Overview

Techi Dam is a concrete thin arch dam situated on the Dajia River in Heping District, Taichung, Taiwan. The structure forms the Techi Reservoir, which covers an area of 454 ha (1,120 acres). Located in the Tachien Gorge, the dam is a significant piece of energy infrastructure operated by the Taiwan Power Company. At a height of 180 m (590 ft), Techi Dam is the highest dam in Taiwan and ranks among the tallest dams in the world. The facility was completed in 1974 following five years of construction and remains operational.

The primary function of Techi Dam is hydroelectric power generation, with an installed capacity of 234 MW. In addition to power production, the reservoir provides essential irrigation water for the surrounding agricultural regions and offers flood control benefits for the Dajia River basin. The dam's design as a thin arch structure allows it to span the narrow Tachien Gorge efficiently, maximizing the hydraulic head for power generation while managing the river's flow. The Taiwan Power Company manages the operational aspects of the dam, ensuring the balance between energy output, water supply, and flood mitigation.

Why it matters

Techi Dam holds a prominent position in Taiwan’s energy infrastructure as the island’s highest dam, standing at 180 m (590 ft). This structural height places it among the tallest dams globally, marking a significant engineering achievement for the region. The facility is situated in the Tachien Gorge within Heping District, Taichung, on the Dajia River. Its primary function is hydroelectric power generation, contributing 234 MW to the grid under the operation of the Taiwan Power Company.

Strategic Role in Power Stabilization

The dam plays a critical role in stabilizing the erratic power output of downstream hydroelectric facilities, specifically the Tienlun and Kukuan dams. By regulating the flow of the Dajia River, Techi Dam ensures a more consistent water supply for these downstream units, thereby enhancing the overall efficiency and reliability of the local hydroelectric network. This cascading effect is vital for managing variable water inputs and maintaining steady power generation across the district.

Flood Control and Multi-Purpose Utility

Beyond energy production, Techi Dam provides essential flood control for the Dajia River valley. The formation of the 454 ha (1,120-acre) Techi Reservoir allows for significant water retention during peak flow periods, mitigating flood risks for surrounding communities and agricultural lands. Additionally, the reservoir supplies irrigation water, supporting local agriculture and enhancing the economic resilience of Heping District. Completed in 1974 after five years of construction, the dam remains a key operational asset in Taiwan’s water and energy management strategy.

Construction and Engineering Challenges

Construction of the Techi Dam began in December 1969, marking the start of a five-year engineering campaign in the rugged Tachien Gorge of Heping District, Taichung. The project was initially conceived with an ambitious design for a concrete thin arch dam standing 237 m high. However, significant economic and technical challenges arose during the early phases of the build, forcing a strategic reassessment of the structure’s dimensions.

To address these complexities, the project enlisted the expertise of prominent French civil engineers André Coyne and Jean Bellier. Their involvement was critical in refining the dam’s structural integrity and construction methodology. Under their guidance and due to the aforementioned constraints, the original plan was scaled down by 25 percent. The final design settled on a height of 180 m (590 ft), a reduction that maintained the dam’s status as the highest in Taiwan and one of the tallest in the world, while ensuring economic viability and technical feasibility.

The construction process involved navigating the challenging topography of the Dajia River valley. The decision to reduce the height was not merely a cost-saving measure but a technical necessity to manage the geological and hydrological variables present in the gorge. Despite the scale reduction, the engineering team successfully completed the structure in 1974. The dam creates the 454 ha (1,120-acre) Techi Reservoir, serving multiple functions including hydroelectric power generation, irrigation, and flood control.

Upon its completion in 1974, the dam was formally named by Chiang Kai-shek, reflecting its significance to the nation’s energy infrastructure. The project is operated by the Taiwan Power Company, which leverages the reservoir’s capacity to generate 234 MW of hydroelectric power. The successful execution of the Techi Dam project demonstrated the capability to adapt large-scale civil engineering designs to local economic and technical realities without compromising functional output.

Construction Timeline

Year Event
1969 Construction begins in December; initial design targets 237 m height.
1970–1973 French engineers André Coyne and Jean Bellier refine design; height reduced by 25% to 180 m due to economic and technical issues.
1974 Dam completed after five years of construction; named by Chiang Kai-shek; operations commence under Taiwan Power Company.

Technical Specifications and Reservoir Capacity

The Techi Dam is a concrete thin arch structure with a variable radius, designed to withstand significant hydrostatic pressure in the Tachien Gorge. Standing at 180 m, it is the highest dam in Taiwan and ranks among the tallest dams globally. The dam spans 290 m in length, forming the boundary for the Techi Reservoir. This structural design allows for efficient load distribution across the gorge walls, optimizing material usage while maintaining stability under variable water levels.

Reservoir and Watershed Statistics

The dam creates the Techi Reservoir, which covers a surface area of 454 ha. The total storage capacity of the reservoir is 218,150 dam³. This water body serves multiple functions, including hydroelectric power generation, irrigation, and flood control for the surrounding Heping District. The watershed area draining into the reservoir spans 514 km², capturing runoff from the Dajia River and its tributaries.

A key component of the reservoir's water management is the diversion from the Zhile River. This diversion channel helps regulate inflow, ensuring consistent water levels for power generation and agricultural needs downstream. The integration of the Zhile River diversion enhances the efficiency of the 234 MW hydroelectric output operated by the Taiwan Power Company.

Parameter Value
Dam Height 180 m
Dam Length 290 m
Dam Type Concrete thin arch (variable radius)
Reservoir Capacity 218,150 dam³
Surface Area 454 ha
Watershed Area 514 km²
Primary River Dajia River
Diversion Source Zhile River

How does the Techi Dam manage flood control?

The Techi Dam integrates significant flood control capabilities into its operational profile, serving the Dajia River basin in Heping District, Taichung. As the highest dam in Taiwan, standing at 180 m, its structural design includes three distinct spillway systems engineered to manage varying flow rates and reduce flood crests for downstream infrastructure, including the Shihgang Dam. These mechanisms ensure that excess water from the 454 ha Techi Reservoir is released efficiently, mitigating pressure on the river channel during peak inflow events.

Spillway Infrastructure and Capacities

The primary flood release mechanism is the crest spillway, which features five radial gates. This system is designed to handle a substantial portion of the reservoir’s outflow, with a designated capacity of 1,400 m3/s. The crest spillway allows for controlled discharge directly over the dam’s thin arch structure, providing a reliable first line of defense against rising water levels in the reservoir.

Complementing the crest spillway are two orifice floodgates located within the dam body. These gates provide additional flexibility in managing water levels, particularly during intermediate flow conditions. The combined capacity of the two orifice floodgates is 1,600 m3/s. This configuration allows operators to adjust discharge rates precisely, balancing the need for hydroelectric power generation and irrigation supply with immediate flood mitigation requirements.

For major flood events, the auxiliary spillway tunnel serves as the highest-capacity release channel. This tunnel can discharge up to 3,400 m3/s, making it the critical component for handling peak inflows. The tunnel’s substantial capacity ensures that even during significant rainfall events, the reservoir can shed water rapidly to prevent overtopping of the main dam structure.

Downstream Flood Mitigation

The coordinated operation of these three spillways results in a total release capacity of 6,400 m3/s. This aggregate capacity is strategically utilized to smooth out flood hydrographs before the water reaches downstream areas. A key objective of this flood management strategy is to reduce the flood crests impacting the Shihgang Dam, which is situated further down the Dajia River. By releasing water in a controlled manner through the Techi Dam’s spillways, the peak flow arriving at Shihgang is attenuated, thereby enhancing the overall flood resilience of the Dajia River system. The Taiwan Power Company operates these mechanisms as part of the integrated management of the Techi Reservoir, ensuring that flood control, power generation, and irrigation needs are balanced effectively.

Hydroelectric Power Generation and Downstream Integration

The Techi Dam’s hydroelectric infrastructure centers on an underground power station designed to maximize the potential of the Tachien Gorge. This facility houses three generators, each with a capacity of 78 MW, contributing to the plant’s total installed capacity of 234 MW (Taiwan Power Company). The underground configuration allows for efficient energy conversion while minimizing the surface footprint in the Heping District landscape. The power station is integral to the dam’s primary function of providing hydroelectric power, alongside irrigation and flood control services for the region.

Annual Energy Production

The Techi Reservoir, covering 454 hectares, feeds the turbines to produce an annual energy output of 359 million kWh (Taiwan Power Company). This production figure represents the direct contribution of the Techi facility to the regional grid. The consistent water flow from the Dajia River ensures reliable generation, supporting the operational status of the dam since its completion in 1974. The efficiency of the 180 m high concrete thin arch dam is critical in maintaining the head pressure required for this level of output.

Cascading Hydroelectric Integration

A key feature of the Techi Dam’s operation is its integration into a cascading hydroelectric system. The tailrace discharge from the Techi power station flows directly into the reservoir of the downstream Qingshan Dam. This strategic discharge allows the water to be utilized again for power generation at Qingshan, before continuing to the Kukuan, Tienlun, and Ma'an dams. This series of dams collectively generates 2.4 billion kWh per year, significantly amplifying the energy yield from the Dajia River basin (Taiwan Power Company). The cascading effect demonstrates an efficient use of the water resource, where the output of one facility becomes the input for the next.

Irrigation Benefits

Beyond electricity generation, the Techi Dam provides essential irrigation water to the lower Dajia River valley. The regulation of water flow through the dam and its subsequent release into the river system supports agricultural activities in the surrounding areas. This dual-purpose functionality enhances the economic value of the infrastructure, ensuring that the water resource serves both energy and agricultural needs. The flood control capabilities further protect the valley, making the Techi Dam a vital component of the region’s water management strategy.

See also