why did ming rulers repair and expand the grand canal
History of the Ming dynasty After lying dormant and dilapidated for decades, the Grand Canal was restored under the Yongle Emperor's rule from 1411–1415. The impetus for restoring the canal was to solve the perennial problem of shipping grain north to Beijing. Shipping the annual 4,000,000 shi (one shi is equal to 107 liters) was made difficult with an inefficient system of shipping grain through the East China Sea or by several different inland canals that necessitated the transferring of grain onto several different barge types in the process, including shallow and deep-water barges.[97] William Atwell quotes Ming dynasty sources that state the amount of collected tax grain was actually 30 million shi (93 million bushels),[83] much larger than what Brook notes. The Yongle Emperor commissioned some 165,000 workers to dredge the canal bed in western Shandong and built a series of fifteen canal locks.[96][98] The reopening of the Grand Canal had implications for Nanjing as well, as it was surpassed by the well-positioned city of Suzhou as the paramount commercial center of China.[99] Despite greater efficiency, there were still factors which the government could not control that limited the transportation of taxed grain; for example, in 1420 a widespread crop failure and poor harvest dramatically reduced the tax grain delivered to the central government.[100]