The relationship between hydroclimate and El Niño/Southern Oscillation (ENSO) has been used in
forecasting rainfall and streamflow. This paper presents a lag correlation analysis using rainfall and
streamflow data from 284 Australian catchments that show that the ENSO-hydroclimate relationship is a lot
stronger when the Inter-decadal Pacific Oscillation (IPO) phase is negative compared to when it is positive.
The remarkable contrast in the hydroclimate-ENSO relationship between the two IPO phases suggests that the
IPO should be considered in developing forecast models, particularly for long lead-times.