Tree water use, bushfires, and the implications for urban and rural water supplies

After a bushfire tree water use is temporarily reduced and runoff for water supplies increases. Then seedlings grow and trees regenerate and use water faster again, reducing runoff. Hydrological measurements suggest that sometimes tree water use may increase greatly beyond that before the fire. This can mean very large losses, on a decadal scale, of catchment water yield for human use. The hypothesis is that tall trees transpire much less than younger ones. Our aim is to (1) test this idea with modern stable isotope techniques, pursue the underlying mechanism and (2) to add estimates of age and heights of trees, and their effects on water use, to models and test them against extensive hydrological records from areas before and after fires.