Posted on March 6, 2023
The River Glyme as it flows into the Blenheim Palace estate has for centuries been artificially straight and narrow. Now it is becoming “sinuous and wiggly” as part of wider efforts to return the Glyme to full health.
Scientists working in the Oxfordshire World Heritage Site are undertaking “stage zero” works which will restore the river to its state pre-human intervention. Similar work has been done to the River Dorn, which also passes through the estate and feeds the Glyme.
“The project is reactivating the ancient course of the River Glyme through Hordley Meadows,” David Gasca Tucker, of Atkins, the engineering group leading the work, told i, “It didn’t use to look like it does now, it was much more sinuous and wiggly.”
As well as placing rivers back in their natural beds, stage zero work includes blocking drains, placing fallen trees in the river and punching holes in its banks to restore flood planes. The aim is also to imitate the work of beavers by creating natural barriers.
The Blenheim project will restore biodiversity and reduce local flooding but is also expected to help manage the pollution from farming and sewage discharges.
Blenheim is downstream of the Woodstock sewage treatment works, belonging to Thames Water, which frequently discharges sewage during rainy periods. Its last release of raw sewage began on December 28 and lasted until January 23, a total of 618 hours.
“It is somewhat distressing,” Dominic Hare, Blenheim’s chief executive told i, “If you test our water quality, as we now do very regularly, it is very high and phosphate is something that you do associate with effluent.”
Returning the Glyme to its ancient course will mean that it passes through sedge and reed beds, which will help filter the water. Its floodplain has also been restored, allowing water to pool rather than washing agricultural pollution into the river. A slower flow will, meanwhile, will allow sediment and nutrients to settle.
“It’s been amazing how quickly that landscape has started to recover,” said Mr Hare, “and of course, it has the bonus of working in harmony with the needs of local people because suddenly floodplains function as they were intended to function
As well as stage zero projects, £6m has been spent dredging the large Queen’s Pool that sits alongside the palace to restore it to its traditional depth.
Enough silt to fill Wembley Stadium will eventually be taken from the lake. This will further slow water flow and allow silt and pollution to drop out of the water column into the lake, leaving cleaner water flowing downstream.
“I’m looking out the windows at the Queen’s Pool and it has changed colour, it’s bluer and clearer,” Mr Hare told i.
Mr Hare explained that they are also planting trees on riparian land across the farmland owned by the estate as part of a wider tree-planting project. This creates a buffer zone where fertilisers and pesticides are not being spread and reduced the flow of runoff into the rivers.
The Glyme feeds into the Evenlode, a major tributary of the River Thames. The Evenlode has been the focus of a years-long project, known as the Evenlode Catchment Partnership, to improve the watershed but still suffers from agricultural and sewage pollution.
The works on the Glyme have been done as part of the partnership, which has funding from Thames Water and the Environment Agency.
Thames Water is committed to a 50 per cent reduction in the total annual duration of discharges across London and the Thames Valley by 2030 and an 80 per cent reduction in discharges within sensitive catchments.
How to fix a river
Our rivers are struggling with everything from sewage and agricultural run-off to heavy metals and pharmaceuticals, and much of the answer lies in better infrastructure. However, given a chance, nature can do a lot of the heavy lifting itself.
As at Blenheim, restoring freedom to rivers by allowing them to flow where they want and flood when necessary can stop problems from being sent downstream. Whether through beaver reintroduction or human intervention, rivers that are slower, with more plant life and surrounding wetlands can filter out many natural pollutants. They also tend to reduce flooding downstream.
Sedge and reeds are highly effective at filtering out sediment and pollutants, while wetlands also create habitat for wildlife.
Creating buffer zones between fields and rivers, with fencing to keep out livestock and wide margins that mean fertilisers and pesticides are not being applied close to rivers is considered best practice. If those buffer zones are planted with trees, this increases the stability of the soil and stops pollutants and sediment from rushing into the river.
Understanding the problem is also half the battle. The Evenlode Catchment Partnership has seen local residents, campaigners and landowners given relatively cheap and versatile sensors so that they can monitor the true state of their river. This allows them to highlight problems themselves rather than wait for a water company or the Environment Agency to spot them.