Investigating land use and groundwater quality in the Eden Valley
The Eden Valley in East Cumbria is underlain by Permo-Triassic sandstone, the major aquifer in North West England.
The aquifer is covered by low permeability till deposits. Concern about rising nitrate trends in some boreholes has prompted collaborative research into groundwater flow systems and timescales in the area.
Land use influence on water quality
The use of slurry and artificial fertilisers following agricultural intensification in the area during the 1980s is believed to be responsible for the rise in nitrate concentrations.
The BGS is undertaking research to enable prediction of future nitrate concentrations at abstraction boreholes and in groundwater discharge to surface water.
How rapidly does rainfall reach the water table?
Deuterium and bromide tracers showed that water travels through the low permeability till at a rate of about 1 to 2 metres per year where the till is less than 2 metres thick.
The results for thicker till were harder to define.
How old is the groundwater at depth ?
The groundwater towards the bottom of a 90 metre borehole was found to be about 60 years old, i.e. it had fallen on the ground as rainfall some time around 1950.
How does groundwater quality change along a flowpath?
This study considered a theoretical ‘flowpath’ from upland outcrop to discharge zone at the River Eden.
The hydrochemistry (particularly nitrate) of samples from discrete intervals in the profile were compared with the proportion of modern water (and year of recharge).
The hydrochemistry (particularly nitrate) of samples from discrete intervals in the profile was found to be strongly related to the age of the water.
What sampling and analytical methods were used?
In the unsaturated zone we undertook hydrochemical profiling using agricultural tracers and dating groundwater in a cored borehole.
Below the water table, a combination of porewater sampling during air-flushed borehole coring, discrete interval sampling using a slimline packer system, geophysical logging and downhole digital imaging were employed in conjunction with ‘modern’ water dating techniques (CFC and SF6) and hydrochemical analysis.
Physical and hydrochemical profiles were developed and key fractures or fracture zones were identified and formed the basis of focused sampling.
Publications
Butcher, A, Griffiths, K, Lapworth, D, Humpage, A and Burke, S. 2009 Investigation of rising nitrate concentrations in groundwater in the Eden Valley, Cumbria. 4, estimating recharge rates through glacial till using an applied tracer technique. British Geological Survey, 23pp. (OR/09/059) (Unpublished)
Butcher, A, Griffiths, K, Lapworth, D, Humpage, A and Burke, S. 2009 Investigation of rising nitrate concentrations in groundwater in the Eden Valley, Cumbria. 4, estimating recharge rates through glacial till using an applied tracer technique. British Geological Survey, 23pp. (OR/09/059) (Unpublished)
Butcher, A. Lawrence, A, Jackson, C, Cullis, E, Cunningham, J, Hasan, K and Ingram, J. 2006 Investigating rising nitrate concentrations in groundwater in the Permo-Triassic aquifer, Eden Valley, Cumbria, UK. In: Barker, R.D.; Tellam, J.H., (eds.) Fluid flow and solute movement in sandstones : the onshore UK permo-triassic red bed sequence. London, Geological Society of London, 285–296. (Special Publication, 263).
Contact
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