Drought analysis of the seyhan basin by using standard precipitation index (SPİ) and l-moments

The aims of this study were to: (1) monitor drought in the Seyhan Basin by using Standart Precipitation Index (SPI) based on long-term monthly precipitation records of 11 meteorological stations and (2) carry out regional frequency analysis using L-Moments method based on recorded precipitation data of the most drought month for each year acquired from Standart Precipitation Index method for each station. SPI values of each station for 3, 6, 9 and 12-month time scales were calculated. According to the results, all stations are on the boundary of drought. Research results show that the wettest station is Ulukışla and the most drought station is Karaisalı with respect to the average SPI values. According to the drought frequency values, however, the station that have the highest drought occurrence frequency is the Karaisalı station, whereas the station that have the lowest drought frequency is the Tufanbeyli station. Results show that Seyhan Basin is on the boundary of drought and mildly wet. Drought occurrence frequency is % 47.7. The index flood method based on L-Moments was used for identification of homogenous regions. Homogenous regions for 3 and 6-month time scales minimum precipitation series couldn?t be obtained. Homogenous regions for 9-month time scale minimum precipitation series were obtained only by dividing the whole basin into two parts. The whole basin is homogenous for the 12-month time scale minimum precipitation series. According to the results, the Pearson Type 3 distribution is found to be most suitable for two homogenous sub-basins with respect to 9-month time scale minimum precipitation series, whereas the Generalized Normal distribution is found to be most suitable for whole basin with respect to 12- month time scale minimum precipitation series. Key Words: Seyhan Basin, Standart Precipitation Index (SPI), Drought, L-moments Regional Frequency Analysis