Assessing the impact of climate change scenario for simulating nonstationary rainfall intensity and duration

The intensity and frequency of extreme storms have been increasing over time due to climate change, challenging sustainable stormwater management. This study examines the impacts of climate change on the precipitation patterns and extremes across the Cedar River Watershed in the Pacific Northwest under the Shared Socio-economic Scenario (SSP-585) obtained from CMIP6 models. Two global climate models (GCMs), namely MIROC6 and CMCC-ESM2, are considered in this study. Prior to generating future extreme storms for the selected GCMs and scenarios, the GCM simulated precipitation data was bias corrected relative to in-situ daily precipitation data. Precipitation data was bias corrected using three different statistical methods (please Named three method); among those Equidistant Quantile Mapping performed best. Bias corrected precipitation from the MIROC6 showed better performance compared to the CMCC-ESM2 in reproducing the observed precipitation statistics. Finally, the bias-corrected precipitation data from MIROC6 was used to develop non-stationary Intensity-Duration-Frequency curves (IDF) to identify the extreme storm events and their return periods. The results indicate that the storm intensities increase (ranging from 2.5% to 30%) over the future periods for all selected return periods, with relatively larger increase for higher return periods i.e., 50-year and 100-year storms. Further, we use the bias corrected precipitation projections and generate mean monthly perception maps of the Cedar River Watershed for the periods of 2020–2039 and 2040–2059.