Trend analysis of precipitation and drought in the Aegean region, Turkey

Trend analysis of precipitation and drought will play a significant role in the future development and sustainable management of water resources. It is the main purpose of this paper to analyse meteorological droughts and trends. The variability of the standardized precipitation index ( SPI ) was investigated at 1, 3, 6, 9, 12 and 24 monthly intervals. The trends of 1, 3, 6, 9, 12 and 24 monthly SPI results were analysed by applying linear regression and the M ann– K endall and S pearman's rho tests at the 5% significance level. The linear slopes of the trends were calculated with a technique proposed by S en. Meteorological data from eight meteorological stations in the A egean region of T urkey were used for the period 1960–2013. The monthly precipitation trend decreases in D ecember, J anuary, F ebruary and M arch in all regions according to the linear regression analysis results. Annual precipitation decreased at five stations. In drought analysis by the SPI , in a short time period (such as 3 months) drought is more frequent but shorter, and as the period increases the duration of drought also increases but frequency decreases. Winter droughts are beginning to occur in the class of ‘severe’ in recent years. In this study carried out for different time periods according to SPI values in all stations, the highest ranges are in the normal and mild drought degrees. In addition, severe and extreme droughts are also seen intensely frequently. Trend analysis of precipitation and drought is compared. The trend analyses of precipitation are in parallel with the results of drought analyses.