Inland Waters Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7
Water quality and sources of pollution (continued)
Contaminants and acidification
Contaminants of inland waters and sediments include metals, pesticides, pathogens (i.e. bacteria, viruses, helmiths and protozoa) and organic chemicals. They can have many effects including:
- acute and chronic ecological impacts - such as fish kills (short-term), bioaccumulation (long-term) and disease
- acute and chronic human and livestock health impacts - humans and livestock can also bioaccumulate certain toxicants from contaminated drinking water or food. Biological contamination can cause disease
- contamination of export produce - Australia exports millions of dollars of vegetables, grain, fruit, meat and poultry products to Asia, America and Europe and has a reputation as being a 'green' producer.
As in 1996, there are no national datasets on the extent and impacts of most contaminants, apart from information on localised known pollution hot spots such as derelict mines in Tasmania, New South Wales, Queensland and the Northern Territory (State of the Environment Advisory Council 1996).
Possibly the most widespread contaminants of inland waters are pesticides, which are used extensively in agriculture especially for the cultivation of cotton, rice, sugar cane and horticultural crops. In urban areas, pesticides are used in the garden and for insect control. Information on pesticides in New South Wales irrigation areas is available and is reported below.
It is likely that there are other chemicals in Australia affecting aquatic flora and fauna, especially in river systems draining urban and irrigated areas where chemical use is high. However, there is little information on the occurrence and ecological affects of these chemicals in the environment.
Endocrine disrupters are another group of chemicals that are known to occur in the Australian environment, but their impact on aquatic flora and fauna has yet to be determined (Australian Academy of Science 1998). The additional research required to assess the impact of endocrine disrupters has been outlined in a Commonwealth government information paper (Commonwealth Government 1998). In the United States, high concentrations of endocrine disrupters have been blamed for:
- vitellogenin (egg-yolk protein) production in male fish near sewerage outfalls
- the feminisation of fish-eating birds in North America - female reproductive tracts in male herring gulls
- same-sex pairing of western and glaucous gulls
- feminised male alligators, with small penises, in Florida
- reproductive failure in minks around the Great Lakes (Australian Academy of Science 1998).
Contamination and the quality of urban and rural drinking supplies are discussed in the Human Settlements Theme Report.
Acidification of inland waters may occur due to exposure of acid sulfate soils, acidic discharge from mine sites or the acidification of soils in agricultural areas. Although acidification of inland waters is currently a localised problem, there is some evidence that this could become a significant problem in the future. As well as having direct impacts on aquatic flora and fauna, acidification of inland waters can increase the leaching of pollutants and nutrients from contaminated sediments.
Pressures: Sources of pollutants
Pollutants in wastewater discharges [IW Indicator 3.6]
Biological contamination
The major sources of pathogens are sewage treatment plant discharges, the leakage of sewers and on-site sewage treatment systems (e.g. septic tanks) and livestock. Most sewage treatment plants disinfect their discharges to kill pathogens, but the effectiveness and reliability of disinfection varies with flow and age of the sewage treatment plant. Septic tanks and aerated spray systems are two examples of on-site sewage treatment systems commonly used in Australia. In some areas, poor maintenance of on-site treatment systems and inappropriate environmental conditions (e.g. soil, rainfall) have resulted in the leakage of untreated sewage into groundwater, rivers and streams. Around the Sydney region, localised sewage contamination of rivers and streams draining semi-urban unsewered areas has been measured and a program to sewer these areas has been implemented (Sydney Water 2000).
Other pollutants
Wastewater from sewage treatment plants and industry can contain pollutants in high enough concentrations to cause ecological harm. Apart from inland sewage treatment plants in the Sydney region, there is no comprehensive information on the quantities of pollutants discharged and their impact on inland waters. More information on pollutants in wastewater discharges will be available when the National Pollutant Inventory is fully implemented.
Pesticide use [IW Indicator 3.5]
For a full discussion of pesticide use and trends see the Land Theme Report. This is summarised below.
Between 1979 and 1994, the total sales of pesticides in Australia increased from $90 million to $650 million per year. Some of the increased spending was due to the higher use of more expensive and selective pesticides instead of cheap broad-spectrum pesticides, and the adoption of low tillage practices.
Wheat, barley, sorghum and oats make up 66% of the cropped area in Australia and herbicides are extensively used for these crops. Insecticides and fungicides are commonly used in cotton, fruit and vegetable farming. Cotton, rice and horticulture are the most intensive users of pesticides because of repeated applications and/or multiple crops within a year. Over 30 different pesticides are commonly used in sugar cane farming, with herbicides (66%) the most commonly used, followed by insecticides (20%) and fungicides (16%) (Hamilton et al. 1996). In terms of future pesticide use, the impact of genetically modified (GM) crops that either have a resistance to herbicides or have been genetically modified to produce natural pesticides (e.g. the Bt gene) is unclear.
Pesticides can find their way into inland waters via:
- excess irrigation water (i.e. tailwater) discharged into rivers and streams
- contaminated groundwater or drainage water
- surface run-off from areas where pesticides have been used
- over-spray and spray drift from aerial and ground spraying operations
- irrigation channels where herbicides have been used to control terrestrial and aquatic weeds
- volatilisation and precipitation
- domestic use of pesticides on gardens and for termite control (Bowmer et al. 1998).
Contamination of inland waters from mining [IW Indicator 3.7]
Australia has substantial mineral resources, and mining has been a common and widespread activity for over a century and a half. Today's environmental regulations ensure that most current mining operations do not pollute inland waters (see the Land Theme Report), though there are a number of operations that are still permitted to discharge contaminated water (e.g. the Ranger Uranium Mine in Kakadu). In the past, when environmental regulation was largely non-existent, mines were often abandoned rather than rehabilitated. Abandoned mines often fill with water which becomes acidic due to exposure of sulfides in the rock to air. This acidic water can eventually find its way into rivers and groundwater. Tailings from the processing of the mineral ores can also be improperly stored and wash into rivers or leach into groundwater. Tailings can contain heavy metals or poisonous substances such as arsenic and mercury used in the processing of ore.
There is limited information on the number, location and impact of abandoned mines in Australia (see Table 23). New South Wales, Tasmania and Queensland are most at risk from abandoned mines because of the longer history of mining and higher rainfall. On the west coast of Tasmania, many abandoned mines are known to have a significant localised effect on surface and groundwaters.
| State | Status |
|---|---|
| New South Wales | Over 300 entries in the Derelict Mines database. Program to assess the impact of abandoned mines currently being undertaken |
| Queensland | Up to 100 abandoned mine sites requiring significant rehabilitation. $18 million spent so far on rehabilitation of mines. The State Government has already undertaken work at Agricola, Horn Island and Chariah mines and at the Gray dumps in Charters Towers. Work is in progress at Herberton and Jibbinbah. Mount Morgan and mines near Croydon are being assessed. |
| Tasmania | Mt Lyell, Storey Creek, Zeehan area and the North-East Tinfields (near Gladstone) |
| Northern Territory | Rum Jungle |
| Western Australia, South Australia & Victoria | No information available |
Causes of acidification of inland waters
Acidification of inland waters can occur due to exposure of acid sulfate soils, acidic discharges from mine sites or the acidification of soils in agricultural areas.
Acid mine drainage (discussed above) is only considered a localised problem and is directly associated with abandoned mines. Acid sulfate soils occur generally below 6 metres AHD (Australian Height Datum) in the coastal catchments of northern and eastern Australia. The disturbance of acid sulfate soils or alteration of groundwater levels in areas containing acid sulfate soils can result in pulses of highly acidic water (<3 pH) entering inland waters.
Naturally acid soils occupy about one-third of Australia, but many soils in agricultural areas have become more acidic because of poor agricultural practices. Acid soils can wash into inland waters causing an increase in water acidity and in the mobility and availability of pollutants and nutrients. The area of soils with a pH less than 5.5 has increased over the past decade to 46.7 million hectares. For a full discussion of soil acidity in Australia see the Land Theme Report.