River Lambourn - Flow Regime

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.

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.

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.