Kerelsplein circular water

smart rainwater basin that collects, reuses and infiltrates water

The climate picture in Flanders and Europe is clearly changing: periods of prolonged drought alternate with short and heavier precipitation periods. This puts our water system under pressure. When cities and towns have to deal with flooding, the water is diverted to rivers and the sea as quickly as possible via existing drainage channels, without contributing to the local water balance.

The Aggeres nv project aims to respond to this by developing an innovative retention and infiltration basin (Retin basin). This is a smart system that combines three functions: capturing rainwater, reusing rainwater, and allowing excess water to infiltrate the soil again.

In collaboration with Aquafin and the city of Roeselare, we applied the Retin basin to the Kerelsplein in Roeselare, an urban sports and playground site with various facilities on the edge of the city.

With the innovative basin, we address three issues. Firstly, the site (with a paved surface area of approx. 11,000 m²) will be disconnected from the Collie pond stream, which will significantly reduce water problems there. Secondly, we are switching a large part of the site's water requirements (sanitary blocks, football field) to rainwater. Thirdly, we are combining the retention basin with an infiltration basin, whereby a clever control system between the two will allow some of the rainwater to infiltrate into the soil.


Partners Aquafin, Stad Roeselare





  1. With the combination of a retention and infiltration basin, we not only buffer water for reuse, but also allow excess water to infiltrate back into the ground, instead of diverting it via sewer channels or streams.
  2. Thanks to the smart control system, we can anticipate flooding by pre-emptively emptying the buffer and thus creating capacity to retain excess water.
  3. In the future, the control of the basin can be 'smartly' linked to weather forecasts to make it work autonomously.
  4. This project is both easily scalable and very widely applicable. The construction techniques used allow the basins to be built in a very short time, and they can also be used in inner cities (under squares, for example).


  1. The flooding in the summer of 2021 made it clear that the infiltration capacity was still insufficient. Our approach had to be broader. So we laid a total of 2 km of underground infiltration pipes over an area of 8 km².
  2. The project has a real exemplary function and raises awareness among institutions about the beneficial reuse of stored water. The knowledge gained has already led to a new project in which we link a buffer for watering sports fields to a sewage treatment plant.
  3. We can let different agencies and partners use a common retention basin. The city of Roeselare, for instance, started thinking about which surrounding infrastructure we could connect to the same basin, both in terms of water intake from the basin and in terms of supply.
  4. We are a small organisation, so this project has weighed heavily on our available hours and other activities. We are therefore looking for additional project managers to focus exclusively on this project.
21 days construction time
500 m stored volume
2.000 m infiltration pipes
3.000 m connected pavements


The Kerelsplein will function as a kind of living lab, where the concept of collecting rainwater, reusing it and allowing it to infiltrate is central.

We want to continue to make the project known and seek opportunities to apply it elsewhere. For example, we are already working on a follow-up project to reuse rainwater and effluent water for irrigation on a golf course via a cleverly managed Retin basin.