The Wieringermeer Polder

The polder, with an area of 21,000 hectares, was constructed between 1927 and 1930. During the construction of the dikes surrounding the polder, which housed the pumping stations Lely and Leemans, the Zuiderzee was still in open connection with the Wadden Sea. Therefore, when the land was reclaimed, there had been saltwater on top.

In earlier land reclamation projects, it was customary for the land to be auctioned after the reclamation and for the farmers themselves to take care of making the reclaimed land suitable for cultivation. Particularly in the case of the Haarlemmermeer Polder, which was drained from 1848 to 1852, this had led to many problems, as summarized in the short poem about the early days of the polder:

The first farmer dies,

the second is in need

and the third has bread

In the Wieringermeer Polder, the additional challenge was that the soil was saline. Consequently, the Central Government itself took responsibility for the reclamation, and development of the polder. The dike construction, the construction of the main water management system and the pumping dry were carried out by the Zuiderzee Project Authority (ZZW), later the Directorate of the Zuiderzee Project of Rijkswaterstaat. The reclamation and development were realized by the Regional Directorate of the Wieringermeer, the later IJsselmeer Polders Development Authority (RIJP). In 1989, the RIJP and ZZW were dissolved, and their activities were transferred to the Directorate of IJsselmeer Area of Rijkswaterstaat.

To gain insight into the best possibilities for reclamation and the suitability of various crops, a small experimental polder of 40 hectares was constructed outside the dike near Andijk from 1926 to 1927 prior to the draining of the Wieringermeer. The experience gained here was subsequently applied to the reclamation of the Wieringermeer Polder. In essence, this involved sowing reeds prior to reclamation, thereby achieving an initial lowering of the groundwater table - especially during the summer period - initiating the so-called ripening of the topsoil and obtaining a certain stability of the topsoil. Ripening is understood to mean the extraction of water and the initiation of the resulting soil transformation processes.

When the stability was deemed sufficient, work began on burning off the reeds, digging trenches, and sowing rapeseed as the first reclamation crop. In the Wieringermeer, the trenches were still dug by hand, which must have been hard work. When, after a few years, the groundwater table had dropped sufficiently due to the trenches, subsurface drainage pipes could be installed in any deepened trenches, and the trenches could be gradually filled in again. After rapeseed came crops such as barley and wheat, especially crops that could be harvested above surface. Finally, all the trenches were filled in, drainage was provided entirely by the subsurface drainage pipes, and the land was suitable for leasing to the new farmers.

The trenches and subsurface drains discharged their excess water into the open  collector drains, from where it was transported via the submain drains and main drains to the pumping stations. Consequently, the system of watercourses was expanded in conjunction with the reclamation works. Prior to the reclamation, the ring dike had been constructed where necessary, the pumping stations had been built, and the main drains and some of the submain drains had been dredged underwater. After falling dry of the land, the main network was supplemented in conjunction with the reclamation by the remaining main, submain and collector drains, as well as the necessary bridges and dams containing culverts.

The initially largest pumping station, Lely, is an electric pumping station with an initial capacity of 1,200 m³/min (cubic metres per minute). Following modernization in 2022, the capacity is now 1,500 m³/min. Leemans, with an initial capacity of 500 m³/min, was a diesel pumping station, as they did not want to be dependent on a single energy source. The discharged water from both pumping stations was discharged into the IJsselmeer.

In 1997, the Leemans pumping station was converted into an electric pumping station with a capacity of 1,500 m³/min, whereby the relatively brackish water was pumped directly into the Wadden Sea via a long pipeline. Since then, an emergency generator has also been installed that can immediately take over the drive in the event of a power failure. The total pumping capacity initially amounted to 12.4 mm/d (millimetres per day) calculated over the surface area of the polder, but was increased to 20 mm/d following the modifications in the pumping stations. After reclamation, the percentage of open water was only 2%. This relatively low percentage was made possible by the development of cracks in the clay soil that occurred during the reclamation. Due to the differences in soil levels, four water level compartments were chosen for the polder, currently with levels of 4.60; 5.40; 6.10; and 6.60 metres below NAP (Amsterdam Ordnance Datum), respectively.

At the end of the Second World War, on April 17, 1945, the retreating German occupiers blew up the dike of the Wieringermeer Polder, causing the polder to be flooded and destroying, among other things, 80% of the buildings. A monument near the site of the dike breach serves as a reminder.

The Wieringermeer Polder was developed as an agricultural polder. However, four villages were developed from the very beginning: Wieringerwerf, Middenmeer, Slootdorp, and the much smaller Kreileroord. Since then, significant urban expansions have been realized, and a large data centre is currently even being built near Middenmeer.