Sun Moon Lake Hydroelectric Power Plant (Daguan / Mingtan Power Plants)

The Sun Moon Lake Hydroelectric Power Plant (日月潭水力發電所) was the centerpiece of Japan's colonial industrialization of Taiwan and, upon its completion in 1934, the largest hydroelectric facility in Asia. The project fundamentally transformed Taiwan from an agrarian colony into an electrified industrial territory.

Origins and Planning (1916–1919)

In the 1910s, engineers of the Taiwan Governor-General's Office surveyed Sun Moon Lake (日月潭, Japanese: Jitsugetsutan) in the central mountains of Nantou Prefecture and recognized its extraordinary potential for hydroelectric generation; in 1918 the Civil Engineering Bureau drew up an outline plan for the works. The lake sits at an elevation of approximately 748 meters, with surrounding mountains providing a natural reservoir. The Taiwan Governor-General's Office established the Taiwan Electric Power Company (台灣電力株式會社, Taiwan Denryoku Kabushiki Kaisha) on 31 July 1919, capitalized at ¥30 million, specifically to develop the Sun Moon Lake hydroelectric project.

Construction (1919–1934)

Construction commenced in October 1919 with an ambitious target of completion by 1924. The engineering plan involved diverting water from the Zhuoshui River (濁水溪) — Taiwan's longest river — through the 15.1-kilometer Wujie Tunnel (武界隧道) into Sun Moon Lake, raising the lake's surface level by approximately 21 meters and merging the originally separate 'Sun Lake' and 'Moon Lake' into a single unified reservoir. The water would then be channeled through pressure penstocks down a 320-meter elevation drop to the powerhouse at the base of the mountains.

The project was plagued by setbacks. The post-World War I recession forced a postponement in August 1922, and after the 1923 Great Kanto Earthquake dried up capital flows to colonial infrastructure projects, the work was formally suspended on 1 December 1923. In March 1928 the American engineering firm Stone & Webster conducted a technical reassessment, which confirmed the project's viability; the Imperial Diet approved its revival in 1929, Matsuki Kanichiro (松木幹一郎) became president of Taiwan Electric Power Company in January 1930, and work resumed on 1 October 1931. Japanese construction firms — including Kajima (鹿島組), Obayashi (大林組), and Okura Civil Engineering (大倉土木) — were mobilized. The Jiji Line railway (集集線), completed in 1922, had been built specifically to transport construction materials.

The First Power Station (第一發電所, now Daguan Unit 1) was completed on 30 June 1934, with a completion celebration held in Taipei on 28 October 1934. The station housed five Pelton-wheel generators of 22 MW each, for a total installed capacity of 110 MW. The first three units were operational by June 1934; the remaining two came online by September. Construction of the Second Power Station (第二發電所, now the Mingtan/Jukong plant, 43.5 MW) followed from December 1935 and was completed in 1937, utilizing the tailwater from the first station.

Engineering Achievement

The project was a monumental engineering feat overseen by ten successive Taiwan governors-general over 15 years. Key infrastructure included: the Wujie Dam (武界壩) on the Zhuoshui River; the 15.1 km Wujie Tunnel bored through the Central Mountain Range; the Shuishe Dam (水社壩) and Toushe Dam (頭社壩) at Sun Moon Lake; five massive steel penstocks channeling water down 320 meters of head; and the powerhouse complex in the Shuili River valley. The project employed thousands of laborers, including indigenous Thao and Bunun peoples displaced by the reservoir flooding.

Wartime Industrial Role (1937–1945)

Following Japan's full-scale invasion of China in 1937 and the onset of the Pacific War in 1941, Sun Moon Lake's electrical output became indispensable to Taiwan's war economy. The plant supplied over 60% of the island's total electricity, powering a rapidly expanding industrial base: aluminum smelting at the Taiwan Aluminum Company (日本アルミニウム株式會社臺灣工場), chemical manufacturing (alloys, sulfuric acid, calcium carbide), munitions production, and food processing for military supplies. The abundant, cheap electricity available after 1934 spurred industrial growth, and until the 1950s the Sun Moon Lake system generated the greater part of the island's electricity.

Both the First and Second Power Stations were fortified with anti-aircraft guns and machine gun emplacements. A decoy 'fake power plant' was constructed in the Beishankeng valley as camouflage, and high-voltage electrical fences surrounded the perimeter.

Allied Bombing (1944–1945)

American strategic planners recognized that destroying Sun Moon Lake would cripple Taiwan's industrial capacity. On 13–14 October 1944, during the Formosa air battle, US carrier aircraft strafed and bombed the First Power Station; some accounts state that Penstock No. 2 (第二號壓力鋼管) was ruptured and never fully repaired, reducing generation capacity to approximately 80%.

The most devastating attacks came on 13 and 23 March 1945, when US bombers (accounts differ on the type and number of aircraft; B-24 Liberators are usually cited, while Taipower's history as quoted in Chinese sources speaks of six B-26s) struck both power stations. The main transformers, penstocks and switchyard of the First Power Station were destroyed, rendering the plant inoperable, and the Second Power Station was also damaged. With the Sun Moon Lake complex knocked out, Taiwan lost approximately 60% of its electricity supply — a catastrophic blow to the island's war production capability.

Post-War Recovery and Legacy

After Japan's surrender in August 1945, the Republic of China government assumed control of Taiwan's electrical infrastructure. Sun Yun-suan (孫運璿, later Premier of the ROC), then a young Taipower engineer, led the restoration effort with assistance from retained Japanese technical personnel. Power generation was partially restored by October 1946.

The First Power Station was renamed Daguan Power Plant Unit 1 (大觀發電廠大觀一廠) and continues to operate today with its original five generators, now rated at 108.3 MW combined. In 1985, the Daguan Unit 2 (大觀二廠) pumped-storage facility was added with 1,000 MW capacity, making the complex one of Taiwan's most important power generation sites. The Second Power Station became the Mingtan Power Plant Jukong Branch (明潭發電廠鉅工分廠). The entire Sun Moon Lake hydroelectric system, including the historic Wujie Tunnel, penstocks, and powerhouse buildings, is recognized as important cultural heritage of Taiwan's Japanese colonial-era industrial modernization.