ABSTRACT Drought-flood alternation (DFA) is a typical extreme event, with impacts on soil and water resources, ecosystems, and socioeconomic systems far exceeding those of droughts or floods alone. Daily precipitation data (1981–2020) were used to identify DFA events in the Poyang Lake Basin based on the 10-day scale standardized weighted average precipitation index (SWAP). Five key indicators were used to analyze DFA characteristics and evolution. Results show that: (1) DFA events mainly occurred from May to July, averaging 9–10 events over 40 years, and were most frequent in the Rao River Basin and upper Gan River (Dongbei area), especially during 2011–2020; (2) On average, DFA events affected 20% of the basin, with peak coverage exceeding 36%. The mean affected area was 34,878.4 km2 for drought-to-flood (DTF) events and 31,633.9 km2 for flood-to-drought (FTD) events. Since 2001, the expansion rate of DFA has been 1.4–1.5 times faster; (3) DTF events had shorter durations and lower intensities, while FTD events showed shorter durations but higher intensities. DFA events were asymmetric: floods tended to last longer in 1981–2000, whereas droughts were more persistent in 2001–2020. These findings support improved identification and monitoring of DFA events, aiding watershed ecological protection, resource management, and disaster prevention.
Xu et al. (Thu,) studied this question.