Dams - are they destroying our ecosystems ? AUSTRALIA VERSUS CHINA

Ecosystem structure and function is a pillar of water integrity – ecosystems lie at the heart of the global water cycle. All freshwater ultimately depends on the continued functioning of ecosystems and thus their management proves incredibly important to the wellbeing of the environment and human supply. This importance of water means that countries must source their water whilst also preserving the health of ecosystems which means that water catchments like dams, which can harm ecosystems must be managed to prevent harm to surrounding ecosystems.

'Ecosystem structure and function is the pillar of water integrity'

Dams have played an important role in human development throughout the world for thousands of years and both Australia and China employ such structures. However, the point of contrast is the management of these dams and the way in which ecological and environmental issues have been navigated and addressed. Sydney’s Warragamba Dam and China’s the Three Gorges are clear examples of the difference in water management and the way in which this impacts ecosystems.

Australia's Warragamba Dam and China's Three Gorges Dam

Due to Australia’s unstable water supply and rainfall, dams are incredibly important in water security, one in particular supplies the majority of Sydney’s water – Warragamba Dam. Although dams have the capacity to be incredibly harmful to the environment, strategic management at Warragamba dam limits such impacts. The Sydney Catchment Authority, a NSW Government agency created under the Sydney Water Catchment Management Act 1998, has acknowledged that Warragamba Dam can affect the natural flow of water downstream. Providing water to the river through environmental flows is one way the SCA helps to restore ecological processes and biodiversity of water-dependent ecosystems. Currently, the SCA releases 43.3 million litre of water per day from Warragamba Dam into the Nepean River for environmental and riparian purposes. These environmental flows have many purposes, protecting aquatic ecosystems, reducing aquatic weeds and frequency of algal blooms, improving river health, improving conditions for native fish, such as eels, carp, trout, macquarie perch, catfish, and goldfish frogs, water birds and river-dependent plants and animals that rely on different flows to trigger migration and breeding as well as protecting river condition for recreation such as boating and swimming. Warragamba Dam, having experienced issues such as a toxic algal bloom in 2007, has implemented rigid rules and management in order to preserve the health of surrounding ecosystems as well as water quality. Other management strategies include:

  • Educating farmers on the importance of erosion control to prevent contamination from faecal matter, to stop algal blooms.
  • Providing grants to help build fences to prevent contamination from erosion and sediment which can lead to algae blooms and negatively impact ecosystem.
  • Frequent testing of the water to ensure highest quality and to monitor the health of organisms and ecosystem
Warragamba Dam

China’s water supply pressures, the result of the ever-growing population and rapid economic growth, has been addressed through the development of dams, most notably the Three Gorges Dam. However, due to poor planning and management, the dam has resulted in significant impacts on the ecosystems of the surrounding regions, in particular the Yangtze river on which it is built. Poor management of the dam has impacted surrounding ecosystems dramatically. One of the most immediate environmental effects of the Three Gorges Dam has been an increase in landslide activity which has led to contamination of the water with fertilisers leading to algal blooms. These landslides are the result of erosion caused by the drastic fluctuation in water levels which weakened the banks. The sediment and silt dumped in the river contains high nutrient levels and thus has led to various algae blooms in regions of the Yangtze River.

A landslide dumping sediment into the Yangtze River

Lack of management of erosion and landslides, such as through the use of barriers or reinforcement, have led to contamination of the water and thus compromise water quality and adversely impacted the health of the river ecosystem. These algae blooms decrease the oxygen content to fatal levels, killing fish and other aquatic organisms, which are all important in maintaining balance in river ecosystems. As well as this, the dam has led to lower temperature and dissolved oxygen content in the water down-gradient from the dam. The presence of the dam disrupts the process of aeration and diffusion, the ways in which oxygen dissolves in the water. Water moves more slowly downstream, making it more difficult for oxygen to be available in the water, thus negatively impacting the health of the ecosystem and aquatic organisms. The poor planning and management of the dam, in particular the lack of water testing, regulation and erosion control, means that the Three Gorges Dam, although solving water supply issues in China, is to the detriment of the Yangtze River ecosystem.

As a result of the Three Gorges Dam and dumping of nutrient rich sediments, the Yangtze River often experiences algal blooms

Whilst Australia is able to employ dams to manage water supply and also maintain the integrity of surrounding ecosystems, China fails to manage many of their dams to minimise the environmental impacts. Warragamba Dam is a prime example of Australia’s ability to effectively manage dams and minimise harm to ecosystems whereas the Three Gorge’s Dam conveys China’s inability, in many cases, to effectively manage their water and the health of ecosystems at the same time.

Created By
Saachi Brajkovic
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Credits:

Created with images by Deni Williams - "Parque Nacional do Iguaçú / Iguaçu National Park" • ibsut - "Warragamba Dam" • 3dman_eu - "river gorge canyon" • 3dman_eu - "river gorge canyon" • kateausburn - "Lake Burragorang Lookout" • RowanTownsend - "Yangtze River, China"

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