All three were built with extra capacity with the future southern polder in mind.
From the en.wikipedia.org
The polder lies lower than the surrounding water on the other side of the dike.
From the en.wikipedia.org
The first polder, Wieringermeer, was dammed in 1929 and fully drained in 1930.
From the en.wikipedia.org
The colour gold indicates the high costs of the project of making the polder.
From the en.wikipedia.org
Important institutes, like the SER, of the polder model were founded in this period.
From the en.wikipedia.org
The first polder mills using a waterwheel could raise water at most 1 meter.
From the en.wikipedia.org
If one station lost power, the other one would still be able to keep the polder dry.
From the en.wikipedia.org
Priority to the early pioneers who had been in the polder since the start.
From the en.wikipedia.org
Originally, this low part of the new polder was destined to become an industrial area.
From the en.wikipedia.org
More examples
Low-lying land that has been reclaimed and is protected by dikes (especially in the Netherlands)
A polder is a low-lying tract of land enclosed by embankments known as dikes, that forms an artificial hydrological entity, meaning it has no connection with outside water other than through manually-operated devices. ...
POLDER is the acronym (POLarization and Directionality of the Earth's Reflectances) used for the name of an environmental satellite radiometer developed by the French space agency CNES.
An area of ground reclaimed from a sea or lake by means of dikes
(Polders) areas of reclaimed land that were once part of the sea bed in the Netherlands. See lsselmeer Polders.
Reclaimed land created by the construction of an embankment or dyke to hold back water that would otherwise flood the new surface.
Tract of low land, reclaimed from marshland, the sea or an other body of water, by endiking it; in a polder, runoff is controlled by sluicing or pumping, and the watertable is controlled and independent of the watertable in the adjacent areas