Developing novel in situ methods to monitor and quantify groundwater storage changes in cold regions

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Background: Vibrating wire piezometers (VWPs) can be used to determine in situ pore water pressure and estimate the flow pattern; however, the data collected are vastly underutilized. Novel data acquisition and analysis approaches using VWPs to determine and quantify groundwater storage changes can be achieved by testing these methods at various scales over a wide range of environments. Objectives: The long-term objective of this research program is to increase fundamental understanding of groundwater storage changes by developing and applying novel in situ methods. This will expand upon current theory and infrastructure to develop and validate new methods to help eliminate guesswork in water balances by quantifying changes in water storage in large- and small-scale catchment areas. An integrative approach combining field, laboratory, and computational techniques will be used to achieve this goal through three short-term objectives (STOs): STO-1: Develop a field-verified method to delineate water storage changes in saturated and unsaturated zones and determine characteristic pore pressure behaviour in response to natural and anthropogenic forcings. The effectiveness of the geo-weighing lysimeter approach for quantifying water storage change in confined aquifers and aquitards will be evaluated at multiple depths and formations. Sensitive VWPs currently installed at five sites in SK will be used to calibrate the geolysimeter capture area and compare the effectiveness of such methods in different materials, depths, and locations to monitor changes in soil moisture (groundwater storage) and define the spatial variability in the application of geo-weighing lysimeters. STO-2: Develop a method or technique in the laboratory to install highly sensitive VWPs in fully or partially frozen material. Lab-scale experiments will be designed and executed to investigate the potential of installing instrumentation in fully or partially frozen geomaterial. Numerical modeling of the thermal characteristics and the ability of the VWP to withstand large temperature changes will be assessed. STO-3: Evaluate the developed methods by investigating vulnerable or actively exploited environments. Methods developed in STO-1 and -2 will be applied to environments where in situ VWPs are rarely used or intended for different uses, including permafrost regions (STO-3a), and waste rock piles and tailings facilities (STO-3b). Impact: The knowledge gained will provide practical and effective methods to monitor groundwater behaviour in response to natural and anthropogenic forcings and help constrain water balance models. Applications include improving water management techniques for mine sites, soil moisture monitoring in the agriculture sector, assessment of permafrost melting in cold regions, and ambient groundwater monitoring programs. The results will also inform future data requirements to facilitate groundwater management and water security both in Canada and globally.