Heading South-West from the DPRK’s capital, Pyongyang, following the path of the Taedong River, you’ll hit the port city of Nampo, beyond which sits the engineering megaproject that is the West Sea Barrage; an enormous dam stretching 8km across the Taedong River where it meets the sea.
The West Sea Barrage is a highlight on any tourist visit to Nampo and serves simultaneously as a railway bridge, dam, lock, and road bridge.
On top of that, it’s an important symbol of pride for the country as the 5-year long project between 1981 and 1986, undertaken by the Korean People’s Army, is considered a major achievement in domestic engineering.
But why build a huge dam just downriver from a key international port which would still need to cater to international cargo traffic. Something which is famously tricky to accomplish with a concrete wall in the way.
Korea’s Geography
Let’s start at the beginning. Korea is a peninsula bordered by the sea on both sides. To the east is the East Sea of Korea, also known as the Sea of Japan by the Japanese. But it’s the western side we’re most interested in. The West Sea of Korea, or Yellow Sea.
The Taedong River Flows into Korea Bay in the West Sea. The Taedong is one of Korea’s most significant waterways along with, in the far north, the Amnokgang between Mt Paektu and Sinuiju and the Tumen River between Mt Paektu and Rajin which serve as international borders between Korea, China and Russia.
The Taedong River however sits at the heart of the nation’s capital, Pyongyang, and therefore potentially it’s most famous. The river flows from the Rangrim Mountain range in northern Korea through the mountains and into Pyongyang, where it flows past many of the DPRK’s most famous monuments and sites.
Why Build a Dam?
So why did the government decide to dam the river? Well, there were three primary goals in the construction of the West Sea Barrage. Firstly, raising the water level on the inland side of the dam would allow larger vessels to dock at Nampo which isn’t situated directly on the sea, but slightly inland.
Secondly, damming the mouth of the river meant the quasi-reservoir which was created behind the dam would be a source of fresh water, an important commodity both for sustaining large cities as well as for farming.
Thirdly, the freshwater could then be pumped into the surrounding areas, already dedicated primarily to agriculture, to irrigate the fields. These areas surrounding the dam are some of Korea’s flattest regions, making them ideal for agriculture.
Much of the country is dominated by mountains making farming tricky, so most of South Hwanghae, North Hwanghae and South Pyongan are used for agriculture, hence the importance of good irrigation.
On top of all these reasons, a dam over the Taedong would connect the city of Nampo with the northern tip of South Hwanghae cutting journey times by road and rail significantly.
So, in 1981 with all these reasons in mind, construction began.
Construction
The construction of the barrage was split into two sections. The most complex section was to sit between the south bank and Pi-do, a small island in the middle of the river. The vast majority of the dam would run between Pi-do and the northern river bank.
The construction teams built what’s called a cofferdam around the intended construction area.
This was achieved by dropping huge 1500 tonne metal cylinders into the water to create a sealed-off area between the riverbank and the island. The water in this area was then pumped out creating a dry construction zone for the workers.
For the remaining section, an earthen dam was built as concrete and sand were poured into the river. Construction on this section started simultaneously from both sides intending to meet in the middle.
Safely confined within the cofferdam, the concrete sluice gates and lock systems were constructed. The West Sea Barrage has 36 sluice gates to control the flow of water from the river out into the sea and 3 locks that allow ships to travel through the barrage.
Eventually, the cofferdam was destroyed allowing the water to once again flow in and hide the vast majority of the construction work beneath the waves. As the main dam neared completion, the water speed increased dramatically. By the time the gap was 60m wide, the water speed had increased up to 20m/s.
Eventually, the earthen dam was complete and the entirety of the Taedong river was only able to flow through the 36 sluice gates allowing engineers to control the flow of water out of the river mouth and into the sea.
The dam was outfitted to include a road and a rail link between the two river banks. In June 1986, the Sohae Kammun Line, or West Sea Barrage Line, was opened linking the two sides for the first time.
As part of the bridge construction, a huge swing bridge was installed over two of the locks allowing for road and rail traffic to cross when cargo ships were not traversing the lock system. The construction of the barrage is hailed in the DPRK as a major engineering achievement and took incredible amounts of natural resources to construct.
Legacy
The Taedong River has long been an important symbol in the DPRK.
Neolithic settlements have sprung up along its banks, it gave birth to the city of Pyongyang and it’s a vital transport waterway, almost an artery running from the West Sea deep into the mountainous north. However, with the construction of the barrage, the river gained even more meaning.
Since 1986, the barrage has featured on banknotes, TV news backdrops and documentaries, both foreign and domestic.
The barrage is a major tourist attraction for foreigners visiting Nampo and has allowed the city to become a major international port on the West Sea.