Water Book

  1. Overview
  2. Foreword
  3. Contents, Acknowledgements
  4. Introduction
  5. Chapter 1: Current water availability and use
  6. Chapter 2: Water values
  7. Chapter 3: Water and climate
  8. Chapter 4: Groundwater
  9. Chapter 5: Water quality
  10. Chapter 6: Urban water sustainability
  11. Chapter 7: Future urban water supplies
  12. Chapter 8: Irrigation
  13. Chapter 9: Water for the environment
  14. Chapter 10: Water in mining and industry
  15. Chapter 11: Conclusions
  16. Endnotes, Index

Chapter 9: Water for the environment

Page 13 of 16

An aerial view of the Coorong and mouth of the Murray River.

By Rod Oliver and Ian Webster

Aquatic and water-dependent ecosystems require surface water flows or access to ground water to survive. They include Australia’s highly valued rivers, lakes, floodplains, wetlands, and estuaries.

Overview

Regulation of rivers with dams and weirs and the extraction of water from rivers and groundwater threaten the viability of these ecosystems, many of which are now degraded.

To function properly, these ecosystems and the species in them require not just adequate volumes of water but the right seasonal pattern and variety of conditions.

Providing water for consumption while providing for ecosystems often involves trade-offs or compromises. A good understanding of the condition of ecosystems under different regimes of water use can help make this trade-offs transparent and identify ways to reduce them.

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Interview with chapter author Rod Oliver

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Transcript

Aquatic ecosystems are those systems that require additional water over and above what they get directly from rainfall. They rely therefore on surface water flows and groundwater resources, so this includes our rivers, wetlands, lakes and estuaries, as well as groundwater dependent ecosystems that exist off groundwater resources.

We’ve regulated our water supplies to provide ourselves with the water we require, but in doing so building dams, changing flow regimes, pumping water from underground supplies, we’ve altered the availability of water for the environment. So we now, in systems where we have... it over extracted water, we now have a fine balance that we must meet so that we can sustain the environment and sustainable environments are now an important part of managing water resources. We need to be able to sustain the environment, but at the same time of course meet our own requirements for productive water use.

Environments need an amount of water of course to keep them alive, but they also need the delivery of water in particular patterns, so flow patterns are important, and also changes in groundwater level heights in response to climate and weather, and we have changed these patterns by the way we’ve regulated the systems. We need to understand much more about the connection between ecosystem health and the way that we supply water to try and sustain these environments, yet at the same time meet our own requirements.

Ecosystems have been effected in many ways, by land clearing, by pest species coming in, by changes in water quality, but certainly in many of the systems in Australia where – and across the world – where water usage has increased dramatically, it is the availability of water that is causing them the greatest problem.

So water for the environment requires trade-offs with water for productive purposes. This means that as water resources become more strained, there is going to be a greater requirement that we’re able to quantify the environmental needs, but also quantify the returns that we’re going to get for the use of that environmental water, just as we do require to look at the returns in irrigation water use, or any of the other productive uses.

We need to have far better models that enable us to make these connections and better assess these trade-offs.

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Interview with chapter author Ian Webster

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The Coorong is a coastal lagoon located at the mouth of the River Murray in South Australia, about an hour’s drive from Adelaide. It’s internationally renowned for its birdlife, and in particular its water birdlife. Many of the birds that live there migrate all the way from Asia.

Most of the freshwater that enters the Coorong comes into the system near its connection to the sea. The Coorong runs in the other direction along the coast, around about a hundred kilometres away from the sea. The Coorong as a consequence is an inverse estuary in which the (indistinct word – 0:34) of the system, in contrast to most estuaries, increases from the mouth towards its far end.

The Coorong is profoundly impacted by the River Murray, the amount of flow that comes through the barrages into one end of the Coorong impacts on its salinity regime, and the construction of the barrages in the 1930s and 1940s clearly altered the flow regimes in the Coorong, as have increased irrigation and water diversion in the River Murray over the last 50 years, and both of these have had profound impacts upon the salinity regime, water level regime, and as a consequence on the ecology of the Coorong.

Our present efforts are directed towards trying to maintain the ecological amenity of the Coorong with the water that we have available to supply to the system.  Scientific understanding of the Coorong has been developed over decades, but over the last five or six years we have improved on our scientific understanding. CSIRO Scientists have developed what’s called a hydrodynamic model of the Coorong, which effectively is a computer model that predicts water levels and salinity within and along the system as these respond to the various driving forces of barrage in-flows, of flows from the drainage area at the south end of the Coorong, to the weather, and to sea level variations.

The ultimate objective of these tools in their application is to ensure that the Coorong remains a suitable habitat for the birds that live in it.

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