GROUNDWATER OF TOMSK OBLAST

P. A. UDODOV, N. A. ERMASHOVA, N. M. RASSKAZOV, A. D. NAZAROV,
V. G. BYKOV, E. S. KOROBEINIKOVA

According to Academician V. I. Vernadsky, “water occupies a special place in the history of our planet. There is no natural body that could compare with it in its influence on the course of the most fundamental, most grandiose processes.”

Water is the mobile medium—and at the same time the least studied one—in which various mineral resources are formed. However, its role is not limited to participation in the formation of minerals. Subsequently it is also the most active factor in their destruction. Therefore at present natural water is used not only as a useful mineral resource, but also as a sensitive indicator of ores, petroleum, gases, and other mineral resources. At the present time, by the hydrogeochemical method, a number of zones of mineralization have already been discovered in the south of Tomsk Oblast [2].

Hydrogeochemical and hydrogeological investigations are carried out by the Tomsk Geological Administration, Tomsk Polytechnic Institute, and other organizations also within oil- and gas-bearing, swampy areas, at deposits of nonmetallic mineral resources, which makes it possible to solve a number of important questions in both practical and theoretical respects.

In mining, the use of water for extracting ore by processing productive solutions recovered from wells has begun. This method of developing ores, including low-grade and “off-balance” ores, as is known, requires neither mines nor underground labor by workers and is economically effective.

Tomsk Oblast possesses large reserves of various types of groundwater, which until recently have clearly been used insufficiently. Its hydrogeological study is poor, with the exception of areas adjoining Tomsk, Asino, and Kolpashevo. But even here the exploration of groundwater began only in recent years.

The principal water-bearing complexes on the territory of Tomsk Oblast, if the section is considered from top to bottom, are the following:

1) Quaternary sandy-gravelly;
2) Paleogene sandy (medium- and fine-grained sands);
3) Upper Cretaceous (medium- and often fine-grained sands);
4) Lower Cretaceous (fine-grained sands, sandstones, siltstones);
5) Jurassic (varigrained sands and sands with interbeds of argillites and clays).

The complex of Paleozoic formations possesses comparatively small reserves of groundwater.

The Quaternary aquifer occurs at depths from 8 to 46 m; it is often nonartesian, but in a number of areas as a whole it has a local head. The specific yields of wells vary from 0.1 to 5 l/sec. Filtration coefficients amount to as much as 45 m/day for alluvial deposits and up to 10 m/day for watershed deposits. At elevations situated below the local base level of erosion, the horizon is closely connected with surface watercourses.

The aquifer complex associated with Paleogene deposits comes to the surface in the southern part of the oblast, while in the rest of the territory it occurs at depths down to 80 m. The waters are artesian; sometimes in valleys self-flow from wells is observed. The specific yields of wells vary from 0.1 to 3–4 l/sec; in one well (the settlement of Cheremoshniki) a specific yield of 11 l/sec was recorded. The horizon often has a hydraulic connection with large rivers, which does not substantially affect water quality, since river waters, before entering the horizon, are filtered through a many-meter thickness of sands, gravels, and loams containing purifying bacteria. The quality of the water is quite satisfactory, although in a number of cases an increased iron content is noted, and in the northern districts—organic matter.

The filtration coefficient varies from 1 to 20 m/day.

Upper Cretaceous deposits occur at depths down to 50 m in the Chulym–Yenisei interfluve, dipping in the northern and eastern parts of the oblast to 200–400 m. The specific yields of wells are 0.06–0.4 l/sec, and rarely 1–1.5 l/sec. With successful well completion they increase to 2 l/sec. The filtration coefficient varies from 0.5 to 10 m/day.

The connection of the waters of this horizon with rivers has not been reliably established; however, as exploration experience in the area of the town of Asino shows, such a connection is not excluded. The waters are highly artesian; self-flow is observed along river valleys. In chemical composition they are predominantly hydrocarbonate–sodium–calcium waters with mineralization of 0.8–1 g/l, while in the northwestern and western parts of the oblast they are chloride sodium waters with mineralization up to 12 g/l. The general direction of groundwater flow is northwestern. In the same direction the temperature of the groundwaters also increases.

Lower Cretaceous deposits have a thickness of 1500–1900 m. Here the waters are associated with sands, sandstones, and siltstones encountered at depths of 300–750 m. They are characterized by high head and self-flow. In the eastern, near-Yenisei part of the oblast, water mineralization is 0.2–0.8 g/l; in the western part, up to 25 g/l. Their mineralization and temperature increase with depth, and also in the direction from east and south toward the north and west. The chemical composition of the water changes from hydrocarbonate–calcium–sodium to chloride–sodium–calcium [1].

The water abundance of the rocks is small: the specific yields of wells vary from 0.01 to 0.3 l/sec with a filtration coefficient of about 0.1 m/day.

The aquifer complex of Jurassic deposits occurs in the near-Yenisei belt at depths down to 30 m, dipping westward to 2500 m. The specific yields of wells do not exceed 0.02 l/sec. In the eastern part, mineralization reaches 0.5 g/l; in the western part, more than 60 g/l; here the highest temperature of groundwaters has also been recorded [1].

The waters of the lower aquifers over most of the oblast contain increased amounts of iodine, bromine, silicic acid, and hydrocarbon gases. At individual points (Chazhemto), hydrogen sulfide has been detected in an amount of 13 mg/l.

As is evident from the brief review presented, the greatest practical interest for water supply is represented by the Paleogene aquifer complex and, in a number of districts, by the Quaternary aquifer complex. Preliminary

it can be concluded that, with proper exploitation of these horizons, most industrial districts of the oblast can be supplied with drinking water in sufficient quantity. Difficulties in this respect were encountered in the north of the oblast; however, even there, waters of appropriate quality were found in Paleogene deposits. Positive results were obtained for the Asino and Tomsk districts.

Within the Ob–Tom interfluve, Quaternary water-bearing gravel–pebble terrace deposits of the Tom River and a water-bearing complex of Paleogene sands with a thickness from 27 to 86 m are widespread.

The depth to the roof of the confined Paleogene aquifer complex is 20–80 m. The head varies from 15 to 70 m. The piezometric level is established at a depth of 2–28 m. Specific yields vary from 2 to 4 l/sec. In chemical composition the water is fresh, moderately hard, hydrocarbonate, calcium–sodium, with mineralization up to 400 mg/l.

According to data from the problem geological laboratory of TPI and the Tomsk municipal sanitary-epidemiological station, the water quality meets the sanitary requirements of GOST; however, an elevated iron content is noted—up to 4 mg/l, and in isolated cases up to 7 mg/l. The groundwater reserves can support the operation of a large water intake.

Waters associated with Cretaceous deposits can be used for water flooding in oil production, which will provide a large economic effect.

The hydrogeological characterization of the territory of Tomsk Oblast given above shows that in deeply occurring horizons over most of its territory there are warm and hot waters with high mineralization and an elevated content of a number of elements and hydrocarbon gases, which are biologically active (mineral).

Of considerable practical interest are the thermal waters of the oblast, which possess large reserves. Unfortunately, they have been very poorly studied. These waters can be used for heating greenhouses and residential premises and for creating swimming pools.

REFERENCES

1. Hydrogeology of the USSR. Vol. 16. West Siberian Plain. Moscow, “Nedra,” 1970.
2. Hydrogeology of the USSR. Vol. 17. Kemerovo Oblast and Altai Krai. Moscow, “Nedra,” 1972.