Cherry Blossoms along the Shore: drought in Kanagawa Prefecture, spring 2026

 

Cherry blossoms! On April 1, Yokohama Local Meteorological Observatory announced its indicator cherry tree reached full blossom. Since then, we have a couple of days for spring storm, but at least around my neighborhood they keep their best. Hurrah! They will be so beautiful even when they are scattering. I hope a couple of more days left for us to steep in their ephemeral splendor … That’s said, something strange is happening. For one thing, the Meteorological Agency announced their weather forecast for this week: it’ll be warm days including several “hot days” with the temperature at the level of June. Their next 3 months’ forecast also says “The average temperature in Kanto Region will be high, and rainy monsoon season could start earlier than usual.” Well, do you remember my “prediction?” Soon after cherry blossoms, summer will come.

The early coming of monsoon season should be welcome. Actually, this winter was so dry in the megalopolis Tokyo area. Kanagawa Prefecture was not an exception, nor Yokohama. Our reservoir lakes for water supply remain in critical condition. As of April 4th, the entire water storage rate for Kanagawa’s main water system, i.e. Sagami and Sakawa River Systems, is 39%. It’s after more than 2 weeks of on-and-off rainy days. The worst is Tsukui Lake with Shiroyama Dam (; my post on Oct 20, 2017). The lakeside Prefectural Park, Tsukui Shiroyama Park, is famous for its cherry blossoms. But … look.

When a reservoir is like this, so is upstream area. This is the recent Yadoriki Stream. The comparison tells obvious: water level is low.

At the end of March 2026.
Right bank is dry enough to become grassland.

Yadoriki Stream in standard March

Yadoriki Water Source Forest is for Sakawa River system whose reservoir lake, Lake Tanzawa, shows 46% of water storage rate, or 51% of average year on April 4th. Tsukui Lake, a reservoir lake for Sagami River, shows 16% of storage rate or 21% of average year. i.e. Yadoriki Stream has more water than the other water source forests in Kanagawa. It’s scary. Kanagawa Prefecture and Tokyo Metropolitan Government have a water sharing agreement, and in normal times the Prefecture diversifies 220 million m3 water per day to Tokyo from Sagami River. Since last month, Sagami River could not continue this, and the supply to Tokyo was reduced to 110 million, i.e. halved, per day. The rainfall from mid-March has not yet let reservoirs recuperate from the drought.

The water level immediately after
the water gate of Shiroyama Dam.
Could you see the water level is so low?

Water source area is like this, and so is the downstream, i.e. Yokohama. We Niiharu Lovers worry if this spring frogs have enough water for their eggs. Next to Yatoda rice paddies in Asahi-Yato of Niiharu, there are two small ponds. They normally hold water for gelatinous frog eggs. If it’s tube-like, they are eggs for toads. If they are foamier, they are for Japanese brown frogs. This year, none. Reason? Both of these bonds are dried up. Frogs need water from February to March for their tadpoles. If there is no water, they do not lay eggs to begin with. “It’s sad.” “Yes. Oh, I’ve found some eggs in ponds next to Ikebuchi Open Space.” “Me too! They are brown frogs, aren’t they.” “But you see? The other day, I’ve been there in dusk and heard an owl hooted in a tree over the pond.” “What!? They are eating eggs and tadpoles.” “Oh yes.” Survival of the fittest. This is a harsh year for frogs in Yokohama.

Dried up

From rice paddies another stream goes to
the (artificial) pond next to Niiharu Community Centre
 in Satoyama Park.
It also has poor level of water.
As the pond in the park is man-made,
it keeps water somehow. But …

Tadpoles in Ikebuchi pond.

If monsoon comes earlier than usual with enough rain, it could give some respite for our water system. Yet, volunteers who nurture Yatoda rice paddies in Niiharu are seriously worrying the prospect of this year’s rice harvest. I guess it’s not a problem only for amateur farmers in our community. With soring energy cost (i.e. it’s more costly pumping from agricultural waterway), low or none water level is worse for agricultural production by pros. Last year’s harsh summer yielded poor crop of potato and onions in Hokkaido, and the cost of these is shooting up now in supermarkets in Yokohama. Let us keep crossing our fingers as the situation improves and we have sufficient water supply this summer. God willing …

Small flow for
Asahi-yato rice paddies this March.
Correction: No flow.

The flows from Niiharu Forest gathers in Umeda River,
then to Tsurumi River.
Inevitably, the water level for Umeda River is low now.
 It would be good news for Egretta garzetta
to procure meals in Umeda River. But …

If you find environmental issues in Kanagawa Prefecture, please make contact with

Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター
657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

Goodbye Cherry Blossoms: Sakura this year around me

 

This year I did not intend to tell you about cherry blossoms. But … I could not resist. I have not been anywhere to admire particularly blossoms this year. Nevertheless, these are photos taken in familiar places for me.

Cerasus jamasakura in Niiharu Citizen Forest 新治市民の森. Late Mr. Nakamaru, the first chair for the Lovers Association of Niiharu Citizen Forest 新治市民の森愛護会, once said cherry blossoms must be seen from afar. Indeed.

This is also from Niiharu, in Ikebuchi Open Space. Personally, I think the beginning of April is the time when Niiharu Citizen Forest is the most beautiful ...

And we can find more cherry blossoms inside Niiharu Citizen Forest. This scenery is from the open space next to the Workshop.

This is the promenade for Satoyama Garden, Yokohama. These old Cerasus Jamasakura go strong.

Cherry blossoms, Someiyoshino, Street in front of the Forest Lab. Next to the venue for art show, there are two elderly care facilities whose buildings are surrounded by Someiyoshino trees … Hmmmm. Grandmas and Grandpas spend their final days with cherry blossoms. I think it’s not bad.

In Yadoriki Water Source Forest, we can spot wild cherry blossoms here and there on the slopes. I have not identified the one in this photo, but chances are, it is Fuji Cherry found especially around Mt. Fuji. Botanically, they are categorized as a species of Fossa Magna Element = endemic species for Fuji-Hakone-Izu National Park, and Tanzawa-Oyama Quasi-National Park. They are found only in deep mountains of the area. The petals of the beau are smaller than Someiyoshino, and the colors are paler. More ephemeral ...

Yadoriki Water Source Forest also has a series of cherry trees near the entrance. They are Someiyoshino planted intentionally 50 or so years ago when the place was a camping facility. Of course, now such an act is not welcomed for the Quasi-national park. Anyway, they are beautiful, aren’t they?

Just like the global stock market, this spring weather in our neighborhoods is jumping around. One day, it’s freezing cold and the next morning is hot requiring half sleeves. I guess plants are confused and decided to flower at once in Yokohama and Kanagawa, as for spring of the places in more northern area.

Chinese fringe flower in a garden next to the Forest Lab.
They are supposed to be full bloom after the cherries.
This year, on one go!

Cherry silver berry is also in full-bloom along Umeda River
 near Niiharu Citizen Forest.
They are also after cherry blossoms.

Lonicera gracilipes var. glabra open their flowers
 finally in April for Niiharu!
 They are supposed to be so before cherry blossoms.

Lots of fertile stems of Field Horsetail (; my post for April 13, 2018).
Er … you’re late!
You should be like that before cherry blossoms!

Violet orychophragmus in Niiharu Citizen Forest.
They are designated as “Invasive Species” to Japan.
 In any case, beautiful …

Mmmmmmmmmmmmm! It’s spring. Though, cold rain this weekend will disperse cherry blossoms, and summer is coming. Goodbye, this year’s cherries. Well, next week, I’ll return photos I’ve taken during this winter. The brown scenery again. Reason? I tell you my recent adventure in Koajiro Forest 小網代の森. To explain it, it’s better using photos taken during winter. Please stay tuned!

Stachyurus praecox in Yadoriki Water Source Forest

If you find environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

Very Dry: what’s happening in Yadoriki Water Source Forest やどりき水源林?

 

It’s dry these days in Kanagawa Prefecture. Although we do not suffer wildfires like in Ofunato 大船渡 or LA, the dryness of our atmosphere can prick our skin … Having said that, it might be a natural thing for our climate. Here is the total amount of rainfall for each January since 1997 around Lake Tanzawa, a neighbor of Yadoriki Water Source Forest.

Sure, 2025 is in the lower precipitation group for January. But there were drier years before … We may not have a problem. However,

These are water blankets found in Yadoriki Stream in January. It spread widely over the water surface.

Normally in our climate, water blankets proliferate when the temperature of water is warm enough, like around 20°C. During our research of the river in December, the average water temperature for Yadoriki Stream was around 10°C, chilly enough for preventing water blanket mushroomed. In January, the precipitation was small and … the water might have warmed more than for average years … Globally warm winter? We were alarmed, and reported the incident to the Prefecture. We‘re watching the situation.

If you find environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

Babys when the planet is boiling: aquatic animals in Yadoriki Water Source Forest, September 2024

 

Last month in September, it was still hot even in Yadoriki Water Source Forest, ASL 390m+. We forest instructors did a little research in Yadoriki Stream to see what kind of water animals we could find in late September. The high season for water play in the Water Source Forest was supposed to be over by the end of August. But this year it was still boiling hot. Inevitably, Water Source Forest had lots of visitors during weekends to have a chill with Yadoriki Stream. It was still summer. We were delighted to wade in the stream and have a chill. Several families leisurely had picnics in a quiet but gargling sound of the river. Ahhhhhhhhhhhh … summer.

We expected the thing we found in water might not have been different from July or August. Nah. Already a little bit of algae started to establish in the nooks of torrent. They were absent just a couple of weeks ago. The algae will be more by December when all the deciduous trees shed their leaves and started their winter sleep. Confused? Well, while trees have lots of leaves and cover water, the amount of sunlight reaches inside the water is limited. It’s not an algae-friendly environment, mate. Finding algae in Yadoriki Stream would mean fall is approaching, perhaps ... already different from the river during high summer. Then, what our hand nets scooped from the river was definitely different from those a month ago. In September, they were few, and tiny, tiny, tiny. “Hmmmmm. No large larva of Tipulidae or Stoneflies …” “Even Japanese freshwater crabs are pequeños.” The largest specimen we could make on that day was only 2cm or so in body length. Cuties. But in terms of “Gotcha!” feeling … er, you know?

Yadoriki Stream, September 2024

I intentionally scooped the point of algae
as it can cradle the aquatic animals.
But no large ones here …

Tiny crab

In the lab

Lots of tiny heptagenioidea. They are cute!

When we recall a standard lifecycle of water animals, there is no secret for these tiny trophies we could have in September. They mate, lay eggs in water, mum and dad died after that, eggs hatch and larvae spend their child days in water, pupate, and emerge to mate. On average, this cycle takes about 1-2 years, but the time they mate is from spring to early autumn. If the eggs hatch early spring, say March, the babies start to dwell in water from that time, together with those which take more than a year before pupating. i.e. If we do research early spring, or winter, we can catch both big and small aquatic animals. In contrast, from late summer to early autumn, those remaining in water are small babies that come out from the egg recently. Larger aquatic animals in July or August already have become adults and lie eggs by September.

Er … sky was very summer on that day.

OK, OK. What I was surprised was, even in this boiling climate, these creatures follow their traditional lifecycle. Or, maybe they cannot change it easily. Procreation for them is often a one-shot event. It’s not uncommon the bugs to die immediately after a successful egg lying. Unlike humans that can enjoy a long summer for reproduction, they have to do it just once with whatever conditions they are thrown at. I don’t know if the baby water animals are OK with ever-lasting summer. Maybe we should continue collecting data to have some idea what is happening for the baby gadflies under climate change …

Though, fruits of Japanese peppers
already took red autumn red color.

If you find environmental issues in waters of Kanagawa Prefecture, please make a contact with Kanagawa Environmental Research Center 神奈川県環境科学センター

1-3-39 Shinomiya, Hiratsuka City, 254-0014
〒254-0014平塚市四之宮1-3-39
Phone: 0463-24-3311
FAX: 0463-24-3300

k-center@k-erc.pref.kanagawa.jp 

https://www.pref.kanagawa.jp/docs/b4f/index.html

After Crashes: beautiful rocks found in the stream of Tanzawa Mountains 1

 

Very large Pyroclastic breccia in front of us,
found in Yadoriki Stream. More to it below.

So, thanks to the birth secrets (; my post last week), what we find beneath Tanzawa Mountains is of volcanic origin, more or less. In my post for July 19, 2019, I told you my adventure with the soil in Tanzawa. Beneath the very thin topsoil, there was 40 cm or so volcanic scoria ashes due to Fuji 1707 tephra. In Tanzawa, typical soil for Kanto region is covered by the thing came from Mt. Fuji in the 18th century. Then, deeper down from that, we can encounter the proof of tectonic crashes since 13 million years ago. How can I see such an ancient mega drama? We don‘t have to dig deep down the mountain. The thing we do is simply do picnic on the valleys of Tanzawa Mountains. There are several good valleys we can visit safely especially for escaping summer heat.

Very thin topsoil of Tanzawa area

You just hike Tanzawa Mountains and cross small mountainous valleys. The rocks and riverbeds there are the basic structure of Tanzawa that made by tectonic collides millions of years ago. The topsoil once covered such ancient earth is washed away by the stream. Often, they are tuff created by volcanic ashes and rocks spewed out by primeval under-oceanic volcanos, and piled up in the bottom of antediluvian ocean. It went through humongous pressure machine of tectonic movements which in the end pushed up the volcanic sediment above the sea level.

It’s near Nishi-Tanzawa Visitor Centre.
Lots of rocks, yeah.

Have you noticed the riverbed often have green colour? It‘s green tuff, made by East Pacific Rim Orogeny from 26 to 5 million years ago. For the other kinds of tuffs, we know Tanzawa has fine tuff, coarse tuff, pyroclastic breccia, tuff breccia, lapilli tuff … Yadoriki stream which run through Yadoriki Water Source Forest is an easy place to find these rocks. Below is from my collection found in the riverbed of Yadoriki Stream.

Green tuff

It’s also green tuff with white stripes.

Seeing it through the microscope,
I think it shows piles of ashes.

Coarse tuff

A microscopic photo of the above rock.
It’s a rock which relatively coarse volcanic ashes,
roughly 1/16 to 2mm in diameter,
piled up at the bottom of the sea,
then went through the tectonic pressure machine.

Lapilli tuff

With microscope,
we can see it is made of 2-64mm lapilli
 with volcanic ashes.

Tuff breccia

Now the size of the lapilli is larger than for lapilli tuff,
but the lapilli is less than 50% of the entire rock.

Pyroclastic breccia

Unlike the previous rock,
now the lapilli occupy more than 50 % of the rock.

These palm-sized rocks are probably from large ones that were cracked by landslides and continuous rapid torrent over steep slopes. When we climb upstream for water sources of mountainous valleys in Tanzawa, we can find huge rocks piling up and the amount of water flowing between boulders is smaller. One evidence that sustains the hypothesis can be found at the plunge pool of Takigo Fall 滝郷の滝, in front of the open space with picnic benches of Yadoriki Forest. The height of the fall is about 30m with average width of 2m. We can approach to the shore of the pool and observe rocky layers of earth. With large lapilli inside, we can recognize pyroclastic breccia. This waterfall is famous for its very fragile walls which killed so many climbers trying to rock-climbing. Either using aids of ropes et al or bouldering, the fragile breccia easily collapses by the weight of a climber. If a person falls down 30m on a rock, it would be an instant death. Such crumbly stone can simply become a small souvenir-sized rocks, right? In the end the rocks here are sedimentary.

The upstream of Yadoriki Stream.
The place is famous for its large boulders covering the riverbed.

The plunge pool of Takigo Fall

The riverbeds of Yadoriki Water System can keep having small rocks even around 1000m ASL. Do you remember my adventure to Ameyama Pass 雨山峠 to Yushin Valley ユーシン渓谷 in 2019? Ameyama Pass is at ASL 957m. From the Yadoriki main stream to the Pass, the entire itinerary is on the rocks and scree. Come to think of it, they were once volcanic ashes and lapilli that went through gigantic pressure of crusts and became a mass. Since then, they continue receiving the same pressure to be pushed up to ASL 1000m and beyond. No wonder they become crumbly … Having said that, the rocks we find in Tanzawa mountains are not sedimentary alone. I’ll tell you the other kind next week. They are also very beautiful. 😄

We’re reaching to the Ameyama Pass …
and the route is still like this.

Oh, by the way,
the riverbed in front of the Open Space near Yadoriki Bridge
 (that red one) is not natural one,
 but goes through riparian works many times.
 Reason?
 Frequent monster typhoons cause landslides often
 along Yadoriki Stream,
and block the water flow
that could trigger debris flow to the communities downstream.
 The prefectural office does continuous construction there,
 but Mother Nature always wins.

If you find environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/