Spatial and Temporal Change of Reference Crop Evapotranspiration in Marmara Region

Abstract

In this study, the annual total ETo values were estimated using the FAO Penman-Monteith method for 18 meteorological stations in the Marmara Region between the years 1990-2020 and their spatial and temporal changes were evaluated. For this purpose, annual total ETo trends were determined for each station using the non-parametric Mann-Kendall test and Sen method, and ETo maps were prepared using the Geographical Information System (GIS) Inverse Distance Weighted (IDW) interpolation method. According to the results of the study, the annual total ETo values varied between 742.3-1440.7 mm. While statistically significant increasing trends were determined in ETo values for Edirne, Kocaeli, Sakarya, Bozcaada, Çanakkale, Kırklareli, Uzunköprü, Tekirdağ, İpsala and Dursunbey stations, the trends were significantly decreasing for Kumköy-Kilyos and Keles stations. However, the increasing trends in ETo for Bandırma, Bursa, Şile, Florya and Gönen stations and the decreasing trend determined for Bilecik were not statistically significant. According to the annual average ETo map, ETo has reached high values in the western parts of the Marmara Region (south of Edirne, west of Balıkesir and Çanakkale), while ETo values have decreased in the east of Kırklareli and Tekirdağ (in the northern parts of the region) and east of Istanbul, Kocaeli and Sakarya (in the eastern parts of the region). In addition, while the average ETo values for long-term years were low in Kırklareli, the east of Tekirdağ, Kocaeli and Sakarya, statistically significant increasing trends were determined in the annual total ETo values calculated from the data of meteorology stations in these provinces.