Determination of climate change impacts on drought and wheat yield in Porsuk creek watershed

Drought is main climatic event affecting to agriculture. The purpose of the study is to determine the effect of climate change on agricultural, meteorological, hydrological drought and wheat yield in Porsuk Creek basin. Drought analyses and wheat yield analyses were carried out with the help of Standard Precipitation Index (SPI), Standard Runoff Index (SRI), Palmer Drought Severity Index (PDSI) and WOFOST model using the past (1970-2018) and future (between 1970-2100) climate data produced according to the optimistic (RCP4.5) and pessimistic (RCP8.5) scenarios of HadGEM2-ES global climate model in Porsuk Creek Basin. The analysis revealed that the basin was located in an arid region; it was determined that hydrological and agricultural droughts were dominant and a meteorologically normal climate prevailed in the past. Sub basin in the study area where agricultural drought is experienced severely are Odunpazarı, Alpu and Tepebaşı, respectively. 1981, 1986, 1989, 2008, 2013, 2015 and 2018 years were dry. While the driest years are expected to be 2056, 2058, 2069, 2070, 2089, 2096; the wettest year is expected to be 2021. Porsuk Creek basin tends to be drought meteorologically and wet hydrologically in the future. In terms of agricultural drought; Although there is a potential for drought over time, it has been determined a normal climate will prevail throughout the basin. Odunpazarı is the driest place hydrologically in the future. When compare the biomass values of the wheat observed in Porsuk Creek basin with estimated by WOFOST model; there were + 23,8% difference for 2016 and + 1,2% difference for 2017 (2017 values>2016 values and estimated>observed). According to the results of the models in the basin; 0,73% wheat yield increase is expected in the near future (2020-2045). It is estimated wheat yield will decrease (%0.43-1.5) in all other periods. Compared to reference (1970-2000) period; climate change will be in the form of temperature and precipitation increases in the future in the watershed. As a result; it is believed that WOFOST can be used in safe in predicting future wheat yield, Although the model tends to predict wheat yield higher than observed values. As a result of this study, important data on drought periods and crop yield estimation have been produced for use by decision makers. In this way; planning of wheat farming will be made as temporal and spatial under drought risk. So, it will help to reduce yield losses.