In the 1950s, the post-war economic boom increased Paris' water needs. The upstream basin of the Seine river, densely populated, presented a risk of flooding over a limited area. It was, therefore, decided to create three large lakes that would regulate its course. Orient Lake extends inside the Forêt d'Orient Regional Nature Park, a 173,000 acres (70,000 ha) natural sanctuary. Over the years, the lake has become of refuge for thousands of birds and diverse fauna. It has been classified as a special area of conservation by the Natura 2000 network since September 1986.