Station-based 34-year trends of rainfall and temperature in the Lake Tana sub-basin, Ethiopia

Abstract

Understanding long-term hydroclimatic variability is fundamental for advancing sustainability-oriented water and land management in climate-sensitive regions. This study investigates spatiotemporal trends in rainfall and temperature in the Lake Tana sub-basin of the Upper Blue Nile Basin, Ethiopia, using data from eleven meteorological stations covering the period 1989–2022. Seasonal and annual rainfall totals, along with annual maximum and minimum temperatures, were analyzed using the non-parametric Mann–Kendall test and Sen’s slope estimator. Results show that approximately 63% of stations exhibit increasing annual rainfall trends; however, statistically significant increases (p < 0.05) were detected only at Gondar and Maksegnit. In contrast, decreasing rainfall trends during the Belg (spring) and Kiremit (summer) seasons (the main rainfall season) were identified at several stations, indicating growing intra-basin rainfall irregularity. Temperature analysis reveals a consistent warming signal across all stations, with statistically significant increases in minimum temperature at Bahir Dar, Woreta, Wotet-Abay, and Gondar. The strongest minimum temperature increases occurred at Woreta (0.163 °C decade⁻1) and Wotet-Abay (0.166 °C decade⁻1). These findings highlight emerging sustainability challenges related to water availability, agricultural productivity, and ecosystem resilience in the Lake Tana sub-basin and emphasize the need to integrate localized climate trend analysis into sustainable development and adaptation planning.