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The Hampstead Ponds or Highgate Ponds are three large freshwater swimming ponds — two designated single sex, and one for mixed bathing — fed by the headwater springs of the River Fleet — in Hampstead Heath, North London, England. The swimming ponds are three out of some 30 ponds on Hampstead Heath.
They were originally dug in the 17th and 18th centuries as reservoirs. A malarial marsh was drained by the Hampstead Water Company in 1777 to meet London's growing water demand.
In 2004, the City of London Corporation, which holds the Heath in trust, since the abolition of the Greater London Council in 1986, tried to close the ponds on the grounds that they were an unsustainable drain on their expenses and posed a health risk to swimmers. The swimmers challenged this and won a victory in the High Court. To defray costs, the Corporation introduced a charge for admission of £2 per session, £1 for concessions. There was some opposition to this on the grounds that swimming there had been free since at least the 1920s, and some ticket machines were vandalised.
Hampstead has three different ponds for swimming - one for men, one for women and one mixed. Only swimmers over eight years of age are allowed; those between eight and 15 years old must be in the care of an adult.
The men's pond had a diving tower but this was dismantled following an accident in the 1970s and only a low level board remains, along with showers and a small sunbathing and changing area.
Winter swimming is usually possible at all three ponds, which remain very popular with users. The Corporation of London website publishes water quality tests. The three ponds are not to be confused with Parliament Hill Lido, built in 1938, now with a stainless steel lining.
Proposals for the ponds and dams
It was announced in 2011 that the City of London proposed extensive works to the ponds and dams which it claims is necessary for safety reasons in the event of a major rare storm. The proposals included measures to improve the water quality of the ponds as well as improvements to the pipes and weirs that allow water to cascade from one pond to the other. These initial recommendations follow engineers reports in 2005 that the hydrology of the ponds was poorly understood. These same engineering reports resulted in engineering works in 2006 on the two ponds in the grounds of Kenwood House to make their overflow structures and dams safer. Since 2011 there has been strong opposition from the swimming clubs and the Protect Our Ponds campaign. Much opposition has resulted and in 2013 a united campaign was launched called Dam Nonsense to oppose the works which the campaign says is unnecessary and in conflict with the Hampstead Heath Act of 1871 which includes all the groups opposed to the proposals. The proposed work on the Hampstead Heath dams is further complicated by the regulations embodied in the 1975 Reservoir Act which only relate to three dams on the Heath and the proposed regulations in the Flood and Water Management Act 2010 which potentially relate to all 14 dams on the Heath.
If the work goes ahead it is likely to involve the closure of all three swimming ponds for a prolonged period of time to enable higher dams to be built which will raise the heights, in the case of the dam above the Men's Swimming Pond by 18 feet. The City of London Corporation has said the work should be carried out urgently to reduce danger of flooding in surrounding built-up residential areas in the event of one of the dams bursting. The initial estimate of the number of lives lost, in the event of a dam collapse in an extreme flood event, was >2000 soles (2006 estimate). This figure has been reduced to <400 soles, but still a significant number of people potential impacted. However the chance of such an event is once in 400,000 years which means such an event is unlikely to ever happen.  At a public meeting to launch the Dam Nonsense Campaign held on 25 November 2013, more than 200 people voted in favour of the campaign with only one vote against.
Note that the regulated dams under the 1975 Reservoir Act are: Model Pond and Men's Bathing Pond on the Highgate Chain. Highgate Number 1 pond would have been covered by the Act but the water level was lowered by the GLC in 1984. On the Hampstead chain, Hampstead Number 1 pond is also regulated under the 1975 Reservoir Act.
The men's and women's ponds are located on the eastern side of the park, off Millfield Lane. The mixed bathing Pond is in the centre of the Heath, and is a 10-15 minute walk from Hampstead Heath railway station and several buses serving South End Green, at the junction of Pond Street and East Heath Road.
- The London Encyclopaedia, Ben Weinreb and Christopher Hibbert, Macmillan.
-  Highgate Mens Pond Association (HMPA) is an organisation of swimmers set up in 2012. It has a chair, secretary and treasurer plus a committee of 12, all democratically elected. It currently (Dec 2013) has 550 supporters on email list, many of whom pay an annual subscription.
- Protect Our Ponds
- The London Encyclopaedia, Ben Weinreb and Christopher Hibbert, Macmillan.* City of London Corporation, Swimming on Hampstead Heath, also gives water temperatures.
- Diving at Highgate Ponds on the Lost Lidos website.