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Published Date: 16/07/2026

Category: News

Why does the Round Pond at Gunnersbury Park look different this year?

The Round Pond at Gunnersbury Park has a lot more algae than usual. With the recent heatwave that we've had, the water level in the pond has gone down, increasing the concentration of nutrients in the water, creating the perfect environment for algae.

The good news is that while this may look unsightly to us, the algae does not affect any of the wildlife living on and around the Pond. It actually creates an additional food source for the waterfowl who live on it. Because the current conditions for algal growth are so good, even if we were to remove the algae by hand or through chemical treatment, it would return to the same levels within 2-3 weeks.

In the past, when the water levels have gotten this low we have refilled up the Round Pond artificially with more water, this plus water treatment has slowed the algae growth. Unfortunately, the only way we have to fill up the Round Pond is through a filtered mains water supply: the same water that would come out of your taps at home.

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Bird Eating Algae

    

How much?

To top up the pond by 50cm is about 3 million liters of water. That’s the equivalent of 15,000 bathtubs worth, or, put another way, the same amount of water that 15 average households would use per year.

Even ignoring the cost, which is substantial, we believe that using this much water during a heatwave is not environmentally responsible.

We know this decision has an impact on the operation of Pedalos in the Park, and for that we are very sorry, we have been speaking with them and working to find a solution, if not for this summer, then for next. We love seeing visitors enjoying the pedalos, as they have done on the Round Pond for over 100 years, but for now, we will not be able to refill the pond, and therefore tackle the ultimate cause of the algae growth.

We will continue to monitor the condition of the Round Pond, and if we believe we need to step in due to environmental concerns, we will discuss options with Thames Water. In the meantime, we are hopeful that the forecasted rain will arrive soon, and help to fill up the Pond naturally.

  

Looking ahead: a more resilient park

This summer has made something clear that our own climate planning already told us. Hot, dry summers are becoming the norm, not the exception and a historic park built around ornamental lakes and formal planting needs a long-term answer to that, not a yearly scramble for mains water. We believe the answer is to install a borehole on our site. A borehole draws water from deep underground, from the natural water table beneath the park, rather than from the treated mains supply that comes into people's homes.

Once installed, it would let us keep the Round Pond and Horse Shoe Pond topped up and irrigate the ornamental planting around the mansions, all without using a single litre of drinking water. It's better for the park's wildlife, because it keeps water levels stable through the driest months without drawing on a stretched public supply and it's better for our long-term running costs, cutting out a bill that currently costs us tens of thousands of pounds a year and will only grow as summers get hotter.

Boating Family Temple View

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We're looking for local partners who share this ambition

Gunnersbury Park and Gunnersbury Museum are managed by the Gunnersbury Museum and Park Development Trust, registered charity number 1168709 . We receive only a fifth of our funding from the local councils. We rely upon support for the ongoing maintenance, repair and improvement of Gunnersbury Park and Museum, so we can ensure it remains a place to relax, play, learn, and celebrate for the next generation. A borehole is a significant investment and one we're now working to fund through grants and partnerships. If you're a local business interested in supporting Gunnersbury's sustainability plans, whether that's the borehole, wider water management across the park, or our broader climate resilience work, we'd like to hear from you.

Get in touch at info@visitgunnersbury.org to talk about how your organisation could help us build a more sustainable future for Gunnersbury Park.