Phosphate filter Kalmthoutse Heide
Phosphate filter Kalmthoutse Heide
Targeted solution restores delicate fen system near Groote Meer
On the border between Flanders and the Netherlands, at the edge of Kalmthoutse Heide, something remarkable is happening. A newly installed phosphate filter now prevents phosphorus pollution from the Steertse Heide from reaching the Groote Meer, one of the ecological gems of the cross-border nature reserve. It’s a subtle intervention — but one that makes a huge difference for one of Western Europe’s most vulnerable fen systems.
Why this intervention was urgently needed
The nature around the Groote Meer is exceptionally nutrient-poor by origin. But over the years, phosphorus runoff from former agricultural land has slowly made its way into this fragile system. The result?
- Acidification and degradation of the soil
- Loss of rare species like the natterjack toad and smooth snake
- Overgrowth and shift in natural vegetation
- Disruption of the area’s delicate ecological balance
Without firm action, this unique wetland would have slowly faded away.
A small-scale filter with long-term impact
Commissioned by Grenspark Kalmthoutse Heide, Witteveen+Bos designed a custom phosphate filter that tackles the root of the problem. Here's how it works:
- Phosphorus in the water chemically binds to iron-rich sand
- The process blocks nutrient-rich water from entering the fen system
- The solution blends discreetly into the landscape
Invisible to the eye — but vital to the ecosystem.
Part of a broader restoration plan
The phosphate filter is just one part of a larger ecological recovery effort:
- The historic Evertandven wetland is being restored to support amphibians, dragonflies and other native species
- A full permit application is in the works, including planning assessments, nature impact studies and environmental evaluations
- All efforts align with a wider, integrated strategy for sustainable nature restoration
Together, these measures strengthen the landscape and reconnect key habitats.
.jpg)
A healthy future for nature and people
This project isn’t a quick fix — it’s a structural, long-term solution. By cutting off phosphorus at its source:
- the Groote Meer’s wetland system can recover
- biodiversity gets room to breathe
- visitors can continue to enjoy this exceptional landscape
- future generations inherit a stronger, more resilient ecosystem
Cross-border collaboration as driving force
This project shows what’s possible when expertise and purpose align. The following organisations joined forces:
- Agency for Nature and Forests (Belgium)
- Province of North Brabant (Netherlands)
- Natuurpunt (Belgium)
- Brabantse Delta Water Authority (Netherlands)
- Grenspark Kalmthoutse Heide (Belgium–Netherlands)
- Witteveen+Bos (project lead and technical design)
Together, they prove that focused action, backed by expertise, can truly turn the tide.
%5B1%5D.jpg)
More information?
Our projects
Every year we work on almost 5,000 projects on water, infrastructure, environment and construction.
