Volume 61 of Advances in Limnology contains 12 peer reviewed, original papers focusing on the hyporheic zone of running waters (the transient zone in fluvial sediments between ground water and surface water). The papers of this special issue address new studies carried out in the River Lahn (Germany), a right-bank tributary in the middle reach of the River Rhine. The studies were conducted in order The papers address students and scientists at universities and research institutions, managers of aquatic ecosystems and watersheds.