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The hydrological drought analysis at Dongting Lake is important for clarifying some of the most complex hydrological issues in relation to the intertwined interactions of a lake-river-reservoir system from the operation of Three Gorges Dam (TGD) located upstream of the central Yangtze River. The assessment metrics for a hydrological drought were established according to the exposed wetlands associated with ecological impacts, and used to determine the characteristic water level for the occurrence and severity of drought. The causal effects of a hydrological drought were analyzed based on the hydrological regimes across lake areas, and the drought impact from the flow regulation in the TGD was evaluated by using a neural network model. The hydrological systems analysis indicates that: 1) the frequency, severity and causes of hydrological droughts varied for different lake areas and seasons due to the specific basin morphology and the deviation of water regimes; 2) the water storage in the Three Gorges Reservoir has advanced the exposed time of wetlands, and has prolonged the autumn drought by approximately 30 %. However, the modeling also reveals that the regular operation of the TGD did not change the natural drought trends at Dongting Lake, and it is not deemed as the primary cause of recent hydrological droughts.

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