They will be closed only for short periods of time and only during the winter when the water temperature and light are too low for algal blooms.

ECONOMIST: Flood barriers

When fog forms below 0C, its super-cooled water droplets remain liquid, even though the temperature is below freezing.

BBC: The quest to see China��s extraordinary frozen fog

The fish face trouble when there is not enough water in a stream, Spence said, or if there are changes in the temperature or habitat of the stream.

BBC: Search the