This is an old photograph - the Surrey Space Centre now stands below the rooftop dish, where you see the prefabs, and a new three-storey extension to that housing the Centre for Communication Systems Research, to the right, has just been completed. The dark spot in the centre at the lake's edge is the channel where water flows down from the higher duck pond.
This is the large view. If you only see white space where you were expecting the lake to be, please try the small view.
Thanks to David Griffiths for creating the lake applet.