and costs of irrigation

There is no doubt about the benefits of irrigation. These are more than evident in the value of irrigated agricultural production and the multiplier effects of this production, at local, regional and national levels. A study of the value of irrigation in New South Wales undertaken in the early 1980s, concluded that for every dollar produced by irrigated agriculture, a further $5.09 were generated in the wider Australian community, while every irrigation job at the farm level created a further 3.74 jobs (Powell et al. 1985, 96). A more recent study of the economic impact of irrigated agriculture in the Shepparton region indicated that irrigated horticulture and dairying accounted for almost 45 per cent of the gross regional product and over 43 per cent of regional employment (SRDB 1996). Places such as Waikerie, Renmark, Mildura, Shepparton, Leeton, Griffith, Narrabri, Wee Waa and St George would not exist without irrigation, or certainly not as they are today, and the agricultural industries over much of the MDB would be very different.

However, there is also no doubt that irrigated agriculture results in significant costs. The controversy centres on the extent of these costs and whether or not they outweigh the benefits, especially in the longer term (see for example Conroy 1995). There are a number of points to be considered. To begin with, 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 (in terms of returns per ML of water used). For example, while fruit, vegetables and dairying are among the most efficient, rice and grazing are the most inefficient, with cotton in between (though closer to the efficient group) (Table 3). These are very generalised figures, however, and there are significant variations in the returns from different commodities produced with irrigation, not only from area to area with any one commodity, but more especially between commodities (Hall et al. 1994; Meyer 1992, 4-9) (Table 4). But there are also other considerations, such as the importance of particular crops to regional economies (as with all of the major irrigated commodities) and contributions to export earnings. However, there is little doubt that irrigated grazing needs very careful examination if its large scale continuation is to be justified.

For a number of reasons, the efficiency of water use is clearly a critical issue. For example, the production of milk from 1ML of water on irrigated dairy farms ranges from 600 litres to 2,000 litres. The increasing demands for the limited water resources, not least in terms of the impacts of irrigation extractions on river flows, water quality and the overall health of the rivers, will almost certainly mean that less water will be available for irrigation in the future. Then there is the question of the pricing of irrigation water. Current charges are highly variable across the MDB (Table 5), but in some areas it is clear that they do not even cover the running and maintenance costs of the supply systems (Hall et al. 1994, 7-8).* Of increasing concern is the contribution of irrigation to rising watertables and salinisation, together with the impacts of drainage from irrigation areas on the salinity of waterways (see Water and Land Salinity). As discussed in other pages (see Land Degradation and Water Quality), there are significant environmental costs flowing from irrigation, and many of these costs can now be quantified.