ASSESSING THE ACIDITY OF WATER DRAINING INTO RIVERS AND ESTUARIES
Effect of Acidity
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: