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| Cow Green Reservoir | |
|---|---|
| Name | Cow Green Reservoir |
| Location | Pennines, County Durham, England |
| Type | Reservoir |
| Inflow | River Tees |
| Outflow | River Tees |
| Basin countries | United Kingdom |
| Area | 2.3 km2 |
| Max-depth | 32 m |
| Volume | 8 million m3 |
| Built | 1967–1971 |
| Operator | Northumbrian Water |
Cow Green Reservoir Cow Green Reservoir is a upland impoundment in the northern Pennines of County Durham, England, created to regulate the River Tees and supply water to Teesside industrial and municipal users. The reservoir sits within a landscape of moraine-dominated moorland and is adjacent to internationally important peatland and calcareous grassland habitats. Controversy during its development prompted landmark disputes involving conservation groups, statutory bodies, and national politicians, linking the project to debates over British Leyland-era industrial policy and postwar regional planning.
Proposals to impound the upper reaches of the River Tees date from early 20th-century water planning studies by regional water authorities and engineering firms in Newcastle upon Tyne and Durham. The scheme gained momentum in the 1950s and 1960s as rapid expansion of heavy industry in Teesside—including ironworks in Middlesbrough and chemical plants in Billingham—increased demand for reliable raw water supplies. Formal authorization was secured through parliamentary powers and planning approvals overseen by the then-national water bodies and ministers in London. Opposition coalesced when environmental scientists, botanists from institutions such as Royal Botanic Gardens, Kew and conservation organisations including the Royal Society for the Protection of Birds and The Wildlife Trusts highlighted the site’s importance for rare upland flora. High-profile public campaigns and representations to members of Parliament of the United Kingdom brought attention from media outlets based in Manchester and Leeds, framing the reservoir as a test case between regional development and nature protection. Construction proceeded following negotiations that led to mitigation measures and the designation of adjacent areas as protected habitat, reflecting evolving national conservation policy in the late 1960s.
The reservoir occupies a glacially scoured valley near the watershed between the upper River Tees and tributaries flowing toward Cumbria and Northumberland. The catchment drains peat-covered uplands dominated by quartzite outcrops and thin acid soils typical of the North Pennines AONB and the Pennine Way corridor. Hydrologically, the impoundment regulates seasonal discharge, attenuating summer low flows that affect abstraction licenses downstream at treatment works supplying Stockton-on-Tees and Hartlepool. In winter and storm events the reservoir provides flood moderation for settlements along the middle River Tees corridor and industrial complexes in the Tees Valley. Water quality is influenced by upland peat leachates, acid deposition phenomena documented by researchers from Durham University and Newcastle University, and by the reservoir’s storage regime controlled by operators based in Newcastle upon Tyne.
Construction between 1967 and 1971 combined earthfill dam engineering with complex upland logistics coordinated by national contractors and consulting engineers headquartered in London and Edinburgh. The dam was formed from compacted glacial till and engineered clay cores, with a reinforced spillway designed to pass extreme return-period floods estimated using hydrological studies from Institute of Hydrology-affiliated teams and government research units. Access roads and borrow pits were constructed across peat and blanket bog, requiring specialist geotechnical work supported by academic advisors from Imperial College London and field teams from regional civil engineering firms. Materials transport involved coordination with railheads in Darlington and temporary construction camps patterned on other major British infrastructure projects such as the Thirlmere Reservoir works. Post-construction monitoring programs installed piezometers, seepage surveys, and instrumentation tied to national dam safety guidelines administered from London.
The reservoir lies beside moorland supporting populations of rare vascular plants and bryophytes studied by botanists associated with Natural England and the Botanical Society of Britain and Ireland. Notable species in the surrounding peatland and calcareous flushes include specialist taxa that had limited ranges within the British Isles, prompting ecological surveys by teams from Royal Society for Nature Conservation-linked groups. The inundation altered habitats for breeding birds such as upland waders, leading ornithologists from Royal Society for the Protection of Birds and local bird clubs in Durham to monitor population changes. Conservation responses included designation of adjacent areas as Sites of Special Scientific Interest and integration into North Pennines Moors management frameworks, involving collaborative management by county conservation bodies and national agencies. Ongoing research by ecologists at Durham University and conservation NGOs continues to assess peat condition, carbon sequestration, and the reservoir’s role in regional biodiversity networks.
The setting attracts walkers, birdwatchers, and anglers using access routes from lanes linked to Appleby-in-Westmorland and local villages in Teesdale. Trails connect to the long-distance Pennine Way and local footpaths maintained by parish councils and voluntary Ramblers groups. Recreational fishing is managed under angling permits issued by the reservoir operator and local angling clubs based in Darlington and Barnard Castle. Visitor facilities are minimal, with interpretation provided by regional heritage organisations and conservation volunteers, while access is subject to restrictions intended to protect sensitive upland habitats and water supply infrastructure administered under statutory provisions from authorities in County Durham.
Category:Reservoirs in County Durham Category:North Pennines