V.V. Kurennoy, Yu.E. Tikhonenkov

All-Russian Research Institute for Hydrogeology and Engineering Geology (VSEGINGEO)

Abstract:The present article discusses results of the work performed in 2002-2004 and devoted to the common hydrogeological zoning of a territory of Russian Federation.

The purpose was the building of the unified information model of hydrogeological structures of an area of Russian Federation as a cartographical basis for a solution of federal and regional problems.

Under a term ‘zoning’ we mean here allocation of geosystems in the lithosphere.

While studying underground waters one encounters some duality. On the one hand it’s a part of a lithosphere, on another - a part of hydrosphere.

In the nature both these aspects are interconnected and are a part of the one object of studying. Nevertheless for the purposes of zoning even under a superficial (overview) studying it is reasonable to consider them separately.

Performing hydrogeological zoning it’s necessary to prepare two maps: structural - hydrogeological zoning and zoning on basins of a subsurface runoff.

Basins of a subsurface runoff are imposed on deep hydrogeological structures and are important for hydrogeological zoning since they concretize formation of resources of underground waters of a zone of free water exchange.

Structure is a geological criterion which is accepted as having priority and the scheme of structural - tectonic zoning of Russia has been put in a basis of specification of working hydrogeological zoning. At zoning on basins of an underground runoff one should take into account a morphostructure attribute, features of a modern relief of regions of free water exchange and also a character of litological sections of a zone.

Hydrogeological zoning is carried out according to the system of subordinated taxonomical units of regional zoning: a province, a subprovince, a region. To each taxonomical unit there correspond specific hydrogeological structures of the first, second and third orders.

The following basic types of hydrogeological structures are allocated:

a) Hydrogeological basins - artesian basins, artesian vaults and artesian ridges;

b) Hydrogeological massifs.

The following basic types of basin of a subsurface runoff are allocated: Continental, Midland, Regional, Complex regional, Inland, Subregional.

The work resulted in two maps of 1:2500000 scale - hydrogeological zoning and zoning on basins of a subsurface runoff.

Key words: Zoning, hydrogeological structures, Artesian basin, subsurface runoff.

Introduction

The present article discusses results of the work performed in 2002-2004 and devoted to the common hydrogeological zoning of a territory of Russian Federation and preparation of schemes of hydrogeological stratification. This task was ordered by the Ministries for natural resources of Russia and executed by the wide group of authors of many institutions under methodical supervising of VSEGINGEO. The purpose was the building of the unified information model of hydrogeological structures of an area of Russian Federation as a cartographical basis for a solution of federal and regional problems on analysis, estimation of conditions and management of the state fund of groundwater mineral resources, realization of a state monitoring of mineral resources, carrying out of estimation researches and other geological explorations.

Under a term ‘zoning’ we mean here allocation of geosystems in the lithosphere. These systems are essentially distinct one from another in the hydrogeological sense. There are two types of zoning: typological and regional. The typological zoning is based on a limited set of a priori defined criteria, each of them can acquire a certain number of values or classification taxones. Thus characteristic features of some a region could be described by its index. Using typological zoning one can group several not necessary neighboring regions having identical values of zoning criteria and give them the same name. The regional zoning is based on studying of unique configurations of properties of the object which makes its separate investigation to be reasonable. Zoning criteria don’t have well prescribed gradations or these gradations aren’t taken into account in a full manner. Under regional zoning each object is treated as being completely different from others and gets the unique index and name.

The territory of Russia has a huge variety of natural conditions. Geographically the environment varies from lowlands to high mountains. Also the climate changes from subtropics to Arctic one as well. The geological structure contains either ancient platforms together with modern systems of island-arches with an active seismic life and volcanism. Such diversity forces one to apply a regional principle of zoning. Traditionally the scale of zoning researches falls in the range 1:5000000 to 1:2500000. In this paper we use the scale 1:2500000.

Historical background

Development of principles and methods of hydrogeological zoning has a long history.

According to N.V.Rogovskaya [4] the map of hydrogeological zoning is a regional basis of hydrogeological typification of a territory. By F.P. Savarensky's opinion the concept of hydrogeological zoning is connected with the concept hydrogeological mapping. The same point of view was clamed by A.M.Ovchinnikov, S.D.Kapranov, N.A.Marinov, T.N.Fedotova. They thought that the common hydrogeological zoning is the small-scale hydro-geological mapping which means not allocating of separate aquifers but their systems.

M.M.Vasiljevsky (1940) proposed that zoning of territories should be carried out consequently through a number of stages: first stage - zoning by a geolog-structural principle; second stage (of the same importance as the first) - subsoil waters, i.e. zoning on basins of underground drains.

During development of types of hydrogeological regions also earlier accepted concepts were taken into account. The essential contribution to a conceptual base of hydrogeological zoning have been brought by M.M.Vasiljevsky, N.I.Tolstihin, G.N.Kamensky I.K.Zajtsev, L.A.Ostrovsky [1, 3, 5, etc.].

Finally the scheme of hydrogeological zoning developed under supervision of L.A.Ostrovsky [2] has been accepted as a basic one. This scheme of zoning further had been advanced (L.A.Ostrovsky, S.L.Pugach, V.V.Kurennoy).

Principles of zoning

While studying underground waters one encounters some duality. On the one hand it’s a part of a lithosphere, on another - a part of hydrosphere. It implies different aspects of scientific research. On the one hand it is possible to study hydrogeological properties of geological objects (type of interstice, permeability), on another - dynamic water-exchange systems, their connection with a surface hydrosphere (areas of recharge and discharge, a direction of motion). In the nature both these aspects are interconnected and are a part of the one object of studying. Nevertheless for the purposes of zoning even under a superficial (overview) studying it is reasonable to consider them separately.

For hydrogeological zoning two main principles are used:

a) For artesian waters - geologo-structural zoning;

b) For groundwaters - features of a modern land-forms which define spatial distribution of basins of a subsurface runoff, and also features of a section of a zone of free water exchange.

Performing hydrogeological zoning it’s necessary to prepare two maps: structural - hydrogeological zoning and zoning on basins of a subsurface runoff. Especially such an approach permits an adequate reflection of conditions of distribution and formation of groundwater of the upper and low horizons which are essentially different.

Basins of a subsurface runoff are imposed on deep hydrogeological structures and are important for hydrogeological zoning since they concretize formation of resources of underground waters of a zone of free water exchange

Structure is a geological criterion which is accepted as having priority and the scheme of structural - tectonic zoning of Russia has been put in a basis of specification of working hydrogeological zoning. At zoning on basins of an underground runoff one should take into account a morphostructure attribute, features of a modern relief of regions of free water exchange and also a character of litological sections of a zone.

Specification of types of hydrogeological structures was based on uniqueness of concepts and a choice of their main attributes (even debatable but reflecting the approaches accepted in the work). These concepts are follows:

Hydrogeological Basin- hydrogeological structures of various types: artesian basins, artesian vaults, artesian ridge, hydrogeological massifs (basins of fracture waters).

Artesian basin - the hydrogeological structure related to cavities (depression, syneclises, etc.), formed mainly by sedimentary laminated rocks, containing pore artesian waters. Artesian basins include also horizons of groundwaters distributed in its boundaries.

Artesian vault - the platform hydrogeological structure related to raisings (crest, anteclises, etc.), overlaid by mainly sedimentary laminated rocks containing pore groundwater.

Artesian ridge - the platform hydrogeological structure related to a contact zone of platform plates.

In artesian basins and vaults it is necessary to allocate the cover and the base. The cover is the mass of sedimentary rocks to which aquifers and complexes of artesian waters (usually pressure ones) are related. The base is the masses of mainly very dislocated and metamorphosed rocks underlying the cover and containing fracture waters.

Specification of types and boundaries of platform hydrogeological structures was based on features of geologic structures of the base having their reflection in a structure of a cover.

Types of hydrogeological structures of folded regions were defined in view of presence of artesian basins of the intermountain troughs formed by sedimentary laminated masses and by dividing them massifs of metamorphic dislocated rocks in which basins of groundwaters or weak-pressure waters (related to decay rocks of a zone of exogenous fracturing) are formed. In these cases boundaries are controlled by orographical factors or linear zones of tectonic fractures.

Types of hydrogeological structures of shields were defined in view of features of water-bearing of massifs of metamorphic and magmatic rocks subjected to exogenous fracturing.

Hydrogeological zoning is carried out according to the system of subordinated taxonomical units of regional zoning: a province, a subprovince, a region. To each taxonomical unit there correspond specific hydrogeological structures of the first, second and third orders.

According to this principle at separation of hydrogeological structures one takes into account: their structural - tectonic and morphostructural position, type of hydrogeological structures and type of groundwater according to a character of permeability of rocks (type of circulation of groundwaters), determining conditions and features of their formation (see Table 1).

Hydrogeological structures of platforms are characterized by primary development of artesian basins - in limits of plates and hydrogeological massifs - within the limits of boards and mountain - folded regions.

Taxonomical row of hydrogeological structures is presented in Table 2.

Results

The work resulted in two maps of 1:2500000 scale - hydrogeological zoning and zoning on basins of a subsurface runoff.

On the map of structural - hydrogeological zoning it has been allocated 161 hydrogeological structures. Detailed distribution of allocated structures on types and orders is presented in Table 4.

Now the improvement of hydrogeological zoning of Russia is under a process both on types and orders of structures within the framework of building of the hydrogeological map of Russia of

Table 1.Typification of hydrogeological structures

Table 2.Taxonomical a line of hydrogeological structures

Typification of basins of an subsurface runoff is resulted in Table 3

Table 3.Types and the basic characteristics of basins of a subsurface runoff

Table 4.Number of isolated hydrogeological structures

On the map of zoningon basins of a subsurface runoff 86 basins have been allocated. Detailed distribution isolated basins on types is presented in Table 5.

Table 5.Number of isolated basins of a subsurface runoff