Trend analysis of annual mean flows in Turkey river basins

Due to global warming, investigating whether there is a statistically significant change in hydrological parameters such as temperature and precipitation, it has become a necessity to take for the necessary measures in advance. In this study, the presence of trends in annual mean flow of 96 stream gaging station located on 26 river basins in Turkey was investigated. Firstly, the homogeneity of annual mean flow records was analyzed by Standard Normal Homogeneity, Buishand, and Pettitt tests. 11 stations, which were found to be inhomogeneous, were excluded from the study. Then, the Mann-Kendall trend test was applied to the streamflow data of the remaining 85 stations. The Sen method was also used to determine magnitude of the trend. In addition to these tests, Şen trend test, which is recently developed, was employed to evaluate trends in three clusters (low, medium and high). According to the Mann-Kendall test results, there is an increasing trends for the streamflow data of 3 stations, while the data of 26 stations have a decreasing trends. No trend was observed for the data of 56 stations. The results of the Mann-Kendall test and the results of the Şen method gave similar results in most stations.