Why is the "Golden Waterway" Grand Canal the lifeline of Hangzhou?

During the Yuan Dynasty (1293), the Beijing-Hangzhou Canal was fully opened, and Hangzhou was still one of the central cities in the south of the Yangtze River. "The southeast is a place of wealth and culture, and the people of Jiangsu and Zhejiang are the source of culture." Travelers and merchants from Western Europe and the Western Regions came to China. Such as Marco Polo, Odoric of Pordenone, Ibn Battuta, Marino Sanudo, etc. The praise of travelers from all countries has given Hangzhou a very high reputation, and Marco Polo called it the most beautiful city in the world. At the end of the Yuan Dynasty, Zhang Shicheng widened the Guantang Canal for the convenience of travel between Suzhou and Hangzhou, and opened a canal from Tangqi to Jiangzhang Bridge. Shangtang River became a tributary, and the newly opened canal replaced the old road of Linping. During the Ming and Qing Dynasties, Longshan River was dredged, the northern section of the canal still followed the Beiguan River, but the main river in the middle of the canal city was changed back to Yanqiao River (Middle River), Qingchun River (East River). Because the canal no longer connects to the river and sea, the economic center of the city further developed to the north. Hushu is known as "Ten Miles Silver Lake House", the rice market is particularly prosperous, and grain is traded in the area of Maiyu Bridge. In the fourth year of Xuande in the Ming Dynasty (1429), Beixin Guan was established to collect ship fees and commercial taxes on the canal. Many tax collection ports and inspection ports were also set up around Hangzhou. Beixin Guan Wharf is the Royal Wharf, and commercial activities are not restricted by the curfew system in the city, so it has become the "Beiguan Night Market". In the first year of Hongzhi in the Ming Dynasty (1488), Choi Boo, a Korean, stayed in Hangzhou for 7 days and returned to his country via the Beijing-Hangzhou Grand Canal through the Dam Bridge. He wrote in "Piao Hai Lu" that the East Canal is a tourist attraction in Hangzhou. In the Ming Dynasty, the number of gates in Hangzhou was changed from thirteen to ten. Because the water level of Longshan River is higher than that of Qiantang River, the ship lock was changed to an earth dam, and ships had to flip over the dam to enter and exit. At the end of the Ming Dynasty, the canal no longer connected to the river. In the Qing Dynasty, a camp was set up under the flag. Yanqiao River was renamed Zhonghe, and Dongyun River was renamed Donghe. Zhejiang governor Mei Qizhao dug a new Henghe, connecting Zhonghe and Donghe. The Qing court dredged the Middle East River many times, and Zhao Shilin, Sun Wencheng, Li Wei, Xu Chengji, Ruan Yuan, Xue Shiyu, Ding Bing, Pan Bingnan and others successively managed the Middle East River. Among them, Zhao Shilin personally went to the field to inspect, and when the canal dredging project was completed, he used more than 13,000 taels of silver. Governor Li Wei presided over the dredging of Shangtang River and Fengkou River.