Australia has one of the most variable climates in the world. Droughts and floods are a noted part of Australia's climate and have an impact on the water sector's ability to balance supply and demand.
Demand for water is influenced primarily by climate and rainfall, population growth and the efficiency of water appliances in the urban sector. Soil type, crop type, commodity prices and irrigation technology are key determinants of demand for water in the rural sector.
During periods of drought, residential water demand is routinely managed through an escalating scale of water restrictions. In the irrigation sector, when water availability falls, allocations against entitlements are reduced to reflect the smaller overall 'stock' available to be shared in that year.
In the past, where water has been supplied predominantly from rainfall dependent water sources, water demand has been managed in response to water availability, and consumption therefore does not represent the true level of demand driven on customer preference.
During periods of drought, real water demand would have been higher than the volume able to be supplied, because the largest component of household demand is outdoor use, which increases with temperature and reduced rainfall in drier seasons. Cooler, wetter conditions will generally lead to a reduced demand in residential and rural areas. During periods of high rainfall, the requirement to irrigate crops, gardens and parks decreases.
Climate change will have an impact on almost every facet of the hydrological cycle and significantly affect Australia's water supply for urban, rural and industrial uses. This is because surface water stored in reservoirs and groundwater is the major source of water across Australia, and is dependent on rainfall and affected by evapotranspiration - the part of the water cycle that removes water from soil and vegetation and into the atmosphere through both evaporation and transpiration.265
The CSIRO reports that there may be less rainfall in southern and eastern areas over the medium to long-term, with droughts becoming more frequent.266 Climate changes would affect water supply and demand in both urban and rural areas, with dry weather periods increasing the strain on existing water infrastructure across Australia.
The millennium drought put enormous pressure on water delivery networks across the country. The length and severity of the drought precipitated an unprecedented water infrastructure investment program, with major metropolitan areas seeking to drought proof their cities through the construction of non-rainfall dependent sources, such as desalination plants in Sydney, Melbourne, South East Queensland, Adelaide and Perth, and recycled water schemes.
Construction of non-rainfall dependent sources of water supply means that restriction policies may not be as severe in the future. This is likely to mean that future consumption in metropolitan areas will not decrease as much as it did between 2005-06 and 2007-08 under drought conditions.
However, desalination facilities can provide only part of the solution to improving Australia's water security. The Audit found that the national capacity of desalination facilities was 539 GL in 2013. This represents only seven per cent of the total water supplied through water infrastructure included in the Audit in 2011-12 (7,641 GL), and 0.6 per cent of total dam storage capacity in 2013 (84,111 GL).267
Audit finding 79. Future climate variability could lead to a need for further water infrastructure to augment supplies. |
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265. Bureau of Meteorology (2010)
266. CSIRO (2014)
267. ACIL Allen Consulting (2014a)