东汉末置定阳县,隋废,唐初复置而寻废。《中国历史地图集》《中国行政区划通史》皆以定阳县治在今浙江常山县东南。今据新出土《赵鼎墓志铭》等考订,定阳县治当在今常山县西北何家乡钱塘村一带。《水经注·渐江水注》中有定阳溪水,流经定阳县。随着定阳县的罢废,“定阳溪”之名稀见于文献记载。明清志书纂修者因误读《水经注》《隋书·地理志》,以衢州府城之东的东溪(今乌溪江)为定阳溪,近代以来不少学者沿袭此说。结合对定阳县治的考订,《水经注》中的定阳溪应为今常山港而非今乌溪江。

Dingyang County (定阳县) was established at the end of Eastern Han Dynasty, subsequently abolished during the Sui Dynasty, briefly reestablished at the beginning of Tang Dynasty, and then abolished again. Previous historical records, including The Historical Atlas of China and The General History of Chinese Administrative Divisions, placed the administrative seat of Dingyang County in the southeast of present-day Changshan County (常山县), Zhejiang. However, recent archaeological discoveries, such as The Epitaph of Zhao Ding (《赵鼎墓志铭》), suggest that the administrative seat was actually located in the area around Qiantang Village, Hejia Township, in the northwest of present-day Changshan County. The Commentary on the Water Classic mentions the Dingyang Stream, which flowed through Dingyang County. With the county’s eventual abolition, the name ‘Dingyang Stream’ became seldom seen in documentary records. Compilers of local chronicles during the Ming and Qing dynasties misinterpreted the Commentary on the Water Classic and the Geographical Treatise of Sui Book, identifying the Dongxi River (now known as the Wuxi River, 乌溪江), located east of Quzhou, as the Dingyang Stream. This error has been perpetuated by many scholars in modern times. By reevaluating the location of Dingyang County’s administrative seat, this paper argues that the Dingyang Stream referenced in the Commentary on the Water Classic is the present-day Changshan Port, rather than the Wuxi River.