On the Groundwater Regime of the Yerunakovsky District of Kuzbass

D. S. Pokrovsky

(Presented by the scientific seminar of the Department of Hydrogeology and Engineering Geology)

The study of the groundwater regime as applied to the conditions of the Kuznetsk Basin is of great importance in connection with the need to forecast water inflows into mine workings and to resolve questions of water supply for industrial and agricultural facilities.

Using the example of the Yerunakovsky coal district, located in the central forest-steppe, hilly, moderately humid part of the southern half of Kuzbass, we consider certain questions of rhythmicity in the groundwater regime.

In the district there are productive deposits of the Kolchugin series of Paleozoic age, represented by interbedded sandstones, siltstones, and argillites with coal seams, folded into gentle brachyfolds and everywhere overlain by a cover of Quaternary deposits with a thickness from 4–5 to 20 or more meters.

The Paleozoic rocks are most water-bearing in the zone of intensive fracturing, whose thickness is 80–100, rarely 150 m on watersheds and 50–100 m in river valleys and depressions of the relief.

With increasing depth, the fracturing of the rocks, their reservoir properties, and their water-bearing capacity decrease sharply, and only individual sandstone horizons have somewhat elevated water abundance.

In the district there are several boreholes drilled in the course of coal prospecting and exploration, at which, over ten years, observations were carried out with sufficient regularity on changes in groundwater levels and borehole yields in cases of self-discharge.

The boreholes were drilled to depths considerably exceeding the thickness of the zone of intensive fracturing and fully expose the most water-bearing rocks. Let us consider questions of the groundwater regime of the zone of intensive water exchange, occurring on watersheds and their slopes, for which the governing regime-forming factors are climatic.

In analyzing the data of regime observations and climatic characteristics, a phenomenon of rhythmicity was noted. Without touching upon the causes of this phenomenon, we shall only note that a number of authors point to a connection between meteorological elements and the groundwater regime and changes in solar activity.

For the study area, regime observations and meteorological data, even for a comparatively short period (7–10 years), make it possible to distinguish a number of rhythms of varying duration.

Changes in the mean annual values of the yields of flowing wells 196, 913, and others (Fig. 1) are rhythmic, with rhythm durations of about 3 years, which are superimposed on rhythmic waves of greater length. Rhythms of this order were noted in the groundwater regime of the Stone Steppe (Korobeinikov, 1964). The materials at our disposal do not yet make it possible to distinguish rhythms longer than 3 years; however, taking into account the regularities in fluctuations of climatic and regime characteristics noted by a number of authors for

Fig. 1. Long-term fluctuations in the yield of flowing wells:
1—well 196; 2—well 913; 3—well 547; 4—well 1014;
5—well 810.

other regions of the USSR, one may assume the existence in the Kuznetsk Basin of rhythmicity with durations of 7, 11–15, and more years (Al’tovskii, 1954; Duginov, Korobeinikov, 1957; Konoplyantsev, 1963, etc.).

As early as 1950, N. S. Tokarev, for climatic characteristics, in addition to rhythms lasting 11 years and more, outlined rhythmicity with periods of 10–23 and 2–5 months and indicated the probability of its universal occurrence. The results of processing meteorological data as applied to our region confirmed the correctness of these propositions.

Rhythms in fluctuations of atmospheric precipitation are characterized by 3-year and 10–23-month durations (Fig. 2). The magnitude of the maxima and minima of the 3-year rhythms amounts to 40–50% of the mean values, reaching, when the maxima of different rhythms are superimposed, 230–270%, and the minima—up to 80%.

The existence of short rhythms made it possible to regard as probable the presence of rhythms of the same duration in fluctuations of the regime characteristics of groundwater.

Figure 2 presents graphs of the rhythmicity of fluctuations in the yields of regime wells, constructed on the basis of processing tabular data by the method proposed by N. S. Tokarev (1950), which makes it possible to eliminate the influence of seasonal fluctuations.

It is not difficult to notice that, against the background of clearly expressed 3-year rhythms, a number of rhythms of shorter duration appear. Rhythms with durations of 10–21, more often 11–15 months, which form part of rhythms of greater duration, are distinguished fairly clearly.

The minima and maxima of 3-year rhythms are usually measured by values on the order of 40%, whereas short rhythms give fluctuations that, as a rule, do not exceed 10–20%. In individual cases, when oscillations of the same sign are superimposed, their sharp amplification is observed, reaching values on the order of 60%. Thus, the amplitudes of fluc—

fluctuations of regime characteristics within the limits of 3-year rhythms are usually 60–80%, reaching in individual cases 90–150%.

In fluctuations of groundwater levels, a shift of the maxima and minima of short rhythms by 2–4 months relative to the rhythms of atmospheric precipitation is observed. The shift of the medium rhythms is small in comparison with their duration, and it may be neglected.

Fig. 2. Rhythmicity in fluctuations of the yields of flowing wells.

It should be noted that there is a certain difference in the manifestation of rhythmicity for groundwaters with different types of regime. Fluctuations of the regime characteristics of the groundwater of the first aquifer from the surface (wells 913, 196) are sharper and show greater similarity with the rhythms of atmospheric precipitation in comparison with waters confined to horizons that have relatively distant recharge areas. For the latter, the maxima even of 3-year rhythms usually do not exceed the mean values by more than 25–30% (well 547, Fig. 2).

The indicated regularities should be taken into account when conducting hydrogeological investigations. Given the presence of rhythms with durations of 3 years and from 10 to 21 months, when forecasting water inflows into mine workings it is necessary to allow for the possible superposition of the maxima of different rhythms, which produces a considerable excess in the water abundance of rocks compared with average values.

The rhythmicity of fluctuations in regime characteristics becomes especially important when comparing the results of hydrogeological surveys carried out at different times, since measurements of spring discharges made at moments of maxima and minima of different rhythms may differ greatly from one another. In this case, in addition to coefficients that account for seasonal fluctuations within the hydrological year, one should introduce a coefficient for reducing spring discharges to mean monthly long-term values within the limits of the rhythms covering the period during which the hydrogeological investigations were conducted. This latter provision may substantially alter the picture of zoning the territory according to the degree of water abundance.

REFERENCES

1. M. E. Altovskii. Periodogram analysis as a method for processing long-term observational materials on the groundwater level. Methodological guide to the study of the groundwater regime. Gosgeoltekhizdat, 1954.

2. V. I. Duginov, V. A. Korobeinikov. Long-term fluctuations of the groundwater level of the Kamennaya Steppe and their relation to fluctuations of meteorological elements. Exploration and Protection of Mineral Resources, 1957, No. 8.

3. A. A. Konoplyantsev, V. S. Kovalevskii, S. M. Semenov. The natural regime of groundwater and its regularities. Gosgeoltekhizdat, 1963.

4. V. A. Korobeinikov. Rhythmicity in long-term fluctuations of the groundwater level. Problems in the study and forecasting of the groundwater regime. Nedra, 1964.

5. N. S. Tokarev. Rhythmic fluctuations of climate and their influence on the regime of surface and groundwater. Proceedings of the Laboratory of Hydrogeological Problems named after F. P. Savarenskii, Academy of Sciences of the USSR, vol. IX, 1950.