Introduction
Fresh water is an essential resource for human life, and ensuring we have a sustainable supply is of critical importance. Global water use tripled during the second half of last century – mainly due to increasing agricultural demands – and the world’s population continues to rise. If we do not address the issue of water sustainability, there will be a big increase in the number of water-stressed people over the next few decades (Hayashi et al 2013).
Australia is the driest inhabited continent (Smith 1998) and we are highly dependent on dams and irrigation systems to maintain our standard of living. However, damming rivers has had a disastrous effect on downstream ecosystems and irrigation has caused a considerable amount of sailinisation (Kingsford 2000, Connor et al 2012). Climate in Australia is very variable and global climate change means conditions are likely to get more extreme. Well targeted research and policy is essential if agricultural production is going to survive into the future (Wei et al 2011).
Water globally
Although the situation is improving, approximately 750 million people worldwide do not have access to clean water for domestic use (WHO 2014). A similar number do not have access to water for their livelihoods. While the number of people without access to water for domestic use is falling, the number without sufficient water for food production is only likely to increase. Water resources are finite and, as the world population grows, there will inevitably be less water available per capita. It is estimated that up to two thirds of the world’s population will suffer from water scarcity in the next few decades (Rijsberman 2006).
With a growing population, finding enough water for food production will become more and more difficult. It takes over 5000 liters of water to produce a typical day’s food in a developed country, or about half that for a vegetarian diet, and by 2030 many countries in Africa and Asia will not be able to feed their populations without importing a large amount of grain (Rijsberman 2006). 3.3 billion people are likely to be water stressed by 2050 (Hayashi et al 2013).
Water in Australia
Australia is the driest inhabited content, with an average annual precipitation of only 455 mm. However, rainfall varies widely across the continent, with some parts much wetter (e.g., Tasmania, with an average of 1352 mm) and some parts are much drier, (e.g., Lake Eyre, with an average of 238 mm). Australia also has the world’s highest year to year variability in rainfall (Smith 1998).
Although Australia is dry, it is very lightly populated, and has more water per capita than most other continents. However, the distribution of this water is not very well matched to population density. In addition to that, much of the water use is not well managed. A lot of irrigation is inefficient and inappropriate and has led to considerable land degradation – the Murray Darling Basin is a particularly bad example (Smith 1998).
An important aspect of the mismanagement of water in Australia is the harm done to floodplain wetlands by dam construction, river diversion, and irrigation. These ecosystems have very high levels of biodiversity and reduced flooding can have devastating impacts on them. Until recently, river management policy was determined by hydrological considerations, rather than ecological ones, but that has begun to change slowly. It is now increasingly understood that water needs to be shared with the environment if ecosystem services are to be preserved (Smith 1998, Hillman 2011).
Murray-Darling Basin
Flowing through four states, the Murray-Darling is Australia’s longest river system, as well as one of the largest in the world – and one of the driest. It hosts a considerable number of nationally and internationally significant ecosystems, plants, and animals (MDBA 2014). It also supports over 40% of the nation’s agricultural production. However, mismanagement of its water resources has caused considerable environmental damage and led to an inevitable long term decline in the economic, social, and environmental value of the river (Hillman 2011).
It is estimated that the flow from the Murray mouth was nearly 12 TL before colonisation – by 1994, this was reduced to approximately 2.5 TL, which fell to effectively zero flow by 2006 (Meyer 2014). This reduction in flow, combined with the effects of irrigation has caused a number of environmental problems along the length of the river system. Native fish species have considerably decreased in number, there has been a significant decline in water bird habitats, lack of flooding and increased salinity has had a major impact on the river red gum (Eucalyptus camaldulensis) populations along the river, and the diversity of aquatic plants has been negatively impacted (Hillman 2011).
Approximately 75% of irrigated land in Australia and 95% of land affected by irrigation induced salinity is in the Murray-Darling basin. Irrigation salinity in this region is only likely to get worse (Smith 1998). The traditional method of preventing a salinity induced reduction in crop yield is to over irrigate in order to flush salt into the ground water. However, the projected effects of climate change are likely to reduce the amount of water available for such an approach, as well as making water supplies more variable, meaning problems caused by salinity will increase (Connor et al 2012).
Conclusion
Increasing population and the effects of climate change will put extra pressure on supplies of water for food production. At the same time, an increasing awareness of the need for environmental water flows will mean competition between agriculture and the environment will become even more intense than it is already – and the environment is likely to lose out. However, floodplain wetlands have considerable ecological value and it is essential that water management ensures these ecosystems are allocated sufficient water to maintain their ecological function (Rogers & Ralph 2011).
References
Connor, JD, Schwabe, K, King, D, and Knapp, K 2012, ‘Irrigated agriculture and climate change: The influence of water supply variability and salinity on adaptation’, Ecological Economics, 77, 149-157.
Hayashi, A, Akimoto, K, Tomoda, T, & Kii, M 2013, ‘Global evaluation of the effects of agriculture and water management adaptations on the water-stressed population’, Mitigation and Adaptation Strategies for Global Change, 18, 5, 591-618.
Hillman, T 2011, ‘Ecological Requirements: Creating a Working River in the Murray-Darling Basin’, in L Crase (ed) Water Policy in Australia: The Impact of Change and Uncertainty, RFF Press, Washington, USA.
Kingsford, RT 2000, ‘Ecological impacts of dams, water diversions and river management on floodplain wetlands in Australia’, Austral Ecology, 25, 2, 109-127.
MDBA 2014, ‘About the Basin’, Murray-Darling Basin Authority, Canberra, ACT. Retrieved from http://www.mdba.gov.au/about-basin on 25/8/14.
Meyer, W 2014, ‘Water and irrigation in Australia – the place of irrigation in the Murray and Murrumbidgee’, seminar presented at University of Adelaide 13th August 2014.
Rijsberman, FR 2006, ‘Water scarcity: Fact or fiction?’, Agricultural Water Management, 80, 1, 5-22.
Rogers, K and Ralph, TJ 2011, ‘Impacts of hydrological changes on floodplain wetland biota’, in K Rogers and TJ Ralph (eds) Floodplain wetland biota in the Murray-Darling basin: water and habitat requirements, CSIRO Publishing, Collingwood, Vic.
Smith, DI 1998, Water in Australia: Resources and Management, Oxford University Press, Melbourne, Vic.
Wei, Y, Langford, J, Willett, IR, Barlow, S, and Lyle, C 2011, ‘Is irrigated agriculture in the Murray Darling Basin well prepared to deal with reductions in water availability?’, Global Environmental Change, 21, 3, 906-916.