About the Catchment Area : Issues & Problems

Water quality monitoring parameters
When monitoring the quality of water in our creeks and rivers, there are a number of things (parameters) that are tested for. These include the following:

Plant Nutrients

• Total Phosphorus
• Soluble Phosphorus
• Ammonia Nitrogen
• Total Kjeldahl Nitrogen
• Nitrate and Nitrite Nitrogen (NOx)

Heavy Metals

• Copper
• Lead
• Zinc
• Chromium
• Cadmium
• Mercury
• Arsenic

Microbiological (as required)

• Faecal Coliforms
• E. coli

Suspended Solids

• Turbidity
• Colour
• Total Dissolved Solids (salinity)
• pH
• Dissolved Oxygen
• Temperature
• Hardness
• Alkalinity
  

Why are these parameters important ?
The significance of each of these parameters is outlined below:

Nutrients
Phosphorus is usually the most significant nutrient in freshwater ecosystems but not in estuarine or marine waters. When present in excess it can cause algal blooms in rivers, ponds and lakes.

Soluble phosphorus is a measure of the biologically available dissolved form of phosphorus, whereas total phosphorus includes dissolved, particulate and organically bound phosphorus.

Nitrogen is usually the most significant nutrient in estuarine and marine waters, but not in freshwater ecosystems. Total Kjeldahl Nitrogen (TKN) is a measure of organically bound forms and includes organic nitrogen and ammonia nitrogen. Ammonia is a bioavailable nutrient. It is very soluble in water. Depending on the pH and temperature, a fraction of the total ammonia exists as an undissociated form (NH3). This can be toxic to some fauna. As pH increases and as temperature increases, the fraction decreases. Oxidised nitrogen including nitrite and nitrate nitrogen, are dissolved bioavailable forms.

Heavy Metals
Although some heavy metals, such as copper and zinc, are important trace elements for aquatic life, they can be toxic to some aquatic biota at higher concentrations.

They also can exhibit additive or synergistic effects, i.e. where there are additive effects from two or more metals present, their individual toxicities are combined; where there are synergistic effects, the combined effect is greater than the sum of the individual effects. Some metals can also bioconcentrate (increase in tissues relative to the amount of exposure), bioaccumulate (store the toxicants and continue to increase through the life of the animal) and biomagnify (increase up the food chain).

Physical Parameters
The pH of water influences many biological and chemical processes. With changes in pH, particularly at a lower pH, can increase the toxicity of some pollutants including metals and ammonia.

Temperature in surface waters varies with normal seasonal climatic fluctuations. Temperature affects the physical, chemical and biological processes in waterbodies, and therefore has an important role in determining the concentration of various water quality variables.

Dissolved oxygen (DO) is important for most aquatic organisms and varies with temperature, salinity, rainfall and diurnally as a result of plant and animal respiration and plant photosynthesis. Organic material in runoff or wind blown leaf litter can decrease oxygen levels during microbial decomposition.

Total dissolved solids (salinity) is a measure of all inorganic salts (major ions) and organic matter (nutrients) that are dissolved in water. Conductivity (specific conductance) is a measure of the ability of water to conduct an electric current and is influenced by dissolved mineral solids.

Salinity can affect aquatic organisms directly through physiological changes or indirectly by changing the species composition of the ecosystem.

Many Australian native aquatic fauna are adapted to relatively high salinities, e.g. many native freshwater fish can tolerate sea water salinity levels. Low salinities are required for domestic water supply, stock water and irrigation use.

Turbidity (measured in Nephelometric turbidity units or NTU) is influenced by the concentration of suspended matter, which consists of clay, silt and fine particles of inorganic and organic matter. Turbidity is a measure of the amount of scattering of light and can be approximately related to visibility.

Microbiological
For many years numbers of faecal coliforms and E. coli (a particular faecal coliform bacterium) have been used as a general indicator of the potential presence of pathogens. These are derived from animal as well as human sources. A wide range of pathogens can possibly exist including Giardia and Cryptosporidium which are resistant to disinfection and are therefore a potential problem for water supplies.

Biological parameters
The aquatic macroinvertebrate fauna, sucha as insects, crustaceans, worms etc,are used as bioindicators of riverine health and overall water quality status. Typically within a waterbody, either a watercourse, pond, lake or wetland, there is a natural assemblage of species and the community can be quite diverse. The community characteristics and diversity is dependent on habitat availability as well as water quality. Obviously a concrete drain would not be expected to have the same aquatic biological community as a watercourse with a diverse habitat structure (logs, reed, beds, pools, riffles, etc.) even if the water quality is similar.

With deteriorating water quality a loss of species usually occurs. The presence of toxic substances can have lethal or sublethal effects. Toxicants at relatively high concentrations can result in direct mortality, with some species being more sensitive than others. Sublethal effects at lower concentrations can eventually result in loss by, for example, affecting the ability to reproduce.

A common pattern with deteriorating water quality is a loss of diversity or species richness, with some pollutant tolerant species increasing in relative abundance through reduced competition or predation.

Water quality is typically highly variable, particularly as a result of episodic storm events. It is generally well known that the bulk of pollutant loads is transported during these events, which can be of quite short duration. A perceived advantage of using the aquatic macroinvertebrate fauna as bioindicators, is that they should give a longer term picture of overall water quality status. However, the characteristics of the biological community are also impacted by loss of habitat through catchment modification. There can also be a pronounced natural seasonal variation in communities as a result of flow patterns, particularly with ephemeral streams.

Source: From a report “Review of Ambient Monitoring Data” by ECO Management Services PTY LTD, November 2001