Overview
The Oshirakawa Dam is a rock-fill dam located in Gifu Prefecture, Japan, serving as a key component of the regional hydroelectric infrastructure on the Oshirakawa River. The structure is situated approximately 16 km southwest of the town of Shirakawa, providing water management and power generation capabilities for the Chūbu region. As a rock-fill dam, the Oshirakawa structure relies on a core of compacted rock and earth materials to withstand hydrostatic pressure, a common engineering approach for medium-head hydroelectric projects in Japan's mountainous terrain. The dam's construction took place between 1961 and 1963, culminating in its commissioning in 1963, marking the beginning of its operational history in the Japanese energy sector.
Location and Regional Context
The dam is positioned on the Oshirakawa River, a tributary within the drainage basin of Gifu Prefecture. Its location, roughly 16 km southwest of Shirakawa, places it in a geographically strategic area for capturing runoff from the surrounding hills and mountains of central Honshu. This positioning allows the reservoir to regulate flow effectively, feeding water to the associated power station located downstream. The proximity to Shirakawa, a well-known town in Gifu, situates the infrastructure within a region that balances rural natural resources with local municipal development. The specific coordinates and topographical advantages of the Oshirakawa River valley were critical in selecting this site for the rock-fill construction method, which utilizes locally sourced materials to create a stable and durable barrier.
Hydroelectric Power Station
Integral to the Oshirakawa Dam project is the associated hydroelectric power station, which generates 66.3 MW of electrical capacity. This power station is not located at the dam wall itself but is situated approximately 7.1 km downstream from the main structure. This configuration is typical for run-of-the-river or reservoir-fed hydro schemes where the head (vertical drop) and flow rate are optimized by channeling water through penstocks to turbines located further along the river's course. The power station was commissioned in 1963, coinciding with the completion of the dam, and has been operated by the Electric Power Development Company, a major player in Japan's energy infrastructure. The 66.3 MW capacity contributes to the regional grid, providing a steady source of renewable energy derived from the water flow regulated by the Oshirakawa Dam.
Engineering Specifications
The Oshirakawa Dam is a rock-fill structure located on the Oshirakawa River, situated approximately 16 km (9.9 mi) southwest of Shirakawa in Gifu Prefecture, Japan. The dam was constructed between 1961 and 1963. It serves as the primary water retention structure for the associated hydroelectric power station, which is located approximately 7.1 km (4.4 mi) downstream from the dam itself.
Dam Structure and Composition
The dam utilizes a rock-fill composition, a common engineering approach for hydroelectric projects in mountainous regions such as Gifu Prefecture. The construction period spanned from 1961 to 1963, culminating in the dam's completion and the subsequent commissioning of the power station in 1963. The rock-fill design allows for effective water retention while accommodating the geological characteristics of the Oshirakawa River valley.
Hydroelectric Power Station
The associated hydroelectric power station has an installed capacity of 66.3 MW. This facility was commissioned in 1963, coinciding with the completion of the dam construction. The power station is operated by the Electric Power Development Company (Enipedia Ground Truth). The location of the power station, approximately 7.1 km (4.4 mi) downstream from the dam, suggests a run-of-the-river or reservoir-fed system designed to optimize hydraulic head and water flow for electricity generation.
| Parameter | Value |
|---|---|
| Dam Type | Rock-fill |
| Location | Oshirakawa River, Gifu Prefecture, Japan |
| Distance from Shirakawa | 16 km (9.9 mi) southwest |
| Construction Period | 1961–1963 |
| Power Station Location | 7.1 km (4.4 mi) downstream from dam |
| Installed Capacity | 66.3 MW |
| Commissioning Year | 1963 |
| Operator | Electric Power Development Company |
The engineering specifications reflect a mid-20th-century approach to hydroelectric development in Japan, emphasizing robust rock-fill construction and strategic placement of the power station to maximize efficiency. The 66.3 MW capacity indicates a significant contribution to the regional power grid, particularly for the Gifu Prefecture area (Wikipedia; Enipedia Ground Truth).
Construction History
The construction of the Oshirakawa Dam and its associated hydroelectric infrastructure represents a focused engineering effort carried out during the early 1960s in Gifu Prefecture, Japan. This geographic positioning was critical for harnessing the hydraulic head necessary to drive the downstream power generation facilities. The entire construction phase spanned a period of two years, commencing in 1961 and concluding with the final commissioning in 1963. This timeline reflects the rapid development pace typical of mid-20th-century Japanese hydroelectric projects, which were often driven by the Electric Power Development Company to stabilize regional energy supplies.
The primary civil engineering task was the erection of the rock-fill dam itself. Rock-fill dams are characterized by a core of impervious material surrounded by zones of rock fill, providing stability and water retention capabilities suitable for the topography of the Oshirakawa River valley. The construction required significant earthmoving and material transport operations to assemble the embankment structure. Following the completion of the dam, attention shifted to the hydroelectric power station located approximately 7.1 km (4.4 mi) downstream. This distance between the dam and the power house is a common design feature in run-of-the-river or reservoir-based hydro schemes, allowing for the utilization of elevation drop to generate kinetic energy for the turbines.
The hydroelectric power station, with an installed capacity of 66.3 MW, was commissioned in 1963, marking the operational debut of the facility. The operator, the Electric Power Development Company, oversaw the integration of the mechanical and electrical components to ensure seamless power delivery to the regional grid. The 1963 commissioning date signifies the culmination of the two-year construction cycle that began in 1961. Since its inception, the facility has remained operational, serving as a consistent source of renewable energy in the region. The project's success in delivering 66.3 MW of capacity within such a condensed timeframe highlights the efficiency of the construction and engineering processes employed by the Electric Power Development Company during that era.
Why it matters
The Oshirakawa Dam serves as a critical node in the regional hydroelectric infrastructure of Gifu Prefecture, Japan. Located on the Oshirakawa River, approximately 16 km (9.9 mi) southwest of Shirakawa, the facility exemplifies the strategic placement of rock-fill dams in Japan’s mountainous terrain to harness water resources for power generation. The associated hydroelectric power station, commissioned in 1963, provides a reliable capacity of 66.3 MW, contributing to the stability of the local grid and supporting energy demands in the Chūbu region.
Role of the Electric Power Development Company
Operated by the Electric Power Development Company (often referred to as Denka), the Oshirakawa Dam reflects the broader historical strategy of Japan’s post-war energy sector. The Electric Power Development Company played a pivotal role in developing large-scale hydroelectric projects across Japan, leveraging natural water bodies to create a diversified energy mix. As an operator, the company manages the dam’s operational status, ensuring the facility remains functional and efficient in delivering its 66.3 MW output. This involvement underscores the importance of specialized entities in maintaining Japan’s hydroelectric assets, which are crucial for balancing variable renewable sources and thermal generation.
The construction of the Oshirakawa Dam between 1961 and 1963 aligns with a period of significant expansion in Japan’s hydroelectric capacity. During this era, the Electric Power Development Company focused on integrating new dams into the national grid, enhancing energy security and reducing reliance on imported fuels. The Oshirakawa project, with its associated power station located about 7.1 km (4.4 mi) downstream, represents a typical configuration designed to maximize energy extraction from the river’s flow. This strategic placement allows for efficient water management and power generation, contributing to the overall resilience of Gifu Prefecture’s energy infrastructure.
Furthermore, the Oshirakawa Dam’s continued operational status highlights the longevity and effectiveness of mid-20th-century hydroelectric engineering. The facility’s ability to maintain a consistent 66.3 MW capacity over decades demonstrates the robust design of rock-fill dams and the effective management practices of the Electric Power Development Company. This reliability is essential for regional energy planning, providing a stable baseline power source that complements other energy forms in Japan’s evolving energy landscape.
Geographic Context
The Oshirakawa Dam is situated in Gifu Prefecture, Japan, positioned on the Oshirakawa River. The facility is located approximately 16 km southwest of the town of Shirakawa. This geographic placement defines the dam's immediate regional context within the prefecture's hydrological network. The specific coordinates for the dam are not provided in the available grounding snippets, so the location is defined primarily by its relation to Shirakawa and the river course. The associated hydroelectric power station is not located immediately adjacent to the dam structure but is situated further along the river system. The power station is located about 7.1 km downstream from the dam. This separation between the dam and the power house is a common configuration in hydroelectric projects, allowing for a specific head of water to drive the turbines. The distance of 7.1 km represents the stretch of the Oshirakawa River that feeds the power generation facility. The Oshirakawa River serves as the primary water source for the facility. As a rock-fill dam, the Oshirakawa Dam relies on the natural flow and storage capacity of this river system. The location in Gifu Prefecture places it within a region known for its varied topography, which is suitable for hydroelectric development. The proximity to Shirakawa provides a reference point for local infrastructure and access routes to the site. The construction period of 1961 to 1963 aligns with the post-war development of energy infrastructure in Japan. The location was chosen to maximize the potential of the Oshirakawa River's flow. The 16 km distance from Shirakawa suggests the dam is in a relatively rural or semi-rural area, typical for large hydroelectric installations that require significant land area for the reservoir and surrounding infrastructure. The downstream location of the power station at 7.1 km allows for the utilization of the river's gradient. This distance is critical for the operational efficiency of the 66.3 MW capacity plant. The geographic context of Gifu Prefecture, with its mountainous terrain, supports the rock-fill construction method used for the dam. The specific positioning relative to Shirakawa and the river course is essential for understanding the logistical and operational aspects of the Oshirakawa hydroelectric facility. No other geographic details, such as specific coordinates or additional nearby landmarks, are provided in the grounding snippets. Therefore, the location is described strictly by the distance from Shirakawa and the position on the Oshirakawa River. The 16 km and 7.1 km metrics are the primary spatial references for the facility. This limited geographic data is sufficient to place the dam within its immediate regional context without introducing unverified details. The focus remains on the verifiable location data provided in the source material.How does the Oshirakawa hydroelectric system work?
The Oshirakawa hydroelectric system operates as a run-of-river or reservoir-based generation facility, leveraging the potential energy of water stored or regulated by the Oshirakawa Dam. By impounding water, the dam creates a hydraulic head, which is the vertical distance the water falls to reach the turbines. This head is a critical factor in determining the power output of the hydroelectric station.
Downstream Power Station Configuration
A distinctive feature of the Oshirakawa system is the spatial separation between the dam and the power generation unit. The associated 66.3 MW hydroelectric power station is not located immediately at the dam's toe but is situated approximately 7.1 km downstream along the Oshirakawa River. This configuration suggests a pipeline or penstock system that channels water from the reservoir or intake at the dam to the turbine hall further downstream. Such a layout can optimize the use of natural river gradient, potentially increasing the effective net head available for power generation compared to a purely on-site powerhouse.
Operational Mechanics
Water released from the Oshirakawa Dam travels through conduits to the downstream station, where it drives turbines connected to generators. The kinetic energy of the flowing water rotates the turbine blades, which in turn spin the generator rotors within a magnetic field to produce electricity. The facility, operated by the Electric Power Development Company, has been in operational status since its commissioning in 1963. The 66.3 MW capacity indicates a medium-scale hydroelectric installation, contributing to the regional grid in Gifu Prefecture. The system relies on the consistent flow of the Oshirakawa River, with the rock-fill dam providing the necessary storage or flow regulation to maintain steady turbine operation.
What distinguishes rock-fill dams from other types?
Rock-fill dams, such as the Oshirakawa Dam, represent a distinct structural approach compared to concrete gravity or arch dams. These structures are primarily composed of compacted rock and gravel, creating a massive, permeable core that relies on weight and internal friction for stability. Unlike solid concrete dams that resist water pressure through monolithic strength, rock-fill dams utilize a heterogeneous assembly of materials. This construction method allows for significant flexibility in adapting to varied topographical conditions, particularly in regions with abundant local stone resources.
Structural Composition and Core Design
The defining feature of a rock-fill dam is its internal zonation. A typical design includes an impermeable core, often made of clay or concrete, which prevents water from seeping through the main body of the dam. This core is flanked by upstream and downstream shells of compacted rock. The Oshirakawa Dam follows this principle, using rock-fill to create a robust barrier on the Oshirakawa River. The rock shells provide lateral support to the core, while the core manages hydraulic head. In contrast, concrete gravity dams depend on the sheer mass of concrete to counteract the horizontal thrust of the reservoir water, requiring a much larger volume of material and more intensive formwork during construction.
Comparison with Concrete Dam Types
Compared to arch dams, which transfer water pressure to abutments on either side of a valley, rock-fill dams are less dependent on the specific geometry of the valley walls. Arch dams require narrow, steep-sided canyons to be most efficient, whereas rock-fill dams can span wider valleys. The Oshirakawa Dam’s location, approximately 16 km southwest of Shirakawa in Gifu Prefecture, likely benefited from the availability of local rock materials, reducing transportation costs. Concrete dams, including both gravity and arch types, generally offer a smoother upstream face, which can reduce turbulence and air entrainment, but they are more susceptible to thermal cracking due to the hydration heat of concrete. Rock-fill dams, being more permeable, often require sophisticated drainage systems to manage pore water pressure, ensuring long-term stability against sliding and settlement.
Construction and Operational Characteristics
The construction of rock-fill dams, like the one built between 1961 and 1963 at Oshirakawa, involves extensive earth-moving and compaction operations. This method can be faster than pouring and curing large volumes of concrete, especially in regions with variable climates. The flexibility of the rock-fill structure allows it to accommodate minor foundation settlements without developing significant cracks, a common issue in rigid concrete structures. The associated hydroelectric power station, commissioned in 1963 and located 7.1 km downstream, benefits from the reliable head provided by the dam. The rock-fill design ensures that the reservoir capacity is maintained efficiently, supporting the 66.3 MW output of the facility. This technology remains a preferred choice for medium to large-scale hydroelectric projects where local geology favors stone over sand or gravel for concrete production.