thalweg doctrine

I talked about international laws in my earlier posts. Very soon, I came to know about the limitations of these laws. I was basically going over the resources available on South Talpatty or Purbasha or New Moore Island dispute between India and Bangladesh (news from latest discussion). After looking at the laws, it seems that they are insufficient to resolve the dispute. The assumptions made in the law definition is limiting it to function in this particular case.

The Law and the premises

Thalweg in transverse section of a river

The law in concern is also known as Thalweg Doctrine. As per wiki -

“The Thalweg Doctrine defines the border between two states separated by a watercourse or flowing body of water as lying along the thalweg, which is the line of greatest depth of the channel or watercourse.”

To illustrate the concept pictorially, I can refer to the pictures.

In the transverse section of the river the thalweg is the deepest part of it. It identifies the main current flow of the river. Looking at the satellite or aerial image of a river, thalweg is difficult to identify, though the main flow of the river can be identified. The concave and convex banks of the river are critical to determine the main channel of the river. The deepest part of the river is shown in the transverse section of the river in the image above. The red arrow marks in the image beside shows the main channel of the river.

The thalweg doctrine is key to border demarcation between nation states. It is used for drawing boundary on the Shatt Al-Arab river between Iraq and Iran. Recently, it was used in International Court of Justice to demarcate the borderline between Namibia and Botswana.

The Dispute

The dispute is between India and Bangladesh over a small uninhabited island named South Talpatty in Bangladesh and Purbasha/New Moore in India. It is a alluvial delta in the river mouth of river Haribhanga which is the border between India and Bangladesh. The size is claimed to be between 2,500 to 10,000 sqkm. As per the daily Star editorial -

“Bangladesh claimed sovereignty over the South Talpatty Island on the grounds that (a) the flows of the border river were to the west of the island and a satellite photograph confirmed the western orientation of the flow and (b) the island was a natural prolongation of the Bangladesh territory.”

It also states -

“India disputed Bangladesh’s position as it claimed that the flows of the border river lay to the east of the island, not west as claimed by Bangladesh. The nub of the dispute over the sovereignty of the island rests as to whether the main flow of the border river Hariabhanga lies to the west or east of the island.“

The bold line actually summarizes contrasting claims by India and Bangladesh. The editorial also clarifies

“It is pertinent to note that two flows — one from the border river and the other from Bangladesh inland river, Raimangal — fall on the estuary. Bangladesh argued that India confused the flow of the Raimangal river with that of the border river, Hariabhanga.”

The Satellite Images

Due to an unprecedented advancement an availability of quality satellite and aerial images, I took my opportunity to verify the claims of India and Bangladesh. I visited the wikimapia and targeted the place in dispute. I observed that no island exist at that place (probably submerged due to high tide), but a marker is left on the site for the island. I verified that the marker is correct as per the longitude and latitude given in the Banglapedia article.

The main flow of Haribhanga shown by wikimapia image

The point of contention, the main channel of the river is really confusing. The dark blue area (main flow) of the river in the left of the map is in contention. It flows to a estuary where it joins another river – Raimangal. Both almost flowed together. The joint flow passes through the East of the island. This is what is claimed by India. We don’t even need a survey to determine the main channel or the deepest point of the river, the entire flow actually goes through the East.

Even if we think that the flow of Haribhanga ends at where its flow meets Raimangal (assume the U shaped area to be the estuary), then the ownership of the island becomes a subject of maritime demarcation, because the extension of boundary beyond the estuary is subject to maritime laws. In terms of maritime boundary, the island is located closer to Indian territory. However, this was not the central point of the claim and this violates the UNCLOS article 7 which says

“Where because of the presence of a delta and other natural conditions the coastline is highly unstable, the appropriate points may be selected along the furthest seaward extent of the low-water line and, notwithstanding subsequent regression of the low-water line, the straight baselines shall remain effective until changed by the coastal State in accordance with this Convention.”

I looked at another high resolution image on the wikipedia (original source) to confirm my observation.

The main flow of Haribhabga flows through east of the island

In this second image, the boundary line between the rivers Raimangal and Haribhanga is also clearly visible (shown by an arrow). It is not possible to confuse between these two river flows, at least in the couple of images I have seen. I got a third map for the same but I did not agree to the demarcation shown in the map (though it showed the island to be in India).

The catch

There is a big assumption in the whole observation. The river-flow has to remain same the same over years in order to have a constant boundary between bordering nations. However, the Gangetic river delta is alive and always forming new alluvial deltas. The rivers are constantly changing their flows. So, it is most likely that surveys in different years could result in different results. In a year the claim of Bangladesh could win, and it could go to India in another (as it is now). The river could start flowing to the West of the island after a few years, or even worse, the delta could be gone for ever if the it flows on top of it.

I understood this after I read the news about how river erosion is affecting Bangladesh. The report adds

“When India and Pakistan were separated in 1947, it was settled for rivers in the bordering areas that the mid-current of the rivers would be treated as the border for the two countries.

“But nothing was told in the law about what will happen if rivers erode or change their courses,” said a retired official of the Directorate of Land Survey who worked on international border for over a decade. …

It is reported that South Talpatti, a small island in the Bay, is not visible anymore on satellite images.”

It’s not difficult to understand the reason. The ever-changing rivers actually makes it more complicated to verify the border claims.It could happen that the survey from Bangladesh side was done when the river indeed used to flow on the West of the island and now it has changed course to move to the East of the same. This points out the flaws in our basic doctrine of demarcation – the thalweg doctrine.

Relation to Maritime Boundary

I also read in some reports that this dispute is key to determine the maritime boundary between India and Bangladesh. However, UNCLOS (the international law of sea) states -

“Where a low-tide elevation is situated wholly or partly at a distance not exceeding the breadth of the territorial sea from the mainland or an island, the low-water line on that elevation may be used as the baseline for measuring the breadth of the territorial sea.”

The disputed island is nothing but a low tide elevation. It also says -

“Rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf.”

So, it could affect the territorial waters but can not affect the EEZ.

The conclusion

The ever-changing river flow in India Bangladesh river boundary causes border changes by land erosion. The flow change also disputes the claim on an alluvial delta island. The international law, which surprisingly assumes the river flow as well as main channel of a river will stay constant over years, is deeply flawed to be used in this context. If the law is observed, the border would always be changing and the delta islands will change hands in few years. Not only in this case, all rivers are known to change their courses over years due to erosion. In a mineral rich river, a change of borderline by a few meters could cause the ownership of a few barrels of oil to the other side of the boundary (read about Iran-Iraq dispute over Shatt Al-Arab). I am really confused how we would solve those cases if we don’t come up with a better doctrine .

Update

One interesting update. I saw the satellite images (posted above) and concluded that the flow of the river is on the West side of the island. An Admiral (Rear Admiral SI Mujtaba) from Bangladesh seems to agree to that with an additional claim attached to it. He claims that India is training the river upfront to divert the flow so that it flows towards the West of the island. Well, I’m no specialist in that matter but it seems it would be a costly affair. Not only that, I doubt how sustainable it would be given the erosive nature of the delta where every river changes its course one in a couple of years or even more frequently. Here is the exact quote from the Daily Star report -

“There is a satellite picture which indicates that the flow of Hariabhanga River is west of South Talpatti. Probably it came to the notice of the Bangladesh government that India has trained the river upstream to divert the flow of the Hariabhanga River west of South Talpatti. If they have trained the river flow it does not mean that that the land belongs to them.”

I believe it is easier to conclude that the rivers change courses normally and switched its flow from one side to the other. Furthermore, he didn’t provide any supporting document (how India is training the river upstream) to strengthen his claim. So, for now, I can ignore his claim.