Hydrogeological conditions of lower part of Tom River basin

Hydro-geological features of the lower part of the Tom River basin with the detailed description of the main water-bearing horizons and complexes, their capacity, structure, water conductivity, composition, etc. are considered. Special attention is given to conditions of recharge and discharge of groundwater. By the results of the carried-out analysis of the hydrodynamic mode of waters under natural conditions, prior to the beginning of operation of Tomsk and Seversk water intakes, and now, the main tendencies of its change under the influence of anthropogenic loads are revealed. The territory of research is located within the lower part of the Tom River basin at the joint of two large hydro-geological structures: West Siberian artesian basin and Kolyvan-Tomsky folded zone. By conditions of arrangement, circulation, recharge and discharge in the area the following water-bearing complexes are allocated: of Neogene-Quaternary deposits; of Paleogene deposits; of Upper-Cretaceous deposits; and fissured water-bearing zone of Paleozoic formation. The water-bearing complex of the Neogene-Quaternary deposits includes hydraulically interconnected waterbearing horizons of lake and marsh deposits, deposits of floodplains of the rivers; over-floodplains terraces, ancient hollows of drain and accumulative plains. The water-bearing complex of Paleogene deposits is the main source of the centralized water supply of Tomsk and partially of Seversk. The water-bearing complex of Upper-Cretaceous deposits is widespread within the characterized area, being absent only in the southeast part of the Ob-Tom interfluve. Underground waters of fissured water-bearing zone of Paleozoic formation are widespread everywhere, appearing on day surface on the right bank of the Tom River and disappearing in the northern and northwest directions. The main role in recharge of groundwater of all water-bearing horizons and complexes is played by the infiltration of atmospheric precipitation with formation of a watershed of underground waters and the radial direction of their movement towards the main areas of discharge - the Ob and the Tom. The draining influence of Tomsk and Seversk water intakes during their functioning led to a decrease in the level of groundwater of the Neogene-Quaternary water-bearing complex with the shift of isolines towards the watershed and to the formation of a depression funnel. The structure of the filtration stream of the water-bearing horizons of the Paleogene complex is similar, but has smoother lines. The filtration stream radially dispersing under natural conditions (till 1973) was essentially broken by the work of Tomsk water intake. It was particularly evident at the sites adjoining the water intaking lines. Thus, long-term operation of Tomsk and Seversk water intakes led to a decrease in levels of groundwater of the Paleogene and the Neogene-Quaternary water-bearing complexes with formation of depression funnels having essentially changed the conditions of their recharge and discharge.

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