The Birch Road Pond had been inaccessible to walkers because of the state of the boardwalk crossing the pond.
In August a band of volunteers connected with Shropshire Wildlife Trust gave up hours of their own time to repair the walkway by the Birch Road recreation area.
But at the weekend the trust found that rails and post had been broken.
Edward Bevan, one of the those involved in the work said: "Sadly our newly repaired boardwalk at Birch Road Pond has already been subject to vandalism."
He said that the area had been under water and inaccessible for two years because an outlet had been blocked downstream.
"The blockage was removed, and the water level restored, so we were able to repair the boardwalks, cut back the overgrown trees, and re-open the reserve to visitors.
“There are many dragonflies, including the common darter and the southern hawker. Moorhens are usually seen hiding in the vegetation, and herons and ducks are frequent visitors.”