G-CANS – Ryukyukan Museum Tour

G-CANS and the Ryukyukan is one of the few places that I had wanted to visit but never thought I’d be able to.  I had seen it at least a year ago on TV and it looked really interesting.  G-CANS, also known as the Metropolitan Area Outer Underground Discharge Channel, is a flood control system that protects much of the Tokyo region.  Due to the increase in urbanization of the Kanto region, flooding has been becoming a greater risk to homes.  In the past, a lot of the flood waters would have flown into the rice paddies in Saitama and northern Tokyo, but today, it risks flooding major urban areas.  The rice fields were essential to containing the flood waters within the basin as it acted as a natural drain and storage for the excess water.  With urbanization, these rice paddies were covered with buildings and asphalt; blocking the soil’s natural ability to absorb the water and creating the need for a huge water bottle for several rivers in the basin in order to prevent floods, especially during a typhoon.  G-CANS took over 27 years to complete and it was operational before the entire system was completed.  It consists of 6.3 km tunnel and network of 5 tanks and a pumping station/tank.  The area G-CANS protects is bounded by the Edogawa River in the east and the Arakawa River in the west.  In this post, I will mainly cover my trip to the Ryukyukan museum and next week we’ll look into the technology into G-CANS itself.

G-CANS – Ryukyukan

The Ryukyukan is not an easy place to visit.  It is located in Saitama within Kasukabe city and near Kasukabe Station.  The closest station is Minami Sakurai on the Tobu Noda line.  I ended up taking a train on the Tobu Tokyo Sky Tree Line to Kasukabe Station and changing to the Noda Line.  It is only 2 stations from Kasukabe, but because you are in rural Saitama, the stations are a little far from each other.  If you are lucky, you can reach G-CANS in about 45 minutes from Asakusa.  Once you get to the station, you are saddled with a big conundrum.  You can either take a 3 km walk from Minami Sakura Station, or take a taxi.  While there is a bus service, the service usually doesn’t arrive at a good time and you’d have to wait a long time or arrive a little late.  To participate in the Ryukyukan tour, you have to arrive 30 minutes early, but in reality, they want you to arrive from 30 minutes early.  It is okay to arrive a few minutes before tour but you do have to register for the tour and make sure you understand the instructions of the tour.  I highly recommend taking a taxi to the Ryukyukan and you should be ready to call for a taxi as they are not readily available at the station.  I went to the Ryukyukan tour on a weekday afternoon, during obon, and there were no taxis at the taxi stand at the station.  It was a little strange but it was a very small station.  If you are looking for something to eat before the tour, I recommend eating somewhere else as the only thing we could find was a McDonald’s or the convenience store.

Tunnel Boring Head

Upon arriving at Ryukyukan, you will find yourself in a large open lot.  There is a little parking and a couple buildings in the lot but things look pretty sparse.  Most taxi drivers will drop you off at the main entrance, which happens to be the bus stop as well.  Around the exterior, you can see some of the pumping stations from outside the building as well as a large cutting head that was used to bore out the tunnels that connect the entire system.  You can easily head into the museum itself right away if you wish to, but I do recommend waiting till the end of the tour if you took a taxi as you’ll have to wait for the taxi to arrive after you call them.  Once you enter the building, you are in the entrance area which is also called the Citizen Gallery.  It is a small gallery they call a museum that showcases some of the local artwork.  They generally have only small time artists from the neighbourhood, specifically children’s work from the local schools.  There is also a staircase located next to the entrance.  You have to ascend the stairs to get to the main registration centre.  The main registration centre is located on the second floor, but in reality it is about 3 floors up.  On the second floor landing, you can see the Citizen Gallery as well as a model of the tunnel boring machine and samples of the cutter heads.  The cutter heads are pretty heavy and require a little muscle to lift them.

Ryukyukan – Citizen Gallery

Once you reach the second floor, you are greeted with signs and boards with signatures of famous people.  The water tank under the Ryukyukan is used often to film various movies and music videos.  Most of the major movies were Ultraman and Kamen Rider, but any movie that needs a large cavernous setting can be filmed in the water tank under the Ryukyukan.  I even read that they filmed a Land Rover commercial inside the water tank.  After you walk through the short hallway, you then enter the main reception area that also houses models and diagrams to help you understand the entire system.  This area is the actual Ryukyukan.  It can be a little confusing to understand things, but from what I understand, the Ryukyukan is the museum and G-CANS is the entire discharge system.  You are not allowed to sign up for your tour until 30 minutes before the tour starts.  Leave that to Japanese bureaucracy.  Signing in for the tour was very straight forward and I was given a special English video explaining the entire system.  Do note that the English video is a little different to the Japanese video and you may have to ask for it, but they offered it to us as we were early.  The video itself is a classic 1980’s style school video with similar era computer graphics and a lot of corny dialogue.  The dialogue wasn’t translated perfectly, but good enough.  The Ryukyukan is partially named after “dragon” in Japanese.  Ryu is the word for dragon, and “Ryukyukan is cooler than a dragon” as the announcer said.  Yes, we all laughed at that.


Once all of the people taking the tour arrive, they ferry you around the museum area.  First, they take you to a large map on the floor and explain why the underground discharge channel was made and what they are protecting.  It was an interesting map and I was able to nearly find my own apartment and probably Ru’s as well!  From there, we are then forced to watch another video, this time in Japanese, explaining the entire system; how it was built; and why it was built.  They continue to explain things in detail after the video such as the location of the various water tanks are in the system as well as how they work.  There were also 2 working models that explained how the water is collected and discharged.  Water from the Ayase and Naka rivers, as well as all of the other small rivers in between have collection sites where the water flows into large silos.  These silos are bigger than a space shuttle, including the booster rockets.  It is bigger than the pagoda in Sensoji as well.  The silos are all connected with tunnels and that is all connected to the pumping station at the Ryukyukan.  When one river starts to swell, the water is diverted into these large silos and since they are all connected, if one river is starting to flood, the entire system can be used in conjunction.  If all of the rivers start to flood, then they can still be used and the water can be pumped out into the Edogawa.  They have a large turbine that turns the water screw that discharges the water into the Edogawa.

Model of the Pumping Station

After the explanation in the main museum room, you are given a small break to use the washrooms before heading to the roof, or penthouse as the elevator liked to call it.  From the roof, they show you all of the various buildings in the area.  They show you where the water is discharged into the Edogawa; the tunnel boring head; a football pitch that is on top of the main water tank; and even some of the famous surrounding buildings.  Since it was summer, the air was too hazy to see Mt. Fuji, but on cooler days Mt. Fuji is visible and it is considered one of the top 100 views of Mt. Fuji in the Kanto region.  Afterwards, you make you way down to the first floor at the Citizen Gallery where they explain the main work of art as well as a large panel of dirt.  They preserved a 10 metre deep cross section of the earth so you can see the various layers of the ground in the area.  It was interesting to see a layer of sea shells around 8 metres deep which showed that the area once didn’t have much land, but rather it was a flooded area.  After getting that small explanation, you are taken across a football pitch to the entrance to the main event, the water tank.

G-CANS Water Tank is under the Football Pitch

As you enter the stairs to the water tank, you are told that photos are not allowed on the steps.  As you descend and ascend the stairs, photos are not allowed and there are large signs that tell you that.  They told me roughly 3 times, probably more, that photos are not allowed there.  I thought the trip to the bottom of the water tank would have been longer but it felt as if it was no more than 5 floors down.  As you start to descent, things get dark very quickly and after you descend about 1 floor, you can feel a sudden change in temperature.  Considering the outdoor temperature was 32C, and inside the water tank it felt like 20C, it was like a sudden shock after you descend underground, but it is nothing you can’t handle.  As you descend, things get damper and damper.  The hand rails are damp to touch and the stairs start getting wet before you have visible water puddles on the ground.  You are then directed to one of the main open areas of the water tank where they explain the tank in more detail.  If my memory is correct, the height of the tank is 18 metres, although the water doesn’t go that high.  The water tank was roughly 177 metres long and 78 metres wide.  You can actually see the water silo that is adjacent to the water tank, but unfortunately you aren’t allowed into that area.  They show you access panels that are used to lower bull dozers and trucks into the water tank.  After they use the tank, they need to bring trucks in to clean the floors.  Once they finish explaining things, you get 10 minutes to walk around and take photos.  The area you are allowed to see is pretty small, but large enough to enjoy it.  If the tour area was any larger, they could lose sight of people and people would be doing many stupid things.

Inspecting the stairs to G-CANS Water Tank

The area you are allowed to walk in is roughly 1/6th of the total area.  That is just my own estimation, so that is probably not even correct.  It is bounded by rope and thankfully the rope is on the floor so it didn’t interfere with my photos.  When I went on the tour, they were filming something, or taking photos for something, which was interesting, but it didn’t make taking photos easy.  On the silo side of the tank, there are large concrete blocks with a rope across it to signify the boundary.  It also serves as a safety for the cleaning trucks to prevent them from falling into the silo itself.  Throughout the water tank, you can feel the humidity and when I went, you could easily see it too.  There was a visible haze as the water was stuck inside the tank.  At times, the water was about 2 cm deep, so having good shoes is highly recommended.  Hiking shoes aren’t necessary, but if you have regular shoes that easily get wet, you might be in trouble.  Most of the area was dry but some areas had puddles.  Once the free time is over, you proceed back up the stairs.  There are small landings as you exit the bottom of the tank and if you look to the side, you can see a buildup of sludge that is several centimetres thick.  After I saw that, I realized why they needed to clean the tank periodically as the sediment was pretty disgusting to see.  As you reach the exit there is another sudden change in temperature that shocks the body again.  Once everyone has exited, they bring you back to the main museum area where you fill out a survey and the tour is over.  You can optionally head into the theatre to watch a video showing even more detail into the system, but I never bothered.

G-CANS Water Tank: Note the haze between the dark portions of the pillars

The Ryukyukan tour is a very fun tour and it is something I don’t regret doing.  It isn’t something that I would do again as it is just too far from my place.  I don’t particularly like heading out to Saitama but if I have to I will.  I usually go to Saitama for football but this was the first time I went for a different reason.  If you cannot speak Japanese, or if your Japanese is very basic, you need to bring someone who can speak Japanese well or fluently.  I did well enough that I could understand most of the tour and had no problems with the instructions.  They generally want you to understand Japanese to a level that they can instruct you on what to do.  The guides do not speak English and they generally won’t try due to the rules on the website requiring you to have a translator.  If you go with someone who is relatively fluent in Japanese, they will have to act as a translator for you and they will have to translate for you.  You have to be together during the speaking portions of the tour.  Otherwise, it is a fun tour to take and you should try to go if you can.

G-CANS Water Silo No. 1

I found this great video of the best part of the tour

G-CANS – Ryukyukan Museum Tour is part of a series of posts on the Metropolitan Area Outer Underground Discharge Channel.  Follow the links below for more information on this system.