The origins cases of the lakes along the middle-lower reaches of the Yangtze River are complicated.Lakes formed mainly by tectonic subsidence are of large scale and depth.But most of the lakes are tributary-mouth depressions, fan-edge depressions and interchannel depressions.The water level of the lakes is controlled by the water level of the main stream of the Yangtze River.During the glacial age and lower sea-level age, the main stream of the Yangtze River had eroded downward, and the lakes along the Yangtze River had dried up.During the postglacial age, the water level of the Yangtze River had risen from the river mouth to upper reach in succession, and in this case, the depressions along the Yangtze River had stored water and lakes came into being.The evolution trend of the lakes along the Yangtze River is that the lakes are filled by silt deposition and their static volumes decrease which lead to the annual change range of the lake level increasing and flood level keeping on rising.This is the main cause of the unceasing flood disasters along the middle-lower reaches of the Yangtze River.