Sayama Lake Is the Popular Name for Yamaguchi Reservoir
Sayama Lake is the common name for Yamaguchi Reservoir, an active water supply facility managed by the Tokyo Metropolitan Government Bureau of Waterworks in the Sayama Hills of Tokorozawa, Saitama Prefecture.
Rather than seeing it only as a scenic lake, walk with an awareness that the natural landscape of the hills sits beside a system that stores water from the Tama River basin and delivers it to the city.
Distinguish the Official Name from the Popular Name
The facility’s official name is Yamaguchi Reservoir, while Sayama Lake is the name long used by the local community.
The name Sayama Lake is said to have been selected through a naming campaign organized by Seibu Railway, which was promoting tourism in the area.
Because signs and maps use both names, searching for “Yamaguchi Reservoir” together with “Sayama Lake” makes it easier to confirm your destination.
It Is a Different Reservoir from Tama Lake
The nearby Murayama Reservoir is known as Tama Lake and is connected to Yamaguchi Reservoir by a connecting pipe so the 2 facilities can be operated together.
Although the names are similar, their locations and nearest stations differ. If you are visiting Sayama Lake, confirm that your destination is Yamaguchi Reservoir on the Tokorozawa side.
Separate Viewing Areas from Managed Zones
You can look across the lake and surrounding mountains from the embankment, but the reservoir is also a managed facility where water quality and equipment must be protected.
Do not go beyond fences or signs, and view the scenery quietly from permitted paths. This is the basic way to protect both the landscape and the water supply system.
See the Structure of the Earth Dam and Intake Towers
Yamaguchi Reservoir is an earth dam that holds back water with compacted soil. It was completed in March 1934, and reinforcement work on the embankment was completed in November 2002.
Unlike a dam with a massive concrete wall, it is characterized by the way its gentle embankment appears to continue into the surrounding hills.
Understand the Scale from the Embankment’s Length and Height
The embankment of Yamaguchi Reservoir is 33.9m high and 716.0m long at the crest.
Rather than simply memorizing the figures, move your gaze from one end of the embankment to the other and compare the difference in elevation between the lake side and city side to appreciate the structure.
Look for the 2 Intake Towers
Yamaguchi Reservoir has 2 intake towers, whose appearance changes with the water level and light across the lake.
The intake towers are part of the water supply facility rather than decorative objects. Observe their form from a distance, but do not cross a fence to approach them.
Storage Capacity Shows the Connection to Daily Life
The effective storage capacity is 19,528,000m3, and the stored raw water is sent to water purification plants.
As you look across the broad lake surface, remember that this water will become a resource supporting daily life after treatment; this changes the meaning of the view.
| Observation Point | Facility Information | How to View It |
|---|---|---|
| Type | Earth dam | See how the earthen embankment continues into the hills |
| Embankment | Height 33.9m; crest length 716.0m | Compare the full length and elevation difference |
| Intake facilities | 2 intake towers | Observe their form and the water level from the path |
| Effective storage capacity | 19,528,000m3 | View the lake as a source of tap water |
How Water from the Tama River Reaches the City
Yamaguchi Reservoir does not rely only on rain falling nearby. Its system channels and stores raw water taken from the Tama River.
Understanding the sequence from water source to storage and purification reveals how this lake in the hills is connected to Tokyo’s water supply network.
Raw Water Is Channeled from the Ozaku Intake Weir
Raw water taken at the Ozaku Intake Weir has sand removed in a sedimentation basin before being carried to Yamaguchi Reservoir through the Ozaku–Yamaguchi Aqueduct.
This offers a clue to why no large river flowing into the lake is readily visible and helps you imagine the artificial route taken by the water.
It Is Operated Together with Murayama Reservoir
Yamaguchi Reservoir is linked by a connecting pipe to the neighboring Murayama Reservoir, and the 2 are operated together according to storage conditions and water demand.
Rather than seeing the 2 lakes only as separate visitor destinations, consider them as a group of regional water supply facilities to better understand their different roles.
The Water Is Sent to Purification Plants and Becomes Drinking Water
The stored raw water is carried to the Higashimurayama and Sakai Water Purification Plants, treated, and then supplied.
Because this is not a place where the lake water can be used directly, do not descend to the shore or throw anything into the water. Keep the distance needed to protect the water source.
Quietly Enjoy Seasonal Scenery and Wild Birds
From the embankment, you can see the Okutama mountain range and enjoy spring cherry blossoms, autumn leaves, and birdwatching.
The view changes with the weather and water level, so instead of rushing to photograph a single attraction, slowly observe the layers of sky, forest, and lake.
Layer the Mountains and Sky from the Embankment
From the open view on the embankment, hills and distant mountains rise beyond the lake, emphasizing the breadth of the sky.
Do not treat clear weather as the only ideal. On a lightly overcast day, notice the contrast between the water and forest; on a windy day, observe the changing ripples for a different view.
Do Not Assume Fixed Dates for Cherry Blossoms or Autumn Leaves
The lakeside is known for spring cherry blossoms and autumn foliage, but the best viewing time changes each year with temperature and weather.
Before choosing a date, check current official information from the municipality and transportation operators. Plan to observe the water facility and terrain even if the flowers or colors differ from your expectations.
Keep Your Distance from Wild Birds
Many wild birds live in the Sayama Hills, including northern goshawks around Yamaguchi Reservoir.
Do not enter vegetation while following bird calls. Avoid feeding birds or making loud noises, and use binoculars to observe them from a distance.
| Season or Conditions | What to See | Walking Tips |
|---|---|---|
| Spring | Cherry blossoms and new growth | Check bloom information and view from paths |
| Summer | Deep greenery and the lake | Rest and prepare for sun and heat |
| Autumn | Autumn foliage and clear distant views | Prepare for cooler evenings |
| Winter | Terrain through bare branches and wild birds | Dress warmly and observe quietly |
Learn About Reservoir Construction and Local Memory
The scenery of Sayama Lake was not created by water collecting in a natural depression. It emerged through the development of a modern water supply and changes in local land use.
Looking at old photographs and local records alongside the present landscape shows that beneath today’s lake surface lie traces of people’s lives and the land’s history.
It Became a Cherry Blossom Destination after Completion
Cherry trees planted after the reservoir was built made the lakeside a popular destination, and the surrounding area became Saitama Prefectural Sayama Natural Park in 1951.
When enjoying the blossoms, also consider how the familiar scenery took shape through planting and designation as a park.
Former Land Lies Beneath the Lake
When the reservoir was drained for repairs in 1975, the ground of the former Ōaza Shōrakuji area appeared for the first time in about 40 years.
Imagining the normally hidden lakebed helps explain how reservoir construction dramatically changed the local landscape.
Read Waterworks Engineering and the Natural Park Together
Yamaguchi Reservoir is a water supply facility, while also offering a close experience of the forests and wild birds of the Sayama Hills.
Rather than treating human-made structures and nature as opposites, consider how the water storage structure, protected greenery, and visitor rules overlap to support the present environment.
Access and Safe Walking Tips
Yamaguchi Reservoir is located at 25-2 Shōrakuji, Tokorozawa, and is a 15-minute walk from Seibu Kyūjō-mae Station on the Seibu Sayama Line.
Events near the station may change pedestrian flows and traffic conditions, so check railway and nearby facility information before departure.
Set Your Destination on the Tokorozawa Side
A search for “Sayama Lake” alone may also display directions for Tama Lake or Sayama Park.
To visit the Yamaguchi Reservoir embankment, confirm your route using the address and Seibu Kyūjō-mae Station, and prepare a map that will also guide you back to the same station.
Choose Walking Shoes and Seasonal Gear
The embankment and surrounding paths are outdoors, with conditions that may include limited shade, fallen leaves, and wet surfaces after rain.
Prepare slip-resistant shoes, a drink, a hat, and rain gear for the season, and stop only where you will not obstruct passage while taking photos.
Give Priority to Same-Day Guidance
The area open to pedestrians and surrounding transportation may change because of water facility maintenance, weather, or events.
Follow on-site fences and signs and official guidance from the facility manager or municipality. If an area is closed, turn back rather than detouring around it.
Summary of a Walk at Sayama Lake
At Sayama Lake, understanding its official role as Yamaguchi Reservoir and viewing the earth dam, intake towers, lake, and forests of the Sayama Hills in sequence reveals the connection between the scenery and the water supply.
Confirm the route from Seibu Kyūjō-mae Station, prepare gear suited to the season and weather, and walk while keeping sufficient distance from managed zones and wild birds.
Check viewing and access conditions on the day of your visit. Respecting the facility that supports the drinking water supply is fundamental to enjoying Sayama Lake for years to come.
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