Dr Richard Knowles, the Cotswolds Rivers Trust chair, discusses the importance of the newly created fish bypass and how 30 years of campaigning has been worthwhile.
Hagley Pool lies at the downstream limit of the Cotswolds Rivers Trust direct involvement with the Thames, but its new fish bypass will be of environmental benefit both locally and upstream into the headwaters of the Thames and its tributaries.
Most people when they think of the Thames in Oxford think of the broad channel on the southern edge of Christchurch Meadow where pleasure boats and rowers ply up and down. In fact, the river in and around the city is divided into multiple channels. Hagley Pool lies north of the village of Wytham on the western side of the city, about a mile downstream of the Thames confluence with the Evenlode and the site of the large Cassington Sewage Treatment Works.
It is at Hagley Pool that the Seacourt Stream exits the navigable main channel and flows south alongside the village of Wytham, before dividing again close to the suburb of Botley. The right-hand western channel, bearing the name Hinksey Stream, flows southward, eventually rejoining the main Thames close to Oxford’s southern bypass. The left-hand eastern channel also takes a new name, the Botley Stream before it merges with another distributary, the Bulstake Stream, and takes another new name, the Potts Stream, and rejoins the parent Thames. All of these, along with a number of others form the patchwork of Oxford’s rivers.
While the Thames occupies an over-widened and over-deepened channel to meet the demands of navigation, historically many of the distributaries have been less damaged by human activities and offer much greater biodiversity in bankside and in-stream flora and provide ideal spawning sites for Thames fish. The Seacourt Stream is the longest and richest of the distributaries and flow loving fish species like chub and barbel travel many miles to spawn on its gravelly riffles.
The newly created and now open, Hagley Pool fish bypass channel is probably the most important bypass in the upper Thames region. Why?
First, a fish bypass channel guarantees future flows, even in drought, in this lovely stream. In 1976 the Seacourt stream dried up completely when the level of the Thames dropped below the fixed crest at Hagley Pool, cutting off the flow of water.
Second, fish will now be able to move between the Seacourt Stream and the navigable channel upstream, removing a major barrier to migration and allowing fish to move may miles upstream or downstream.
The third reason is more complicated, but explains why creating the bypass channel has been funded by Thames Water. A few miles upstream of Hagley Pool are Thames Water’s Farmoor reservoirs. These are filled by taking water from the Thames, and so large has been this abstraction that nearly all of the Oxford distributaries have been significantly degraded since the reservoirs were built in the 1960s and 70s with some so damaged that their value as spawning sites has been hugely diminished. Their degradation has enhanced the value of the Seacourt Stream as the channel with the least damaged habitat.
Thames Water, recognising the impact of the Farmoor abstraction on Oxford’s rivers, have funded and commissioned the construction of the channel with the full support of Environment Agency fisheries and conservation staff. For the Cotswolds Rivers Trust, and our partner organisations the Upper Thames Fisheries Consultative and the North Oxford Angling Society, seeing the channel dug and opened is a triumph after a 30-year campaign. Yes, that is how long it has taken! Securing agreement for the project from all relevant parties has been a tortuous process.
Today, as the water flows down it for the first time the channel looks bare and still needs the addition of gravel to enhance its bed, but this is a time for celebration, and a showcase of collaborative efforts.
Finally, a big thank you to all who have helped bring this project to fruition. We are especially grateful to Steve Tuck of Thames Water and Stuart Manwaring and Graham Scholey of the Environment Agency for their consistent support for this project.
