Climatic drivers of Victorian streamflow: Is ENSO the dominant influence?

This study investigates the relationship between Victorian streamflow and a number of large-scale climate drivers, including the El Nino/Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). It is found that identifying a "dominant" climate driver, at least in the case of Victorian streamflow, is not a clear cut exercise. Importantly, it is shown that ENSO alone explains only a very small proportion of Victorian streamflow variability, particularly in autumn (a critical time in Victoria's hydrological and water resources management cycle). This is a crucial insight given that most seasonal forecasting schemes currently used in Australia are based primarily on ENSO relationships. The results presented here show that stratification of Victorian streamflow according to multiple large-scale climate drivers, and antecedent catchment conditions, provides significantly differing streamflow distributions. Therefore, incorporation of (a) antecedent catchment conditions into the forecasting framework and (b) improved insights into the multiple interactions between all relevant large-scale (and local) climate drivers should improve seasonal streamflow forecasting ability.