Analysis of variations in the regime of rivers and lakes in the Upper Volga and Upper Zapadnaya Dvina based on archaeological-geomorphological data

The geomorphological and altitudinal positions of occupational layers corresponding to 1224 colonization epochs at 870 archaeological sites in river valleys and lake depressions in southwestern Tver province. A series of alternating low-water (low levels of seasonal peaks, many-year periods without inundation of floodplains) and high-water (high spring floods, regular inundation of floodplains) intervals of various hierarchical rank was identified. In low-water epoch, an increase was recorded in the share of settlements on low elevations, including river and lake floodplains now subject to inundation. The archaeological epochs 2–3 Ky in length were found to form the following series from high-water to low-water: Mesolithic (11.8–8.0 Ky ago)-Iron age (2.8–0.3)-Neolithic (8.0–5.0)-Bronze epoch (5.0–2.8). The first half of the Iron age (2.8–1.8 Ky ago) was extremely water-abundant, while its second half (middle ages) was dry (relative to the present time). A correlation between the hydrological and temperature regimes was identified: low-water epochs closely correlate with warm epochs, while high-water ones correlate with cold epochs. This can be associated with the specific features of the present-day type of water regime with dominating spring flood; this regime is supposed to have existed during the most part of the Holocene: the runoff and the levels of floods decline during warming epochs and increase during cooling epochs.