Characterization of groundwater–lake water interactions at Pyhäjärvi, a lake in SW Finland

This paper presents the first attempt in Finland to collect detailed observations on surface water and groundwater interactions. We focused on a 10-km northeastern shoreline of Pyhajarvi, where the potential groundwater discharge areas are associated with the esker aquifers. The methods used during 2008 and 2009 involved winter mapping, lake water and lake bed sediment temperature measurements, pH and electrical conductivity measurements, seepage meters, mini-piezometers, and chemical (PCE/TCE) and isotopic tracers. The main aims of this study were to compare the applicability of the methods used and evaluate the results obtained. The results from the various methods correlated and confirmed the groundwater discharge (4.69 x 10 -5 cm s -1 to 4.80 x 10 -3 cm s -1 ) into lake water at the shoreline. Further research is needed to obtain a quantitative estimation of groundwater seepage in Pyhajarvi.