4610.0.55.007 - Water and the Murray-Darling Basin - A Statistical Profile, 2000-01 to 2005-06
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 15/08/2008 First Issue
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CHANGE IN AGRICULTURAL WATER USE OVER TIME
When water availability is high, for example, when water storage is elevated, high water allocations (or some equivalent) are typically announced by water management authorities and farmers decide how to use the available water. For example, cropping farmers might choose to plant relatively large areas of annual crops like rice and cotton which require more water per unit area. When water availability is low, water management authorities announce lower allocations (or some equivalent) and irrigators are faced with decisions about how to manage the limited water resource. Cropping farmers might choose to switch from crops that typically use more water (e.g. rice - 12 ML/ha in 2005-06, see table 3.22) to alternatives which use relatively less (for example, cereals other than rice - 2 ML/ha). Alternatively, they might decide to trade some or all of their allocation and/or not sow a crop. When there is low water availability, farmers with perennial plantings like fruit and grapes stand to lose not only their annual crop, but their assets of trees or vines if they decide not to irrigate. If their water allocation at the beginning of an irrigation season is insufficient to produce a grape or fruit crop, they may choose to purchase additional water or sacrifice their harvest to preserve their trees or vines. Pastures and cereals are also irrigated to feed livestock, either from direct grazing or through hay/silage production. When relatively less water is available and adequate pasture or cereals cannot be grown to sustain livestock, farmers may need to purchase additional livestock feed, sell their livestock, or agist them elsewhere which has additional costs. Technical efficiency refers to the economic value added for a given amount of water. For irrigators, technical efficiency is influenced by factors like wastage, evaporation, and production technologies (The Treasury: Roberts, Mitchell & Douglas 2006). To improve the technical efficiency of on-farm irrigation, improvements in technology, infrastructure and water management practices are required. A change in technical efficiency can be measured through monitoring water application rates over time, and taking account of climatic conditions (e.g. rainfall). This can be supplemented through assessing the irrigator uptake of more efficient technologies and practices (see 'Irrigation practices' section later in this chapter). The following section examines water availability and the related change in water consumption, irrigated area and application rates by different crops and pasture between 2000-01 and 2005-06. As an indicator of surface water availability, water storage in large dams situated within the MDB has been plotted over the same period for comparison with water consumption change. Rainfall anomalies from 2000-01 to 2005-06 have been presented in Chapter 1. Water storage in the MDB, July 2000 - June 2006 Large dams are defined as dams with a crest or wall height of greater than 15 metres, or as dams with a dam wall height of greater than 10 metres while also meeting another size criteria e.g. having a crest more than 500 metres in length; creating a reservoir of no less than 1,000 ML; the ability to deal with a flood discharge of no less than 2,000 cubic metres per second; or being of unusual design (ANCOLD 2008). Using this definition, there are 105 large dams in the MDB (see map E.3 in the Explanatory Notes) with a storage capacity of 24,365 GL. As shown in graph 3.18, water storage in large dams located in the MDB was relatively high between July 2000 and December 2001 (greater than 50% for this 18 month period). From January 2002, the combined storage level in large dams in the MDB did not increase above 50% except for a brief period in late 2005. There is a pattern of increased storage in the winter and spring months of almost every year. However, the amplitude and duration of water storage increase varies, and this impacts on the volume in storage. It is difficult to determine the relative impacts on storage of evaporation, water use and water transfer for management purposes between large dams. Crop irrigation in the MDB Irrigated pasture for dairy and other livestock Irrigated pasture uses more water than any other crop or pasture grown throughout Australia (3,800 GL or 36% of water used for irrigating crops or pasture in 2005-06, see Water Use on Australian Farms 2005–06, cat. no. 4618.0). The MDB grew 67% of Australia's irrigated pasture (by area) in 2005-06. In addition, irrigated pasture consumed more water (2,537 GL) than any irrigated crop or pasture in the MDB. Irrigated pasture in the MDB is mainly used for grazing livestock (1,981 GL) and cutting for hay or silage (531 GL). The area of irrigated pasture fluctuates from year to year. For example, the area of irrigated pasture in the MDB decreased from 760,000 ha in 2000-01, to 551,000 ha in 2002-03, and increased to 717,000 ha in 2005-06 (table 3.21). In 2005-06, the Dairy industry accounted for 39% of the total irrigated area of pasture in the MDB. Water was used by dairy farmers for irrigating pasture for grazing, hay/silage and seed production, livestock drinking, and dairy shed washdown - in total 1,287 GL, or 17% of MDB agricultural water consumption (table 3.20). A similar quantity of water (1,284 GL) was used to irrigate pasture for other livestock in 2005-06, and accounted for 17% of the total agricultural water consumption in the MDB. Dairy farming water consumption fluctuates to some degree from year to year. For example, water consumption decreased from 1,693 GL in 2000-01 to 1,227 GL in 2002-03 (table 3.20). From 2002-03 to 2005-06 the volume of water consumption did not reach the 2000-01 level. The proportion of agricultural water used for dairy farming in the MDB fluctuated between 15%–19% from 2000-01 to 2005-06 (table 3.20). This was relatively less than for annual crops like rice (9%–23%), cotton (17%–26%) and cereals other than rice (7%–17%). Between 2000-01 and 2005-06, the variation in water consumption by pasture for other livestock (and the proportion of agricultural water used), exhibited a similar pattern to dairy farming. Water was irrigated onto pasture with an application rate of 3.5 ML/ha, less than the average rate for all crops/pasture (4.5 ML/ha) in 2005-06 (table 3.22). This rate was lower than in 2000-01 (4.2 ML/ha). Cotton The MDB grew about 92% of Australia's irrigated cotton (by area) in 2005-06. In addition, cotton was consistently the crop with the highest water consumption in the MDB from 2000-01 to 2005-06. Cotton water consumption was almost 1,600 GL in 2005-06 (table 2.20). Cotton water consumption fluctuates significantly from year to year, and the area of crop grown is dependent on water availability (see graph 3.19). In 2000-01, when water storage was relatively high in large dams servicing cotton growing areas in northern New South Wales and southern Queensland, the area of irrigated cotton (405,000 ha, table 3.21), volume of water consumption (2,599 GL, table 3.20), and proportion of agricultural water consumption in the MDB (25%) were all high. In 2003-04, when there was lower water storage, less irrigated cotton was planted (174,000 ha), a lower volume of water was consumed (1,186 GL), and the proportion of agricultural water consumption accounted for by this crop dropped to 17%. Within large dams servicing cotton growing areas, the lowest water storage levels in the seven years to June 2007 were recorded in the six months between January and June 2007 (graph 3.19). This indicates that water consumption, area irrigated, and production were very low in 2006-07. Water was irrigated onto cotton at a rate of 6.4 ML/ha in 2005-06, the second highest application rate of the major irrigated crops and pasture (table 3.22). This rate was lower than for the previous two years when the highest rates were recorded (6.8 ML/ha). As outlined above, in 2003-04, water availability was very low. Because there was less rainfall to supplement irrigated cotton, more irrigation water was required. Rice and other Cereals In 2005-06, all of Australia's rice and the vast majority (88%) of other irrigated cereals (referred to as 'cereals') were grown in the MDB. Between 2000-01 and 2005-06, more water was consumed by rice and cereal crops than by fruit, grapes or vegetables, but less than by pasture or cotton (table 3.20). The volume of water applied to rice and cereals fluctuated significantly during the 2000-01 to 2005-06 period. The pattern of water consumption for both crops between 2000-01 and 2005-06 coincided with the change in water availability over the same period. When there was more water stored in large dams (e.g. in 2000-01, graph 3.18), water consumption for rice was higher relative to other years (table 3.20). However, when water availability was restricted, rice water consumption decreased. The opposite trend applies to irrigated cereals, i.e. when water availability was restricted (e.g. 2002-03), water consumption was relatively higher than in years when water storage was high (e.g. 2000-01). This suggests there is crop substitution by irrigators depending on relative application rates (rice 12–14 ML/ha, cereals 2–3 ML/ha) and water availability from season to season. Irrigation application rates of cereals appear to have decreased slightly from 2000-01 to 2005-06 (table 3.22). Of the major crops and pasture irrigated, cereals are irrigated with the lowest application rate. By contrast, rice requires the highest application rate of water. Since 2002-03, rice farmers have significantly reduced the application rate of that crop from 14.1 ML/ha to 12.3 ML/ha in 2005-06. Grapes The MDB grew the majority of Australia's irrigated grapes - 58% of Australia's irrigated area of grapes, in 2005-06. Grape growing consumed 515 GL of water in 2005-06 (table 3.20). From 2000-01 to 2005-06, significantly less water was irrigated onto grapes than onto pasture, cotton, rice or cereals, but more than for fruit or vegetables. Being a perennial crop, the volume of water applied to irrigated grapes tends not to fluctuate from year to year to the extent of annual crops such as rice, cotton or cereals. The proportion of water used to grow grapes in the MDB compared to other agricultural commodities increased slightly between 2000-01 and 2005-06, from 4% to 7% of MDB agricultural water consumption. The volume of water applied (469 to 515 GL), gradually increased between 2000-01 and 2005-06 in the MDB (table 3.20). This is consistent with the increase in area of irrigated grapes over the same period (84,000 to 106,000 ha, table 3.21). The irrigation application rate for grapes was relatively consistent between 2000-01 and 2004-05 (at around 5.5 ML/ha), however it decreased to 4.9 ML/ha in 2005-06. This application rate was lower than for rice, cotton and fruit, but higher than for cereals and pasture (table 3.22). Fruit The MDB grew just over half of Australia's irrigated fruit - 53% of Australia's irrigated area, in 2005-06. Irrigated fruit consumed 413 GL of water in 2005-06, and between 2000-01 and 2005-06 consumed less water than most crops except vegetables (table 3.20). Like grapes, irrigated fruit crops are perennial and therefore require relatively regular annual volumes of water to sustain production. The proportion of water used by fruit in the MDB compared to other agricultural commodities remained relatively constant (approximately 5% of MDB agricultural water consumption) between 2000-01 and 2005-06. The area of irrigated fruit (59,000 to 75,000 ha, table 3.21), and volume of water applied (372 to 413 GL, table 3.20) increased over this period. The fruit irrigation application rate, ranging from 5.5 to 6.5 ML/ha, was more variable than that for grapes between 2000-01 and 2005-06 (table 3.22). This application rate was higher than for each major crop and pasture in the MDB except rice and cotton. Vegetables The MDB grew about 28% of Australia's area of irrigated vegetable crops in 2005-06. In the MDB, vegetables use less water than all of the major crops and pastures, just 2–3% of all agricultural water consumption between 2000-01 and 2005-06 (table 3.20). In the MDB, the area of irrigated vegetables, and volume of water applied, both decreased slightly from 37,000 ha and 166 GL in 2000-01 to 32,000 ha and 152 GL in 2005-06 in the MDB (tables 3.20 and 3.21). The irrigation application rate for vegetables was reasonably consistent, ranging between 4.3 and 4.9 ML/ha in the 2000–01 to 2005–06 period. These application rates are similar to the 2005–06 average application rate for all irrigated crops and pasture in the MDB (4.5 ML/ha, table 3.22). Other crops and livestock uses of water Other agriculture includes agricultural activities like the irrigation of other broadacre crops (e.g. oilseeds) and plant nurseries, the watering of livestock, and the washdown of stock enclosures, for example, piggeries. Dairy shed washdown and dairy livestock watering are excluded from this category, and instead are included within dairy farming. The quantity of water consumption by other agriculture is substantial and ranged from 460 GL to 596 GL in the period from 2000-01 to 2005-06 (table 3.20). The decrease observed in 2002-03 relative to other years reflects changes in livestock numbers.
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