Distribution of Cl-36/Cl ratios in a river-recharged aquifer was investigated in the Oderbruch area, northeastern Germany. The aquifer is confined up to 3.5-4 km inland, where it changes to an unconfined condition. The Cl-36/Cl ratios in the confined area were in the range between 4.6 x 10(-14) and 23.1 x 10(-14), showing a peak at 2-3 km away from the river. A plot of Cl-36/Cl vs. reciprocal Cl- concentrations indicated possible effect of the Cl- concentration variation on the observed Cl-36/Cl ratios. After accounting for this effect, the estimated Cl-36 fallout rates for the last 30 yrs show reasonable agreement with the Dye-3 data and the mid-latitude background value. The results suggest that a local Cl-36 fallout curve can be constructed from groundwater when dispersive mixing is of minor importance. (C) 2009 Elsevier B.V. All rights reserved.