Cambodia has signed the agreement for the Funan Techo integrated water resources management project, according to the Khmer Times.

The Funan Techo project is among the most consequential infrastructure schemes in mainland Southeast Asia, and among the least covered outside the region. It concerns water, trade routes and the relationship between four countries that share one river.

Why a canal is a foreign policy question

Cambodia’s seaborne trade has historically moved down the Mekong and through Vietnamese territory to reach the sea. A domestic route from the Mekong to Cambodia’s own coast would change that, reducing dependence on a neighbour for access to international shipping.

Framed that way, the project is straightforwardly about sovereignty, and that is how Cambodian officials have presented it. A country that must ship through another country’s ports is exposed in a way that is invisible until relations deteriorate.

Vietnam’s concern is hydrological rather than commercial. The Mekong Delta is among the most productive rice-growing regions in the world and is already under pressure from upstream dams, reduced sediment flow and saltwater intrusion driven by sea level rise. Any diversion of dry-season flow matters at the margin, and the delta is close to that margin.

The disagreement about the numbers

Assessments of how much water the project would divert vary substantially, and the reasons are worth understanding.

A navigation channel and an irrigation scheme have very different water demands, and a project described as integrated water resources management may include both. What matters is not the average annual volume but the dry-season minimum, when the delta is most vulnerable — and dry-season figures are exactly what published documentation has tended to be thinnest on.

Regional water researchers have consistently called for fuller technical disclosure and for assessment under the Mekong River Commission’s procedures. Cambodia’s position has been that the project falls within its rights over a tributary system and that its obligations have been met.

Both positions rest on contested readings of the 1995 Mekong Agreement, which requires prior consultation for some categories of project and only notification for others. Which category a scheme falls into is therefore the whole argument, and the agreement has no binding enforcement mechanism.

The structural problem with shared rivers

The Mekong runs through or alongside six countries. Each has a sovereign right to develop water within its territory, and each is affected by what the others do.

International water law offers principles — equitable and reasonable utilisation, an obligation not to cause significant harm — that are genuinely in tension with each other and that no body has authority to adjudicate here. The Mekong River Commission is a coordinating and technical organisation, not a regulator, and China is not a full member.

The result is a system in which each state acts within its rights and the cumulative effect falls on whoever is furthest downstream. Vietnam is furthest downstream.

Why so little of this is reported

It is slow. Infrastructure projects generate a signing, then years of construction, then effects that appear gradually in salinity readings and rice yields. There is no day on which anything visibly happens.

It is also technical, and the disputes turn on hydrological modelling that is hard to summarise and harder to verify independently. Both features are reasons for the story to be covered rather than reasons for it not to be: the Mekong Delta feeds a large share of Southeast Asia, and decisions being taken now determine what it produces in twenty years.

Sources

• Khmer Times, Agreement for the Funan Techo integrated water resources management project officially signed, 10 September 2026, via ISEAS Daily News on Southeast Asia
• 1995 Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin
• Mekong River Commission procedures for notification, prior consultation and agreement
• Published research on Mekong Delta salinity intrusion, sediment flow and upstream development