Abstract: Affected by the changing environment, the inconsistency of time series has posed increasing impact on drought frequency analysis, which, however, lacks consideration of such inconsistency. We propose to analyze drought frequency in consideration of the inconsistency of time series under the circumstance of hydrological alteration by diagnosing the variations of time series, extracting drought variables, and constructing Copula joint distribution function. With the Poyang Lake as the study object, we examine the monthly water level series from 1955 to 2015 of Hukou station by the proposed method. Results manifest that downward alteration of water level series occurred in 2003, after which the drought duration and drought intensity escalated, and the return period of drought events with the same frequency plunged. Water resources management departments in the Poyang Lake area should adjust timely the countermeasures to drought events to respond to the challenges posed by hydrological alteration.

Key words: hydrological alteration, inconsistency, Copula function, drought frequency, Poyang Lake