Abstract: Against the backdrop of intensified global climate change and human activities, hydrological processes of rivers predominantly replenished by snow and ice melt exhibit obvious nonstationary characteristics. Estimation of river ecological flow should reflect hydrological alteration and meet the needs of dynamic water resources management. Using the Buha River which is a tributary of Qinghai Lake as a case study, moving T-test and Pettitt non-parametric change-point test were used to diagnose abrupt changes in discharge and classify runoff stages. Ecological flows were preliminarily estimated using hydrological and hydraulic methods in combination with ecological flow satisfaction assessment, and the ecological flows for naked carp (Gymnocypris przewalskii) migration period were calibrated based on riverbed substrate stability. The results showed that the runoff regime of the Buha River during 1956-2020 exhibited significant stage-wise characteristics, with an abrupt change point around 2001. After 2001, the multi-year mean discharge increased by 15.98 m³/s compared with the preceding period. During naked carp migration period, compared with ecological flow estimates based on the 1956-2000 flow series, the ecological flow estimated from the 2001-2020 flow series for May and June was 14.65 m³/s (Tennant method), an increase of 6.04 m³/s over the previous period. The ecological flows for July and August were 42.70 m³/s and 42.30 m³/s, respectively (Q90 method), increasing by 12.04 m³/s and 20.98 m³/s, respectively. During the non-migration period, the recommended ecological flow range was 1.67-38.20 m³/s (Q90 method). Compared with ecological flow estimates based on the 1956-2000 flow series, the ecological flows for January-April and December remained largely unchanged, whereas those for September-November increased significantly, by 23.84 m³/s, 16.61 m³/s, and 4.64 m³/s, respectively. This dynamic estimation method provides a scientific basis for ecological flow accounting and optimal allocation in rivers subject to severe hydrological alterations.