4 Inland water | 2 State and trends of inland water environments
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
At a glance
Many of Australia’s inland water environments are in a degraded condition. In southern Australia, and particularly the Murray–Darling Basin, this has resulted from relatively high levels of water resource development, compounded by an extended drought. Although the floods of 2010 in south-eastern Australia have relieved the drought, the degree of eventual ecological recovery is unknown. In south-western Australia, the current drought (now believed to reflect a changed climate) has led to a decline in river and wetland health as a result of low flows and high stream salinities (from lack of dilution). Northern Australian and Tasmanian inland water environments are generally in good condition.
Nutrient levels in guidelines for fresh water are exceeded in all metropolitan areas and most areas of intensive agriculture. Monitoring of water quality, and interpretation of trends and causes, are inconsistent and sparse. It is therefore not possible to identify improving trends resulting from improved land practices.
Ecological processes have been altered to some degree across most parts of the continent. For much of northern and remote Australia, these changes are not significantly affecting ecosystem function and, with a few exceptions, there is little evidence that populations of aquatic species are declining. In most southern regions, inland water ecological processes have changed substantially since settlement and ecosystem function is significantly affected, with significant declines in many native species populations.
The concept of ‘environmental health’ of our inland water systems considers our rivers, wetlands and groundwater systems as ecological systems, including flora and fauna and their habitats, and the linkages between water systems and their catchments and climate. The health of inland water systems depends on their capacity to support key environmental functions (temperature regulation, nutrient and carbon cycling, salt balance and sediment transport) and to support communities and populations of native species. A healthy system is one that has retained its character, biodiversity and functions over time and is more resilient than a system with deteriorated health to pressures and changes in environmental conditions, including climate change, resource use, pollution and invasive pests.7
The health of our inland water systems is relative. We need to ask: relative to what? There are no generally applicable benchmarks for the diverse ecosystem functions and species that make up inland water ecosystems. Instead, ecological assessments generally use a ‘reference condition’ with which actual conditions are compared. This reference is normally the state of the ecosystem with no history of human disturbance.8-9
The assessment in this report recognises that, since humans have shaped the condition of our inland waters for more than 50 000 years, it is not possible or appropriate to separate Aboriginal influences from such a reference condition. The same conclusion was drawn for a North American application, in which Native American influences on the ecosystem were considered as integral to the ecological reference condition.10 Therefore, for the purposes of this assessment, the reference condition of the health of our inland water systems is their condition before European settlement.
The use of this benchmark does not imply that we should restore inland water ecosystems to their near-original condition—it is simply the condition from which we measure change where we can.
A review of all state and national environmental programs determined that no suitable, single ecological indicator of water stress was readily available.11 In this assessment, we look at the major dimensions of the state and trend of our inland water ecosystems:
- how the flows and levels of water in our environment have changed
- how the quality of water in our environment has changed
- how ecological processes and species populations have changed.