27-8 Geochemical and Hydrogeological Characterization of a Buried Valley Aquifer to Improve Water Security

Session: Environmental Geochemistry and Health (Posters)

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Across the Western Plains of North America, groundwater often serves as the primary source of potable water outside urban centres. Buried valley aquifers typically provide sufficient supply for rural homes and small farms; however, water quality is variable, influenced by interactions with underlying bedrock formations and overlying sediments. To characterize the mixing and evolution of groundwater in these environments, we investigated a buried valley aquifer beneath a pitted delta located west of Edmonton, Alberta, Canada. While the geometry of these aquifers is relatively well mapped, their geochemical composition, flow dynamics, and connections to recharge zones remain poorly understood.

Publicly available groundwater data, including Provincial groundwater quality maps and a domestic well water quality database, were used as sources of major ion chemistry, which was visualized using Piper diagrams to depict hydrochemical facies. Furthermore, chemical mass balance techniques were coupled to thermodynamics calculations to generate activity-activity plots that both considered local mineralogy and water temperature, providing further insights into spatial differences in groundwater chemistry. These analyses were compared with mineralogical assessments of pitted delta sediments using X-ray diffraction (XRD), in order to better understand the controls on groundwater chemistry.

To better understand groundwater evolution, a geochemical mixing model and steady-state groundwater flow model are used together to evaluate the water balance and water quality within the buried valley aquifer. The mixing model defines the relative contributions of deeper, older groundwater and shallower, recently recharged water to the buried valley aquifer. Simultaneously, the groundwater model identifies flow directions, recharge-discharge patterns, and spatial mixing zones that influence water quality. By integrating these approaches, the study aims to enhance understanding of processes influencing groundwater evolution in buried valley aquifers and support future water security planning for the Edmonton region. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9456

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