Can a delta drown? Philip Minderhoud shared the evidence at Waterproof 2026

At Waterproof 2026, earth scientist Philip Minderhoud opened his talk with an image of a church steeple rising from the sea. What followed was a 15-minute keynote address that reframed the urgency of climate adaptation and set fifty roundtables in motion.

What a drowning delta looks like

The audience at the Fokker Terminal in The Hague had barely settled when Philip Minderhoud shared a photograph on the screen. It was a church steeple. Surrounding it, was open water as far as the drone could capture. This was not a flood, but the permanent new reality of a village in the Philippines. “This is the people attending the last mass,” he said, “before they abandoned their entire village.”

Two crises

Minderhoud is an associate professor at Wageningen University & Research and an advisor at Deltares. He specialises in Coastal-Deltaic Land Subsidence and Relative Sea-Level Rise, in other words: the way deltas sink and what that means when combined with rising sea-levels. His participation at Waterproof 2026 was a call to look at both crises at the same time. The one visible and the one happening invisible happening under your feet.

That invisible crisis is land subsidence driven largely by one thing: the extraction of groundwater. When water is pumped from deep aquifers, the clay layers above slowly compress and reorient: an irreversible process. Groundwater, Minderhoud explained, does not just carry water. It carries the elevation of the land itself. Over extracting it and you pay with altitude.

Subsidence up to 20 cm/year

In the Mekong Delta, subsidence rates have more than doubled in fifteen years. In the Pampanga delta north of Manila – where Minderhoud conducted a field survey in September 2024 – the ground is sinking up to 20 centimetres per year. He showed what that looks like on the ground: schools with flooded classrooms that open and close with the tides; roads raised a metre and a half; special tricycles built taller to navigate high-water streets; a relocation site for a thousand families, itself partially submerged within years of construction and rice fields that turned to open water between 2020 and 2024.

77-132 million more people at risk

The scale of the exposure is larger than most risk assessments suggest. More than 90% of coastal hazard assessments use satellite elevation data referenced to a global geo-id model that, in tropical regions, significantly underestimates actual sea level. In parts of Southeast Asia, the difference is up to a metre. A paper he co-authored in Nature (Seeger & Minderhoud, March 2026) calculated that this systematic error means between 77 and 132 million more people are exposed to the impacts of one metre of relative sea-level rise than current projections show. “If sea level in reality is higher for your particular island or coastal city than was previously assumed,” he said, “the impacts will happen sooner than projected.”

Our responsibilty: the impact of a failed pilot

His conclusion was pointed: the sector spends its energy adapting to what is visible at the surface. However, the more effective intervention is to address the drivers underneath. Reduce groundwater extraction. Protect aquifers. Understand the system before you design for it. He closed on a slide that underlines the responsibility water professionals have: “A failed pilot for us may mean losing their homes for them.”

What water professionals would do about it

After the keynote, fifty roundtables were asked one question: what bold action should the global water sector take to accelerate climate adaptation and be ready to pitch at the UN Water Conference in December? The responses, collected live via Mentimeter, mapped the priorities of a sector in the middle of rethinking its own defaults.

Alternative water solutions
The most recurring suggestion was structural action on groundwater. Tables called for a moratorium on commercial extraction in vulnerable coastal zones, groundwater pricing modelled on carbon trading and serious investment in surface water alternatives, such as fixing leaking pipes (globally, around 50% of extracted groundwater leaks away before it reaches users), harvesting rainwater and scaling desalination and wastewater reuse.

Always consider systematic change
Nature-based approaches attracted both strong support and sharp critique. The emerging consensus: stop funding isolated interventions, start designing for systems. “From nature-based solution towards nature-based system approach” was one of the most submitted responses. “Don’t do a pilot – they are about the livelihoods of real people. Always consider systemic change,” submitted another table.

Include community and intergenerational knowledge
Community knowledge and local ownership featured prominently. Participants called for youth at the steering wheel of climate decisions, intergenerational knowledge in adaptation planning and local communities holding formal ownership over their own rivers and groundwater. One table asked a question that lingered: “What can we learn from our grandfathers and grandmothers?”

Scale up investment capacity
Regarding finance, one number stood out. Total global green bond issuance: $3 trillion. Total blue bond issuance for water: $15 billion. “If we’re really serious about water, we need to scale up investment capacity 100 times by 2030.” True-cost pricing, watershed investment funds and debt forgiveness for low-income countries were all proposed as mechanisms to move that number.

Look beyond the water sector
Across themes, one message recurred: the water sector cannot solve this alone. Proposals included requiring 50% non-water-sector representation at the UN Water Conference committee, bringing colleagues from finance, agriculture and tech into the dialogue and going to other sector’s conferences rather than only hosting your own.

Whats next?

The outputs from the session will be carried forward by Partners for Water as direct input to the UN Water Conference agenda in Dubai on 8-10 December. Philip Minderhoud’s question – can a delta drownclearly answered at The Hague. The harder question is what the world does about it before the window closes.