Causes of high sediment concentration in winter and low sediment concentration in summer in Qiantang River estuary

The reason is that the Qiantang estuary has a large sediment concentration in summer and a strong summer monsoon, which is greatly supported by waves.

The Qiantang River estuary has high sediment concentration in summer, strong summer monsoon and great wave support. Therefore, the sediment concentration in Qiantang River estuary is high in winter and low in summer, and the sediment carried by tidal current changes with the flow velocity. The sediment concentration in Jianshan and Yan Guan is the largest, with the measured maximum sediment concentration as high as 5 1kg/m, and the average sediment concentration in Ganpu is generally 3-4 kg/m, and the average sediment discharge per tide is about100000 tons.

In the sea area east of Jinshan, salinity is distributed horizontally, with high in the south and low in the north.

Due to the strong tidal current, the mixing of salt and fresh water in Qiantang River estuary belongs to vertical uniform mixing type, and the boundary of salt water intrusion moves up and down with the runoff of Qiantang River. In dry season, salt water can be traced back to Hangzhou, which affects the industrial, agricultural and domestic water consumption in Hangzhou.

The river bed in the estuary is wide and shallow, with a low tide depth of1~ 3m and a wide intertidal zone. Under the action of strong pulsating tidal current diverging from the flow path, with the increase and decrease of the contrast between runoff and tidal current, the riverbed is severely deformed.

In the autumn when the runoff is weak and the tide is strong, the main trough swings in the direction of rising tide, and in the season when the runoff is high, the main trough swings in the direction of falling tide. With the alternation of wet year and dry year, the swing of the main trough has also changed for many years.