Abstract. Lacustrine groundwater discharge (LGD) can play an important role for lake water balances and lake water quality. However, quantifying LGD and their spatial patterns is challenging as pronounced spatial variability is paired with a large spatial extent of the aquifer–lake interface and factors controlling LGD patterns are not well understood. We used intensive field measurements including 520 vertical temperature profiles in the near shore area, sediment temperature measurements with a fibre-optic cable along 6 transects from shoreline to shoreline and radon measurements of lake water samples to identify LGD patterns at a lake in north eastern Germany. Sediment characteristics, topographic indices and gradients of the groundwater flow field were considered as potential controls of small scale and large scale LGD patterns. The results revealed that LGD was concentrated in the near shore area with stronger rates and higher variability in the northern part of the lake. LGD generally decreased with distance to shore and offshore LGD was insignificant except for some local hotspots of LGD on steep steps towards the lake bottom. Large scale groundwater inflow patterns were correlated with topography and the groundwater flow field whereas small scale patterns correlated with grainsize distributions of the lake sediment. Regression models using external controls as explanatory variables had limited power to predict LGD rates, but results encourage the use of topographic indices and sediment heterogeneities as an aid for targeted experimental designs.
Artificial Sweeteners Identify Spatial Patterns of Historic Landfill Contaminated Groundwater Discharge in an Urban Stream
