郭守敬
During the Yuan dynasty, the Mongolian emperors abandoned the ruined site of Zhongdu and its more meager water sources in favor of the Gaoliang watershed. The imperial engineers Liu Bingzhong and Guo Shoujing directed the construction of the new Imperial City of Khanbaliq (Marco Polo's Cambaluc &amp; the Chinese Dadu) around Zhangzong's former palace and Lake Taiye, which was an important part of the capital's water supply. The lake was expanded until it covered the area of the present northern and central "seas" and three palaces were built around it. The purity of the reservoir was protected by law: from its source at a spring on Yuquan Mountain to Lake Taiye, the Jinshui was given separate passes where it crossed other streams and commoners were forbidden to bathe, wash clothes, water livestock, or dump trash along its course.