Tachikawa Yagawa Green Space Walk: Springs, Hake Cliffs and History

Tokyo’s springs are slowly disappearing — except in Tachikawa, where the count hasn’t moved in 20 years. A walk to the Yagawa stream, fed by cliffs called “hake”.

日本語で読む（Japanese version）

Tokyo’s natural springs are slowly disappearing. Yet if you follow the Tokyo Metropolitan Government’s survey down to the line for the city of Tachikawa (立川), the number has not moved by a single spring in twenty years.

Tachikawa, in the western half of Tokyo, is known for its station-front walkways, its monorail and its big shopping complexes. Nobody thinks of it as a place where water wells up out of the ground. Until a little while ago, neither did I.

But leaf through the Metropolitan Government’s documents and Tachikawa’s name turns up in an unexpected place. Among the 57 sites the government selected as “Tokyo’s Famous Springs”, number 22 is the Yagawa Green Space in Hagoromocho, Tachikawa. And another government page goes out of its way to add, about the little stream that flows out of it, that it does not dry up even in winter.

Two stops from Tachikawa Station on the Nambu Line, in the middle of a residential district, a stream is born that never runs dry all year. Where does the water come from? Why does it not stop even in winter? And what does the cliff the locals call hake have to do with it? Looking for answers, I head south.

What the Yagawa Green Space is: 2.1 hectares of wetland left among the houses

First, where it is.

According to the city of Tachikawa, the Yagawa Green Space (矢川緑地, Yagawa Ryokuchi) lies at the southern edge of Hagoromocho, next to the city of Kunitachi. It covers about 2.1 hectares. The Metropolitan Government’s record is more precise: 21,071.70 square metres. A green space measured to two decimal places somehow inspires confidence.

Through the middle of it runs a small river called the Yagawa. The city describes it as a stream about 1.3 kilometres long that rises from the Tachikawa terrace, flows down from south-east Tachikawa through south-west Kunitachi, and joins the Yaho irrigation channel beyond the cliff of the Aoyagi terrace. 1.3 kilometres. Under twenty minutes on foot. Living in Tokyo, you tend to assume rivers come from deep in the mountains over dozens of kilometres. This one spends almost its entire life, from birth to being swallowed by an irrigation channel, on the border between two towns.

The Bureau of Environment’s guide to its woodland walking trails describes the Yagawa as a small stream about two metres wide, gathering the spring water that wells up at the foot of the Tachikawa terrace cliff. Two metres. You could probably jump it with a run-up. Better not, of course. As we will see, a great many residents live in this stream that a landing shoe should not be stamping on.

Inside the green space, the city says, a wetland spreads on the south side upstream, and woodland stands on the north side downstream. In the wetland you walk along boardwalks and see the wetland plants up close. The woodland is made up of trees such as Japanese white oak, zelkova and konara oak. According to the Metropolitan Government’s record, the north bank holds trees planted under the conservation programme and the south side is the wetland.

Stand on the boardwalk and reeds and sedges press right up beside your feet; beyond them you can see the roofs and upstairs windows of houses. There is hardly any boundary between wetland and housing. In this town there are people who look down over a reed bed from their upstairs balcony. I envy them a little.

In February 2003 the Tachikawa Greening Promotion Council chose the city’s green landmarks as the “Twelve Green Views of Tachikawa”. The Yagawa Green Space is number five, under the theme “original landscape”. Its highlights are given as a rare treasure house of plants blessed with abundant spring water, with many wild birds and nature to enjoy to the full. The council also wrote that it hoped the twelve views would become a modern green cultural heritage following on from the “Twelve Views of Tachikawa Village”, a city-designated tangible cultural property. Picking green landmarks now as cultural treasures of the future: patient, good work.

But where does this wetland’s water come from? Look at the map and there is no mountain upstream. There is only a step in the ground.

Hake: the terrace cliff that is the secret of Tachikawa’s landscape

In one word, Tachikawa’s landscape is a staircase.

The Bureau of Environment explains the Tachikawa and Kokubunji cliff lines as chains of river terraces created when the ancient Tama River cut into the Musashino Plateau (the broad upland on which western Tokyo sits) as its course shifted southwards. The river cuts into the plateau, shifts a little south, and cuts again. Each time a lower flat surface is formed, and a cliff is left between the surfaces. In academic terms, such a chain of cliffs is called a gaisen, a cliff line.

Local people have called these cliffs by other names. The Tachikawa Tourism and Convention Association introduces a town-walking course around the Yagawa Green Space as a course exploring the hake, the geographical feature of the Tama River basin from Tachikawa to Kokubunji. About a spring on the Kunitachi side, the Metropolitan Government writes: “Mama is the local word for ‘cliff’.” One cliff, several names: hake, mama. Proof, surely, that people here have spent their lives climbing up and down cliffs every day. In neighbouring Koganei, names such as the “Hake Path” and the “Hake-no-Mori Art Museum” survive today.

Among those cliffs is one that carries Tachikawa’s name: the Tachikawa cliff line. According to the Metropolitan Government, it is a terrace cliff about 40 kilometres long, running from around Ome Station on the JR Ome Line to roughly the border of Chofu and Komae cities. Downstream it has almost no height, but in its upper reaches around Tachikawa it is some 15 metres high. Of 40 kilometres of cliff, the tallest stretch is around Tachikawa.

There is another fact I would like to tell the citizens. The Kokubunji cliff line, which passes near the well-known Setagaya neighbourhoods of Seijo Gakuen and Futako-Tamagawa, begins, according to the Metropolitan Government, at Sunagawa No. 9 in Tachikawa. It runs south-east along the Nogawa River, approaches the Tama River near Futako-Tamagawa Station, and continues to around Den-en-chofu in Ota ward, some 30 kilometres in all. Upstream in Tachikawa it has almost no height; downstream from Seijo Gakuen it exceeds 20 metres. The first step of the 20-metre cliff that frames the streets of Seijo Gakuen is in Tachikawa.

Cliff lines run all over Tokyo. According to the “Comprehensive Policy on Securing Greenery” adopted by the Metropolitan Government and its municipalities in 2010, there are about 40 cliff lines large and small in Tokyo, about 230 kilometres in total, 45 percent of them covered with green. When the government began an effort to protect this cliff-line greenery across municipal borders, it chose as its model the cliff lines formed by the Tama River, with the Tachikawa cliff line at their core. One of the templates for protecting Tokyo’s cliffs was Tachikawa’s cliff.

The cliff itself is being protected, bit by bit. The Tachikawa Cliff Line Green Conservation Area was designated in November 1994 and spans six cities: Kunitachi, Tachikawa, Akishima, Fussa, Hamura and Ome. It covers 28,014.39 square metres. According to the Metropolitan Government, housing and farming have spread so far that only about 23 percent of the Tachikawa cliff line’s area is still woodland. More than three-quarters of the cliff has already become houses and fields. Living above the cliff, living below the cliff — most of us, it turns out, live on a cliff.

Tachikawa’s name is used in geology too. In the cross-section the Metropolitan Government drew to explain how springs emerge, the layer of red earth covering the plateau surface is labelled the “Tachikawa Loam”. The name of the town you live in is the name of the soil. When I learned that, I thought people in Tachikawa could be a little prouder of what is under their feet. I, at least, have started brushing the red earth off my soles with more care.

So how do this cliff and this red earth produce water? The mechanism turns out to be surprisingly simple.

How the springs work, and the figure of 5,758 cubic metres a day

The Bureau of Environment defines a spring as groundwater emerging naturally at the foot of a plateau cliff, in a valley among hills and so on. There are broadly two types, and springs that emerge from the face of a plateau cliff are called the “cliff-line type”. The Yagawa’s water is this type.

The government’s diagram tells the story. Rain falling on the plateau soaks into the red earth on the surface — the loam layer. Beneath it is a layer of gravel, and the water flows through that as groundwater. Where the edge of the plateau is cut off by a cliff, the groundwater’s path is exposed partway down the cliff face, and water seeps out there. The cliff is a cross-section of the groundwater. The diagram puts the catchment that feeds a cliff-line spring — the area that gathers its rain — at roughly 0.1 to 1 square kilometre. Smaller than I thought. Rain falling on a few blocks, at most, of the housing above the cliff comes out, in time, at the foot of the cliff.

How much water emerges at the Yagawa? Every year the city of Tachikawa surveys the cliff-line springs and publishes the results in its “Tachikawa Environment Book”. The appendix of the 2025 edition lists measurements from fiscal 2024. At 9:02 a.m. on 10 July, the spring at the entrance to the Yagawa Green Space was recorded at 5,758 cubic metres a day. North of the green space, 1,192; beside the Benzaiten shrine, 620; and inside an ordinary residential lot nearby, a spring of 1,245.

Convert 5,758 cubic metres a day into seconds and you get about 67 litres a second. In two-litre plastic bottles, more than 33 every second, all day without a break. A kitchen tap turned full on could never keep up with what is welling up, silently, in a corner of a residential district.

Compare the other sites in the same table and the Yagawa’s abundance stands out. The Fujimi Green Space in Fujimicho: 4 cubic metres a day. The grounds of the Agriculture, Forestry and Fisheries Promotion Foundation: 28. The Benten spring under the railway viaduct in Fujimicho: 495. Among Tachikawa’s springs, the Yagawa is in a different order of magnitude.

Water temperatures are recorded too. At the entrance to the Yagawa Green Space in July, about 20°C. Measured at the same spot on 15 January: 15.2°C. A midwinter stream above 15 degrees. Water that must be far cooler than the air at the height of summer and far warmer than the air in winter. Looking at the figure, I thought of how much colder my own tap water is in winter, and felt slightly beaten.

The volume, however, does drop in winter. In the January measurement the same entrance spring gave 673 cubic metres a day — about an eighth of July’s. It does not dry up, but it thins out considerably. And in the winter survey, many other sites are recorded as “not measured” — there was nothing to measure.

Cliffs that run dry, and a cliff that doesn’t

Not every spring in Tachikawa keeps flowing.

The Environment Book also carries reports from citizens’ groups. A group that has looked after the nature of the Tachikawa cliff line at the Fujimi Green Space summarises two years of observing the spring’s flow. From spring to autumn, mostly 50 to 200 cc a second. After heavy rain, over 1,000 cc a second; in September 2024 it recorded 5,000 cc a second. A week or so after heavy rain it returns to normal. And in winter it often dries up. The group wonders whether, for such a small catchment, rainwater soaks in and flows through the ground especially fast.

Two springs on the same Tachikawa cliff line: the one in Fujimicho dries up in winter, while the Yagawa in Hagoromocho does not. The Metropolitan Government’s trail guide says of the Yagawa that “it does not dry up even in winter”. What separates them?

I do not have the whole answer. But there are clues. The city’s walking-route commentary says that several other springs from the Tachikawa terrace cliff line join the Yagawa. The Environment Book’s table, too, records at least five outlets on the Yagawa: the entrance, the north side, north of the pond, beside the Benzaiten, and inside a residential lot. It is not a stream relying on one spring, but a stream that bundles together water seeping out all along the cliff. When one tap stops, others are still open. That is probably half the reason it holds up in winter.

The other half may lie in the land above the cliff. What feeds the springs is the rain falling above the cliff, and whether that rain can soak into the ground depends on how much of the land up there is paved. I will try to trace that answer at the end of this article, through the Metropolitan Government’s survey figures.

The Yagawa in numbers

• 1.3 — kilometres, the length of the Yagawa. Born, and merged into an irrigation channel, within a twenty-minute walk.
• 7 — the Yagawa Green Space’s number among Tokyo’s conservation areas. Designated in 1977.
• 21,071.70 — square metres, the area of the Yagawa Green Space on the Metropolitan Government’s record. Measured to two decimal places.
• 5,758 — cubic metres of spring water a day, measured at the green space’s entrance on 10 July 2024. More than 33 two-litre bottles a second.
• 15.2 — degrees Celsius, the water temperature at the same spot in January. Rather warm, for a midwinter stream.
• 22 — the Yagawa Green Space’s number among “Tokyo’s 57 Famous Springs”. It is the only one chosen from Tachikawa.

Tokyo’s seventh conservation area: how the Yagawa came to be protected in 1977

The Tokyo Metropolitan Government has a system of “conservation areas” to protect nature, based on the “Ordinance on the Protection and Restoration of Nature in Tokyo”. I choose to believe the name is long because there is a lot it wants to protect.

According to the government’s list, there are five kinds of conservation area — natural environment, forest environment, satoyama (the managed countryside of woods, fields and paddies around a village), historic environment and green space — and as of the end of March 2026 they are numbered up to 53. Number 1 is the Nobidome Aqueduct Historic Environment Conservation Area, designated in December 1974. Numbers 2 to 6 were designated together on 26 December 1975: Nanakuniyama in Machida, Kaido in Musashimurayama, Higashi-Toyoda in Hino, the Katsunuma Castle site in Ome, and the Shiroyama of Yaho in Kunitachi. And number 7 is the Yagawa Green Space Conservation Area, designated on 31 March 1977.

Seventh in Tokyo. By the youth of its number, the Yagawa is one of the pioneers among Tokyo’s conservation areas. To protect a two-metre-wide spring-fed stream flowing between houses — Tokyo in 1977 showed a sharp eye. The boundaries were changed in 1983 and 1985, giving today’s 21,071.70 square metres.

Tachikawa is a city with close ties to the system. Count through the government’s list and four conservation areas extend into Tachikawa: the Nobidome Aqueduct, the Yagawa, the Tamagawa Aqueduct and the Tachikawa cliff line.

The government recorded the vegetation at the time of designation. Reading it, you get a good picture of the wetland’s cast. On the right bank of the Yagawa — the south side — in the main wetland, and around two spring areas on the left bank, grow reed, bulrush, ogi silver grass, chigozasa, azesuge sedge, numatoranoo loosestrife, arrowhead and mizosoba knotweed. On the left bank, watercress and grassy-leaved sweet flag; at the pond’s edge, yellow iris. In the stream itself, matching the differences in depth and speed of the water, bur-reed, watercress, sekishomo tape grass, mizosoba, mizohozuki monkeyflower and kawajisha speedwell grow intertwined.

Orandagarashi — “Dutch mustard” — is watercress. Watercress thriving in a spring-fed brook: a scene from some cool highland retreat, within walking distance of a Nambu Line station. But you may not pick plants in a conservation area. Any urge to make a salad should be taken out on the watercress sold near the station.

The record also notes that where the water level has dropped and the ground has dried, roadside weeds such as dock have begun to move in. A wetland does not stay a wetland if left alone. When the water drops, it dries; when it dries, other plants arrive. So people tend it. According to the Metropolitan Government, conservation work at the Yagawa is done by the “Yagawa Fureai Volunteers”, including mowing and managing the wetland. The city also notes that the government, through the Tokyo Environmental Public Service Corporation, runs nature-experience programmes in the conservation areas that beginners can easily join, and is looking for new volunteers.

The designation record also notes vegetation hard to picture in today’s green space. “Weed community of abandoned paddy fields”: in paddies no longer farmed grew Philadelphia fleabane, genge, kitsune-no-botan buttercup, shepherd’s purse and suzume-no-teppo foxtail. Genge is Chinese milk vetch — the flower that once turned the spring paddies a pale purple. The description of another, a “roadside weed community”, speaks of a vacant lot in a built-up area without much coming and going, with only a few garden trees.

Then, in 1977, on the banks of the Yagawa there were abandoned paddy fields and vacant lots with leftover garden trees. Now, planted woodland grows on the north bank and boardwalks cross the wetland on the south side. The milk-vetch paddies have vanished from the Tachikawa side. But paddy fields themselves survive a kilometre or so downstream, at the Yagawa Ondashi in Kunitachi.

A wetland is a joint work by nature and people. When I walk the boardwalk and look at the neatly trimmed edge of the grass, I see someone’s morning in it.

So who lives in this carefully tended wetland? Leaf through the list of residents and you find the names of endangered species among them.