How does the Beijing-Hangzhou Grand Canal solve the water level difference caused by the north-south topography?

The water level of the Beijing-Hangzhou Grand Canal changes greatly from south to north. In order to solve this problem, three methods are mainly adopted.

Cut straight and bend.

Many sections of the Beijing-Hangzhou Grand Canal are not directly built into straight lines, but deliberately built into twists and turns. Curved reach can effectively eliminate the water level difference caused by different ground heights and ensure the river surface to be flat.

Build a weir.

The Beijing-Hangzhou Grand Canal connects many rivers. The water level of some rivers is lower than that of canals. For example, the water level of Huaihe River is lower than that of canals. People built weirs at the junction of the canal and Huaihe River to stop water, so that ships could pass through the upper and lower weirs, effectively solving the problem of water level difference.

Braking again

Heavy sluice is to build two gates before and after the reach where the water level difference needs to be solved. Before the ship reaches the back gate, close the front gate and open the back gate, and release water between the two gates to make the water level between the two gates consistent with the back river; After the ship reaches the front door, close the back door and open the front door, so that the water level between the two doors is consistent with the river in front. So that the ship can sail smoothly.

—— The above content is taken from Millay's children's book Field Natural History Class.