Scientific publications

The article presents the results of the study of contemporary and historical sedimentation in 66 waterbodies of different types in the middle course of the Volga (ponds, lakes) within the Chuvash Republic, Republic of Tatarstan, and Republic of Mari El. In terms of physical geography, the study area is situated in the provinces Volga Upland and Low-lying Trans-Volga. Seasonal and long-term variation of the rate of sediment accumulation was assessed, the main typological properties of top-core and stratified sediments (texture and organic matter) were characterized. Volga Upland and Low-lying Trans-Volga region were found to have the same range of lacustrine sedimentation rates. At the currentstage of the natural-anthropogenic transformation of the region’s limnic systems,

sediments are being accumulated at a rate of 1600 g/(m2・year). Regional sediment increments (3–7 mm/year) fall within the range of mean multiannual values typical for lakes and storage reservoirs in the Middle Volga drainage basin, representing the universal patterns of sedimentation in waterbodies situated under similar physic-geographical

conditions. The autochthonous mode of sedimentation was found to prevail in waterbodies of the low-lying Trans-Volga region and the terrigenous mode in the Volga Upland. The pace of contemporary and historical sedimentation in the waterbodies is quasi-stationary, suggesting their sedimentation balance is governed by natural factors. A regional scale of sedimentation rates has been worked out, and the waterbodies were ranked by the current rate of sediment accumulation. It is predicted that current sedimentation rates will persist in a majority of the region’s waterbodies; the highest sediment increments (more than 6000 g/(m2∙year)) are expected for overgrowing lakes in the low-lying Trans- Volga region.