Investigation of water pressure transients beneath temperate glaciers using numerical groundwater flow experiments

Abstract

Recent work has identified groundwater flow through basal till aquifers as a key control on melt-season pressure transients beneath alpine glaciers, with potential implications for climate change studies, glacial geomorphology, tracer test interpretation, and the sediment load and chemistry of glacially derived waters. In this study, we investigate heuristically such subglacial Darcian flow processes using standard groundwater modelling techniques. Our primary result is that a one-dimensional, transient, confined flow model with recharge, implemented numerically using time-varying specified-head and no-flow boundaries, reproduces overall observed subglacial hydraulic behaviour very well and permits effective visualisation of aquifer responses under different conditions. Spatial variability in hydrogeological parameters is shown to have significant effects, but may be difficult to incorporate reliably into site-specific models and to identify unambiguously in borehole pressure data. Time-variance in areal recharge, if present, is apparently not observably expressed in the system, but time-variance in transmissivity may be significant for some glaciers. Copyright (C) 2000 John Wiley & Sons, Ltd.