River Lambourn
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The River Lambourn is a chalk stream in the English county of Berkshire. It rises in the Berkshire Downs near its namesake village of Lambourn and is a tributary of the River Kennet.
The upper reaches of the river are seasonal, with a perennial source derived from a number of springs located upstream of the village of Great Shefford. At times when the water table in the chalk aquifer feeding the river is high (usually between November and March) the source of the river migrates upstream. The normal seasonal source of the river is from springs in Lynch Wood on the edge of the village of Lambourn, but when groundwater levels are exceptionally high the source migrates even further upstream to the hamlet of Upper Lambourn.
Along the winterbourne section of the river are located the villages of Eastbury and East Garston, while along the perennial section of the river are the villages of Great Shefford, Welford, Boxford, Bagnor, Donnington and Shaw. Below Shaw is the confluence of the River Lambourn with the River Kennet, located between Newbury and Thatcham.
The River Lambourn itself has a single perennial tributary, the Winterbourne Stream, which joins it at the village of Bagnor.
[edit] Flow regime
The River Lambourn is almost unique for a chalk stream in southern England in that its flow regime remains near-natural in form; not being significantly modified by groundwater abstraction. Ironically, this situation developed because of a major groundwater abstraction project. In the 1960s the long term water supply situation for London was regarded as vulnerable and one avenue investigated to rectify this was to use untapped water resources naturally stored in the chalk aquifer of low population density areas of south east England. One such area was the West Berkshire Downs, including the catchment of the River Lambourn. The plan was to abstract groundwater from the chalk aquifer during times of drought and then use the existing river system as a natural conduit to transport the water to London, via the River Kennet and the River Thames.[citation needed]
An area in the catchment of the River Lambourn was selected as a pilot study to assess the feasibility of the project, and the Lambourn Valley Pilot Scheme was undertaken between 1967 and 1970. The final conclusion from the pilot study was that the overall scheme appeared feasible and a significant number of large abstraction boreholes and observation boreholes, together with pipelines and control equipment, were installed in the Lambourn catchment and also in other nearby river catchments. The project, named the Thames Groundwater Scheme, was completed in 1976 to coincide with the most serious drought in 50 years, but on final testing of the scheme it was found that the effective increase in river flow downstream was minimal, and essentially the project was a failure.[citation needed]
Almost all of the infrastructure for the project (now known as the West Berkshire Groundwater Scheme) is still in place and maintained, albeit on a rather shoestring budget. But the lasting legacy of the scheme is that the catchment has been preserved as a near-natural groundwater system, almost totally unaffected by groundwater abstractions. This factor made it an ideal candidate for selection as one of the flagship research sites for the NERC LOCAR research project investigating permeable (i.e. groundwater dominated) catchments.[citation needed]
