In antiquity, the river was a major tributary of the Huai River in central China. Tributaries such as the Fan (反), Sui (睢), Tong (潼) and Yi (沂) swelled its banks as it passed through present-day Yutai, Pei, Xuzhou, Suqian, and Siyang counties in Shandong and Jiangsu. Its confluence with the Huai occurred at Sikou (泗口) or Qingkou (清口) at present-day Huai'an in Jiangsu.
From a very early date, the Huai was connected with the Yellow River through the Honggou Canal (t 鴻溝, s 鸿沟, Hónggōu, "Canal of the Wild Geese"). In 486 BC, King Fuchai of Wu built the Hangou Canal (t 邗溝, s 邗沟, Hángōu), connecting the Huai and Honggou to the Yangtze River to their south. Amid his ongoing wars against Qi and Jin, in 483 and 482 BC, he further expanded this network with the Heshui Canal (t 荷水運河, s 荷水运河, Héshuǐ Yùnhé), connecting the Si with the Ji River, which ran parallel to the Yellow River through densely peopled districts in what is now western Shandong.
In 1194, at the time of the Song and Jin Dynasties, the Yellow River altered its course southwards, engulfing the lower reaches of the Si River below Xuzhou City and those of the Huai River below Huai'an. As a result, the Si River no longer exists in Jiangsu Province.
During the 1851–1855 Yellow River floods, the Yellow River once more altered its course northwards, assuming the course of the former Ji River and again passing north of the Shandong Peninsula in 1852. However, due to the large amount of silt carried by the river, it left behind a 4-to-6-metre (13 to 20 ft) high layer of mud in the lower reaches of the Si River’s former course.
- Needham, Joseph; et al. (1971), Science & Civilization in China, Vol. IV: Physics and Physical Technology, Pt. III: Civil Engineering and Nautics, Cambridge: Cambridge University Press.
- Zhao Dingxin (2015), The Confucian-Legalist State: A New Theory of Chinese History, Oxford: Oxford University Press.