Detecting the vulnerability of groundwater in semi-confined aquifers using barometric response functions

JOURNAL OF HYDROLOGY

卷:520

Article

Odling, N. E.¹  Serrano, R. Perulero¹  Hussein, M. E. A.²  Riva, M.^3,4  Guadagnini, A.^3,4 

[1] Univ Leeds, Sch Earth & Environm, Leeds LS2 9JT, W Yorkshire, England

[2] AMEC Black Cat LLC, Doha, Qatar

[3] Politecn Milan, Dipartimento Ingn Civile & Ambientale, I-20133 Milan, Italy

[4] Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA

关键词: Barometric response function;    Semi-confined aquifer;    Groundwater vulnerability;    Numerical modelling;    Monitoring boreholes;   

DOI  :  10.1016/j.jhydrol.2014.11.016

来源: Elsevier

【 摘 要 】

The use of barometric response functions (BRFs) for detecting the presence of fully penetrating, highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored. BRFs are determined from borehole water level (WL) and barometric pressure (Bp) records. Past studies have shown that confining layer properties can be estimated from BRFs, providing a potential link between BRFs and the concept of groundwater vulnerability. Existing analytical models that predict the BRF from system properties assume homogeneity within the aquifer and its confining layer, conditions which are seldom satisfied in nature. The impact of partially and fully penetrating, high diffusivity heterogeneities within a confining layer (representing potential high flow pathways for contaminants) on the BRF is investigated through a suite of three-dimensional, transient numerical simulations of the confining layer-aquifer system. The results are interpreted through comparison with a modified pre-existing analytical model for the BRF. Comparison of numerically and analytically calculated BRFs reveals that the key effect of a localised, fully penetrating, high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the BRF gain with only minor changes to the phase. This impact on the BRF decreases with increasing distance from the heterogeneity. The importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the BRF to only a minor extent. Data from a study of the Chalk Aquifer (E. Yorkshire, England) which is semi-confined by heterogeneous glacial sediments display variations in BRFs which are qualitatively similar to those shown by the numerical results. It is suggested that the variation in BRFs estimated from borehole records across a semi-confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination, and thus provide a tool to improve groundwater vulnerability assessment. (C) 2014 Elsevier B.V. All rights reserved.

【 授权许可】

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