“…Despite the wide range of variability in SGD calculations (depending on techniques, sediment type, location, etc. ), which can vary from 0.01% to 80% of the total river flow, the importance of SGD in the global water cycle is unquestioned because of the high ratio of SGD to surface runoff (e.g., Bokuniewicz, 1980;Gallagher et al, 1996;Schlüter et al, 2004). For the Polish coastline alone (500 km), the total value of groundwater discharge to the Baltic Sea was calculated to be approximately 1.45 km 3 yr −1 (Kryza and Kryza, 2006), while estimations of 4.4 km 3 yr −1 were reported by Peltonen (2002) for the whole Baltic Sea.…”