Statistics of extremes and estimation of extreme rainfall in semi-arid climate area using Regional Frequency Analysis

摘要

Extremely great floods are among environmental events with the most disastrous consequences for the entire world. Estimates of their return periods and design values are of great importance in hydrologic modeling, engineering practice for water resources and reservoirs design, etc. Regional rainfall frequency analysis resolves the problem of estimating the extreme rainfall events for catchments having short data records or ungauged catchments. This paper analyzes the maximum daily rainfall data recorded from 48 gauging sites in Cheliff basin, Algeria to derive regional rainfall frequency curves. On the basis of the L-moments and using a new cluster's algorithm, the region is subdivided in three subregions whose homogeneity is tested using the L-moments based heterogeneity measure. General extreme value (GEV) distribution is identified as the robust distribution for the study area. The estimation of precipitation quantiles corresponding to various return periods has been developed by using either L-Moments method or pooled station-year method. The comparison between quantiles estimated by these regional approaches or estimated by fitting a statistical distribution from local available rainfalls shows significant differences.