Advance in the study of drought frequency analysis

China frequently experiences large scale drought events. The latter have become one of the most important restraining factors affecting the socioeconomic development. Drought frequency analysis can reveal the characteristics of drought occurrences and their spatial and temporal distributions. Such an analysis is essential to the water resources planning, designing and management, as well as the risk-based management of drought disasters. In this paper, research progresses are systematically reviewed on the definition and identification of droughts and on the point to regional frequency analysis of droughts. The concerning issues are also reported on. In addition, the drought definitions applicable to drought frequency analysis are highlighted. The main problems in drought identifications are discussed. Three approaches for regional frequency analysis of droughts are summarized. Finally, it is proposed that the description and identification of droughts should take full advantages of the regional information on the hydrographical and meteorological characteristics, the atmospheric circulation condition, as well as the cause and extent of droughts. The basic theoretical issues in the distribution of variables, the drought return period and the empirical frequency need to be further studied. There should be paid more attention on the analysis of regional drought frequency and drought characteristics related to runoff, soil water and water system.