The rainfall pattern over Australia is strongly seasonal with the summers in the south being mostly dry and hot and the winters being wet and cooler. By contrast, the tropical regions to the far north have wet summers with the October to April monsoon driving rainfall patterns in the northern part of the Wheatbelt.
The majority of the Australian Wheatbelt averages 300 to 600 millimetres of rainfall annually with production timetables varying from region to region depending on the timing of growing season rainfall. Generally, farms closer to the coast receive higher and more reliable rainfall, with conditions becoming drier and more volatile further inland.
Within each of the Wheatbelt regions agricultural productivity and land prices are determined primarily by the level of rainfall. Hence, it is common practice for Australian farmers and agricultural investors to categorise farms according to the level of rainfall they receive. The three commonly used rainfall categories are:
Due to the relatively low levels of rainfall over much of the Wheatbelt, river flows and underground water resources available for irrigation are minimal. As a result, almost all grain in Australia is produced under a ‘dryland cropping’ system (i.e. crops are rainfed as opposed to irrigated).
The north is home to most of Australia’s irrigated crop production (although this is predominantly cotton and sugar country, so much of the irrigated area would not be classified as Wheatbelt territory). When irrigation dams are at full capacity, more than 400,000 hectares can be irrigated, but given the high variability of rainfall in the north, irrigated crop production is actually more volatile over the long term than some of the more reliable rainfed regions of the Wheatbelt.
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