Hydrological drought in two largest river-connecting lakes in the middle reaches of the Yangtze River, China

Poyang and Dongting Lakes are two important river-connecting lakes with a complicated water system pattern in the middle reaches of the Yangtze River, China. Recently, extreme drought events occurred frequently in the two lakes. This study analyzed the characteristics and differences of hydrological droughts in Poyang and Dongting Lakes during the period of 1964–2016 and explored the correlation between drought and large-scale climate indices. The results showed that the hydrological droughts of Poyang and Dongting Lakes became increasingly serious. Especially after 2003, both lakes entered the dry season earlier and the intensity of drought was increased. The hydrological drought of Poyang Lake was more serious than that of Dongting Lake in spring (16.40%) and winter (14.26%), while the autumn drought in Dongting Lake (32.46%) was severer than that in Poyang Lake (27.65%). The spring droughts in the two lakes were significantly associated with droughts in their local catchments with the joint probabilities of 10.84 and 9.52%, while the autumn droughts were consistent with the hydrological droughts of the Yangtze River with large joint probabilities (26.39 and 27.76%). The changes in large-scale climate indices more significantly affected the drought in Poyang Lake than that in Dongting Lake, especially in autumn and winter.