UK ECN site. Wroxham Broad is a shallow, lowland lake formed from the flooding of mediaeval peat diggings that were abandoned in the 14th century. The broad has an area of 34.4 ha and an average depth of 1.3m. It is located in the middle reach of the River Bure, close to the upper tidal limit, at an elevation of less than 10m above o.d.. The lake lies on the west side of the river with two navigable openings onto the river. It is separated from the river channel by a narrow bank covered with trees. The broad has been subject to serious eutrophication, largely as a result of the discharge of treated sewage effluent to the river Bure. Since 1986, a programme of phosphorus removal at the major sewage treatment works affecting the river has been in operation, and this stretch of river is now designated a Sensitive Area under the Urban Waste Water Treatment Directive. The low gradients of the area, and seasonally low flows of recent years, mean that the flushing rate of the lake is slow, although exact retention times are unknown. The surrounding catchment is underlain by Quaternary deposits of Norwich Crag, with chalk at depth, and superficial glacial till and outwash deposits. The area is subject to intensive agricultural activity, although surrounding the broad itself there are small areas of wet woodland (alder carr). The broad is used extensively for recreational purposes, particularly in the summer months. [Photo copyright Philip Ashton/NWT Natural Connections]