Investigation of Groundwater Contaminant Discharge into Tidally Influenced Surface-Water Bodies: Experimental Results

Abstract

An investigation of the effect of tidally influenced water elevations on the concentration of groundwater contaminants discharging to a surface-water body is studied using a one-dimensional homogeneous sand column. A constant water level is imposed upstream, and the downstream water level is controlled by a wave generator that controls the hydraulic head to mimic a 12-h tidal fluctuation. The experimental results demonstrate that the tidal fluctuations in the downstream reservoir result in a decrease in average contaminant concentration at the point of discharge to the tidally influenced surface-water body. The further upstream an observation well is located, the smaller the amplitude of the concentration oscillation. Fourier analysis suggests that the dominant frequency of the pressure at different locations along the length of the column is identically two cycles per day and that the concentration data have a dominant frequency of two cycles per day, but also exhibit harmonics.

Transient forcing effects on mixing of two fluids for a stable stratification

“…A similar effect of the interface location on mixing is observed when considering a Dirichlet‐type boundary condition (see Figure d), with a maximum impact for small distances of the interface from the boundary. This is consistent with Chen and Pinder [, ], who numerically and experimentally demonstrated that the further the interface is from the boundary, the smaller the impact of the temporal fluctuating boundary conditions on dispersion. However, in this case, an increase in the storativity causes the transient‐induced mixing to increase (see Figure c).…”