DETECTION OF TREND OR CHANGE IN ANNUAL FLOW OF AUSTRALIAN RIVERS

Changes in streamflow volumes resulting from climatic change can affec t the management of water resources. However, the detection of a stati stically significant trend can be difficult because of the large inter annual variability and the relatively short period of instrumental rec ord. In this paper, five statistical tests are applied to the historic al annual streamflow series of 30 unregulated Australian rivers, locat ed in protected natural catchments, in order to detect trends or chang es in the means. The Student t-statistic is also used to describe the relationship between interannual variability and the magnitude of chan ge and length of data required to identify a statistically significant trend. The analysis indicates that, with the current data set, there is no clear evidence to suggest that the greenhouse effect is impactin g on Australian streamflow volumes. The change required to identify a statistically significant change in the mean is directly proportional to the interannual variability, and less dependent on the length of da ta available. The interannual variability of Australian streams is twi ce that of Northern Hemisphere streams, therefore, a greater change is required in Australian flow volumes before a statistically significan t change,can be identified. The analysis of available historical recor ds, however. indicates that statistically significant trends can be de tected in the future flow volumes if the scenarios predicted by the GC Ms are realized.