Field Survey: Oi River Basin

Hi, this is Abdul Moiz, D1 student from the Kawasaki Research Group. Even though this article is a little bit overdue, today I'll be writing about our field trip to Oi River Basin on 28^th and 29^th May 2018. I took a Shinkansen (bullet train) from Tokyo Station to Shizuoka Station in the morning, where we were supposed to meet up. In addition to teachers and students from the River and Environmental Engineering Laboratory (REEL), we were also joined by two professors from Yangon Technological University (YTU) and two personnel from Chubu Electric upon arrival at Shizuoka station.

Shinkansen to Shizuoka Station

We rented a couple of cars at Shizuoka Station and started moving up the mountainous route towards the first dam site. There were a lot of turns along the way and this was probably the first time I felt sick in a car. However, soon we arrived at the Ikawa Dam site and I started to feel a little bit better.

Ikawa Dam

Ikawa Dam is the downstream-most dam site in the cascade of hydropower dams owned by Chubu Electric in the Oi River Basin. This was exciting for me since this was the first time I was going to get to see how a system of hydropower dams operated in real-life.

We also got to see the inside of Ikawa Dam where the temperature suddenly dropped by 10 degrees Celsius. Also, coming out from the bottom of the dam were a couple of penstocks which carry water from the dam to the hydropower station for power generation.

Penstock at Ikawa Dam

We also got a chance to take a very memorable group photo at the bottom of Ikawa Dam.

Group photo at Ikawa Dam

Once we started moving further upstream, we saw a very serious issue related to sediment accumulation. Large amounts of sediments entered into the river and raised the depth of the riverbed, causing a risk to the storage capacity of downstream dams. Landslides also caused a sudden influx of sediments at certain locations.

Sediment issues near Hatanagi-I Dam

The red bridge in the picture below was reconstructed and raised, however because of the accumulation of sediments the bridge is now only a few meters above the riverbed. This photograph perfectly demonstrates how serious the issue of sediment accumulation is in the upper reaches of this river basin.

Sediment accumulation has decreased the depth of riverbed

In addition to sediments, because of the landslides, several wood logs also get accumulated at the upstream of Hatanagi-I Dam. Another interesting fact was that all of these dams had little to no staff in them and everything was being operated remotely from a control center.

Wood logs have accumulated upstream of Hatanagi-I Dam

We stayed at a rest house located in between Hatanagi-I and Hatanagi-II Dams. It was a quiet place with very few visitors, however, it was quite popular for its onsen. Shiozawa-san also presented his research about dam operation in Oi River Basin to professors from REEL and personnel from Chubu Electric.

Shiozawa-san is presenting his research to Chubu Electric personnel at Akaishi Onsen Shirakaboso

The next morning, we went downstream of Ikawa Dam and visited Nagashima Dam. This dam is owned by MLIT and is also used for other purposes such as flood control and water supply.

Nagashima Dam

Group photo at Nagashima Dam

Moving further downstream, we visited the Shiogo control center. This is where all of the dam and weir gates were being remotely operated from. All of the dams were being observed by using CCTV cameras and a large screen showed the status of all gates, and if any one of them had some issues, a warning was displayed and a team was dispatched to check the issue. In addition to hydropower, other power generation stations, such as wind power were also being operated from this central station.

Shiogo control center

The staff did mention that because of this centralized and integrated control center, the number of personnel had to be reduced. In future, other power generation sources will also be operated from this center and it is expected that the number of staff may be further reduced. However, such kind of integrated operation could lead to better decision-making for power generation and dam operation.

Although over the past I have read a lot of material and papers related to the operation of a system of hydropower dams, this was probably the first time I got to see that operation in real-life and thus gained a better and more holistic understanding of the whole situation.