Examination of hydro climatic trend and drought analysis for climate resilience in the eastern escarpment of Abaya Chamo sub-basin, Rift Valley Lake Basin, Ethiopia.

Abstract

A robust assessment of hydroclimatic variability is critical for strengthening drought resilience and optimizing water resource management in climate-sensitive and data-limited regions. This study provides one of the first comprehensive integrated hydroclimatic analyses of the eastern escarpment of the Abaya-Chamo sub-basin, evaluating multi-decadal trends in rainfall, temperature, streamflow, and drought through the Mann-Kendall trend test, Indicators of Hydrologic Alteration (IHA), and drought indices derived using DrinC software. Rainfall trends were largely insignificant across five monitoring stations, except at Hagereselam station, which exhibited an upward trend. Maximum monthly temperatures increased significantly at all stations except Dilla, while minimum temperatures rose at Fisehagenet, Yirgachefe, and Hagereselam. Streamflow analysis at the Tore gauging station revealed elevated low flows, reduced peak flows, slower recession rates, slightly decreased winter discharges, more frequent pulse events, and a reversal in flow direction. Drought assessment using SPI-6 and RDIst-6 indicated increased frequency and severity in recent decades, with Arbaminch, Yirgachefe, Dilla, and Hagereselam being particularly affected. The most severe drought levels were recorded at Yirgachefe (index score -3.31) and Arbaminch (index score -3.27) stations. Short-term indices (SPI-6 and RDIst-6) were more effective than 12-month indices in capturing recurring drought episodes, highlighting the importance of multi-scale drought monitoring. By linking meteorological drought with hydrological regime alterations, this integrated framework provided a comprehensive understanding of drought propagation and hydroclimatic interactions. These findings provide essential guidance for adaptive water governance and region-specific drought mitigation in a region increasingly vulnerable to climate change and broader climate drivers such as El Niño-Southern Oscillation (ENSO), underscoring the urgency of timely interventions in response to ongoing climatic variability.