Frequency analysis of mean monthly streamflow in Çoruh basin, Turkey

This paper analyzes mean monthly stream-flow data recorded from 29 stream-flow gauging sites in Çoruh basin, Turkey. In regional mean monthly stream-flow analysis based on L-moments, at first, discordancy measures have been used to screen data on each of the 29 gauging sites. Homogeneity of the basin has been tested using L-momentbased heterogeneity measure. We divided Çoruh basin into 5 subregions and single sites. A number of L-momentsbased frequency distributions (i.e., generalized logistic (GLO), generalized extreme value (GEV), generalized Pareto (GPA), generalized normal (GNO), Pearson type III (PE3), and 5-parameter Wakeby (WAK) distribution) have been used in order to find a suitable distribution for quantile estimates. We determined that the GNO, GPA, and WAK distributions appeared to be a robust distribution in Çoruh basin. Finally, we carried out the Monte Carlo simulations for the quantile estimation accuracy. As a result, the GPA, GNO and WAK distributions generated similar quantiles.