Oxfordshire has a number of major rivers; the Leach, Windrush, Evenlode, Glyme, Cherwell, Ray, Ock, and Thame and many smaller tributaries that flow through the county and into the Thames. Wild Rivers and streams in semi-natural landscapes are typically associated with complexes of wetland habitats including floodplain wetlands, fens, wet grassland, oxbow lakes, permanent and temporary ponds and wet woodland.
Through pilots the Environment Agency found that improvements to water quality are most effectively delivered by local partnerships, and that a river catchment was a good ecological unit to use. Each catchment has a host organisation whose role is to deliver wildlife and water benefits through bringing together partners, identifying work and finding funding.
The River Evenlode rises out of the limestone that underlies the Cotswolds, flowing south-east towards the clay vales of the River Thames. The catchment contains 16 river water bodies including the Evenlode, and major tributaries the Glyme and Dorn. The landscape in this catchment is some of the finest in the county, forming part of the Cotswolds AONB, the remains of the ancient Royal Hunting forest of Wychwood and the World Heritage Site of Blenheim Palace.
The river habitat and fish populations in the Evenlode catchment are degraded through a combination of historical channel modification and pollution (sediment and phosphate) from waste water and rural areas. In many places rivers been over-deepened, widened and straightened, resulting in uniform channel morphology, a river divorced from its floodplain and extensive in-channel siltation. There are also numerous weirs, (35 on the Glyme), impounding the flow and creating barriers to fish movement. The combined impacts leave the catchment vulnerable to flooding and pollution and contribute to reduced water quality, biodiversity and fisheries interest.
To help tackle these issues, Wild Oxfordshire has worked in the Evenlode Catchment since 2014, securing funds and developing a wide successful partnership of conservation bodies, farmers, commercial companies and statutory agencies.
The Cherwell and The Ray
The Cherwell and Ray catchment is hosted by the Berks, Bucks & Oxon Wildlife Trust (BBOWT), with the support of the Environment Agency and The Rivers Trust. Giles Strother is the project officer for the Cherwell, Ray and Windrush.
The catchment of the Cherwell is divided into two sub-catchments of differing character: the River Cherwell and the River Ray (the Cherwell’s largest tributary).
From its headwaters near the village of Charwelton (Northamptonshire), the River Cherwell flows southwards, passing through Banbury and Kidlington before flowing into the Thames at New Hinksey (Oxford). Other than these key urban areas, the Cherwell catchment is very rural, with a high proportion of arable land as well as some improved pasture. The underlying geology is clay. For much of its length, the Cherwell runs parallel with the Oxford Canal, crossing it at Nellbridge and sharing the same channel between Enslow and Shipton-on-Cherwell.
The catchment of the River Ray is predominantly rural. From its headwaters near Quainton, the Ray flows slowly south-west to its confluence with the River Cherwell at Islip.
The Ray is of particular significance as, despite heavy modifications to its channel, its floodplain includes areas of nationally rare species-rich meadow (including several SSSIs). BBOWT now manages a number of these sites, including Meadow Farm, a site of historical importance with medieval ridge-and-furrow farming techniques still visible today. BBOWT’s wider vision is to connect its nature reserves and the wider River Ray landscape through its Upper River Ray Floodplain Living Landscape project.
Further downstream, the RSPB manages a large nature reserve at Otmoor, famous for its bird life. Both the Ray and the Cherwell form part of the RSPB’s wide reaching Futurescapes project for the Upper Thames River Valleys, highlighting once again the national importance of this area.
The Freshwater Habitats Trust (FHT) was appointed as the catchment host for the Ock in 2013 and is leading the development of the catchment partnership with the support of the Environment Agency.
The Ock rises in Little Coxwell and flows eastward for 38km to join the Thames at Abindgon. The Ock catchment is characterised by clay, but is bordered to the north by limestone and sandstone which form a small escarpment, and to the south by chalk which forms an upland ridge. Spread across the catchment are a range of springs, headwaters, ponds, small lakes, and the larger streams and rivers. The catchment is also well-known for its fens, and wet meadows, all of which are affected by the quality and quantity of the water in the environment.
The 2013 water quality data from the Environment Agency suggests that water quality across the different streams and brooks is generally “Moderate” or “Poor”. Factors influencing the water environment in the Ock catchment are likely to be rural and urban diffuse pollution, waste water discharges, road run-off, loss of habitat and biodiversity and invasive non-native species.
The Windrush catchment is also hosted by the Berks, Bucks & Oxon Wildlife Trust (BBOWT), with the support of the Environment Agency and The Rivers Trust. It is a sub-catchment of the much larger Cotswolds catchment, and includes, as well as the River Windrush, the River Leach and the River Thames from its confluence with the Leach at Lechlade-on-Thames to its confluence with the Evenlode at Cassington.
The Windrush catchment is full of character, with a number of projects currently working towards improving its value for people and wildlife. The catchment is divided between Gloucestershire in the west and Oxfordshire in the east, with the River Windrush flowing through the Cotswolds Area of Outstanding Natural Beauty. The River Thames flows through the southern part of the Windrush catchment, and forms the southern boundary of BBOWT’s largest nature reserve, Chimney Meadows (also a National Nature Reserve). This reserve lies at the centre of BBOWT’s Upper Thames Living Landscape project, which aims to manage, restore, and recreate floodplain habitats.
Poor water quality is a persistent problem in the Catchment and Windrush Against Sewage Pollution (WASP) are a charitable trust working to put an end to this issue. WASP collect and analyse data on water quality, the processes that lead to sewage pollution and the impact it has on the environment. As well as informing the public WASP also engages with companies and government agencies to push for responsible sewage management.
The Freshwater Habitats Trust (FHT) and the River Thame Conservation Trust (RTCT) were appointed as the joint catchment hosts for the Thame in 2013 and are leading the development of the catchment partnership with the support of the Environment Agency.
The River Thame catchment straddles two counties (Buckinghamshire and Oxfordshire) and encompasses two significant towns (Aylesbury and Thame). The proposed HS2 rail link will also run across the catchment. Land use is, however, predominantly agricultural with few protected areas, except on the catchment periphery, notably SSSIs along the Chilterns escarpment to the east and the Bernwood/Shabbington forest complex in the west. Numerous tributaries feed into the River Thame: as well as four brooks (Denton, Baldon and Gainsbridge brooks and the Milton Ditch) in the Lower Thame that form the core of the ongoing FHT/RTCT Catchment Restoration Project.
The 2013 water quality data from the Environment Agency suggests that water quality across the different streams and brooks in the catchment are either “Moderate” or “Poor”. No areas of the catchment achieve “Good” status. Factors influencing the water environment in the Thame catchment are likely to be urban and rural diffuse pollution, waste water discharges, road run-off, habitat/land.
The South Chilterns
The South Chilterns catchment is hosted by the South Chilterns Catchment Partnership with the support of the Environment Agency. The South Chilterns operational catchment includes part of the Chilterns Area of Outstanding Natural Beauty (AONB). It has three distinct geographical areas: in the West is the river Pang, a chalk stream in a rural area flowing through Pangbourne; the navigable river Thames flows through the middle of the catchment between Wallingford and Cookham; and in the east is the river Wye, an urban chalk stream rising near High Wycombe.