There is evidence to suggest that the Great Forester River undergoes periodic episodes of impairment due to temporary decreases in water quality. The most dramatic of these was a major spill of pyrethrum in Hogarth Rivulet in April 1994. This resulted in the destruction of aquatic fauna  within Hogarth Rivulet and the Great Forester River with dead fish and the endemic freshwater crayfish Astacopsis gouldi being found up to 15 km downstream from the spill. The Department of Primary Industries, Water and Environment undertook a program to study the effects of such a major pollution event as well as to investigate and monitor the aquatic ecosystem recovery processes in the Great Forester River and the relative roles of tributary recolonisation in comparison with lateral movement of organisms within the main channel. Maxwell et al (1997) found that the invertebrate communities had recovered from the initial impact of the spill within a relatively short period of time. Within two months of the spill, over half of the taxa found at the control sites were found at the impacted sites. After 10 months, the invertebrates had established community structures similar in numbers and composition to the control sites. The species of most concern is the giant freshwater crayfish Astacopsis gouldi. Because of its low fecundity and territorial nature, it has a low rate of dispersal and it was hypothesized that recolonisation of the lower section of the Great Forester River could take a number of years.

Aquatic Ecology Of Rivers In the Great Forester Catchment
A Report Forming Part of The Requirements for State of Rivers Reporting

Tom Krasnicki River Health Officer Land and Water Assessment Branch DPIWE.
Report Series WRA 99/07 June 1999.