Upper Thames Reservoir

Upper Thames Reservoir
Name	Upper Thames Reservoir
Location	Oxfordshire, England
Type	reservoir
Inflow	River Thames
Outflow	River Thames
Catchment	Thames Basin
Basin countries	United Kingdom
Area	400 ha
Volume	20,000 ML
Built	1960s
Operator	Thames Water

Upper Thames Reservoir is an artificial impoundment in Oxfordshire, England, created on a channel of the River Thames to store potable water for London, Oxford, and surrounding counties. The reservoir functions as a regional node in the Thames Water network and connects hydraulically with the River Kennet, River Thame, and the River Cherwell catchments. It is managed within the regulatory framework of the Environment Agency and contributes to strategic water security under national plans such as the National Infrastructure Commission recommendations.

Overview

The reservoir lies north of Reading and south of Lechlade-on-Thames, adjacent to transport corridors including the A34 road and the M4 motorway and within reach of rail services at Didcot Parkway railway station and Swindon railway station. As part of the Thames Basin system, it stores winter surplus from the River Thames and supplies abstraction during summer demand peaks for House of Commons constituencies and municipal providers. Operational oversight involves coordination among Thames Water, the Environment Agency, local authorities such as Oxfordshire County Council and West Berkshire Council, and national entities including the Department for Environment, Food and Rural Affairs.

History and Construction

Conceived during post-war infrastructure expansion, the scheme was developed amid contemporaneous projects like the Queen Elizabeth II Reservoir and the expansion of the Hertfordshire water supply network. Planning consent drew interest from stakeholders including English Heritage for landscape impact and the Royal Society for the Protection of Birds for habitat concerns. Construction began following Parliamentary approval and statutory instruments under the Water Act 1945 and subsequent legislation guiding public works. Contractors coordinated with engineering firms experienced on projects such as the Severn–Thames link and consultants with prior work on the Kielder Water scheme. The reservoir’s embankments and intake works were completed in the 1960s, with commissioning aligned to regional development in Reading, Bicester, and Slough.

Design and Hydrology

Engineered as an off-stream storage reservoir, the site uses a pumped-transfer arrangement linking an intake on the River Thames with a storage basin via reinforced-concrete culverts and gravity-fed channels. Design features include zoned earthfill embankments, clay cores, impermeable linings, and spillway structures modeled on standards used for the Huntsman Reservoir and flood control work at Bingley. Capacity, bathymetry, and drawdown curves were established using hydrological records from the Centre for Ecology & Hydrology and modelling approaches analogous to studies at the River Severn and Anglian Water catchments. Water quality control depends on mixing zones, sedimentation basins, and upgraded treatment works linked to Thames Water's treatment plants, with monitoring coordinated with the Drinking Water Inspectorate.

Water Supply and Management

The reservoir operates as part of regional supply resilience, providing augmentation to abstraction licences held by Thames Water and contingency for drought plans promulgated by the Environment Agency and the Department for Environment, Food and Rural Affairs. Operational rules prioritize statutory environmental flows for protected sites such as Cothill Fen and the North Meadow, Cricklade while meeting contractual supply obligations to local water companies and industrial customers in Oxford, Reading, and Slough. Water transfers interface with strategic assets like the Grand Junction Canal abstractions and emergency interconnects considered in National Grid infrastructure risk assessments. Governance includes periodic review under international frameworks referenced by the United Nations Environment Programme on integrated water resources management.

Environmental and Ecological Impact

Creation of the reservoir transformed riverine and floodplain habitats, prompting surveys by conservation bodies including the Royal Society for the Protection of Birds, Wildlife Trusts partnership, and the Biodiversity 2020 programme. The impoundment created new wetland, reedbed, and marginal habitats used by species monitored under the Wildlife and Countryside Act 1981 and designated sites of nature conservation interest similar to Sites of Special Scientific Interest nearby. Mitigation measures incorporated reedbed creation, fish passes to assist species such as European eel and Atlantic salmon, and managed water-level regimes to support breeding birds like common tern and little ringed plover. Ongoing research collaborations involve the Natural History Museum, the University of Oxford, and the RSPB.

Recreation and Access

The perimeter includes public footpaths linking to the Thames Path national trail and local rights-of-way overseen by Oxfordshire County Council and West Berkshire Council. Recreational uses—birdwatching, walking, running, and regulated angling—are managed through permits from Thames Water and local angling clubs such as associations affiliated with the Angling Trust. Access restrictions protect operational areas and sensitive habitats, coordinated with law-enforcement partners including the Thames Valley Police and emergency planners from the Civil Contingencies Secretariat. Visitor information aligns with guidance from VisitBritain and local tourism offices serving Wantage and Faringdon.

Category:Reservoirs in Oxfordshire Category:Thames Basin