Hydrological Drought Analysis of Upper Ceyhan Sub-Basin Using Standard Precipitation Index and Standard Runoff Index

Since Türkiye is located in the Mediterranean climate zone, the impacts of global climate change are manifested in the form of decreased precipitation and consequent drought. Water resources are directly affected by drought. By analysing the impacts of drought on water resources, it can be ensured that measures can be taken before drought occurs and the impacts of droughts can be reduced in regions with high drought risk and drought probability. This study aims to analyse hydrological droughts in Upper Ceyhan Sub-basin by using Standard Precipitation Index (SPI) and Standard Runoff Index (SRI) methods. In SPI index calculations, monthly total precipitation data for 63 years for the period of 1960-2023 for Göksun and Elbistan Meteorological Observation Stations, monthly precipitation data for 53 years for the period of 1970-2023 for Afşin station, and flow data for the period of 1971-2015 at Karaahmet, Gözlerüstü and Hanköy flow monitoring stations were used for SRI index. SPI and SRI values were calculated and compared for a 12-month period. It was determined that hydrological droughts (lack of precipitation, low flow) occurred in the Upper Ceyhan Sub-basin in 2001, 2007, 2013, 2014, 2015, 2016, 2017, 2023; 617 dry months were experienced in the period of 1960-2023 and the probability of occurrence of dry periods was approximately 31%. It is considered that the results of this study will provide significant information that can guide decision makers in the Upper Ceyhan Sub-Basin water management and especially for water allocation, assessment of drought conditions and impacts and taking measures.