2002 Annual

Monday, 14 January 2002: 3:43 PM
The impact of hydrological processes before and after a bushfire in a watershed in southeastern Australia
Milton S. Speer, Bureau of Meteorology, Sydney, NSW, Australia; and L. M. Leslie, S. Liu, R. P. Morison, and L. Qi
The annual total stream flow in the Goulburn River watershed, New South Wales, Australia, covering the period from the early 1970s to 1997, is analyzed before and after the bushfire that occurred in the 1979/80 fire season. It is found that there was no significant increase in water yield immediately after the bushfire. However, there was a reduction in water yield 2-4 years after the 79/80 fire. This confirms other studies on a similar watershed with a similar vegetation cover of Eucalyptus. There is a connection between the 79/80 fire and the peak in potential evaporation that occurred in both Scone and nearby Paterson in 1980, which needs further investigation.

The seasonal patterns of potential evaporation and precipitation are characteristically high in summer and low in winter. High flow usually occurs in the autumn and spring, which is different to the summer peak that occurs in northern hemisphere watersheds such as is in China. The calculated seasonal pattern of evapo-transpiration in the Goulburn watershed using the water balance method is also used for precipitation. This confirms other studies that transpiration is the main cause of the impacts of fire on hydrological processes, although the seasonal pattern is different. Good simulation results of discharge in the Goulburn watershed are obtained using the Chinese Xinanjiang model.

The results achieved from the combination of the hydrological model, the SVAT dynamic model and a high-resolution mesoscale numerical weather prediction model, are very promising in depicting a dynamically consistent and accurate prediction of the impacts of fire on the hydrological processes in the Goulburn watershed.

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