What Is the Submerged Forest of Lake Shūsen?
At Lake Shūsen in Semboku City, Akita Prefecture, a submerged forest appears in spring, when snowmelt raises the lake level and trees with fresh young leaves rise from the water.
The scene brings together the blue lake, fresh greenery reflected on the surface, and the quiet of the mountains. It does not appear on the same dates every year, as it depends on snowfall, weather, and the dam's water level.
A Lake Created by Yoroibata Dam
Lake Shūsen, pronounced “Shūsenko,” is the reservoir of Yoroibata Dam, which was built on the Tamagawa River.
The lake's scenery is shaped by water stored in this multipurpose dam, which uses the abundant snowmelt in the area for agricultural and industrial water, among other purposes.
Because the lake extends along National Route 341, it is difficult to grasp changes in the water level or the positions of the trees by simply driving past. It is important to decide on a viewing point in advance.
A Spring Landscape Where Snowmelt Surrounds the Trees
The submerged forest appears when abundant snowmelt raises the lake level and the trunks of trees standing along the shore become immersed in water.
Young leaves emerge above the surface, and the lake's blue overlaps with the fresh greenery, creating the distinctive impression that the trees are floating on the water.
This is not a forest that permanently retains the same appearance. Understanding it as a landscape formed only while the water level is high makes it easier to appreciate whatever conditions you find during your visit.
Judge the Best Time by the Water Level
Usually Best from May to Early June
The submerged forest usually appears for about 1 month, from May to early June.
The leaves begin to turn green around late April, and the scenery reaches its peak in May. The reservoir level is then lowered in preparation for heavy summer rain, so early June is the usual guideline for viewing.
In some years it remains visible until around mid-June. Because the ending time varies with the water level each year, it is more reliable not to judge the best time by the calendar alone.
A Reservoir Level of 319 Meters or Higher as a Guide
The submerged forest can be seen when the reservoir level at Yoroibata Dam is generally 319 meters or higher.
Even in May, a lower reservoir level exposes too much of the trunks, while a higher level changes how much of the trees appears above the surface. Check the day's water level rather than expecting the exact same conditions as in photographs.
The reservoir level at Yoroibata Dam is published through the Akita Prefecture River and Erosion Control Information System, although the information may be temporarily unavailable during inspections or for other reasons.
| Item to Check | Guideline | How to Use It When Deciding Whether to Visit |
|---|---|---|
| Viewing season | Usually May to early June | Allow for differences from year to year |
| Leaf development | From around late April | Check the progress of the fresh greenery |
| Reservoir level | Generally 319 meters or higher | Check observation data shortly before visiting |
| End of the viewing season | Water level is lowered in preparation for heavy summer rain | Prioritize the water level over the date |
View the Submerged Forest from Shin-Tamagawa Bridge
Shin-Tamagawa Bridge Is the Viewing Point
The submerged forest can be viewed from Shin-Tamagawa Bridge on National Route 341.
From the bridge, you can look down on the rows of trees and the expanse of water, allowing you to observe the density of the forest together with the lake's color.
When the water level is low, a marsh-like landscape may appear. Even after the submerged forest has ended, you can see seasonal changes along the lakeshore.
Avoid Obstructing Traffic on the Bridge
Shin-Tamagawa Bridge is part of National Route 341. Do not step into the roadway or remain in one place for a long time, and always give priority to traffic.
When taking photographs, watch for nearby vehicles and pedestrians, do not climb over the railing, and do not spread equipment into the passage area.
Avoid viewing from the bridge in rainy weather or at dim times of day when visibility is poor.
Plan Parking and Access in Advance
There Is No Parking Near the Submerged Forest
There is no parking near the submerged forest, so use Lake Shūsen Dam Park.
Avoid parking on the shoulder. Besides obstructing traffic, it can lead to accidents on mountain roads with poor visibility.
Assume that the viewing point and parking area are some distance apart. Bring comfortable walking shoes, rain gear, and a drink, and allow plenty of time for the round trip.
Distance and Travel-Time Guidelines by Car
The location is Yoroibata, Tazawa, Tazawako, Semboku City, Akita Prefecture, about 13 kilometers from JR Tazawako Station.
It is about 75 minutes by car from the Morioka Interchange on the Tōhoku Expressway via National Routes 46 and 341.
Weather, construction, and road conditions can change travel times in the mountains. For peace of mind, check road information immediately before departure and plan to travel during daylight hours.
| Stage of the Trip | What to Check | Actions to Avoid |
|---|---|---|
| Before departure | Weather, roads, and water level | Judging the best time by the date alone |
| Parking | Location of Lake Shūsen Dam Park | Stopping on the shoulder near the submerged forest |
| Walking | Footing and sunset time | Walking in a group that spreads toward the roadway |
| Viewing | Traffic and other visitors | Climbing over the railing or spreading out equipment |
Capture the Blue Lake and Fresh Greenery in Photographs
Shoot Wide Views and Details Separately
First capture a wide view of the water and the extent of the submerged forest. Then focus on the rows of trunks, young leaves, and reflections on the surface to record both the scale of the location and its seasonal atmosphere.
Reflections are easier to see when the wind is light. Since you cannot choose the weather, on days with waves make use of the rhythm of the trees and the shimmer of the light.
The appearance of the cobalt blue changes with the sky, light, water quality, and water level. It is also important to preserve the conditions of the day instead of processing images into colors far removed from the actual scene.
Drone Photography Requires Applications and Advance Notice
When flying a drone over the reservoir, complete any applications required under the Civil Aeronautics Act.
If flying toward the mountain side, an application to the Akita District Forest Office is required, as is advance notice to the Yoroibata Dam Management Office.
Take care not to affect the dam through a crash or oil spill, and do not fly if you cannot complete the necessary procedures.
Check the Construction Scheduled from Spring 2027
The Submerged Forest Is Expected to Be Unavailable During Construction
Because water levels will be adjusted for major improvement work at the Yoroibata Power Station, the submerged forest is expected to be unavailable during the construction period from spring 2027 through fiscal year 2031.
Construction affecting the submerged forest is scheduled from March 2027 to March 2032, and spring 2026 was the final opportunity to view it before construction.
Do not rely only on past photographs; check the planned reopening before visiting.
Confirm the Planned Reopening After Construction
Viewing is expected to resume in spring 2032, but conditions may change depending on construction progress and reservoir-level operations.
For questions about the construction, contact the Akita Prefectural Tamagawa Power Management Office. For the submerged forest and dam conditions, contact the Yoroibata Dam Management Office.
Tourism information is also available from the Semboku City Tazawako Tourist Information Center “Folake” and the Tazawako-Kakunodate Tourism Association.
Summary of the Submerged Forest at Lake Shūsen
The submerged forest at Lake Shūsen is a spring landscape that appears when snowmelt raises the reservoir level at Yoroibata Dam and lakeside trees with young leaves become surrounded by water.
The usual viewing season is from May to early June, a reservoir level of generally 319 meters or higher is a guideline, and the viewing point is Shin-Tamagawa Bridge on National Route 341.
Do not park near the submerged forest; use Lake Shūsen Dam Park and act with consideration for road traffic and the dam environment.
Because the forest is expected to be unavailable during construction from spring 2027 through fiscal year 2031, check the reopening status before visiting.
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