Trend detection of streamflow variables in Turkey

This paper applies a procedure that identifies trends in streamflow variables in Turkey. The procedure utilizes the Mann-Kendall non-parametric test to detect trends. The research investigates three annual streamflow variables including annual minimum, mean and maximum streamflows and monthly mean streamflows for a network of 84 Turkish streamflow gauging stations in 26 basins of Turkey. The application of trend detection technique to fifteen streamflow variables has resulted in the identification of significant decreasing trends at the 0.05 level appearing mostly in the basins in western Turkey whereas almost no evidence of significant change was experienced with a general downward direction in the rest of the country. Of the 26 basins, however, only basins with the number of 14-16 and 22-25 exhibited significant increasing trend for small number of stations located mostly in the Black Sea and partly central and eastern Anatolia regions. The number of stations showing a decreasing trend is more than threefolds the number of stations with an upward trend whereas the significant downtrend exceeded the uptrends by twentyfolds. Besides, almost half of the decreasing trends were found statistically significant while approximately 8% of the increasing trends exhibited significant trend. © by PSP