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

Recent work has identified groundwater flow through basal till aquifers as a key control on melt-season pressure transients beneath alpine glaciers, w ith potential implications for climate change studies, glacial geomorpholog y, tracer test interpretation, and the sediment load and chemistry of glaci ally derived waters. In this study, we investigate heuristically such subgl acial Darcian flow processes using standard groundwater modelling technique s. Our primary result is that a one-dimensional, transient, confined flow m odel with recharge, implemented numerically using time-varying specified-he ad and no-flow boundaries, reproduces overall observed subglacial hydraulic behaviour very well and permits effective visualisation of aquifer respons es under different conditions. Spatial variability in hydrogeological param eters is shown to have significant effects, but may be difficult to incorpo rate reliably into site-specific models and to identify unambiguously in bo rehole pressure data. Time-variance in areal recharge, if present, is appar ently not observably expressed in the system, but time-variance in transmis sivity may be significant for some glaciers. Copyright (C) 2000 John Wiley & Sons, Ltd.