Catchment area 48.6km2, length 13.7km. Not designated artificial or heavily modified.


Waterbody Description

The river is aquifer supplied in the Jurassic Limestone area of the southern Cotswolds. Its reactive flashy nature results in high seasonal flow variations. The top spring appears at Trewsbury Farm with additional springs adding to form an obvious river in woodland within the Kemble Parish. There is a gauging station after the village of Ewan. It flows through open pasture becoming progressively more shaded in a largely uniform channel. There are modified sections through the parishes of Kemble, Pool Keynes and Somerford Keynes where the channel splits and the original channel has been straightened, reducing the length and capacity. The bulk of water flows through a mill leat channel, modified since 1980 to become straight and uniform, above the lowest slope point to supply several mills. Along with seasonal drying, the modifications have further reduced the natural flow levels and the ecological value. There are some natural meandering sections and woodland through Neigh Bridge Country Park. In Ashton Keynes, the river runs along the high street with sharp turns. There has been extensive channel modification with straightening, enlargement, and embankments to prevent flooding. Several small bridges cross the channel here and small weirs hold water at low flows. The river flows into the Leigh Parish joining Swill Brook at Waterhay bridge, becoming more permanent and flowing on towards Cricklade.


Land use and designations

Land use through Kemble and Pool Keynes parishes is largely semi-improved pasture with some woodland and bankside hedgerows. The land is owned by Bathurst Estate, livestock farmers and small holdings. Public access includes the Thames path (184 miles source to Woolwich) and Sustrans Cycle route. The Thames and Severn Way canal runs through the catchment and over the river and the dismantled railway also crosses the river by Kemble. Around Ashton Keynes gravel pits have been converted to recreational lakes many of which are surrounded by second homes. The Neigh Bridge Country park is managed by Cotswold Water Park Trust and land is managed for general amenity at the Lower Mills Estate holiday complex.

There is no significant flood risk for Kemble, Ewan and Pool Keynes. Somerford Keynes is in the floodplain, and a flood alleviation scheme, with various embankments, channel realignment and a floodwall, was constructed in the late 1990’s. Ashton Keynes is also in the floodplain; a channel diverts some water away from the village to a gravel pit and surrounding properties are at risk from surface water flooding. A weir upstream of Ashton Keynes also diverts some water to Swill Brook.



Emergent vegetation at the source to Somerford Keynes, included Fool’s water Cress, Lesser water-parsnip and Water Crowfoot.

In Ashton Keynes also Branched Bur-reed, Bulrush, Reed Canary Grass, Reed Sweet Grass, Water-starwort, Common Club-rush (Bulrush), Water Plantain, Branched Bur-reed, Tufted Hair Grass, Water forget-me-not, Watermint and Meadowsweet.


From source to Somerford Keynes water levels are too low to provide habitat for significant fish. The Thames is known to have a reasonable fish species range of largely coarse fish including chub, dace, perch, roach, minnow, bullhead, pike and occasional trout particularly downstream of Ashton Keynes.

Signs of otter and water vole were recorded throughout the Pool Keynes to Ashton Keynes stretches. The following bird species were recorded: Kingfisher, grey wagtail, dunnock and song thrush (red listed) species and typical hedgerow and pasture birds and some riparian species such as pied wagtail, heron, and mallard.


Main conclusions

Overall the Thames through Kemble Pool Keynes and Somerford Keynes parishes is of significant ecological value but more for its linear scrub & tree habitat temporal habitat rather than a typical river habitat. There is also an important linear pond habitat in Ashton Keynes. The annual drying up of the channel above Ashton Keynes means this section of river will only ever be suitable to species able to cope with the frequently dry conditions such as sticklebacks or micro-crustacea.

  1. Water with Integrated Local Delivery (WILD) Project, River Thames Management Plans

Kemble Parish (December 2015) Pool Keynes Parish, (February 2016) Somerford Keynes Parish (January 2016) Ashton Keynes Parish (March 2016), Leigh Parish (March 2016)

In Cycle 1 the waterbody failed for ecology under fish from 2009 and dissolved oxygen levels in 2014. due to naturally low flows, poor morphology, urban modifications, and presence of signal crayfish. It was however reclassified as good in 2015. In 2016 Cycle 2 it was failing again for ecology due to poor dissolved oxygen status.


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