Overview

The Longshou II Dam, also known as Longshou No. 2, is a significant hydroelectric infrastructure project located on the Heihe River in Gansu Province, China. Classified as a concrete-face rock-fill dam, it serves as a key component of the Gansu Heihe Rural Hydropower Development initiative. The facility is operational and supports a power station with an installed capacity of 157 MW, contributing to the regional energy grid. The dam is situated approximately 35 km southwest of Zhangye, positioning it within a strategic corridor for water resource management and power generation in the province.

Structurally, the Longshou II Dam stands 146.5 m high and creates a reservoir with a total storage capacity of 86,200,000 m3. The dam features a controlled chute-type spillway located on the right bank, designed with a discharge capacity of 2,696 m3/s to manage river flow effectively. Water is conveyed from the reservoir to the downstream power station through a tunnel that spans 1.7 km in length. This configuration allows for efficient energy extraction from the Heihe River's flow.

The Longshou II Dam operates within a broader cascade system on the Heihe River. It is located upstream of the Longshou I Dam, which is an 80 m tall double-curvature arch dam with an installed capacity of 52 MW. Further upstream, the Xiaogushan Dam, a gravity structure, diverts water to a 102 MW power station. This arrangement of dams optimizes the hydraulic head and water distribution across the region, enhancing the overall efficiency of the hydroelectric development in the area.

What are the technical specifications of Longshou II Dam?

The Longshou II Dam is a concrete-face rock-fill structure situated on the Heihe River in Gansu Province, China. It is part of a cascading hydropower system, located upstream of the Longshou I Dam and downstream of the Xiaogushan Dam. The facility supports a 157 MW power station operated by Gansu Heihe Rural Hydropower Development.

Water management at the site relies on a controlled chute-type spillway located on the right bank of the river. This spillway has a discharge capacity of 2,696 m3/s, allowing for effective regulation of the reservoir levels. Power generation is facilitated by a 1.7 km long tunnel that delivers water from the dam to the downstream power station. The construction sequence included river diversion in June 2002, followed by the filling of the dam body in September 2002. The first generator became operational on 17 August 2004, with the remainder of the units coming online by the end of that year.

Parameter Value
Dam Type Concrete-face rock-fill
Height 146.5 m
Reservoir Capacity 86,200,000 m3
Spillway Type Controlled chute (right bank)
Discharge Capacity 2,696 m3/s
Intake Tunnel Length 1.7 km
Installed Capacity 157 MW
Operator Gansu Heihe Rural Hydropower Development
Commissioning Date 17 August 2004

The technical design of the Longshou II Dam complements the broader Heihe River hydropower scheme. The upstream Xiaogushan Dam is a gravity dam with a 102 MW power station, while the downstream Longshou I Dam is a double-curvature arch dam with an 80 m height and 52 MW capacity. This configuration allows for optimized water flow and energy extraction along the river corridor. The concrete-face rock-fill construction method provides structural stability suitable for the regional geological conditions.

Construction history and timeline

The development of the Longshou II Dam followed a structured sequence of engineering phases, beginning with initial assessments and culminating in full operational status within a four-year window. The project’s foundation was laid with the first feasibility study conducted in 2000, which established the technical and economic viability of the concrete-face rock-fill structure on the Heihe River. This preliminary analysis preceded the physical mobilization of construction resources and the commencement of earthworks.

Early Construction Phases

Active construction efforts intensified in the early 2000s, with river diversion works officially starting in December 2001. This critical infrastructure step was necessary to manage the Heihe River's flow, allowing for the systematic filling of the dam's body. By June 2002, the river diversion was successfully completed, marking a significant milestone in the hydrological management of the site. Following this achievement, the filling of the dam's body commenced in September 2002, initiating the gradual rise of the 146.5-meter-high structure that would eventually withhold a reservoir capacity of 86,200,000 cubic meters.

Commissioning and Operational Status

The transition from civil engineering to electromechanical integration concluded with the commissioning of the power station. The first generator at the Longshou II Dam became operational on 17 August 2004, bringing the facility to its initial power output capability. The remaining generators were brought online by the end of that same year, solidifying the plant's total installed capacity of 157 MW. The entire project, operated by Gansu Heihe Rural Hydropower Development, was thus fully integrated into the regional energy grid within the 2004 calendar year.

Year Event
2000 First feasibility study carried out
December 2001 River diversion construction began
June 2002 River diversion completed
September 2002 Filling of the dam's body began
17 August 2004 First generator operational
End of 2004 Remaining generators operational

How does Longshou II Dam fit into the Heihe River cascade?

The Longshou II Dam functions as the central component of a coordinated hydropower cascade on the Heihe River in Gansu Province. This integrated system relies on the sequential arrangement of three distinct dam structures to optimize water flow and energy generation. The Longshou II Dam is situated upstream of the Longshou I Dam and downstream of the Xiaogushan Dam, creating a linear progression of hydraulic control and power production along the river’s course.

Upstream and Downstream Relationships

The cascade begins with the Xiaogushan Dam, a gravity dam located upstream of the Longshou II structure. This facility diverts water to a power station with an installed capacity of 102 MW. The water then flows into the reservoir of the Longshou II Dam, which withholds a volume of 86,200,000 m3. The Longshou II Dam is a concrete-face rock-fill structure standing 146.5 m high. It supports a 157 MW power station, with water delivered to the turbines via a 1.7 km long tunnel.

Downstream from Longshou II is the Longshou I Dam. The positioning of these dams allows for the staged release of water, where the output of the upstream facilities feeds into the intake of the downstream units. This configuration is typical for river cascade systems, maximizing the hydraulic head and flow consistency for each individual power station.

Cascade Comparison

Dam Name Type Height Capacity Position
Xiaogushan Dam Gravity [?] 102 MW Upstream
Longshou II Dam Concrete-face rock-fill 146.5 m 157 MW Central
Longshou I Dam Double-curvature arch 80 m 52 MW Downstream

The operational synergy of these three dams is managed by Gansu Heihe Rural Hydropower Development. The Longshou II Dam was commissioned in 2004, following feasibility studies in 2000 and construction starting in 2001. The integration of these structures ensures efficient utilization of the Heihe River's water resources, with each dam contributing specific capacities to the regional grid. The precise sequencing allows for flexible power generation, adapting to seasonal flow variations and downstream demand.

Why it matters

The Longshou II Dam represents a significant engineering achievement in the development of the Heihe River basin in Gansu Province, China. As a major concrete-face rock-fill dam, it serves as a critical component of the regional energy infrastructure, contributing 157 MW to the local power grid. This facility is operated by Gansu Heihe Rural Hydropower Development, underscoring the strategic importance of hydropower in the rural energy mix of northwestern China. The dam’s construction and operation reflect a deliberate technical choice to utilize concrete-face rock-fill technology, which offers specific advantages in terms of material efficiency and structural adaptability for the Heihe River’s geological conditions.

Engineering Significance of Concrete-Face Rock-Fill Design

The decision to construct Longshou II as a concrete-face rock-fill dam highlights a sophisticated approach to hydroelectric engineering. This design features a 146.5 m high structure that withholds a reservoir capacity of 86,200,000 m3. The concrete face provides a watertight barrier over a rock-fill core, allowing for efficient use of local materials while maintaining structural integrity under varying hydraulic loads. This technology is particularly suited to the terrain of Gansu Province, where the availability of high-quality rock fill and the need for a robust, flexible dam structure are critical. The dam’s spillway, located on the right bank, is a controlled chute type with a discharge capacity of 2,696 m3/s, ensuring effective water management during peak flow periods.

Role in the Heihe River Cascade System

Longshou II Dam is not an isolated structure but an integral part of a multi-dam cascade system on the Heihe River. This arrangement allows for optimized water flow and energy generation, with Longshou II regulating the water supply to the downstream facility. Additionally, the Xiaogushan Dam, a gravity dam upstream of Longshou II, diverts water to a 102 MW power station, further enhancing the cascade’s overall efficiency. This interconnected system maximizes the hydropower potential of the Heihe River, providing a stable and renewable energy source for the region.

Regional Energy Impact

The commissioning of Longshou II Dam in 2004 marked a milestone in Gansu Province’s energy development. This rapid deployment was made possible by the efficient construction process, which began with river diversion in December 2001 and the start of dam body filling in September 2002. The 157 MW capacity of the power station significantly boosts the regional energy supply, supporting both industrial and residential demand. The dam’s strategic location, 35 km southwest of Zhangye, facilitates the transmission of electricity to key urban centers in Gansu Province, contributing to the province’s energy security and economic growth.

Geographical and hydrological context

The Longshou II Dam is situated on the Heihe River in Gansu Province, China, specifically located 35 km southwest of Zhangye. This positioning places the facility within a critical hydrological corridor in northwestern China, where the Heihe River serves as a primary water source for the regional ecosystem and agricultural output. The dam functions as a concrete-face rock-fill structure, designed to manage the flow and storage of water from this significant river system. Its location is strategically chosen to optimize the hydraulic head and water availability for power generation while integrating with the broader river management strategy of the Gansu Heihe Rural Hydropower Development operator.

Hydrological Integration and Reservoir Capacity

The dam creates a reservoir with a total capacity of 86,200,000 m3. This storage volume is essential for regulating the seasonal variations typical of the Heihe River basin, ensuring consistent water delivery to the downstream power station. The structure stands 146.5 m high, providing the necessary elevation difference to drive the hydroelectric turbines. Water is conveyed from the reservoir to the power station via a 1.7 km long tunnel, a design choice that minimizes evaporation losses and allows for efficient energy conversion in the arid climate of Gansu Province.

Position within the Heihe River Cascade

Longshou II operates as part of a coordinated cascade system on the Heihe River. This upstream positioning allows Longshou II to regulate the inflow to Longshou I, optimizing the combined output of the two facilities. Further upstream, the Xiaogushan Dam, a gravity dam, diverts water to a 102 MW power station, contributing to the multi-stage energy extraction from the river's flow. This integrated approach maximizes the hydropower potential of the Heihe River in the Zhangye region, balancing energy production with water resource management for the surrounding areas. The operational status of Longshou II, commissioned in 2004, reflects the maturation of this hydroelectric infrastructure in the province.

What distinguishes concrete-face rock-fill dams from other types?

Concrete-face rock-fill dams (CFRD) represent a distinct engineering approach to hydroelectric infrastructure, differing fundamentally from the gravity and arch structures found elsewhere in the Heihe River cascade. The Longshou II Dam employs this technology, featuring a core of compacted rock fill overlaid with a thin, flexible concrete slab that acts as the primary water barrier. This construction method contrasts sharply with the Longshou I Dam, located downstream, which is a double-curvature arch dam, and the Xiaogushan Dam upstream, which is a gravity dam. Each type relies on different physical principles to withstand hydrostatic pressure and maintain structural integrity.

Structural Mechanics and Material Efficiency

The engineering rationale for selecting a CFRD for Longshou II often centers on material efficiency and foundation adaptability. Unlike gravity dams, which rely on their sheer mass to resist the horizontal thrust of the water, CFRDs utilize the interlocking friction of rock fill. The concrete face, typically only a few meters thick, provides a relatively impermeable skin. This allows for significant savings in concrete usage compared to a conventional gravity dam of similar height, particularly in regions where high-quality rock aggregate is abundant but cement production or transport costs are high. The 146.5 m height of the Longshou II Dam demonstrates the scalability of this design, capable of withstanding substantial head pressure while maintaining a lighter overall footprint than a pure gravity structure.

Comparison with Arch and Gravity Dams

The contrast with the neighboring dams highlights the specific advantages of the CFRD design. The downstream Longshou I Dam, an 80 m tall double-curvature arch dam, transfers water pressure laterally into the valley walls. This design is highly efficient but requires narrow, steep-sided canyons with strong abutments to effectively channel the thrust. In contrast, the upstream Xiaogushan Dam, a gravity structure, depends on weight to prevent sliding and overturning, often requiring a broader base and more uniform foundation conditions. The CFRD design of Longshou II offers a middle ground, providing the flexibility to adapt to varying foundation geologies while maintaining the vertical profile necessary for efficient water diversion through its 1.7 km tunnel system. This diversity in dam types within the same cascade allows engineers to optimize each structure for its specific local topographic and geological constraints.

See also