PH
Low water PH in the Clarence Catchment is mainly related to the distribution of potential acid sulfate soils (soils containing iron sulfide) in floodplain areas.
These soils were mostly formed in the last 10 000 years in coastal areas with the mixing of land sediments high in iron oxide, with organic matter and sea water.
Iron sulfides in potential acid sulfate soils are oxidised when exposed to air forming sulfuric acid. This is leached into ground water and water courses during rains. Low soil and water PH can result in aluminium from the soil going into solution. Aluminium is toxic to most aquatic life forms, and has been linked to red spot disease in fish.
Testing for water PH is normally done in the field using PH indicator paper, or a PH meter. Potential acid sulfate soils are often field tested using a hydrogen peroxide test.
Dissolved oxygen
Dissolved oxygen levels in natural water bodies can be highly variable depending on water flow, weather conditions, position and depth in a water body, algal growth, organic matter present, and water temperature (colder water has higher saturation levels of dissolved oxygen).
Dissolved oxygen is essential for nearly all aquatic life forms. Most "healthy" rivers have high average levels of dissolved oxygen. Rivers in "stress" often have low levels of dissolved oxygen, or are prone to oxygen "crashes". Many fish kills are caused by "crashes" in oxygen levels.
Dissolved oxygen is normally field tested with a dissolved oxygen meter.
Nutrients
The main nutrients which are tested in water are phosphorus and nitrogen. Both of these nutrients have several forms in water bodies. They are often tested as "total phosphorus" and "total nitrogen".
The main impact of these nutrients is usually increased growth of all aquatic algae. Blue green algae (toxic algae) outbreaks are usually a result of high levels of phosphorus, nitrogen and high water temperature.
Excessive algal growth in water can result in low dissolved oxygen, and fish kills in severe cases. This results from oxygen use by aquatic micro organisms that decay dead organic material. Algae can also impede the growth of sea grasses in the estuary.
Laboratory tests are normally used for phosphorus and nitrogen. Streamwatch kits have a field test for phosphorus and nitrogen.
Suspended sediment
Suspended sediment has the following impacts in the catchment:
Suspended sediment is often measured in the field with secci discs, or perspex tubes. It can also be measured with a range of other devices.
Faecal coliforms
Faecal coliforms are bacteria found in the intestinal tracts of humans and most other mammals. They are used as an indicator of faecal pollution (and potential pathogens) in water. Testing is done by taking a water sample, and culturing colonies on agar plates in a laboratory. The higher the number of colonies counted per 100ml of water sampled, the higher the level of faecal pollution (human or animal). It is not always an effective way of assessing health risk because faecal coliforms have different survival times in water to other bacteria, viruses, and parasites. Also outbreaks of various diseases in the population can lead to an increase in the level of pathogens in water bodies, without a corresponding increase in faecal coliforms.
Organic materials (biological oxygen demand)
Organic materials in water create a biological oxygen demand when they are broken down by micro organisms. This can reduce disolved oxygen levels in water.
Chemical contaminants and heavy metals
These are toxic to aquatic organisms in varying concentrations, and have the potential to affect human health (particularly when concentrated in fish, crustacea and shell fish). Heavy metals and chemical contaminants are normally bound to sediment particles. They can be mobilised from sediment in conditions of low PH (such as in acid sulfate runnoff areas). Heavy metals and chemical contaminants are normally tested by sediment sampling, or sampling of shell fish (they bio accumulate).
(values derived from Australian water quality guidelines for fresh and marine waters - Australian and New Zealand Environment and Conservation Council)
1. Healthy waters
Protection of aquatic ecosystems
Dissolved Oxygen > 6 mg/l or 70% saturation
PH 6.5-9.0
Phosphorus and nitrogen Not high enough to cause abnormal levels of algal growth (Total P < 50ug/l, Total N < 500ug/l, Chlorophyll-a < 10ug/l)
Metals and pesticides Non-toxic levels (see guidelines)
Protection of human consumers of fish, crustacea and shellfish
Metals and pesticides Non-toxic and non tainting levels (see guidelines)
Faecal coliforms mean < 14 faecal coliform organisms /100 ml
Gonyaulax shellfish toxins < 0.8 ug/g shellfish
Ciguatera-like toxins < 20 mouse units/100 g shellfish
2. Recreational Water Quality
Protection of visual amenity
Algae < 15,000 to 20,000 cells/ml
Clarity visual clarity should not be reduced by more than 20%
Colour natural hue not changed by more than 10 points on Munsell Scale. Natural reflectance not changed by more than 50%.
Oil, debris Oil and petrochemicals should not be noticeable as a visible film or detected by odour.
Protection for secondary contact recreation
Faecal coliforms < 1000 faecal coliform organisms / 100ml
Algae < 15,000 to 20,000 cells/ml
Visual clarity should not be reduced by more than 20%
Colour natural hue not changed by more than 10 points on Munsell Scale. Natural reflectance not changed by more than 50%.
Toxic chemicals Should not exceed levels for untreated drinking water
Oil, debris Oil and petrochemicals should not be noticeable as a visible film or detected by odour.
Protection for primary contact recreation
Faecal coliforms < 150 faecal coliform organisms / 100ml
Algae < 15,000 to 20,000 cells/ml
Visual clarity should not be reduced by more than 20%
Colour natural hue not changed by more than 10 points on Munsell Scale. Natural reflectance not changed by more than 50%.
PH 5.0-9.0
Temperature Should be in range 15-35 degrees Celsius.
Toxic chemicals Should not exceed levels for untreated drinking water
Oil, debris Oil and petrochemicals should not be noticeable as a visible film or detected by odour.
3. Drinking water supply
Protection of drinking water supply with disinfection
PH 6.5-8.5
Dissolved oxygen > 6.5mg/l or 80% saturation
Sodium < 300mg/l
Hardness (as CaCo3) < 500mg/l
Iron < 0.3mg/l
Manganese < 0.1mg/l
Zinc < 5mg/l
Aluminium < 0.2 mg/l
Ammonia < 0.1mg/l
Chloride < 400mg/l
Copper < 1.0 mg/l
Total dissolved solids (salts) < 1000mg/l
Organics < 0.2 mg/l
Algae < 5000 cells/ml, < 2000 cells/ml if cyanobacteria
Toxic substances Non-toxic levels (see guidelines)
Phenolics Total phenols < 2 ug/l
Sulfate < 400mg/l
Hydrogen Sulfide < 0.05 mg/l
Taste and odour Not objectionable
Protection of ground water without disinfection
Faecal coliforms zero
All other parameters as above.
4. Agricultural water supply
Protection of livestock supplies
Faecal Coliforms > 1000 faecal coliform organisms / 100ml
Dissolved Oxygen > 6 mg/l
PH 6.5-9.0
Phosphorus and nitrogen Not high enough to cause abnormal levels of algal growth
Metals and pesticides Non-toxic levels (see guidelines)
Protection of irrigation supplies
Faecal Coliforms > 1000 faecal coliform organisms / 100ml
Algae should not be visible
Heavy metals and trace ions below toxic levels to plants (see guidelines)
Total dissolved solids (salts) < 500-1500mg/l depending on soils and crop
Protection of livestock supplies
Faecal Coliforms > 1000 faecal coliform organisms / 100ml
Algae < 10000 cells/ml
Major ions and nutrients below toxic levels (see guidelines)
Pesticides below toxic levels (see guidelines)
Protection of farmstead supplies
As for drinking water supply with disinfection.
5. Industrial water use
Protection of industrial supplies
Major ions below levels that cause problems in equipment and manufacturing processes (see guidelines).