FIGURE 9.34 The Huang He’s changing course. The lower course of the Huang He has changed its direction of flow many times over the last several thousand years. In 2000 b.c.e., it flowed north and entered the Bo Hai, south of Beijing. Then it repeatedly shifted to the east, then southeast, like the hand of a clock, until it joined another river, the Huai, and finally cut south all the way to the Chang Jiang delta at Shanghai. Now it once again flows into the Bo Hai. The Da Yunhe (Grand Canal), considered the oldest and longest canal in the world, was completed about 610 c.e. and originally was built to carry troops and supplies north. Later, in the eighteenth century, it was used to carry taxes (in the form of grains) to the capital, Beijing.