Abstract
Global atmospheric and oceanic perturbations and local weather variability induced factors highly alter the rainfall pattern of a region. Such factors result in extreme events of devastating nature to mankind. Rainfall Intensity Duration Frequency (IDF) is one of the most commonly used tools in water resources engineering particularly to identify design storm event of various magnitude, duration and return period simultaneously. In light of this, the present study is aimed at developing rainfall IDF relationship for entire Rwanda based on selected twenty six (26) rainfall gauging stations. The gauging stations have been selected based on reliable rainfall records representing the different geographical locations varying from 14 to 83 years of record length. Daily annual maximum rainfall data has been disaggregated into sub-daily values such as 0.5 hr, 1 hr, 3 hr, 6 hr and 12 hr and fitted to the probability distributions. Quantile estimation has been made for different return periods and best fit distribution is identified based on least square standard error of estimate. At-site and regional IDF parameters were computed and subsequent curves were established for different return period. The moment ratio diagram (MRD) and L-moment ratio diagram (LMRD) methods have been used to fit frequency distributions and identify homogeneous regions for observed 24-hr maximum annual rainfall. The rainfall stations have been divided into five homogeneous rainfall regions for all 26 stations. The results of present analysis can be used as useful information for future water resources development planning purposes.
Highlights
Induced atmospheric water vapour content as result of raising global temperature resulted in increased maximum precipitation
Based on the least standard error of estimate, best fitted probability distributions are identified and subsequent quantiles have been computed for different return period
Rainfall station clustering has been made taking into account the annual maximum rainfall depth of 24-hr duration
Summary
Induced atmospheric water vapour content as result of raising global temperature resulted in increased maximum precipitation. Rainfall Intensity-Duration-Frequency (IDF) relationship is one among the plethora of tools used for planning, designing and operating water resource development infrastructures [1] [2]. It gives an idea on return period of rainfall intensity which can be expected within a defined period [3]-[7]. It provides a concise information between the maximum intensity of rain that falls within a given period of time [8]-[10]. Cheng & Agha Kouchak [13] argues that stationary time series assumption may reduce the extreme precipitation magnitude and increases the flood risk
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