9: Actions Arising from the Management of Pollutants

Waterways can be polluted from many sources (point or non-point) and through a variety of processes, including storm events and ground water seepage.

The characteristics of the catchment, land use practices, waste disposal methods, sewage treatment facilities and irrigation practices all contribute to pollution problems in a receiving water such as Lake Burley Griffin.

Controlling the pollutants entering the Lake is often difficult as it depends on the activities of a large number of individuals and agencies involved in the management of upstream catchments.

The Water Quality Management Plan focuses on early detection of pollutants entering the Lake, and on providing management actions where possible.

Health risks and environmental concerns can arise from elevated bacterial levels, toxic algal conditions and other undesirable events.

The monitoring of the benchmark values helps detect possible threats to water quality and provides a sound basis for actions to protect public health and environmental quality.

The water quality monitoring should also be able to identify events which make the water unsuitable for human recreational use.

A number of commonly occurring events can pollute Lake waters. Such events and associated changes identified in this Water Quality Management Plan include the management of:

Management of water quality during the above events is outlined in the following sections. There may be other events that could be considered equally harmful to water bodies and have the potential to change the water quality characteristics. They will be identified and incorporated in this plan as the knowledge of their detrimental effect becomes available.

9.1 Managing Stormwater Pollution

Understanding the Problems

Stormwater can contain nutrients, sediments, trace metals and micro-organisms.

Stormwater run-off can contribute significantly to the growth of microbes in a recreational water body, particularly at times of heavy rain when street gutters and stormwater systems that often contain decaying organic matter are flushed out by large volumes of water.

In some cases, sewer systems, which are connected to trunk sewers or treatment facilities, may overflow during heavy rains. Leaking sewers, which are difficult to detect, may also drain into the stormwater system and reach recreational water bodies.

Dry weather urban run-off may also contain high levels of contaminants, which may be of concern, particularly after a long dry period.

The land use patterns of the catchment can influence the quality of inflow to the Lake. The Lake's catchment comprises urban and rural lands. Where wildlife or domestic animals are found in dense populations, this may also add microbes in high densities in the run-off to the Lake.

Monitoring

Management

9.2 Managing Accidental Sewer Overflow

Understanding the Problems

Potential sources of microbiological contamination can occur from sewage resulting from system failures in sewage treatment facilities, leaking sewer lines, or heavy rainfall causing surface water run-off overflow.

When excessive rainfall occurs, some sewerage systems may not be able to process the subsequent volume of stormwater entering the system. This may result in releases of untreated or partially treated sewage into rivers and lakes. Flooding may also contribute to this problem.

Other sources of sewage release may include those from sewerage systems that are poorly maintained and through accidents, error, or deliberate action, from boat and recreational vessel holding tanks, sewer pump-out facilities, and portable toilets.

Septic systems, particularly when poorly maintained or during flooding, can introduce pollutants into receiving waters. This may occur in parts of the upstream catchment, but the risk from this source of contamination is very low.

Monitoring

Management

9.3 Managing Unacceptable Water Quality Conditions at Designated Recreational Sites

Understanding the Problems

A number of factors can contribute to the change in water quality conditions at designated recreational sites. As mentioned previously, surface water run-off can contribute significantly to growth of microbes in a recreational body of water, particularly after heavy rains.

Decaying green waste (water plants) usually found in the water body and foreshores, if not collected within a reasonable time, can contribute to the build-up of microbes. Excessive numbers of water birds, especially around sites with limited water circulation, may also contribute to the growth of microbes in the water.

Another source of microbiological contamination is the users themselves. At sites where high use is found, constituents of residual faecal matter may be washed off the body on contact with water, with most of it washed off within a relatively short time after submersion. Hence swimmers, bathers, waders, surfers, the fishing population, and others who may come into contact with water may all contribute to the contamination to which they are exposed.

Contamination due to accidental faecal releases or by intentional faecal releases are also possible, due to a lack of proper sanitary facilities near every potential recreational area.

Monitoring

Management

9.4 Managing Elevated Bacterial Levels

Understanding the Problems

In the past, elevated bacterial levels at certain times of the year have been a concern. Such events were sporadic, occurring in the late summer and early autumn period. However, the number of such events has probably increased in the last three years.

From the investigations completed into the cause of the events, the in-lake growth of bacteria has been reported as the probable reason for such bacterial blooms. Other sources of pollution (such as birdlife, stormwater overflow, etc.) may also contribute to this problem. These blooms seem to occur in February/ March, when water temperatures are at their maximum.

To assess the public health risk, further works are in progress, particularly to study the pathogenic nature of the organisms responsible for the elevated counts and the environmental conditions that trigger their growth.

Appropriate application of these findings can only be implemented after gaining approvals from relevant Commonwealth and ACT Government agencies. Until such time, all decisions on water quality conditions arising from elevated bacterial counts are to be based on ANZECC/ARMCANZ (2000).

Monitoring

Management

9.5 Managing Algal Blooms

Understanding the Problems

During the warmer months of the year, algal blooms can occur in the Lake. High concentrations of nutrients, combined with low flows, warm temperatures and other suitable environmental factors determine the frequency and extent of such algal blooms. They can occur when the concentration of nutrients is fairly low, but blooms are more frequent when the concentration of nutrients is high.

While algae perform an important role within aquatic ecosystems, excessive concentrations can have a detrimental effect upon the aquatic environment. Blue-green algae are a major concern because they have the ability to out-compete most other algal species in marginal light conditions. Additionally, under bloom conditions they can produce toxins and seriously reduce the aesthetic, recreational and sometimes public health qualities of the water.

Monitoring

Management

9.6 Managing Chemical Spills and Industrial Waste

Understanding the Problems

Inland waterways are susceptible to receiving contamination from chemical spillage and industrial wastes. The contamination may consist of industrial wastes that may be stored or transported in large quantities. This can lead to fire risk, toxicity, mechanical dangers and environmental threats.

These may occur due to deliberate dumping or accidental spillage from boats and land based activities. Generally, stormwater from industrial and urban catchments can also contribute to contaminants in the waterways.

Management of spillage requires an understanding of the type, volume and extent of the spillage. Such incidents of spillage are usually identified by the Lake maintenance crew, which has experience in managing such contamination. The crew also carries a spill response kit for immediate action (if necessary).

The crew undertakes a series of tasks to minimise damage to the ecology of the Lake with an assessment of any fire risk, toxicity, and environmental threats.

Monitoring

Management

9.7 Communications

Continuing assessment of the water quality conditions, dissemination of appropriate information to event managers, the public and regulatory agencies, and initiating appropriate response plans are vital to the management of this Water Quality Management Plan. To address these management issues, the proposed communication strategy will include:

Current Water Quality Information

The current status of water quality conditions is to be made available to the public through the Authority's:

Content of Public Information

The information to be made available will include:

Stakeholder Briefing

To disseminate water quality information, stakeholder briefings are recommended at appropriate times. Information on such briefings will be made available either through the Authority's web page or through letters.

Liaison with ACT Government Agencies, Contractors, Lake Users

Where management measures require closures/prohibition of the use of the Lake, the Authority will advise the following agencies over the phone of the intended actions:

9.8 Use of Legislation

9.8.1 Legislation Governing Management Actions

Legislation governing management of the Lake is the National Land Ordinance 1989 and the applied provision of the Lakes Ordinance 1976.

Activities such as the erection of warning signs and the issuing of public notices prohibiting the use of the Lake are controlled by provisions of the Lakes Ordinance 1976.

Prohibition of the use of the Lake area or parts of the Lake for health-related concerns is provided for by the following sections of the Lakes Ordinance 1976:

  1. 21. Subject to subsection (3), the Minister may, by notice published in a newspaper circulating in the Territory, prohibit entry to a lake area.
  2. Subject to subsection (3), the Minister may, by notice published in a newspaper circulating in the Territory, declare an area of a lake to be a prohibited area.
  3. The Minister shall not prohibit entry to a lake or declare an area of a lake to be a prohibited area unless -
    1. the condition of the waters of a lake or that area, as the case may be, is such as to constitute a threat to the health of a person entering those waters;
    2. the prohibition or declaration is reasonably necessary in connection with the maintenance or preservation of a lake or the maintenance, preservation or testing of an associated work;
    3. the Commissioner of Police has given to the Minister a certificate in writing stating that the prohibition or declaration, as the case may be, is reasonably necessary to enable members of the Police Force of the Territory to carry out their duties in a lake or in a lake area;
    4. by reason of an emergency in a lake or a lake area, it is necessary or desirable to do so; or
    5. to do so is otherwise in the public interest.
  4. The Minister may cause a boundary of a prohibited area to be defined by such means as he thinks necessary.

Section 15 of the Lakes Ordinance 1976 provides for the erection of signs for warning against lake-based activities.

The Authority's role in managing the Lake derives from the functions of the Authority set out in Section 6 of the Australian Capital Territory (Planning and Land Management) Act 1988. Additional information about the statutory responsibilities of the Authority can be found on this web site.

9.8.2 Other Relevant Legislation

In addition to provisions of the Lakes Ordinance 1976, there are several pieces of Commonwealth and ACT legislation which have implications for the Water Quality Management Plan. They include:

9.9 Roles and Responsibilities

Various agencies perform roles and exercise responsibilities in relation to water quality and associated activities in and around Lake Burley Griffin. They include: