Trends Observed in the Numbers of Rainy Days in Turkey’s River Basins and Planning-Tourism Policy Suggestions

Precipitation variability is an important indicator for freshwater renewability and hydrometeorological hazards. The number of rainy days, one of the parameters considered within the scope of precipitation variability, is evaluated in determining the seasonality and intensity of the precipitation. In this study, which aims to analyze the trends observed in rainy days in Turkey’s river basins since the 1960s, the annual and seasonal rainy day series of 100 different stations were analyzed with the Mann-Kendall test. Statistically significant decreasing trends were determined in the number of annual, winter and spring rainy days series. These trends are prominent mainly in the basins located in the northwestern and southern parts of the country. At the same time, decreasing trends in closed basins and the Euphrates basin, which is Turkey’s largest basin, are also remarkable. The decrease in the number of rainy days may cause hydroclimatological results such as the shrinking of the rainy period and/or propagation of the dry sequences; the decrease in the total precipitation or the increase in the precipitation intensity and thus the frequency of the heavy rains. All these processes emphasize the importance of water and water-related natural disaster management in Turkey’s river basins.