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A strategic programme for NERC Lowland catchment research
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Characterising permeability distributions in Chalk catchments: summary

A fuller description of this project is also available.

Overview of project

First principles suggest that Chalk rivers, springs and wells are protected from land surface contamination by solutes diffusing from fractures into the porous matrix. Using artificial and environmental (CFC) tracers to mimic contaminants, the study investigated the amount of flow that has short residence times and little potential attenuation by diffusion while flowing through voids greater than about l mm wide. It also investgated and what proportion of flow passes slowly through smaller voids, with maximum attenuation, therefore protecting water resources and river ecology.

Aims

The aim was to develop a conceptual model of water and potential contaminant fluxes from land surface to rivers via the Chalk aquifer, to underpin future basin management and risk analysis.

Main findings

  • The Chalk contains preferred flow horizons with vertical gradients of hydraulic head between them
  • Tracer tests reveal karstification of the Chalk. Flows from sinks to springs had velocities of thousands of metres per day, which are comparable to those observed in highly karstic aquifers
  • Karst features in the Pang and Lambourn area show zoning that corresponds to the structure of permeability in the sub-surface More about the main findings of this project

Description of activities

  • Field survey of 128 stream sinks and 26 springs in the Pang and Lambourn catchments
  • Qualitative natural gradient tracer tests using bacteriophages and dye tracers
  • Quantitative tracer testing using fluorescent dyes
  • Single borehole dilution tests, together with borehole geophysics and imaging, were used to develop a methodology to identify the location of fractures where water flowed into boreholes More about the activities carried out by this project

Areas of application

  • Source protection zone policy
  • Catchment management planning on the Chalk or other aquifers prone to karstification

Researchers' details

Principal Investigator:

Co-investigators:

More researchers who worked on this project More researchers who worked on this project

Publications

All publications from this and other LOCAR projects are listed in the publications database.

Selected publications from this project are listed below. The full list of publications and recommended reading can be viewed in the project description Full publication list for this project

Selected publications

Van den Daele, G F A, Barker J A, Connell L D, Atkinson T C , Darling W G & Cooper J D, 2007. Unsaturated flow and solute transport through the Chalk : tracer test and dual permeability modeling. Journal of Hydrology, 342, 157-172.

Maurice L D, Atkinson T C, Barker J A, Bloomfield J P, Farrant A R & Williams, A.T., 2006. Karstic behaviour of groundwater in the English Chalk. Journal of Hydrology, 330, 63-70.

Mathias S A, Butler A P, Atkinson T C, Kachi S & Ward R S, 2006. A parameter identifiability study of two Chalk tracer tests . Hydrology & Earth System Sciences Discussion, 3, 2437-2471.

Full list of publications resulting from this project Full publication list for this project

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