This is the Plan d'Eau ("water level") which refers not just to the pond but the area around it. A plan d'eau is a leisure area, complete with water, which is purpose built for communal use.
I don't know if the water in Preuilly's plan d'eau is ever used for leisure activities, but the field is where some local events are held - the Brocante Vide-Greniers, or attic clearance sale - being one. It used to be crossed by electricity pylons, but these were demolished last year - one assumes they were no longer in use and just cluttering the place up.
The photo was taken on Christmas Day, when the pond was frozen.