Hydrological implications of the Southern Oscillation: variability of the rainfall-runoff relationship

Abstract

A connection between El Nino Southern Oscillation (ENSO) and weather phenomena in eastern Australia has been recognized for several decades. However, little work has been devoted to addressing how this correlation affects hydrological system behaviour within regional-scale catchments. In this study, spatially distributed ENSO effects are evaluated in terms of monthly rainfall, evaporation, streamflow and runoff characteristics for a 1300 km 2 catchment. The catchment is located in southeastern Australia where previous studies have indicated only modest ENSO influences on rainfall variability. Spatial and temporal analysis indicates that strongest ENSOmdticed rainfall variability occurs during summer months. Additionally, the strength of the relationship is variable in space indicating that topographic controls may affect ENSO influences on rainfall totals and intensities. However, analysis of runoff shows substantially magnified ENSO-induced variability in comparison to the induced variability in rainfall. This may be attributable to the nonlinearity of runoff generation. Differences in antecedent moisture storage conditions will exist but may also be enhanced by complementary ENSO influences on daily rainfall intensities and mean monthly evaporation and temperature totals. The degree of the nonlinearity displayed by the hydrometeorological processes presented demonstrates that the significance of ENSO forecasts for surface water resource management should be assessed with direct regard to streamflow generation rather than on the basis of rainfall totals alone.

Rainfall and streamflow response to El Niño Southern Oscillation: a case study in a semiarid catchment, Australia

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“…Rainfall-runoff responses are typically nonlinear (Wooldridge et al, 2001, Zubair, 2003. In practice, runoff in these environments is threshold driven.…”

On the identification of ENSO-induced rainfall and runoff variability: a comparison of methods and indices

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Towards understanding hydroclimatic change in Victoria, Australia – preliminary insights into the "Big Dry"

“…However, the rainfall-runoff regression relationships used by Cai and Cowan (2008b) do not take into account any soil moisture carryover and therefore the inherent nonlinearity in the rainfall-runoff relationship (e.g. Wooldridge et al, 2001), and the importance of antecedent soil moisture conditions (e.g. Kiem and Verdon-Kidd, 2009), is likely to have been underestimated (e.g.…”