Reconstruction efforts mark the beginning of the period of the “latter” Han. The Bian canal had greatly suffered from inundations, and the repair works were directed by an engineer called Wang Ching. In 70 AD the Emperor Mingdi inspects this work:
“Since the dike ruptures at the outlet of the Bian canal, more than sixty years have passed. [….] The original emplacements of the gates have been lost in the middle of the river. Large expanses of water have formed, to the point that one could no longer recognize the original banklines. But now, the dikes have been reconstructed and the canal has been repaired, the flow stopped, and gates put back into place. The river (Yellow) and the canal (Bian) flow separately and have returned to the original beds. Because of this, we have sacrificed the most beautiful jade and the purest animals to the spirit of the river.”[420]
About 80 AD the Shaobei (today the Afentang dam) was also rebuilt; it dated from
the period of springs and autumns.
An agricultural crisis afflicts the empire of the “latter” Han from 170 AD. Major new floods occur on the lower course of the Yellow River. The desperation of the affected population once again creates a fertile ground for agitators; a large revolt is organized in 185 by the secret society Yellow Turbans. Although the revolt is quashed the dynasty does not survive it, being abolished in 220 AD.
The result of this collapse is a schism of the empire into three kingdoms, during which new hydraulic projects are undertaken. Avast irrigation system is put into service in 189 in the region of the ancient dam Shaobei, with numerous weirs built on small rivers. New transport canals linking the Jiang and the Hutuo in the north are built to support the offensive of the northern sovereign Cao Cao against his rival Yuan Shao in 204 AD. South of the Yangtze, dam-reservoirs are still being built in the 4th century AD; the Han canal, linking the Huai to the Yangtze, is also rebuilt during this period. These new canals already prefigure the future Grand Canal, whose construction accompanies the rebuilding of the empire. But it will be three long centuries, the chaotic period of the Chinese middle ages, before this construction begins.
