Background The Dahan River is the main river in northwestern Taiwan and is one of two tributaries that join in
Taipei to form the
Tamsui, Taiwan's largest river system. Originating in the
Xueshan Range, the river begins life as a fast-flowing mountain stream prone to flooding during
typhoons. The Dahan skirts, but does not cross, the
Taoyuan Plateau, which lacks a reliable water supply of its own. The plateau has been farmed since 1680 using thousands of artificial ponds to capture rainfall; in 1928, when Taiwan was
under Japanese rule, the Taoyuan Canal was dug to divert water from the Dahan (then known as the Takekan River) onto the plateau. River water enabled the irrigation of an additional of land in the Taoyuan area. In order to improve its economic self-sufficiency, the government initiated the construction of Shihmen Dam, Taiwan's first multi-purpose water project. The Shihmen Development Commission was established to oversee the project. The initial budget for the dam was NT$1.4 billion, with approximately half of that as low-interest aid loans from the United States through the
Agency for International Development.
Construction Starting in July 1955, access roads and worker facilities were constructed at the dam site, and the area of the future reservoir was prepared to accommodate flooding. About 2,000 people (416 families) living in the Dahan River valley would be displaced by the project; they were relocated starting in 1956 to areas along Taiwan's northwest coast. Although the government built new homes, schools and other infrastructure as well as providing land compensation to families, the resettlement programme was the subject of bitter controversy. The dam was designed by Tippetts-Abbett-McCarthy-Stratton, with construction overseen by
Morrison-Knudsen (known previously for its work on
Hoover Dam). Heavy construction began in late 1959 when large equipment arrived at the dam site. Although work was interrupted several times by typhoon flooding, the river was successfully diverted into a tunnel in December 1960. into the reservoir – taking 23 years off its expected lifespan. About of canals were added to the existing irrigation system, including the new Shihmen Canal, bringing the total to , and a treatment plant with 30,000 tons per day capacity was constructed to provide municipal water supply. However, due to the project's high capital cost, the actual annual
return on investment was only 1.5 percent: "It stands as an engineering monument of which the Chinese people may be proud. But it was purchased at far too high a cost in terms of tens of millions of dollars of alternative developmental opportunities foregone." ==Dam details==