High-Resolution Dynamic Pore Pressure Monitoring to Determine Hydraulic Parameters in a Multi-Layered Bedrock System for Improved Aquifer Vulnerability Assessment and Monitoring

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Johnson, Kathleen

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University of Guelph

Abstract

Approximately 30% of Canadians rely on groundwater for their basic water needs. The City of Guelph is one of the largest cities in Canada to rely solely on a fractured rock dolostone aquifer for its drinking and fresh water supply. For this study, a vertical string of 21 pressure transducers was deployed behind a FLUTe liner in a borehole, within 250m of a municipal supply well in Guelph, Ontario, to record depth-discrete pore pressure transients over 60 days at 10s frequency. Regression deconvolution was used to determine the loading and pumping response functions using input variables including barometric pressure, Earth tides, river stage and pumping rates from 2 nearby municipal wells using distributed lags. Loading response functions determined over two time periods showed changing loading efficiency (LE) conditions relating to changing pumping or vadose zone conditions. Twelve hydrogeologic units were delineated, including four discontinuous aquitard units. An updated conceptual site model with lithostratigraphy was calibrated with the hydraulic data analysis providing hydraulic parameter estimates for LE, transmissivity and storativity in support of future 3D flow system numerical modelling.

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groundwater, fractured rock, Guelph, high-resolution, pore pressure

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