Drought Analysis in Long and Short Term Periods: Bursa Case

Natural disasters are important in human life. Drought is a disaster that depends on climatic and regional characteristics and affects all lives negatively. A detailed analysis of the region is necessary to determine the drought and take necessary measures. The researchers used different drought indices to determine drought. Standardized Precipitation Index (SPI) is one of the most commonly used drought indices that accounts different time scales. In this study, Bursa, Iznik, Keles, Mustafakemalpaşa, Uludag stations with long-term precipitation data in Bursa were examined for 1969-2015. The trend of precipitation data was determined by linear regression analysis. Precipitation data were standardized and evaluated according to the runs analysis. Lastly, drought analysis was performed for the periods 1, 3, 6, 9, 12, 24 and 48 months by the Standard Precipitation Index (SYI) method, which is widely used in our country and in the world. There was no significant trend in annual and monthly rainfall data. It was found that the monthly precipitation showed downward trend at Iznik, Keles, Uludag stations in December and at Bursa station in October. A statistically significant trend (5% risk) was not found in other months. Results of Standardized Precipitation Index are showed similarity which drought, normal and wet period rations in all stations. However, while normal or mild droughts are more frequent in short-term periods (3-6 months), severe or very severe droughts have been observed over long-term periods (12-24-48 months).