Abstract
Measuring groundwater flux in lakes is particularly challenging as it is lower, spread over large areas, and is highly heterogeneous when compared to other groundwater flow systems. As techniques have improved, it has become increasingly clear that the hydraulic conductivity of the lakebed, or groundwater-surface-water interface (SWI), is more heterogeneous than previously thought and is the source of the highly heterogenous flux observed in previous studies. Processes that control hydraulic conductivity across the interface, and causes of the heterogeneity across spatial scales, are poorly understood. This research examines and contrasts the current techniques used to measure groundwater flux and hydraulic conductivity in lakes, especially at the SWI. Furthermore, the possible sources of the heterogeneous flux patterns at the SWI are reviewed. As an application, the measurements of hydraulic conductivity - which controls groundwater flux- at the SWI was performed in two stormwater detention ponds on FGCU campus. Results showed that spatial and especially bathymetry-related hydraulic conductivity patterns were found and those agreed with the literature. Hydraulic conductivity was higher within the littoral zone and lower at deeper sites farther away from shore. Additionally, the hydraulic conductivity in relation to the organic matter content was significantly different between ponds but overall, there was lower hydraulic conductivity seen in the pond with higher organic matter. Although not a novel finding, this study highlights the importance of heterogeneity in the hydraulic properties of the SWI and the difficulties current techniques have in measuring the hydraulic properties of the SWI.
