Practical application of 25 years' research into the management of shallow lakes

The Norfolk Broads are a series of shallow, man-made lakes dug in medieval times for peat extraction, in Eastern England. Their eutrophic state has been well-documented and, since the early 1980s, their restoration has been attempted using a variety of techniques. The restoration began with the removal of point sources of phosphorus from sewage treatment works, which then revealed the role of sediment release when lake phosphorus levels failed to decline following inflow phosphorus levels. Small-scale removal of sediment layers in isolated broads demonstrated the feasibility, both technical and economic, of this technique, but experience then showed that sediment removal alone could not provide long-term restoration. Biomanipulation following sediment removal now offers the most reliable route to restoration, but the mechanisms by which a stable submerged plant community can be maintained after biomanipulation are still not clear.