HGS RESEARCH HIGHLIGHT – Rapid transport from the surface to wells in fractured rock: A unique infiltration tracer experiment
Levison, J., & Novakowski, K. S. (2012). Rapid transport from the surface to wells in fractured rock: A unique infiltration tracer experiment. In Journal of Contaminant Hydrology (Vol. 131, Issues 1–4, pp. 29–38). Elsevier BV. https://doi.org/10.1016/j.jconhyd.2012.01.001
“This experiment, interpreted using the discrete-fracture capability of the numerical model HydroGeoSphere, showed that solute transport from the surface through thin soil (less than 2 m) to wells in fractured bedrock can be extremely rapid (on the order of hours.”
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In this study, researchers investigated the dynamics of rapid transport from the surface to monitoring wells in fractured rock environments using a unique infiltration tracer experiment. The focus was on understanding how tracers or contaminants move quickly through fractures to wells, which is crucial for assessing water quality and contamination risks.
The field and numerical experiment involved introducing a tracer at the surface and tracking the progress as it moved through the fracture network to the wells. The research demonstrates how quickly solutes can move from the surface to wells in fractured bedrock, particularly in settings with thin overburden. Central to the study is the use of HydroGeoSphere (HGS), Aquanty’s powerful modelling platform that simulates the interactions between surface water and groundwater. Using HGS, researchers tracked the movement of a fluorescent dye applied to the land surface in an agricultural field near Perth, Ontario, Canada. This approach revealed that rapid transport through fractures can significantly influence groundwater quality, highlighting the importance of understanding fracture networks to predict contamination risks.
Fig. 4. HydroGeoSphere domain (not to scale).
HGS was employed to enhance the understanding of tracer transport dynamics, and model the discrete-fracture capability, showing how contaminants navigate through thin soil layers and fractured bedrock. The model illustrated how fractures control the speed and direction of tracer transport and helped assess how different fracture configurations and hydraulic properties influence this process. This model allowed researchers to compare the transport dynamics and maximum contaminant concentrations at different aquifer depths.
A key feature of HGS is its ability to simulate the complex pathways and rapid transport of contaminants in fractured rock environments by pairing porous media flow and transport with discrete fracture networks. The model's ability to integrate these factors provided a comprehensive understanding of how quickly and extensively contaminants can spread in such settings.
Abstract:
A unique infiltration tracer experiment was performed whereby a fluorescent dye was applied to the land surface in an agricultural field, near Perth, Ontario, Canada, to simulate the transport of solutes to two pumped monitoring wells drilled into the granitic gneiss aquifer. This experiment, interpreted using the discrete-fracture capability of the numerical model HydroGeoSphere, showed that solute transport from the surface through thin soil (less than 2 m) to wells in fractured bedrock can be extremely rapid (on the order of hours). Also, it was demonstrated that maximum concentrations of contaminants originating from the ground surface will not necessarily be the highest in the shallow aquifer horizon. These are important considerations for both private and government-owned drinking water systems that draw water from shallow fractured bedrock aquifers. This research illustrates the extreme importance of protecting drinking water at the source.
“The breakthrough curves generated in HydroGeoSphere were corrected for mixing in the borehole by using a simple analytical solution”