The Cotswold Water Park is the United Kingdom's largest marl lake system, straddling the Wiltshire–Gloucestershire border, northwest of Cricklade and south of Cirencester. There are 180 lakes, spread over . The park is a mix of nature conservation activities, including nature reserves; recreation, including sailing, fishing, a country park and beach with water sports and play areas; rural villages; and holiday accommodation. It is a significant area for wildlife and particularly for wintering and breeding birds. The local wildlife trusts (Gloucestershire and Wiltshire) are involved in partnership with the Cotswold Lakes Trust charity in working with local communities and organisations in the area. Origins The lakes were created in the second half of the 20th century by extraction of glacial Jurassic limestone gravel, which had eroded from the Cotswold Hills, and these filled naturally from rivers and streams after workings began to be exhausted in the early 1970s. Location Information may be found in detailed maps of locations and facilities, the Local Biodiversity Action Plan and other publications produced by the Cotswold Lakes Trust. It is that part of the Upper Thames catchment in North Wiltshire and south Gloucestershire which has been subjected to over 50 years of sand and gravel extraction. For ease of orientation, the Cotswold Water Park is split into three areas. The western section encompasses the villages of South Cerney, Cerney Wick, Ashton Keynes, Somerford Keynes, Poole Keynes, Siddington, Oaksey, Minety and Leigh; and includes the uppermost reaches of the River Thames, as well as its tributaries including the River Churn, Swill Brook and Cerney Wick Brook. The central section encompasses Driffield, Ampney St Peter, Poulton, Down Ampney, Meysey Hampton, Cricklade, Latton and Marston Meysey; and features further Thames tributaries such as the Ampney Brook. Gravel extraction in the Latton area in the 1990s created additional lakes. The eastern section includes Fairford, Kempsford, Lechlade, Buscot, Inglesham and Castle Eaton; and features additional Thames tributaries including the River Coln and River Leach. Lechlade in the eastern section marks the start of the navigable River Thames. The Cotswold Water Park area sits low in an historic river valley and as such is exposed to fluctuations in ground water levels. Much of the farmland in this area is made up of flood meadows which take up water from the River Thames. Many of the lakes are connected by underground culverts, allowing transfer of water between them. There is also