In the Perk Polder in Zeeland (NL), a new tidal area and nature reserve is being built outside the dikes on behalf of Rijkswaterstaat: 75 hectares of salt marshes and mud flats are being added to the Western Scheldt. An opening was made in the sea dike on 25 June 2015, allowing water from the Western Scheldt to flow in and out of the polder twice a day at high and low tide. Local farmers were concerned that the freshwater lens in Kloosterzande, which they use a source of groundwater for irrigation, would be affected. A unique seepage system designed to protect the freshwater lens has been installed on the edge of the polder and the new tidal area.
Since 2010, Deltares has been studying the impact of the new tidal area on the groundwater in the adjoining land. We conducted an extensive baseline measurement of the hydraulic head, the water table and the transition zone between the fresh and salt groundwater. The results in June of 2015 showed that the tidal area would have only a limited negative impact. After a further six months of monitoring and fine-tuning, it was concluded in December that the facility was working so well that the size of the freshwater lens will actually increase. The barrier would also seem to be a promising approach for small oceanic islands worldwide that will help to mitigate the negative consequences of sea-level rise such as salinisation. That is good for the cultivation of crops and food, and for drinking water.
You can think of the Perk polder - with the seepage barrier that protects the freshwater lens and allows it to get larger - as a field laboratory where we can both measure the effects of sea-level rise and compensate for those effects with the innovative seepage barrier.
We can learn a lot from the seepage barrier we built with help from Deltares. It gives us the opportunity to market the know-how we have in the Netherlands about water management to the rest of the world
In this project Deltares worked together with the following partners: