Overview
The Miho Dam is a multi-purpose embankment dam situated on the Kawauchi River, which serves as a tributary to the broader Sakawa River system. Located within the town of Yamakita in the Ashigarakami District of Kanagawa Prefecture on the main island of Honshū, Japan, the facility represents a significant piece of regional hydraulic infrastructure. The dam is operational and functions with an installed hydroelectric capacity of 7.4 MW, having been commissioned in 1978. Its strategic placement allows it to harness the water resources of the Kawauchi River to provide both energy generation and essential water supply services to the surrounding areas.
A defining characteristic of the Miho Dam is its integration into a prominent natural landscape. The structure lies entirely within the boundaries of the Tanzawa-Ōyama Quasi-National Park. This location places the engineering project directly within a protected environmental zone, balancing the demands of modern energy infrastructure with the preservation of the regional topography and biodiversity. The dam’s presence in this quasi-national park highlights the intersection of Japan’s hydroelectric development and its efforts to maintain scenic and ecological integrity in the Kantō region.
As a multi-purpose facility, the Miho Dam serves dual roles that are critical for local resource management. The primary function is hydroelectric power generation, contributing 7.4 MW to the local grid. This capacity, while modest in the context of national output, provides a steady and reliable source of renewable energy derived from the water flow of the Kawauchi River. In addition to power generation, the dam plays a vital role in water supply management. By regulating the flow of the tributary, it ensures a consistent water source for downstream users, supporting both municipal needs and agricultural activities in the Yamakita area and the wider Ashigarakami District.
History of Development
The development of the Miho Dam was driven by the need to harness the water resources of the Sakawa River, a tributary stream of the Sakawa River in the town of Yamakita, Ashigarakami District, Kanagawa Prefecture on the island of Honshū, Japan. The dam is located within the borders of the Tanzawa-Ōyama Quasi-National Park. The multi-purpose dam was constructed to meet the growing water and energy demands of the region, particularly the industrial demand from Kawasaki-Yokohama.
The construction of the Miho Dam took place from 1969 to 1978. The project was carried out by Kumagai Gumi, a prominent Japanese construction company. The dam was commissioned in 1978, marking the completion of a significant infrastructure project in the region.
The Miho Dam is a hydroelectric powerplant with a capacity of 7.4 MW. It is currently operational and continues to contribute to the energy supply of the region. The dam's location on the Kawauchi River, a tributary stream of the Sakawa River, allows it to effectively utilize the water resources of the area.
How was the Miho Dam designed and constructed?
The Miho Dam is a rock-fill structure with a concrete center portion, situated on the Kawauchi River, a tributary of the Sakawa River in Yamakita, Kanagawa Prefecture, Japan.
Technical Specifications
The dam features a design height that was adjusted from an initial 100 meters to 95 meters during the planning phase. It includes five spillways to manage water flow. The associated Tanoiri Hydroelectric Power Plant has a rated capacity of 7,400 KW. The plant is operational and was commissioned in 1978.
| Parameter | Value |
|---|---|
| Type | Rock-fill with concrete center portion |
| Height | 95 meters |
| Initial Design Height | 100 meters |
| Spillways | 5 |
| Power Plant | Tanoiri Hydroelectric Power Plant |
| Rated Capacity | 7,400 KW |
| Commissioned | 1978 |
| Status | Operational |
What was the social impact of the dam's relocation?
The construction of the Miho Dam necessitated the relocation of 233 households, a significant demographic shift for the town of Yamakita in Ashigarakami District, Kanagawa Prefecture. This displacement occurred within the borders of the Tanzawa-Ōyama Quasi-National Park, where the dam sits on the Kawauchi River, a tributary of the Sakawa River. The social impact of these relocations extended beyond mere housing adjustments, influencing the nomenclature and local identity associated with the infrastructure project.
Renaming and Local Identity
Initially, the project was referred to as the 'Sakawa Dam', reflecting its position on the tributary of the larger Sakawa River system. However, as the relocation of the 233 households progressed, local stakeholders sought to preserve the historic place names associated with their displaced communities. An agreement was reached to retain these historic local designations, leading to the official name change from 'Sakawa Dam' to 'Miho Dam'. This renaming decision was a direct response to the social dynamics of the relocation, ensuring that the identity of the 'Miho' area was not lost to the broader geographical label of the Sakawa River.
The integration of the dam into the local community identity was thus shaped by this compromise. By adopting the name 'Miho', the infrastructure project acknowledged the specific social fabric of the relocated households. The dam, commissioned in 1978 with a capacity of 7.4 MW, became a symbol of this local negotiation between modern hydroelectric development and the preservation of historic place names. The multi-purpose nature of the dam, situated within a quasi-national park, further embedded it into the regional landscape, balancing energy production with the social memory of the 233 families who moved to accommodate the project. The operator of the facility remains unspecified in cited sources, but the social agreement regarding the name 'Miho' stands as a key aspect of the dam's historical context.
Significance
The Miho Dam functions as a critical node within the Sakawa River basin, serving the dual needs of energy generation and water resource management in western Kanagawa Prefecture. Located on the Kawauchi River, a primary tributary of the Sakawa River, the facility contributes to the hydrological stability of the region. The dam’s operational status, established since its commissioning in 1978, ensures a consistent water flow that supports downstream infrastructure. This water security is vital for the Kawasaki-Yokohama industrial area, one of Japan’s most significant manufacturing and commercial hubs. The reliable supply from the Sakawa River system helps meet the municipal and industrial water demands of this densely populated coastal zone, buffering against seasonal variability in precipitation.
Recreational and Environmental Role
Beyond its utility functions, the Miho Dam is a major recreational asset, creating Lake Tanzawa. This reservoir is situated entirely within the borders of the Tanzawa-Ōyama Quasi-National Park, integrating energy infrastructure with natural conservation. The lake serves as a key destination for outdoor activities, including boating, fishing, and hiking, drawing visitors from the greater Tokyo metropolitan area. The dam’s multi-purpose design allows for simultaneous power generation and leisure use, maximizing the land’s value. This integration is characteristic of modern Japanese dam projects, which often balance engineering needs with public access to green spaces. The preservation of the surrounding parkland helps mitigate the visual and ecological impact of the hydroelectric facility.
Regional Infrastructure Context
The Miho Dam’s capacity of 7.4 MW represents a modest but steady contribution to the regional power grid. While smaller than some major hydroelectric installations in Japan, its location in the Ashigarakami District provides strategic flexibility for the local grid operator. The dam exemplifies the multi-purpose nature of regional water management in Kanagawa, where single facilities often handle power generation, flood control, and water supply. This approach contrasts with single-purpose dams found in other regions, highlighting the efficiency of the Sakawa River system. The facility’s long-term operation since 1978 demonstrates the durability of its design and the sustained importance of the Kawauchi River’s flow for both energy and water security in western Kanagawa.
Geography and Environment
The Miho Dam is situated within the administrative boundaries of Yamakita, a town located in the Ashigarakami District of Kanagawa Prefecture on the island of Honshū, Japan. The structure rests on the Kawauchi River, which functions as a tributary stream feeding into the larger Sakawa River system. This geographic positioning places the hydroelectric facility directly within the protected borders of the Tanzawa-Ōyama Quasi-National Park, integrating the infrastructure into a significant natural landscape recognized for its topographic and ecological value.
River System and Hydrology
The Kawauchi River serves as the primary water source for the dam’s operations. As a tributary of the Sakawa River, it contributes to the broader hydrological network of the region. The dam’s construction on this specific waterway allows for the regulation of flow and the generation of hydroelectric power, with an installed capacity of 7.4 MW, as commissioned in 1978. The interaction between the dam structure and the river dynamics is central to the local water management strategy, balancing energy production with the natural flow characteristics of the tributary.
Environmental Context and Lake Tanzawa
The reservoir formed by the Miho Dam is known as Lake Tanzawa. This body of water plays a dual role in the local environment, serving both ecological and recreational functions. Within the Tanzawa-Ōyama Quasi-National Park, Lake Tanzawa contributes to the regional ecosystem, providing habitat for local flora and fauna while maintaining the water quality essential for the downstream Sakawa River. The lake also supports tourism activities, offering scenic views and recreational opportunities that leverage the natural beauty of the park. The integration of the dam within this quasi-national park underscores the balance between infrastructure development and environmental preservation in the area.
Operational Details
The Miho Dam operates as a multi-purpose hydroelectric facility on the Kawauchi River, a tributary of the Sakawa River in Yamakita, Kanagawa Prefecture. The plant has an installed capacity of 7.4 MW and has been operational since its commissioning in 1978. Located within the Tanzawa-Ōyama Quasi-National Park, the dam integrates energy generation with regional water resource management and recreational use.
Hydroelectric Generation
The primary energy infrastructure associated with the Miho Dam is the Tanoiri Hydroelectric Power Plant. This facility utilizes the hydraulic head created by the dam on the Kawauchi River to generate electricity. With a capacity of 7.4 MW, the plant contributes to the local grid in the Ashigarakami District. The operational status of the plant remains active, maintaining its role in the region's energy mix since 1978. The specific technical configuration of the turbines and generators is managed to optimize the flow of the Kawauchi River, which feeds into the larger Sakawa River system.
Water Supply and Reservoir Management
Beyond power generation, the Miho Dam serves critical water supply functions for the surrounding communities in Kanagawa Prefecture. The reservoir created by the dam helps regulate the flow of the Kawauchi River, ensuring consistent water availability for municipal and agricultural use. The management of the reservoir involves balancing the hydraulic needs of the Tanoiri Power Plant with the storage requirements for water supply. This multi-purpose approach is typical of dams in the Tanzawa-Ōyama region, where water resources are shared between energy production and local consumption.
Recreation and Environmental Context
The Miho Dam is situated within the borders of the Tanzawa-Ōyama Quasi-National Park, which influences its operational and recreational management. The reservoir and surrounding areas provide recreational opportunities for visitors to the park, including hiking and nature observation. The location in a quasi-national park requires careful environmental management to preserve the natural landscape while maintaining the dam's infrastructure. The integration of the dam into the park's ecosystem highlights the balance between energy infrastructure and environmental conservation in Honshū's mountainous regions.