Thermal gradients as a tool for estimating groundwater advective rates in a coastal estuary: White Oak River, North Carolina, USA

We calculate rates of groundwater discharge into the White Oak River in coastal North Carolina, using time series measurements of the thermal structure of shallow estuarine sediments recorded over a period of four months. Computer models using numerical solutions to the advection–diffusion equation show that sediment thermal structure is not explained by purely conductive heat transport. Results of models that incorporate groundwater advection from an underlying source closely mimic field observations of sediment temperatures, verifying that thermal data can be used to monitor groundwater discharge. An advantage of this technique is that it provides insight into temporal variations in groundwater flow rates. Thermal methods may thus be useful for quantifying groundwater flux in areas where low volumes of discharge cannot be detected by direct observation.