Compartmentalisation and groundwater‐surface water interactions in a prospective shale gas basin: Assessment using variance analysis and multivariate statistics on water quality data

Wilson, Miles. P.; Worrall, Fred; Clancy, Sarah. A.; Ottley, Christopher. J.; Hart, Alwyn; Davies, Richard. J.

Abstract

An environmental concern with hydraulic fracturing for shale gas is the risk of groundwater and surface water contamination. Assessing this risk partly involves the identification and understanding of groundwater‐surface water interactions because potentially contaminating fluids could move from one water body to the other along hydraulic pathways. In this study we use water quality data from a prospective shale gas basin to determine: if surface water sampling could identify groundwater compartmentalisation by low‐permeability faults; and if surface waters interact with groundwater in underlying bedrock formations, thereby indicating hydraulic pathways. Variance analysis showed that bedrock geology was a significant factor influencing surface water quality, indicating regional‐scale groundwater‐surface water interactions despite the presence of an overlying region‐wide layer of superficial deposits averaging 30–40 m thickness. We propose that surface waters interact with a weathered bedrock layer through the complex distribution of glaciofluvial sands and gravels. Principal component analysis showed that surface water compositions were constrained within groundwater end‐member compositions. Surface water quality data showed no relationship with groundwater compartmentalisation known to be caused by a major basin fault. Therefore, there was no chemical evidence to suggest that deeper groundwater in this particular area of the prospective basin was reaching the surface in response to compartmentalisation. Consequently, in this case compartmentalisation does not appear to increase the risk of fracking‐related contaminants reaching surface waters, although this may differ under different hydrogeological scenarios.

Citation

Wilson, M. P., Worrall, F., Clancy, S. A., Ottley, C. J., Hart, A., & Davies, R. J. (2020). Compartmentalisation and groundwater‐surface water interactions in a prospective shale gas basin: Assessment using variance analysis and multivariate statistics on water quality data. Hydrological Processes, 34(15), 3271-3294. https://doi.org/10.1002/hyp.13795

• Journal Article Type: Article
• Acceptance Date: Apr 25, 2020
• Online Publication Date: Jun 3, 2020
• Publication Date: Jul 15, 2020
• Deposit Date: May 28, 2020
• Publicly Available Date: Jul 2, 2020
• Journal: Hydrological Processes
• Print ISSN: 0885-6087
• Electronic ISSN: 1099-1085
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 34
• Issue: 15
• Pages: 3271-3294
• DOI: https://doi.org/10.1002/hyp.13795
• Public URL: https://durham-repository.worktribe.com/output/1269855