What did Tuoshanyan Weir look like?

A stone barrage weir spanning a tributary of the Fenghua River. The dam body slopes slightly downstream, and the overflow face is stepped for energy dissipation.

How did Tuoshanyan Weir work?

Rising tide → seawater advances upstream → weir blocks salt water → ebbing tide → upstream fresh water overflows the weir crest and flushes away salt water → the storage area behind the weir remains fresh → supplies irrigation and domestic use.

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Tuoshanyan Weir

A lateral overflow weir that uses tidal patterns to automatically block saltwater intrusion while storing upstream freshwater. Defends against seawater backflow while conserving upstream fresh water.

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Scientific Principle

Tidal hydraulics: weir height is precisely set above the high-tide level and below the normal upstream water level. Density difference (freshwater floats above saltwater) assists stratified management.