The influence of climate change and variability on the IFD Curves in NSW, Australia

In this study, the possible impacts of climate change and multi-decadal climate variability on intensity-frequency-duration (IFD) curves were investigated using both stationary and non-stationary generalized extreme value (GEV) distributions. The current study covers rainfall data recorded over 41 years for two rainfall stations, namely, Gowrie-055194 and Sydney Airport-066037, located within New South Wales state in Australia. Three future times (2030, 2060, and 2100), as well as 15 rainfall durations ranging from 6 min to 3-days, are considered. Consideration of the location parameter of the GEV distribution is influenced by climatic change and/or climate variability, providing a more consistent set of IFD curves. It is found that when the future period increases, the relative differences between the stationary and non-stationary IFD curves generally increase. When the new IFD curves (i.e., derived from the stationary and non-stationary approaches) are compared to the Australian Rainfall and Runoff (ARR) IFD curves, it is clear that the ARR IFD curves and the new stationary IFD curves are more closely aligned compared to the non-stationary IFD curves. The findings of this research are useful and provide valuable information for future planning of water resources, environmental and urbanization plans. It is essential to understand the expected behavior of hydro-meteorological processes regarding the possible changes in the rainfall design.