Lake Ikawa Is a Reservoir Created by the Construction of Ikawa Dam
Lake Ikawa is a reservoir formed when Ikawa Dam was built on the middle reaches of the Oi River in Aoi Ward, Shizuoka City.
Water flowing from the Southern Alps, power generation facilities, lakeside settlements, and transportation together create a single landscape, revealing the character of Ikawa as a place shaped by both nature and civil engineering.
The Dam and Lake Were Completed in 1957
Ikawa Dam was built in 1957 (Showa 32).
As the river was blocked to store water for power generation, the water surface spread upstream and created the new landform known as Lake Ikawa.
Remembering that the lake and dam were completed in the same year helps connect postwar power development with changes in the local community.
A Reservoir about 10 Kilometers in Circumference, Surrounded by Mountains
Lake Ikawa is a reservoir with a circumference of about 10 kilometers.
Rather than forming a straight shoreline, the lake reaches into mountain valleys, so the width of the water, the distance to the opposite shore, and the overlapping ridgelines change depending on where you look from.
Instead of memorizing its size only as a number, compare the views from the dam, ferry, and lakeside road to better understand its complex outline.
View Nature and Power Development Together
Water flowing into the lake is sustained by rainfall and forests in the mountains, and that water is used for power generation through the dam.
When viewing the color of the water and the vegetation on the mountains, also consider the sequence of water intake, storage, and power generation. This reveals the relationship between the scenery and the energy that supports everyday life.
| Perspective | What to Observe | What It Reveals |
|---|---|---|
| Mountains | Forests and valleys | Terrain that collects water |
| Lake surface | Inlets and water level | Outline of the reservoir |
| Dam | Dam body and equipment | Roles of water storage and power generation |
| Settlement | Boats and roads | Relationship between the lake and daily life |
Recognizing Japan's First Hollow Gravity Dam
Ikawa Dam was the first hollow gravity concrete dam built in Japan.
It supports water pressure with the immense weight of its concrete while incorporating hollow spaces inside the dam body, a design that reflects careful use of materials and construction methods beneath its exterior.
Understand Gravity and Hollow Construction Separately
Gravity refers to the principle of using the dam body's own weight to withstand water pressure, while hollow describes the empty spaces inside it.
Do not oversimplify it as a lightweight facility merely because it is hollow. It is important to understand the structure as a way to reduce the amount of concrete while maintaining the necessary strength.
Even when the hollow spaces themselves cannot be seen from outside, the design can be understood by combining observations of the dam's shape with exhibition explanations.
Learn More about Hydroelectric Power at the Ikawa Exhibition Hall
Chubu Electric Power's Ikawa Exhibition Hall stands at the dam and explains how hydroelectric power works, the role of the dam, and the relationship between nature and electricity.
Learn about the flow of water in the exhibition before viewing the lake and dam body, or visit the exhibition after seeing the landscape to answer questions. Either order helps connect the facility with the terrain.
Opening days and conditions of use may change, so check before visiting.
Compare the Different Landscapes around the Lakeshore
Lake Ikawa is surrounded by mountains, and its impression changes according to the height and direction from which the water is viewed.
Instead of making a distant view under clear skies your only goal, observe the depth of the valleys, waterside vegetation, and boundaries between artificial structures and nature. This offers an experience less dependent on the weather.
Compare the Water and Dam Body from the Dam Side
Near the dam, you can contrast the calm upstream water with the role of the dam body in sending water downstream.
From inside the safety barriers, trace the shoreline, slopes, and ridgelines from bottom to top to understand how blocking the valley created the lake.
Do not cross into controlled areas or beyond no-entry signs, and follow any guidance concerning photography of the equipment.
Layer the Colors of the Seasons along the Lakeshore
Spring buds, deep summer greens, and autumn foliage change the appearance of the water.
Because peak viewing dates vary with the weather, do not fix your plans around a single date. Check local information before visiting, and even when the colors are still subtle, look for differences between conifers and broadleaf trees and their reflections on the water.
| Observation Point | Foreground | Distant View |
|---|---|---|
| Near the dam | Dam body and water | Upstream mountains |
| Lakeside road | Vegetation and shoreline | Overlapping inlets |
| On the ferry | Waves and rock walls | Continuous shoreline |
| Former railway path | Rails and tunnels | Lake and forest |
The Lake Ikawa Ferry Carries on the Region's Transportation Role
The Lake Ikawa Ferry did not begin solely for sightseeing. It was created to support residents' travel after the formation of the reservoir cut off access to the opposite shore.
It began as a project of the former Ikawa Village in 1958 (Showa 33) and continues to convey the history of how the lake changed everyday travel routes.
Boats Replaced Roads Lost when the Lake Was Created
When riverside roads were replaced by the lake, the way people reached places that had once been connected by land also changed.
The ferry made the water a new transportation route and took on the role of linking Ikawa's main village with the opposite shore.
When boarding, observe not only the scenery but also the locations of the piers and the direction of the settlements to understand the ferry's significance as transportation for residents.
Distinguish the Local Transportation Route from Lake Cruises
There is a route serving local transportation as well as sightseeing trips around the lake.
Boarding points, reservations, and operating methods differ by purpose, so decide where you want to go and how you will return before checking the appropriate service.
Water Levels and Weather Affect Operations
The ferry is affected by the dam's water level, water releases, wind, and weather, and may not always be available.
Do not rely on old timetables or travel accounts. Check the operating status for the day, whether reservations are required, and the boarding location.
Follow the crew's instructions on board and observe all indicated safety measures, including remaining seated and wearing a life jacket.
Trace the History of Dam Construction along the Former Railway Path
The former railway path on the Lake Ikawa lakeside trail follows a discontinued rail line once used to transport materials during construction of the dam.
Looking out over the lake from a path that retains rails and short tunnels lets you experience the layers of time as transportation built for construction became a walking trail.
Learn about the Tracks that Led toward Former Dohira Station
During construction of Ikawa Dam, the railway extended toward former Dohira Station, which served as a delivery point for materials.
Observing the rails underfoot, the curves, and the cuttings in sequence helps you imagine how the route followed the gradient and terrain to carry heavy materials.
Some sections of rail can be difficult to walk on, so choose a safe place to stop when taking photographs and watch your footing.
Alternate between Tunnels and Lake Views
Light and temperature change inside the short tunnels, and the lake and mountains open into view again at each exit.
Check the surface before entering a dark area, and watch for slippery conditions after rain or during the fallen-leaf season.
Follow posted local guidance whenever information is provided about trail access or maintenance.
Combine Train, Boat, and Walking Routes at a Comfortable Pace
The Lake Ikawa area lies in the mountains, and planning connections as you would at an urban tourist destination can leave too little time for waits and the return trip.
Check the Oigawa Railway Ikawa Line, local buses, ferry, and walking sections separately, and plan around the mode of transportation with the least frequent service.
Ride the Southern Alps Abt Line to Ikawa Station
The Southern Alps Abt Line of the Oigawa Railway connects Senzu Station and Ikawa Station. The train journey through the mountains is itself an introduction to the lake.
Operating sections and schedules may change, so check service information and connections before departure and plan backward from your return train.
Check Road Restrictions when Traveling by Car
Conditions on mountain roads may change because of weather or construction, and distance on a map alone is not enough to estimate travel time.
Check road restriction information and local signs, allow for detours and narrow sections, and plan to arrive during daylight.
Do Not Try to Fit Too Much into 1 Day
Trying to visit the dam, exhibition hall, ferry, and former railway path in a short period can make transportation the main part of your day rather than exploration.
Choose one theme, such as a day for learning how power generation works, a day for discovering the lake and settlements from the water, or a day for enjoying the former railway and trains. This lets you travel at a relaxed pace despite transportation constraints.
| Theme | Main Places | Check First |
|---|---|---|
| Learn about power generation | Dam and exhibition hall | Opening and road conditions |
| Discover the lake | Ferry and main village | Reservations and operating status |
| Explore transportation history | Former railway path | Access conditions and gear |
| Enjoy the railway | Ikawa Line and Ikawa Station | Round-trip times and connections |
Summary: Connect Water, Electricity, and Daily Life at Lake Ikawa
Lake Ikawa is a reservoir about 10 kilometers in circumference, created by Ikawa Dam upon its completion in 1957. Its landscape brings together water from the Southern Alps and Japan's first hollow gravity concrete dam.
The ferry preserves the story of how residents' transportation changed when the lake was created, while the former railway path records the transport of materials during dam construction. Combining train, boat, and walking routes offers a three-dimensional understanding of the region's transformation.
Before visiting, check ferry operations, opening information, road conditions, and trail access, and allow extra time for mountain weather and your return journey.
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