Evaluating hydroclimate dynamics: trend analysis and change detection for enhanced drought monitoring in the upper Blue Nile basin

Hydroclimatic changes are key indicators of climate change, and tracking their direction of change is essential for effective water resources management. This study analyzed the trends and change points in the annual and seasonal time series TerraClimate data of key hydroclimate variables (rainfall, potential evapotranspiration (PET), maximum temperature (Tmax), and minimum temperature (Tmin)), and the Standardized Precipitation Evapotranspiration Index (SPEI) from 1958 to 2023 in the upper Blue Nile basin. The modified Mann–Kendall and Sen's slope estimator tests were employed for the trend analysis, while Pettitt's test detected abrupt changes in the time series data. Moreover, the sensitivity of SPEI to rainfall and PET was evaluated using correlation analysis. Results showed a significant increase in Tmin, Tmax, and PET, especially in spring in the western parts of the basin. Rainfall trends were mixed, mostly showing non-significant changes, except in winter. Change point analysis revealed significant shifts in SPEI and hydroclimate data, showing declines in SPEI and rainfall, with increases in PET, Tmin, and Tmax after their change points. Correlation analysis confirmed that rainfall has a stronger relationship with SPEI than PET. The findings of this study could serve as a proxy for climate change and guide the implementation of adaptive measures.