This is number 9 in a series of "FrogFacts" sheets produced by The Frog and Tadpole study group of NSW. Whilst it mentions frog species that are not found in Central and Northern Australia, the principles apply:
"Freshwater bio-indicators are animals and plants that can be used to determine the state of health of freshwater habitats.
Some creatures are very sensitive to water-borne pollutants while others less so. Changes in the abundance and diversity of these animals can be used as a measuring tool to determine water quality."
