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ASSESSING THE ACIDITY OF WATER DRAINING INTO
RIVERS AND ESTUARIES
The effect of acidity on fish
Fish and other aquatic life are very sensitive to changes of acidity in water. High levels of acidity in water that flows into our rivers and estuaries can make fish prone to disease (particularly "red spot" disease), can reduce fish spawning, and, in extreme cases, can cause fish kills. Acid water can also kill bottom-dwelling animals that fish rely on as a food source.Fish normally need the pH of water to remain in the range of 5 to 8 to remain healthy. Most water that drains from land into rivers and estuaries falls within this range. However, water that drains from swampy areas near rivers and estuaries may be very acidic. These areas are often underlain by sulfide-rich soils called acid sulfate soils. When these soils are exposed to air by drainage or excavation, sulfuric acid is formed which can leach into drainage water. This acidic water can then flow into rivers and estuaries.
Drainage from areas with acid sulfate soils commonly has a pH of less than 4 , and may be as low as 2 in extreme cases. You can download a booklet from the following web site that gives additional information about acid sulfate soils in Australia:
http://www.ea.gov.au/coasts/programs/cassp/booklet.html
