Title: Rising groundwater levels in the chalk-basal sands aquifer of the Central London basin
Author: Environment Agency Thames Region
Document Type: Monograph
Annotation: EA additional title info:May 2002
Abstract:
This 2002 report is the eleventh annual report that the Environment Agency (and previously the National Rivers Authority) has produced on rising groundwater levels in the Chalk aquifer beneath London. The rising groundwater levels are the result of a significant reduction in groundwater abstraction from the Chalk aquifer beneath London since the mid-1960s. Prior to this the Chalk aquifer had been increasingly exploited through the development of groundwater sources during the 19th and first half of the 20th centuries. By the time abstraction peaked in the 1960s, groundwater levels below central London had dropped to 88 metres below sea-level, creating a large depression in the water-table. The subsequent reduction in abstraction has resulted in groundwater levels recovering by as much as 3 metres per year in places in the early 1990s. This has led to a gradual re-filling of the water-table cone of depression. It should be understood that the Chalk aquifer is confined over most of London by a layer of London Clay, up to 80 metres thick in places. This prevents the water table actually bursting through at ground level but causes artesian pressure to build up underneath the London Clay as levels rise, slowly increasing its saturation. It is this re-saturation which could affect the stability of certain foundations and tunnels in the London Clay.
Publisher: Environment Agency
Publication Date: 2002
Publication Place: Reading
Subject Keywords: Groundwater; Groundwater monitoring; Water levels; Water abstraction; Aquifers
Geographic Keywords: EA South East; London catchment
Extent: 45
Permalink: http://www.environmentdata.org/archive/ealit:1288
Total file downloads: 305
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