Sediments in reservoirs represent a large carbon sink and document information about sources and transformations. However, quantity and quality of sedimentary organic matter (OM) will be altered in the water column and sediments. The sedimentation and degradation of particulate OM as well as the influence exerted by land use in the catchment were studied in two pre-dams of a drinking water reservoir. The pre-dam with agricultural land use in the catchment had a higher sedimentation rate in the water column but a lower burial rate of OM in sediments compared to the pre-dam whose catchment is dominated by forest. Besides land use, the bathymetry of the pre-dams was identified as an additional factor influencing the source composition and bioavailability of OM in sediments. Aquatic proteins and carbohydrates exhibited a higher degradability than lipids, and therefore modified the bulk carbon and nitrogen stable isotope ratios of sedimentary OM.