Investigating the effect of potential evapotranspiration onhistorical drought indices i̇n şanliurfa province

Drought, which has been increasing in recent years due to climate change, is of great importance for water resources planning and management. In this thesis, it is planned to calculate the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index ("SPEI") values at 3, 6 and 12 month time scales using the available monthly average precipitation, monthly average temperature, monthly maximum temperature and monthly minimum temperature data to be obtained from the General Directorate of Meteorology (MGM) for the meteorological observation stations in Şanlıurfa province located in the Southeastern Anatolia Region. It is aimed to examine the characteristics of droughts that occurred in the past periods, to evaluate the applicability of the selected indices for the region, their performance and the relationships between them. In addition, two different values of SPEI will be emphasized by using Thornthwaite and Hargreaves models for potential evapotranspiration (PET) values in SPEI calculation. It is aimed to examine the temporal variations of SPI, SPEI(H) and SPEI(T) values at different time scales and to determine the effects of these scales on the drought trend. The effects of the length of the drought period on the three calculated indices will be investigated and the changes in the average and longest drought periods will be examined. This study aims to reveal the drought identification, detection and monitoring potential of the SPI and SPEI methods in the region and it is envisaged that it will