Rainfall Intensity Duration Frequency (RIDF) Relationships under the Changing climate (Case study on Upper Blue Nile River Basin, Ethiopia)
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Date
2011-09
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Addis Ababa
Abstract
The main focus of this study is to see how intensity of rainfall changes in the Upper Blue Nile River Basin under the conditions of the changed climate. Predicted future climate change impacts indicate that there will be increases in rainfall, leading to an intensification of the hydrologic cycle. One of the expected consequences of change is an increase in the magnitude and frequency of extreme events (e.g. high intensity rainfall, flash flooding, severe droughts, etc.). Water management infrastructure designs are typically based on the use of local rainfall Intensity Duration Frequency (IDF) curves which are with the assumptions stationary of the future extreme events. However; this assumption is not valid under changing climatic conditions that may bring shifts in the magnitude and frequency of extreme rainfall. Such shifts in extreme rainfall at the local level demand new regulations for water infrastructure management as well as changes in design practices. IDF curves were constructed for observed as well as projected rainfall events after climate change and compared to see the changes. The methodologies implemented to assess changes in rainfall magnitude resulting from climate change are at first the regional downscaled grid rainfall data was downscaled to point level and further projected under current and future climate scenarios using statistical downscaling method. Then, disaggregation of daily rainfall into hourly ones was done by rainfall ratio method. Lastly, the statistical analysis of rainfall of various durations was done to develop intensity duration frequency relationships under the different possible climate scenarios. The results this research indicate that rainfall magnitude (as well as intensity) will be different than historically observed for a range of durations and return periods. Keywords: SDSM, intensity duration frequency curves, Upper Blue Nile, Climate change, extreme rainfall events
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Keywords
SDSM, Intensity duration frequency curves, Upper Blue Nile, Climate change, Extreme rainfall events