Hydraulic processes controlling recharge through glacial drift

Cuthbert, Mark (2006). Hydraulic processes controlling recharge through glacial drift. University of Birmingham. Ph.D.

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Abstract

The research aims to further the understanding of hydraulic processes governing recharge through glacial drift (superficial deposits) at a range of scales by investigating the Potford Brook catchment, Shropshire, UK. At the local scale (10s m to km), an original application of the electrical resistivity tomography (ERT) method and coring have enabled a better understanding of the drift architecture and conceptual hydraulic models of recharge to be derived. At the site scale (cm to 10s m) hydraulic and hydrochemical/tracer test data suggest that recharge occurs through preferential pathways in variably saturated till. Furthermore, near-vertical hydraulically active fractures, thought to result from desiccation/freeze thaw processes and infilled with material derived from clasts in the till, have been observed. This is some of the first evidence of hydraulically significant fracturing in British glacial till. The permeability of a 6 m thick till deposit is thus approximately one order of magnitude greater than the matrix permeability. Potential travel times of contaminants to the till water table (<2 mbgl) may be as high as 1 cm/d. In glaciofluvial deposits, preferential flow is also shown to be significant and lateral flow is caused by perching on underlying glaciolacustrine materials. The vertical flow to the sandstone aquifer through the glaciolacustrine deposits has been shown, for the first time, to be just a few mm/a. Aquifer recharge may be enhanced locally in areas of patchy till/glaciolacustrine deposits due to the delayed infiltration of lateral subsurface flows and runoff. Temperature effects on the resistivity of the shallow subsurface can be very significant complicating the interpretation of time series ERT images. The results have important implications for sustainable catchment management and aquifer vulnerability.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):