Drought projection in the Urmia Lake basin under SSP Scenarios until the End of the 21st Century

The Urmia Lake basin is one of the most vulnerable areas to frequent high-intensity droughts in Iran. The aim of this study is to project meteorological drought in the Urmia Lake basin through the 21st century. For this purpose, the standardized precipitation-evapotranspiration index (SPEI-1) was investigated using the bias-corrected CMIP6 models under SSP1-2.6 and SSP5-8.5 scenarios during the period 2026-2100. The performance of individual CMIP6 models and multi-model ensemble (MME) generated by the independent weighted mean (IWM) method with three metrics including NRMSE, MBE, and PCC were evaluated. Overall, all individual CMIP6 models showed a good performance in the Lake Urmia basin, despite some overestimations of precipitation. However, the generated CMIP6-MME has increased the PCC values in all stations to 0.99. The CMIP6 MME showed a good performance of the SPEI-1 index in autumn, winter, and spring against observation from ground stations in the historical period. The result indicates a significant increase in drought events mainly in the west and north of the Urmia Lake basin in the warm period of the year during the 21st century. The severity and the percentage of below-normal years for the basin-averaged drought in the middle 21st century (2051-2075) is more than the ones in the far future (2076-2100), especially for the SSP5-8.5 scenario. These results can provide a basis for the development of drought adaptation plans in the Urmia Lake basin.