Regional Frequency Analysis of 6 hours Maximum Rainfall over the Upper Euphrates–Tigris basins, Turkey

Abstract

Accurately estimating design rainfall or in other words, probable maximum rainfall has a crucial efficiency on fulfilling the expected benefit from any hydraulic structure since the value predicted as design criteria directly influences its planning, management and cost. What amount of a hydro-climatic variable which takes place under the influence of many environmental factors in a given region would be in future time is estimated based on its statistical behaviour. In many efforts related to water resources, the curve (IDF) representing the relationship among intensity, duration frequency of rainfall is basis for design rainfall amount required in the construction of any water-related structure. The availability of information extracted the curve of IDF substantially depends upon the frequency analysis and reliability of the current data. In this sense, the reliability of the data is very important as well as frequency analysis. The 6 hours maximum rainfall amounts from 18 sites in Upper Euphrates–Tigris basins were used as a material for regional frequency analysis based on L-moments approach. The existence of discordant stations was checked with discordancy measure for whole sites in the study area. First, single homogeneous region was tried to be formed. However, due to the irregularity value of Mardin station being greater than the critical value, no single homogeneous region could be obtained. Clustering analysis method was applied to obtain sub homogeneous regions. According to the dentograms of clustering analysis, the basin was divided into two sub homogeneous regions. Mardin station has been ignored in the study due to its discordant in the sub-regions. The generalized extreme value distribution was selected as the most appropriate regional distribution for the sub-regions.

Keywords

• Euphrates–Tigris basin
• Maxima rainfall
• L-moments

Kaynakça

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