Affiliation:
1. British Geological Survey, Maclean Building, Wallingford OX10 8BB, UK
2. British Geological Survey, Kingsley Dunham Centre, Keyworth NG12 5GG, UK
3. University College London, Department of Earth Sciences, Gower Street, London WC1E 6BT, UK
Abstract
AbstractThe Chalk is an unusual karst aquifer with limited cave development, but extensive networks of smaller solutional conduits and fissures enabling rapid groundwater flow. Small-scale karst features (stream sinks, dolines, dissolution pipes, and springs) are common, with hundreds of stream sinks recorded. Tracer velocities from 27 connections between stream sinks and springs have median and mean velocities of 4700 and 4600 m d−1. Tests to abstraction boreholes also demonstrate very rapid velocities of thousands of metres per day. Natural gradient tests from observation boreholes have rapid velocities of hundreds of metres per day. There is strong geological control on karst with dissolution focused on stratigraphical inception horizons. Surface karst features are concentrated near the Paleogene boundary, or where thin superficial cover occurs, but rapid groundwater flow is also common in other areas. The Chalk has higher storage and contaminant attenuation than classical karst, but recharge, storage and flow are influenced by karst. Point recharge through stream sinks, dolines, losing rivers, vertical solutional fissures, and soakaways enables rapid unsaturated zone flow. Saturated zone networks of solutional fissures and conduits create vulnerability to subsurface activities, and enable long distance transport of point source and diffuse pollutants, which may be derived from outside modelled catchment areas and source protection zones.
Publisher
Geological Society of London
Subject
Geology,Ocean Engineering,Water Science and Technology
Reference161 articles.
1. Adams B. (ed.) 2008. The Chalk aquifer of the North Downs. British Geological Survey Research Report, RR/08/02 .
2. Characterisation of fractured carbonate aquifers using ambient borehole dilution tests;Journal of Hydrology,2020
3. Allen D.J. and Crane E.J. (eds) 2019. The Chalk Aquifer of the Wessex Basin. British Geological Survey Research Report, RR/11/002, https://nora.nerc.ac.uk/id/eprint/522484/1/RR11002.pdf
4. Allen D.J. , Brewerton L.J. 1997. The physical properties of the major aquifers in England and Wales. BGS Technical Report, WD/97/34 , Environment Agency R&D Publication, 8.
5. Allshorn S.J.L. , Bottrell S.H. , West L.J. and Odling N.E. 2007. Rapid karstic bypass flow in the unsaturated zone of the Yorkshire chalk aquifer and implications for contaminant transport. Geological Society, London, Special Publications, 279, 111–122, https://doi.org/10.1144/SP279.10
Cited by
7 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献