Shihmen Dam is a major rock fill dam across the Dahan River in northern Taoyuan City. It forms the Shihmen Reservoir, Taiwan’s third largest reservoir or artificial lake. It provides irrigation in Taoyuan, flood control for the Taipei Basin, and hydroelectricity and domestic water supply for more than three million people in northern Taiwan.
Completed in 1964 after nine years of construction, Shihmen was Taiwan’s first multi-purpose water project and a major step towards the island’s economic independence after World War II. Year-round water releases from the dam enabled additional rice harvests and doubled Taoyuan’s annual agricultural output, while the reservoir became a major tourist destination due to its scenic beauty and plentiful fisheries. However, the project was criticized for its high cost and its impact on local communities, as more than 2,000 people were displaced to make way for the reservoir.
Like many other reservoirs in Taiwan, Shihmen has suffered from sedimentation, reducing its capacity by over a third. Efforts to reduce the rate of sediment accumulation, including dredging, check dam construction and watershed restoration work, have had a limited effect. This has diminished both the Shihmen Dam’s capability to contain floods and provide water during droughts.