The Barmah river red gum forest is part of a larger tract of such forest along the Murray River. It is known that river flooding provides an important source of water for the sustenance of these forests. The contribution of Murray tributaries to the flooding was examined. The main stem of the river above lake Hume was the single most important source. Removal of this would lead to a 55% decrease in forest flooding. Removal of either the Ovens or the Mitta Mitta would lead to a 30% reduction, while removal of Kiewa river would lead to reduced 15% of flooding. No particular tributary can be regarded as a source of extreme forest floods since all tributaries more or less act in concert. A backwater influence of high water levels at the down-stream confluence of the Goulburn and Murray River leads to high water level in Barmah. However, because of the short-lived nature of such high water levels it is unlikely that such floods penetrate very far into the forest.