Lake · Netherlands
IJsselmeer
The IJsselmeer is a huge freshwater lake in the middle of the Netherlands. It used to be part of the sea, until people built a long dyke across a bay and turned the salty water into a lake in 1932.
Picture credit: Dominicus Johannes Bergsma (CC BY-SA 4.0) · Dominicus Johannes Bergsma (CC BY-SA 4.0) · Dominicus Johannes Bergsma (CC BY-SA 4.0) · Wikimedia Commons
Where is IJsselmeer?
Countries on its shores: the Netherlands.
Largest body of water of: the Netherlands.
Middle of the lake: 52.82° N, 5.25° E
The story behind it
Long ago, this water was a bay of the sea called the Zuiderzee. Then the Dutch built the Afsluitdijk, a dyke 32 kilometres long, and in 1932 the bay was closed off from the sea. After that, the river IJssel and other rivers kept pouring in fresh water, and slowly the salt was washed out. Its water level is kept a little below sea level, and extra water flows out through sluice gates in the dyke into the Wadden Sea. More than half of the old bay was drained to make new farmland, called polders. In the 1970s another dyke split off the southern part, which is now a separate lake, the Markermeer. Towns such as Enkhuizen, Stavoren, Hindeloopen, Lemmer and Urk lie on the shore. The IJsselmeer is the biggest lake in the Netherlands, but it was made by people with a dyke, not by nature.
Find it on the globe
IJsselmeer is there as a small blue dot with its name, right on the water. From far away the planet is only a blue ball; detail arrives as you zoom in, and this one appears once you are close enough. Open it on the globe.
It sits at its real coordinates, not near them — the same numbers listed in the facts above. Switch off the layer for this kind of place and it disappears again; the buttons for that are down the right-hand edge.
Questions children ask
How big is the IJsselmeer?
The IJsselmeer covers about 1 100 km²; some sources give up to 1 137 km². It is wide but shallow: on average only about 4.5 metres deep, and 9 metres at the deepest.
Was the IJsselmeer always a lake?
No. It was once a salty bay of the sea called the Zuiderzee. In 1932 the Afsluitdijk closed it off, and river water slowly turned it into a freshwater lake.
Is the IJsselmeer protected?
Yes. Since 2000 the IJsselmeer has been a protected wetland under an international agreement called the Ramsar Convention. Nature experts hope that fish such as smelt, flounder and eel will become more common here again.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
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