昆明湖
The inclusion of the Jinshui and Gaoliang rivers gave Dadu a larger supply of water than the Lotus Pool which had nourished Ji, Youzhou, and Nanjing for the previous 2,000 years. To boost water supply even more, Yuan hydrologist Guo Shoujing built channels to draw additional spring water from Yuquan Mountain in the northwest through what is today the Kunming Lake of the Summer Palace through the Purple Bamboo Park to Jishuitan, which was a large reservoir inside Dadu. The expansion and extension of the Grand Canal from Dadu to Hangzhou enabled the city to import greater volumes of grain to sustain a larger population. The completion of the Tonghui Canal in 1293 allowed barges from Tongzhou to sail through the city right to the gates of the imperial palace at Shichahai. In 1270, Dadu had a population of 418,000 and another 635,000 in the surrounding region. By 1327, the city had 952,000 residents with another 2.08 million in the surrounding region.