A booklet for Students and the Community
Chapter 6
Drought Hazards and Disasters
Although a few regions of Australia have a high annual rainfall, we
live in the world’s driest continent. As
our climate varies greatly from region to region, and from year to year, we need be able
to endure regular droughts. On average,
drought is Australia’s most costly natural hazard in economic terms.
WHAT IS DROUGHT?
The Bureau of Meteorology defines drought as a prolonged, abnormally dry period when there is not enough water for users’ normal needs. However, low rainfall does not necessarily constitute a drought. If this was so, most of Australia’s interior would suffer from permanent drought.
WHAT ARE THE CAUSES?
Natural Rainfall Variations
In Australia, even when our weather is not affected by global weather shifts, our rainfall pattern is among the most variable in the world. This is due to our size, location, geography and climatic range, and means many areas are subject to the regular threat of drought.
El Niño/Southern Oscillation - The causes of drought originate with the fluctuations in global climate, which are a combination of the systems of atmosphere, oceans, ice masses and biosphere. The most widely known recurring climatic irregularity that develops every few years is known as the El Niño phenomenon. This is a name given to unusually warm ocean currents off the equatorial Pacific coast of South America. El Niño is actually an extreme swing in a recurring air pressure shift across the Pacific Ocean called the Southern Oscillation. Many droughts affecting eastern and northern Australia are a direct result of a strong swing in the Southern Oscillation, accompanied by cooler than normal ocean currents off northern Australia.
FEATURES OF AUSTRALIAN DROUGHT
Characteristics
Frequency - Long-term averages indicate that in terms of rainfall, out of every 10 years, we have about 3 good years, 4 average years, and 3 bad ones. Research also reveals that very severe drought affects some part of Australia every 18 years approximately.
Intensity and Duration - Drought intensity is a measure of rainfall deficiency over three months. For a particular region, between 5 and 10% above the lowest on record is rated as serious and less than 5% above lowest on record is rated as severe. Occasionally, droughts last for 7 or 8 years, but within that period the severity may fluctuate with spells of rainfall, although still well below average. Other droughts are shorter (one or two years) but more intense with very little rain recorded (see Case Studies).
Extent and Predictability - It is unlikely that the entire country could suffer drought at the same time. Some droughts can be localised with other relatively close areas receiving normal rainfall. Often regional droughts are not related to El Niño events, so they are even more difficult to predict.
Effects
Agricultural and Environmental - The effects of drought firstly impact on agriculture causing reduction or loss of water supplies, crop failures and livestock losses. They can also lead to environmental damage through vegetation and wildlife loss, erosion, and toxic algal blooms in depleted dams, rivers and lakes.
Communities - In the country or city we may face severe water restrictions and will be affected by rising food prices, reduced supply and in extreme cases in some countries, devastating famine (eg China in 1877-78 when 9.5 million people starved to death). Other drought-related hazards in Australia are heatwaves, duststorms and bushfires, all of which can impact on communities.
AUSTRALIAN DROUGHTS - CASE STUDIES.
1. Intense Drought - Early 1980s
The most intense period of drought in European settlement was in 1982-83, when very large areas of central and eastern (particularly south-eastern) Australia had record low rainfall. This was part of the 1979-83 drought and, although no known deaths from starvation or disease resulted, the total impact on the economy was estimated at $7 billion (1997 values) in reduced productivity and insurance claims. This cost was due to an average drop of almost 40% in cereal grain, cotton and sugar production, and the loss of millions of livestock as well as tonnes of topsoil blown away in duststorms. By February, 1985, even major rivers like the Murrumbidgee stopped flowing, reduced to a string of pools and the Blowering, Burrinjuck, Hume, Wyangala and Keepit Reservoirs were all down to 6% of capacity. Agricultural losses resulted in high unemployment in rural areas, and the drought culminated in the horrific February 1983 ‘Ash Wednesday’ bushfires across Victoria and South Australia.
2. The 1990s North-Eastern Australia Drought
A prolonged, severe drought gripped north-eastern NSW and most of Queensland from 1991 until late 1995 in most areas. Although less intense and widespread than the early 1980s drought, it lasted much longer, persisting in parts of central Queensland through 1996. Most areas between Cairns and Bundaberg, and inland roughly parallel with the coast, almost as far west as Longreach, suffered the lowest rainfall on record. Several major reservoirs in both States went dry and many others fell to dangerously low levels. Water had to be trucked to many towns for up to a year in some areas. Huge agricultural losses occurred in the eastern states as average rural production fell by over 10%. This largely contributed to the total estimated cost of the drought of $5 billion in 1997 values.
DROUGHT PROTECTION AND SURVIVAL
On the Land
We have to accept that droughts are a natural recurring hazard of the Australian environment. Farmers can prepare by developing plans which cover all aspects of managing a farm and take into account variable climatic conditions, especially drought. To further ensure an economically and environmentally sustainable agricultural business, advance strategies could include:
u appropriate additional fencing and pest/vermin control measures;
u planting drought-resistant crops and pasture;
u stabilising soil which is degraded or subject to erosion;
u increasing water and stock-feed storage capacities and planting shelter-belts; and
u considering options for agistment and protecting plant and native species during drought.
Plans need to be specific to each farm but consistent with regional catchment management plans.
In Towns and Cities
Water authorities plan for water shortages in towns and cities with reserve capacity in reservoirs. During prolonged drought however, such stores may run low, requiring water restrictions. As an individual, the best place to prepare for droughts in urban centres is in the garden. Over half of city household water is used on gardens and lawns. Plan water-use wisely by reducing areas of grass, mulching garden beds and choosing dry-climate plants. In the home we should always conserve water, especially during drought, by having shorter showers, turning off dripping taps, using water-efficient appliances, re-using water and collecting rain water in tanks.
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EMERGENCY MANAGEMENT AUSTRALIA, PO
Box 1020 Dickson, Australian Capital Territory 2602, AUSTRALIA Telephone: + 61 (0) 2 6266 5402 Facsimile: +61 (0) 2 6266 5029 Email: ema@ema.gov.au AUSTRALIAN EMERGENCY MANAGEMENT INSTITUTE,
Mount Macedon Road, Mount Macedon, Victoria 3441, AUSTRALIA |
| This page was last updated May 31, 2001 |
