Effects Of Thermal Variability On Flow Dynamics In The Hyporheic Zone


Effects Of Thermal Variability On Flow Dynamics In The Hyporheic Zone


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Geography, Geology and the Environment


Eric Peterson

Mentor Department

Geography, Geology and the Environment


Heat is a naturally occurring and cost-effective tracer to study groundwater flow to, from, and throughout the subsurface. Heat has been used extensively to identify gaining and losing portions of streams and for the quantification groundwater discharge. Connecting ground and surface reservoirs is an area known as the hyporheic zone (HZ) where waters from either source interact. The flux of water throughout the HZ is controlled by stream bedforms, sinuosity, surface water velocity, local water table, seasonality, and sediment hydraulic conductivity. The HZ is known to fluctuate in size seasonally where it is slightly smaller in the winter and larger in the summer. Hydraulic conductivity has been defined as being dependent on both the viscosity and density of water, and it is well established that temperature influences both variables. In most studies, these changes have been neglected because of the little effect viscosity and density has on hydraulic conductivity. However, these variations are important to understand because an increase in hydraulic conductivity will result in an increase in groundwater velocity, which has implications relating to residence time and therefore subsurface nutrient processing. To better understand how water temperature effects flow dynamics in the HZ, multiple two-dimensional models will be created using the free USGS software VS2DHI to determine hydraulic conductivity under both hot and cold thermal conditions. Data were collected from a series of varying temperature hydrologic flume trials where the effects of hyporheic flow altering variables like sinuosity, surface water velocity and volume, and bed-forms were able to be reduced to a minimum. Stream substrate was a homogenous, fine-grained sand to reduce complexity and analyze only the changes resulting from thermal conditions. We expect that hydraulic conductivity in the HZ will be greater under warm conditions and lower under cool conditions, which will govern flow dynamics. Understanding these changes could help prepare us for future urban expansion, climate change, and other changes that could modify surface and ground water temperatures.


Authors: Jake Reidel and Eric Peterson

Effects Of Thermal Variability On Flow Dynamics In The Hyporheic Zone