Water levels in Wanstead Park - City of London
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Water levels in Wanstead Park

There are four lakes at Wanstead Park, owned by the City of London Corporation. These lakes, along with one owned by our neighbour Wanstead Golf Club, comprise a cascade that forms the signature feature of what was once one of England’s most significant Georgian gardens.

The lake system in Wanstead Park

The lake system was mostly constructed in the 1730s and 40s from existing water features such as smaller ponds but features such as the Ornamental Water was a smaller river fed directly by the River Roding.

The way the lake system works has changed over time with water being sourced from a system of weirs and later from the park's owners’ right to temporarily dam the River Roding to top up the water or flush the lake out. The Basin and the southern chain of lakes, on the other hand, occupied a partly natural valley and were fed by groundwater supplemented by water channelled from the Leyton Flats area.

Impacts on the water level

Years of changes in the landscape has meant that the cascade system has been no stranger to water shortages. In particular, over the past 200 years, the cascade has seen the abandonment of no less than four lakes which were once part of the system. It has also seen the loss of the Holt Channel, which supplied water from the area around Leyton Flats, and the truncation of the Epping Ridge groundwater by the North Circular and the Central Line. Moreover, the cascade has had to contend with damage from Edwardian sewer digging; enemy action during World War II and the loss of river abstraction rights following national water shortages in the late 20th Century.

Most recently, the Ornamental Water, which is at the end of the cascade, has especially suffered reduced water levels due to an issue arising further upstream in the cascade system.

Floating pennywort at Perch Pond

Usually, water passes from Heronry Pond through Perch Pond and then into the Ornamental Water; however, Perch Pond has been contaminated with floating pennywort - an invasive non-native plant species. This North American exotic, which is able to propagate itself from both seeds and even the tiniest plant fragment, has the potential to inundate the entire lake cascade out-competing all native plants and irreparably damaging the cascade’s ecosystem.

For this reason we can no longer let water go from the Perch Pond into the Ornamental Water. To add to the problem, the Ornamental Water lies on very porous river bed sediments and does not hold water well.

Addressing the issue 

In 2016, around 40 tonnes of weed was removed from Perch Pond and a monthly herbicide treatment of remaining colonies was carried out. Though much reduced in extent, there are still colonies of floating pennywort across the pond and treatment will continue for the next three to five years.

In the meantime we are looking at a variety of solutions to augment the water supply to Ornamental Water, including the possibility of installing a pipe to take water from the borehole directly to the Ornamental Waters or the winter pumping of water directly from the River Roding. As this would require a new pumping station, an investment of this magnitude would need to be carefully considered within an overall water conservation plan.

Placing a filter on the current spillway outfall from Perch to Ornamental is not permissible due to Reservoir Act 1975 dam safety precautions.

At present the best option may be to design of an off-dam siphon and filtering system which could be installed later this year as well as continued treatment of the Pennywort.

Leaks at the Heronry Pond

The Heronry Pond is a concrete-lined lake which leaks and has to be filled through pumping water from a borehole that takes water from an underground aquifer. However, following a £35,000 investment, the borehole pump which stopped pumping in November 2016 has now been replaced and is pumping 288,000 litres of water each day to restore water levels in this part of the cascade. Fish from the Heronry Pond were moved to the Perch Pond. Once levels return to normal, we can restock the Heronry with fish.

The current lake cascade system is only viable if we pump 294 million litres of good quality drinking water from our 88m aquifer borehole. Our understanding is that this supply may become increasingly restricted over time, and in planning a long term sustainable future we need to put in place measures to reduce the cascade’s demand for water from the aquifer.

Long term solutions 

The City of London recognises the importance of Wanstead Park as the most extensive designed waterscape in London and is currently examining the long-term future of this ailing Georgian lake system. The long-term solution to developing a sustainable cascade system is likely to rely on a series of measures including improved catchment harvesting such as that we have recently achieved at Jubilee Pond on Wanstead Flats; improved water conservation through lake relining and the use of novel water sources such as winter Spate River pumping. Such a ‘hybrid’ solution will demand significant investment by the City of London Corporation and potential partners such as the Heritage Lottery Fund; London Borough of Redbridge and Thames Water.

We will continue to keep you updated as we progress with the options being explored. Thank you for your patience whilst we work hard to find a workable solution to this important part of Epping Forest.

23 March 2017
Last Modified:
29 September 2017