Hydrological resilience to climate extremes and its implications for water security in the data-scarce Baro river basin

Abstract

Hydrologic resilience is one of the important issues that has to be addressed for sustainable water resources management. This study evaluates hydrological resilience to climate extremes in the Baro River Basin, Ethiopia, by examining how the basin resists, recovers from, and adapts to hydroclimatic extremes. The study combines drought indices, precipitation extremes, streamflow variability metrics, and event-based resilience analysis for evaluating the control mechanisms of hydrological vulnerability and water security under climate extremes. From the results, a highly variable runoff-dominated hydrologic system with a low baseflow index (~ 0.12), strong rainfall seasonality, and increasing magnitude of precipitation extremes was observed. Compared to droughts, flood threshold exceedances are more frequent and exhibit longer recovery periods: 2,264 floods and 684 droughts in the period between 1990 and 2018. A total of 2,264 flood and 684 drought threshold exceedances were identified. After applying event pooling and independence criteria, the effective number of independent events was substantially lower. The larger frequency of flood exceedances reflects the sensitivity of the basin to short-duration runoff responses rather than discrete independent flood occurrences. Moreover, it was observed that floods take longer recovery times, with a mean of 36 days and a median of 29 days, compared to droughts having a mean of 21 days and a median of 13 days. Overall, the basin appears resilient under average conditions but becomes highly vulnerable once critical thresholds are exceeded, emphasizing the growing sensitivity of hydrological systems to intensified and persistent climate extremes.