Spatiotemporal Climate Variability and Change-Point Analysis in the Fincha–Chomen Reservoir Catchment, Western Ethiopia

Abstract This study examined climate variability and trends in theChomen-Fincha Lake catchment area following the construction of the Fincha dam. Long-term climate data were obtained from satellite-based datasets, including CHIRPS rainfall data and TerraClimate temperature records. The study aimed to assess trends and detect possible shifts in rainfall and temperature patterns across selected towns in the catchment. To analyze the temporal trends, non-parametric statistical methods were employed. The Mann-Kendall trend test was applied to detect the presence and direction of monotonic trends, while Sen's slope estimator was used to determine the magnitude of change in the climatic variables. In addition, Pettitt's change-point test was used to identify the time at which significant shifts in the climatic series occurred. The results revealed considerable inter-annual variability in both rainfall and temperature during the study period. While some stations exhibited statistically insignificant trends, others showed significant increasing or decreasing patterns, indicating spatial variability in climatic changes across the catchment. The Pettitt test further identified specific years when abrupt changes in climate variables occurred, suggesting possible shifts in the local climate regime. These findings indicate that climate variability has been evident in parts of the Chomen-Fincha Lake catchment area since the construction of the dam, with potential implications for water resources management, agricultural production, and ecosystem stability in the region. The study highlights the need for continuous climate monitoring and adaptive management strategies to mitigate the impacts of climate variability in dam-influenced catchment systems.