The Dahan River begins in the Xueshan Range in Hsinchu County, near the border of Shei-Pa National Park, at the confluence of Takekan Creek (大嵙崁溪）and the Baishi Creek (白石溪）near Jianshi town. The Takekan, the larger of the two is sometimes considered part of the main stem. It flows north through a narrow gorge and receives the major tributaries of Sanguang Creek (三光溪), Lala Creek (拉拉溪), and Xibuqiao Creek (西布喬溪) from the east. At the Dongyanshan (East Eye Mountain) Recreation Area in Fuxing, it turns west and flows into Shihmen Reservoir, which is formed by the Shihmen Dam. Below the dam it flows northeast across Daxi District, then into the Sanxia District of New Taipei City, where it receives the Sanxia River (三峽溪). It continues to flow northeast across New Taipei City until its confluence with the Xindian River, which forms the Tamsui River.