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 (condition)

Condition: Pollutants in inland waters

  • Pesticides in inland waters
  • Biological contamination of inland waters
  • Waterways affected by increasing acidification
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    Pesticides in inland waters [IW Indicator 3.5]

    The monitoring of pesticides in inland waters is not undertaken routinely in Australia and apart from the irrigation districts of New South Wales, there is little recent information. Most monitoring in New South Wales has been focused on irrigation and drainage canals and tailwater, rather than rivers and streams (Bowmer et al. 1998). There is also information on pesticide contamination of groundwater, which is presented in Groundwater pollution. As pesticides may break down, attach to sediment or be diluted by the time tailwater and drainage water mixes with rivers and streams, it is difficult to assess the impact of pesticides on aquatic ecosystems with the current data available.

    Pesticides have been monitored in rivers and streams draining cotton growing areas of northern and central NSW (Cooper 1996; Muschal 1998). Table 24 presents a summary of pesticides monitoring in New South Wales irrigation districts since 1990 and their compliance against water quality guidelines for the protection of aquatic ecosystems (ANZECC/ARMCANZ 2000b; ANZECC/AWRC 1992) and for drinking water (NHMRC/ARMCANZ 1996). The Australian Drinking Water Guidelines recommend that no pesticides should be detected in drinking water. They have also established health guidelines based on 10% of the acceptable daily intake for an adult.

    Table 24: A summary of pesticides detected in irrigation districts of New South Wales
    Catchment/area Pesticides detected Source of contamination Reference
    Coleambally Irrigation Area (1991-93) Endosulfan, Atrazine, Diuron, Metolachlor, Simazine, Diazinon, Malathion, Thiobencarb & Molinate Where found: Drainage water Buchan 1994
    Coleambally Irrigation Area (1994-95) Endosulfan, Atrazine, Diuron, Simazine, MCPA, 2, 4-D, Thiobencarb & Molinate Where found: Drainage & supply water Bowmer et al. 1998
    Murrumbidgee region NSW Molinate, Malathion, Chlorpyrifos & Atrazine Crops: Rice & maize
    Where found:
    Drainage water
    Bowmer et al. 1998
    Murray Irrigation Area
    (1991-93)
    Molinate, Malathion, Diuron, Atrazine & Bromacil Where found: Drainage water Shepheard 1994
    Murray Irrigation Area
    (1994-95)
    Endosulfan, Atrazine, Diuron, Metolachlor, Simazine, Diazinon, Bromacil, MCPA, 2, 4-D, Malathion,Thiobencarb & Molinate Where found: Drainage water, supply water, lakes, streams & rivers Bowmer et al. 1998
    Gwydir River Basin Endosulfan, Atrazine, Diuron, Prometryne & Chlorpyriphos Crops : Irrigated cotton, sorghum, maize
    Where found: Rivers & streams
    Cooper 1996
    Gwydir River Basin Endosulfan, Atrazine, Amitraz, Chlorpyrifos, Profenofos, Diuron, Fluometuron, Metolachlor, Pendimethalin, Prometryn, Simazine & Trifluralin Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Muschal 1998
    Border River Basins Endosulfan, Atrazine, Diuron, Fluometuron, Metolachlor & Prometryn Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Muschal 1998
    Border River Basins Endosulfan, Atrazine, Diuron & Prometryne Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Cooper 1996
    Namoi River Basin Endosulfan, Atrazine, Chlorpyrifos, Dimethoate, Diuron, Fluometuron, Metolachlor, Pendimethalin & Prometryn Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Muschal 1998
    Namoi River Basin Endosulfan, Atrazine, Prometryn, Diuron & Chlorpyrifos Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Cooper 1996
    Macquire River Basin Endosulfan & Diuron Crops: Cotton, sorghum
    Where found:
    Rivers & streams
    Cooper 1996
    Macquire River Basin Endosulfan Crops: Cotton, sorghum
    Where found: Rivers & streams
    Muschal 1998
    Darling River Endosulfan, Atrazine, Diuron, Fluometuron, Metolachlor & Prometryn Crops : Irrigated cotton, sorghum, maize
    Where found:
    Rivers & streams
    Muschal 1998

    A pesticide in bold indicates that the concentration of that pesticide exceeded guidelines for the protection of aquatic ecosystems.
    A pesticide in italics indicates that the concentration of that pesticide exceeded guidelines for drinking water.

    In most areas, Endosulfan concentrations have regularly exceeded the guideline for the protection of aquatic ecosystems with fish being particularly susceptible to this pesticide (see the Land Theme Report). This broad-spectrum insecticide is used to eradicate a wide range of crop pests, but its use is greatest in cotton and rice cultivation.

    In northern New South Wales, Endosulfan levels have been decreasing (except in the Darling River) since the early 1990s (Muschal 1998) due to improvements in education, regulatory control and the implementation of best management practices. The decrease has been measured despite the fact that the total area planted for cotton in the region increased by 50% between 1990 and 1998. The second mostly commonly detected pesticide in northern and central New South Wales rivers and streams was Atrazine, a herbicide commonly used in canola, sorghum and sugar cane cultivation, fruit orchards and in forestry, but not for irrigated cotton. Poor run-off management and cultivation adjacent to unvegetated drainage lines are thought to be the cause of the high concentrations of Atrazine in some rivers and streams (Muschal 1998).

    Other pesticides that were regularly found in drainage water, rivers and streams in concentrations that could potentially affect aquatic flora and fauna were Molinate, Malathion and Chlorpyriphos. In the Murray and Coleambally Irrigation Areas, concentrations of the herbicide Molinate were regularly found to exceed drinking-water guidelines in drainage water from irrigated rice farms following spraying (Bowmer et al. 1998). High levels of most pesticides in drainage and irrigation water were directly associated with the application of pesticides in surrounding farms.

    The illegal use of DDT in the Ord River catchment in Western Australia has also been detected (DEP 1998).

    The Ord River diversion dam in NW Australia was completed and commercial-scale irrigation commenced in 1963. In 1972 the main dam was opened providing a water storage capacity in Lake Argyle of 10.76 billion m, which is several times the capacity of Sydney Harbour.

    The Ord River diversion dam in NW Australia was completed and commercial-scale irrigation commenced in 1963. In 1972 the main dam was opened providing a water storage capacity in Lake Argyle of 10.76 billion m, which is several times the capacity of Sydney Harbour.

    Source: Cassia Read.

    Biological contamination of inland waters

    As estuaries and the coastal zone are more popular areas for water-based recreation, there is only limited information on the biological contamination of inland waters nationwide. Apart from New South Wales and the Australian Capital Territory, the other states and territories do not undertake regular bacterial monitoring of inland waterways to assess their suitability for water-based recreation. In 1997/98, sites in most major rivers in New South Wales met bacterial guidelines for swimming (DLWC 2000; Sydney Water 1999). The exceptions were sites in the Hawkesbury-Nepean River, Barwon River, Hunter River, Macquarie River and southern river regions.

    Contamination of drinking water supplies by pathogens is an emerging issue (see case study below). The Human Settlements Theme Report contains a detailed discussion on the quality of drinking water in urban and rural centres.

    Waterways affected by increasing acidification

    Disturbance of acid sulfate soils has resulted in highly acidic pulses of water affecting some northern New South Wales coastal catchments (NSW EPA 1997) and northern Queensland coastal catchments (Qld EPA 1999). Other catchments where water acidity is considered a significant issue are Gippsland, Wimmera and the Murrumbidgee (NLWRA 2001a). Of major concern is the increasing trend in water acidity of inland waters in Victoria. Although many of the increases in water acidity were small, they were statistically significant and suggest that there are catchment-wide changes in land and water chemistry occurring. Increasing land and water acidification has been linked with major impact on terrestrial and aquatic ecosystems (Harris 2001). In the Hamilton and Wimmera-Mallee catchments, increasing alkalinity of rivers has been measured. This is also indicative of fundamental changes in land and water chemistry.