Climate Change Impacts on Surface Water Budget Components Using High-Resolution Regional Climate Data for Snow-Dominated Basins in Türkiye

Date

2023-12-11

Author

Karaköse, Buse

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In recent years, there has been an increasing global concern regarding the issue of climate change. As a result of this phenomenon, there has been a noticeable trend towards water scarcity, often accompanied by extreme weather events, floods, and droughts. This thesis focuses on the impacts of climate change on surface water budget components of seven snow-dominated basins (Tigris, Euphrates, Aras, Coruh, Western Black Sea, Eastern Mediterranean, and Susurluk) in Türkiye. A comparative analysis was conducted between a 20-year reference period (1995-2014) and a corresponding pseudo-future period (2081-2100), examining the observed changes between the two intervals. The high resolution (4 km) data used in this study were obtained by Weather Research and Forecasting (WRF) simulations using ERA5 reanalysis data for the 1995-2014 and using perturbed ERA5 reanalysis data by the Pseudo Global Warming (PGW) method (with 13 Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Models (GCMs) under Shared Socio-Economic Pathway, SSP5-8.5 emission scenario) for 2081-2100. This study is the first water budget analysis conducted in Türkiye using high spatial resolution data (4 km) obtained with the latest version of GCMs and high emission scenario. Firstly, precipitation, Evapotranspiration (ET), and Snow Water Equivalent (SWE) maps for the reference period throughout Türkiye and anomaly maps showing the difference between the future and reference periods were created. Secondly, water budget analyses were carried out for the catchments selected in this study. With this analysis, the relationship of the water budget variables, both within themselves and with each other, could be observed inter and intra-years. According to the water budget analysis, a 1.4%, 4%, and 1% decrease in precipitation is expected in the Tigris, Eastern Mediterranean, and Susurluk basins, respectively. In comparison, an increase of 6.3%, 33%, 29%, and 3.8% is expected in the Euphrates, Aras, Coruh, and Western Black Sea basins. Thirdly, focusing on the SWE variable, the changes in the average SWE values and inter-annual variability were examined. It has been determined that there will be a substantial decrease in peak SWE values and a shrinkage of approximately 20%-40% in all selected basins during the snow season. Additionally, the study scrutinized how terrestrial water storage anomaly (TWSA) is influenced by variables such as snow water equivalent anomaly (SWEA) and soil water storage anomaly (SWSA). Based on TWSA graphs, it has been predicted that the impact of snow will be substituted by soil water storage. Moreover, the Eastern Mediterranean and Tigris basins will experience the most significant reduction in peak storage values in March, with a decline of 36% and 25%, respectively. Finally, the evaluation of surface runoff fraction values indicates that peak values occurred earlier in the future, especially in the Tigris and Euphrates basins. These findings suggest that snowmelt periods will occur earlier in the future period, and precipitation type will change from snow to rain.

Subject Keywords

Climate Change, Water Budget, Weather Research and Forecasting Model, Pseudo Global Warming, Coupled Model Intercomparison Project Phase 6 Global Climate Models

URI

https://hdl.handle.net/11511/108200

Collections

Graduate School of Natural and Applied Sciences, Thesis