Abstract :
Continuous wavelet transforms (CWTs) are used to identify the temporal variability of rainfall and runoff and their relationship. The wavelet analysis is applied to rainfall and runoff records from Peak Hill and Neurie Plains, in the upper Bogan River catchment in central western New South Wales, Australia, as well as to the large-scale circulation index SOI. A method utilising wavelet analysis is being developed to identify and isolate the ‘naturalʹ climatic components of the hydrological record, by using SOI correlations, as well as to distinguish the influence of other non-stationary trends, such as anthropogenic land use changes, on runoff records over time. Results using the Morlet wavelet show that the variability of both rainfall and runoff as well as their relationship has changed over time. A wavelet spectrum analysis shows a change in dominant frequency since the 1950s. Climate induced catchment response is at short time scales (27–32 months over the time period 1911–1996). The relationship between the SOI and rainfall is stronger from the 1950s onwards, with a dominant frequency of SOI at 27 months. The non-stationary, multiscale time series analysis could be important in floodplain management and development decisions, for the insurance industry, and in engineering, by identifying past changes, by detecting streamflow response to climate changes, and by aiding in future flood and drought predictability.
