Water yields from catchments fall significantly for 20 to 40 years if trees are killed by bushfire or timber harvesting . The MMBW began research into forest cover on water supplies as early as 1948 . In the early 1960s they set up a new series of paired catchment experiments in wet mountain forests near Healesville to measure the long term impacts of timber harvesting and bushfire on water quality and quantity . It took another 10 years for the results to emerge more clearly . It was found that while timber harvesting had an impact , the most dramatic threat to stream flows remained catastrophic bushfires like those on Black Friday in 1939 or Black Saturday in 2009
Black Saturday
Black Saturday bushfires
Eucalyptus regnans