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Recharge to the chalk aquifer beneath thick till deposits in East Anglia

Marks, R.J.; Lawrence, A.R.; Whitehead, E.J.; Cobbing, J.E.; Darling, W.G.; Hughes, A.G.. 2004 Recharge to the chalk aquifer beneath thick till deposits in East Anglia. Nottingham, UK, British Geological Survey, 59pp. (IR/04/007) (Unpublished)

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Abstract/Summary

This report describes the results of a project to investigate the Chalk-till groundwater system in East Anglia and to estimate rates of recharge through thick till (boulder clay) deposits. The project has involved drilling two cored boreholes, monitoring groundwater levels, sampling Chalk and till groundwaters and porewaters, and development of a conceptual model of Chalk-till groundwater hydrogeology. The main findings of the report have been: • the till has a significant impact on recharge quantity and distribution. Beneath the interfluves recharge appears to be lower than previously estimated (Klink et al. 1996, Soley and Heathcote 1998), probably <20 mm/a and possibly as low as 5 mm/a. Recharge to the Chalk aquifer is enhanced at the edge of the till sheet because of runoff from the till; • the Chalk groundwater beneath the interfluves is old (probably a minimum of several hundreds of years) and has negligible nitrate concentrations. This groundwater makes only a relatively small contribution to the active circulation system in the valleys, which is normally characterised by modern (post-1960s), high-nitrate waters; • the Chalk-till groundwater system and the spatial distribution of recharge to the Chalk aquifer determine the shape and dimensions of the catchment areas of abstraction boreholes. This in turn controls the proportion of modern water pumped by abstraction boreholes, which has implications for the concentration of nitrate in pumped water. One consequence is that boreholes close to the edge of the till are likely to pump a greater proportion of modern recharge than previously believed, probably with higher nitrate concentrations.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: BGS Programmes > Groundwater Management
Funders/Sponsors: NERC, Anglian Water Services
Additional Information. Not used in RCUK Gateway to Research.: In April 2000, the British Geological Survey (BGS) funded, as part of its core science programme, a 3 year research project to investigate and quantify recharge to the Chalk aquifer beneath thick till (boulder clay) deposits in East Anglia. This project met the criteria for core funding in that the research was of national/strategic value given (a) the importance of the Chalk aquifer to the UK water industry, (b) the sizeable area of Chalk outcrop in East Anglia that is overlain by thick till deposits and (c) the considerable uncertainty whether any significant recharge does occur through the till and, if it does, the recharge mechanism. In addition to the funding under the BGS core programme, Anglian Water Services (AWS) contributed financially to the project, and were interested in this research for two principal reasons: • an understanding of recharge to the Chalk, through till deposits, should allow a better delineation of the catchment areas for abstraction boreholes (at least in areas where till cover is significant). This, in turn, should help with modelling groundwater flow to abstraction boreholes, which is an essential first step when attempting to predict future groundwater nitrate concentrations; • the research may indicate whether a useful resource of low nitrate groundwater exists in the Chalk aquifer beneath the till which might be suitable for blending. This report was prepared for AWS and is an initial assessment of the research to date. A full Summary Report will be prepared by April 2004. This item has been internally reviewed but not externally peer-reviewed
Additional Keywords: GroundwaterBGS, Groundwater, Aquifer characterisation, Catchment processes, Environmental tracers, Groundwater dating, Groundwater modelling, Groundwater monitoring, Groundwater quality, Groundwater resources, Hydrogeological data, Major aquifers, Nitrate pollution
NORA Subject Terms: Earth Sciences
Hydrology
Related URLs:
Date made live: 20 Oct 2010 14:10
URI: http://nora.nerc.ac.uk/id/eprint/11670

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