[15] In the last decades, important investigations of regional estimates and mapping of natural resources of ground waters and underground sinks in individual large regions were carried out in a number of countries. As a result of these investigations, charts of underground sinks were contrived and published, among which, we name, first of all, the charts of underground sink of the USSR territory on scale 1:5000000 (1964) and 1:2500000 (1977), chart of underground sink of Central and Eastern Europe on scale 1:1500000 (1982), and World chart of hydrogeological conditions and underground sink on land on scale 1:10000000 (1999). Charts of larger scale were contrived for specific artesian basins and hydrogeological structures.
[16] The distribution of the main quantitative characteristics of natural resources of ground waters over the territory of regions is characterized by strong inhomogeneity and differentiation by the main geological structural elements and landscape climatic zones [Vsevolozhsky, 1983; Dzhamalov, 1973; Zektser, 1973]. The most general regularity is the different character of the distribution of underground sink parameters within platform (plane) territories and mountainous folded constructions when the variations in the values of long-term absolute values range from less than 0.1 to 6.0-6.8 l s-1 and from 0.1 to 30-50 l s-1 over 1 km2, respectively. In the territory of the Former Soviet Union, more than 55% of the total volume of underground sink is formed within mountainous folded regions, approximately 42% correspond to vast spaces of plates (Russian, West Siberian, Turan), and only 3-4% of the total underground sink falls on the territory of crystalline shields.
[17] In the mountainous folded regions, the distribution of underground sinks is determined mainly by sharp variations in the types of geofiltration media and orographic increase in precipitation with increasing altitude. For example, high values of the absolute values of underground sink in Caucasus, Carpathians, and Balkans, are caused by wide spreading of penetrable fissured rocks in the mountainous folded constructions and highly penetrable psephitic sediments in depressions between mountains, which forms favorable conditions of ground water supply together with deep erosion broken topography and large amount of the atmospheric precipitation [Fidelli, 1980].
[18] The role of ground waters in the formation of water balance and water resources of the regions is characterized quantitatively by the coefficients of underground sinks and coefficients of underground supply of rivers.
[19] The coefficient of underground sink is the ratio of underground sink to atmospheric precipitation. The coefficient shows, what part of the atmospheric precipitation (usually in percent) is spent on ground water supply. Within the territory of one country, this coefficient is on the average equal to 9% and varies from 1% and less to 50% and greater. The main peculiarities of the distribution of coefficients of underground sink are determined by the influence of a complex set of natural factors, the main among which is the ratio of the atmospheric precipitation to evaporation, and the composition and thickness of the rocks in the aeration zone.
[20] Latitudinal zonality is a general feature of plane territory: coefficients of underground sink decrease from northwest to southeast from 10-20% in the zone of excessive moisture to 1% and less in the steppe and semi-desert regions. In a number of regions this regularity is distorted by anomalies: mainly by an increase in the coefficients of underground sink.
[21] Ground waters are non-uniformly used in the territory of the Russian Federation. Most widely they are used in Bryansk, Vladimir, Tver, Kaluga, Orel, Smolensk, Tula regions, Marii-El and Mordoviya republics, Belgorod, Voronezh, Kursk, Lipetsk, and Tambov regions, Krasnodar territory, Kabardino-Balkar, Chechen, Ingush, and North Osetia republics, Orenburg region, Bashkortostan, Altai territory, and Gornyi Altai republic, Tomsk, Chita regions, Krasnoyarsk territory, Buryatia republic, Amur, Kamchatka, and Sakhalin regions. The proportion of ground water use in all these regions ranges from 70 to 100%. Ground waters are poorly used in Novgorod, Archangelsk, Murmansk, Kostroma, Yaroslavl, Astrakhan, Omsk regions, in Karelia republic, where their proportion ranges from 3 to 20% [Yazvin and Zektser, 1996].
[22] At present, more than 60% of the cities in the Russian Federation have centralized sources of ground water supply. Let us consider in more detail the structural of economical drinking water supply in the largest cities of Russia (with a population greater than 250 th. people). Water supply of 34 of the total 77 such cities (44%) is performed mainly from the surface water sources (more than 90%), 24 cities (31%) are supplied with drinking water mainly (90%) by ground waters. The rest 19 cities (25%) have mixed sources of water supply [Zektser, 2001].
[23] Non-uniform use of fresh ground waters in the territory of the Russian Federation is related, first of all, to the peculiarities of hydrological and hydrogeological conditions determining the value of prognostic exploitation reserves of ground waters and possibilities of their replenishing both in the natural and distorted conditions.
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