Statistical analysis of attributions of climatic characteristics to nonstationary rainfall‐streamflow relationship

Abstract This study demonstrates the benefits of using a simple statistical analysis to investigate the attributions of climate variables to the nonstationary rainfall-streamflow relationships. Rainfall and streamflow data from 65 catchments in southeast Australia are used to quantify the rainfall-streamflow relationship prior to, during, and after, the 1997–2009 Millennium Drought. The results showed that: 1) the annual streamflow is strongly correlated to the annual rainfall, however the relationship is different in the different hydroclimate periods; (2) the number of rainfall days and the mean length of wet-spell (MeWS) are the two most “stable variables” that can best predict annual streamflow in the different hydroclimate periods, followed by the maximum and 99th percentile of 90-day accumulated total rainfall (D90Max and D90P99); (3) the combination of MeWS with several other rainfall characteristics can explain the nonstationary rainfall-streamflow relationship through the different hydroclimate conditions in the eastern part of the study region; and (4) the relative difference in the key rainfall characteristics can help explain the nonstationary rainfall-streamflow relationship. The results here can help identify the key rainfall and climate characteristics to be considered in assessing the impact of climate variability and change on streamflow, and potentially for developing hydrological models that can be better extrapolated to predict streamflow under a changing climate.