Background

Preamble

This overview outlines how bushfires affect streamflow quantity and quality. The effects in the short term (months) are quite different to those in the long term (decades), but both can have significant impacts on the quantity of flow in streams and rivers, the quality of those flows, and the follow-on effects for water supply and the environment.

The fires that occurred in the summer of 2002/03 in Victoria, NSW and the ACT have coincided with perhaps the largest drought on record. At the time of writing, many of these fires are still burning. As a result, the intensity and extent of these fires are far more severe than the “Ash Wednesday” fires in 1983, and comparable to the “Black Friday” fires of 1939. Aside from the tragic human and property losses already experienced, we can expect major changes to occur in water catchments that will affect all water users – human and otherwise.

Physical, chemical and biological processes in natural ecosystems are all disturbed when wildfire consumes a forest. To describe the expected consequences of forest fire, we will here outline the kinds of changes that occur, then apply that to water-related issues.

The diversity of forest types, topography, soils and rainfall patterns across southeast Australia means that catchments can respond to fires in markedly different ways. The impacts of fire described below are necessarily general in nature, but exceptional or extreme responses often occur. Thus, we do not intend to describe either the worst or the best consequences of fire, but we do try to alert the reader to the range of impacts that might be anticipated. The publications listed on this website describe a wealth of observations from historical fires. As always, application of those experiences to a catchment burnt in the current fires should be done with extreme caution, and only after we have a sound understanding of the factors that determine the response of each catchment.

This site also contains answers to a list of Frequently Asked Questions (FAQs). In most cases, the background to the FAQs will be described or mentioned here. Keywords are given for the major topic areas, and these are linked to the publications that are listed on this website. In some cases, key references are also given throughout these background pages.