Assessment of Climate Change Impacts on IDF Curves in Qatar Using Ensemble Climate Modeling Approach

Abstract

Design rainfall in the form of Intensity–Duration–Frequency (IDF) relationship is widely used in hydrologic design. This study assesses the impacts of climate change on IDF relationship in Qatar. The relationship between current (2010–2039), intermediate future (2040–2069) and the far future (2070–2100) IDF curves is examined. An unbiased selection of suitable Coupled Model Inter-comparison Project Phase 5 (CMIP5) model scenarios provides the basis for this analysis. A total of 61 Global Circulation Models (GCMs) with 609 emission scenarios are considered. Samples are drawn from the selected multi-model ensemble and provide projections of the rate-of-change between current and future IDFs as predicted by the selected climate models and individual scenarios. A bootstrap analysis of the current period (2010–2039) is carried out and compared with historical data. Both the median and the upper 68% confidence intervals from the climate change analysis show increased rainfall from present to the future. Only the lower 68% confidence intervals show a decreased rainfall. The upper 68% confidence intervals (approximately 66% of the 84-percentile value) from the climate change analysis are adopted to predict the future design rainfall providing a reasonable degree of safety for design of infrastructure with long design horizon. The results indicate an increase of up to 50% for the 100-year rainfall event from current to the intermediate scenario (2040–2069). The rate-of-change of the far future (2070–2100) is at similar level to the intermediate period.