LELYSTAD, Netherlands — Wildlife is flourishing inside an artificial archipelago on a lake just northeast of Amsterdam. Red clover, reeds and more than 100 other plant species grow, while thousands of birds fly overhead, feeding on the insects and small fish below.

More than 40 years after the authorities in the Netherlands, a country that takes pride in its innovative methods of water management, caused an environmental calamity on what is now a lake known as the Markermeer, an ambitious if costly solution is bringing it back to life.

The Dutch government built a dam in 1976 sectioning off the lake, one of Europe’s largest and shallowest bodies of freshwater, but the dike trapped sediment, muddied its waters and damaged its wildlife.