Lake Dredge

In April 2022, we will begin the first dredge of Queen Pool in over 100 years, removing enough silt over nine months to fill Wembley Stadium to the top!

The final stage in a larger project which has seen successful repairs to both the Vanburgh Bridge and the Cascades, the dredge will remove over 300,000 cubic metres of silt from Queen Pool. This will return the lake to its ideal depth of two metres from its current shallows of 30cm.

One of the first things that will be happening is the moving of the water voles, you may see traps around Queen Pool and the Great Lake. This is part of our Remo-voles program.



We need to move the water voles to protect them during the Lake Dredge starting in March 2022, this activity will take place where the voles reside, and the vehicles and heavy equipment will disturb the voles. They are moving to a safe place for the duration of the work allowing them to continue to live happily in the local area. We are working with Ecologists to make sure that the moving of the voles follows the good practice set out in the water vole Conservation Handbook, and fully licensed by Natural England.

History of the Lake

Queen Pool is the upper lake at Blenheim Palace and was created by Sir Capability Brown around 1763 as part of his extensive re-landscaping of the Park and Gardens.  The man-made lake gets its name from a fish pool that was known to be a favourite place of Queen Philippa, wife of then-king Edward III. When it was submerged into the new lake, the name stuck.

The lake has been dredged twice before to our knowledge: partially in 1840 and then fully in 1895-96 when the 9th Duke of Marlborough received the dowry from his marriage to Consuelo Vanderbilt.

Why do we need to dredge?

An important part of the Blenheim World Heritage Site, Queen Pool has become heavily silted which puts its well-developed ecosystem at risk. The biggest threat comes from the lake’s significant build-up of silt: the water is currently only 30cm deep when it should be around two metres to support the existent ecosystem and the creatures who depend on it.

The lake’s ecosystem is high in nitrogen and phosphates creating the perfect environment for algae, an important food source for the lake’s many fish, amphibians, and insects. The area is a designated Site of Significant Scientific Importance and attracts many overwintering wading birds which rely on the lake for food.

The Dredge

We’d originally planned to perform a dry dredge, but after the work on the Cascades, we’re able to complete a wet dredge which is far less disruptive.

We have an area management plan to reduce impact on the lake residents. While the fish were moved to the Great Lake when the water level was lowered in October 2018, from autumn 2021 we will be relocating water voles and safeguarding the area for all wildlife.

The dredge itself will begin in April 2022, following the installation of equipment from February 2022, and some vegetation removal to ease hauling. With the machines working 12 hours a day, 5 days a week the dredge is scheduled to complete in December.

The Dredge in numbers

3 Diggers – on a floating platform

6 Hoppers – bringing the silt to land

9 months – how long the dredge will take

300,000 Cubic Metres – of silt will be removed. That’s enough to fill Wembley Stadium to the top.

100 Acres of farmland – where the silt will be transferred and spread for drying

3 months – how long it will take to remove all the equipment once the dredge is complete.

Our team setting out our remo-vole traps around Queen Pool