Within the Basin of the River Kura the Following Hydro-Geological Regions of Groundwater

Introduction

Despite the abundance of water resources in whole in Georgia, significant negative economic changes(destabilization) are emerging in the catchment area of the KuraRiver due to the constantly increasing loads to the river system.

As known, ecological destabilization has an effect not only on the internal policy of the country, but also on international relations, as it infringes the interests, sometimes vital, of neighbouring countries. The KuraRiver basin encompasses rather large areas of four states – Turkey, Armenia, Georgia and Azerbaijan (Armenia is completely in this basin), and, hence, solution of water problems of the KuraRiver becomes of international importance. Without any doubt, due to constantly aggravation of negative effects of ecological changes, solution of the issue of ecological destabilization is becoming urgent.

At present theissue of the reconsideration of water economy policy of the country is acute (critical), the basis of which should become the complex use of surface and ground water resources envisaging, along others, both strong control of water intake and transition to water use management. With the purpose of geological and hydro-geological substantiation of such a scheme complete survey of surface and ground waters is necessary. Below is given a general description of hydro-geological conditions of the KuraBasin which should serve as a basis for the assessment of its resources.

Hydrological Peculiarities of the KuraRiver Basin

According to the geological structure and geo-morphological and hydro-geological conditions in the Eastern Georgia within the basin of the KuraRiverthe following first priority hydro-geological regions of ground-water are distinguished:

1. The pressure-water systems of the Greater Caucasus;
2. Artesian basins of eastern submergence of Trans-Caucasian intermountain trough or the Kura artesian basin;

1. The pressure-water systems, ad-artesian basins and hydro-geological bodies of the Lesser Caucasus

Within the pressure-water systems of the Greater Caucasus are distinguished the following second priority hydro-geological areas: Kazbegi-Mtatusheti (I1) and Mestia-Tianeti (I2) pressure-water systems and the area of interstitial water of Keli-Kazbegi lava flows (I3).

Within the Kura artesian basin the following artesian basins are distinguished: Kartli (II1), Alazani (II2) and Iori-Shiraki (II3) artesian basins.

Within the territory of the Lesse Caucasus are distinguished Akhaltsikhe (III1), Tbilisi (III3), Marneuli-Gardabani (III4) ad-artesian basins, Trialeti pressure-water system (III2) and Samtskhe-Djavakheti (III5) hydro-geological bodies (Fig. 1).

Intensive development of exogenous and tectonic fissuring, porosity, facies-lithologic diversity of rocks, intense rugosity, plicate (folded) and breaking (discontinuous) tectonics – all this taken together condition the richness of ground-water resources and heterogeneity water-bearing horizons and complexes distinguished by individual hydro-dynamic features and mineralization peculiarities and chemical composition of ground-waters.

Particularly important role in the accumulation and movement of ground waters play the tectonic structure and geo-morphological conditions – synclinal feature, interchange of non-watertight and retainer (water-proof) rocks, high hypsometric position of supply (feeding) areas condition wide spread of pressure water-supply horizons and complexes within the artesian basins.

Disjunctive (Alternative) transgressions, splitting the whole thickness of sedimentary deposits, in its turn, contribute to the movement of ground waters from the deep horizons into the upper ones, being favourable to hydro-geological connection (link) between them, conditioning hydro-chemical and geo-thermal anomalies in the upper floors of hydro-geological section.

Description of Main Horizons and Complexes

1.1. Water-bearing horizon of contemporary (present-day, new) alluvial sediments are developed in the vallies of the KuraRiver and its big tributaries: Liakhvi, Ksani, Aragvi, Alazani, Iori, Khrami and others. It is composed of pebbles with the sandy and sandy-uliginous filler with the layers and sand lenses, clay sand, loams and clay, encompassing flood-lands and above flood-lands river terraces. Horizon capacity varies, mainly within 3-10, seldom reaching 15 meters. Filtration coefficient (factor) amounts to 10-100, more rarely to 200-500 m/24 h.

The horizon is fed with the rivers water and at the same time, being unloaded into river, consequently – the waters of the horizon are in the hydraulic relation with the rivers waters. Water-bearing horizon is rich in water, while the water of the horizon is of high drinking quality.

On the basis of the ground waters of this horizon big water intakes of centralised economy and drinking water supply for Tbilisi and Mtskheta (on the Aragvi and Ksani rivers) Gori (on the Liakhvi river) Akhaltsikhe and Khashuri (on the Kura river) Telavi and Gurjaani (on the Alazani river), Sagaredjo and Tianeti (on the Iori river), Marneuli (on the Khrami river) and other settled areas have been constructed.

Operating (Operational) supply of the horizon varies (fluctuates) mainly within 0,2-3,0 m3/sec. Particularly large deposits (Bulachauri, Misaktsieli, Natakhtari, Saguramo) with the overall operational supplies up to 10 m3/sec., belong to the Aragvi river valley (table 12).

Underground waters are characterised with good drinking quality, low mineralization (0,3 – 0,65 g/l), hydrocarbon-calcium content; total hardness – 3-4 mg/equiv, temperature – 12-160C, pH – 6,8-7,0.

1.2. Water-bearing horizon of old quaternary alluvial and proluvial sediments is particularly widely spread within Tirifino-Mukhrani, Marneuli-Gardabani, Alazani valleys and the Iori plateau – Iori valley. The horizon is comprised of boulder pebbles, mellow (porous) conglomerates, shingle, sand, clay sand, and loam. The horizon capacity is 10-500 m.

Within the area of Tifino-Mukhrani valley – Kartli artesian basin – the water-bearing horizon is represented mainly by mellow (porous) conglomerates in the lower part of the section and pebbles with the clay and loam layers – in the upper one. Similar situation is observed in Mukhrani valley.

Because of Igoeti and Kartalini elevations the under-ground waters of the horizon are devided into two flows – Tirifino-Saltvi and Mukhrani ones. In the northern strip of the valley the Bazaleti and Ertsoi troughs form independent basins of underground waters with comparatively small capacity.

Ground waters - filtrates of the main water-way of the Kura river tributaries from the left side – after the debouchments (outflow from the gorge) overflow the depression bottom comprising of the low-penetrating conglomerates of myo-pliocene age forming high-capacity ground-water flows. In the northern part of the valley the groundwater surface sharplydeclines southwards, depositing at the depth of 10-25 meters below the soil surface. Still southwards,in parallel with the plateauing, pebbles are replaced in facies with clay and loam and downstream horizons of ground waters are formed beingdischarged (unloaded) southwards of the axial line of the depression in the form of high-capacity Degot-Urbnis-Bebnis, Mukhrani-Natakhtari group sources with the total debit over 3, 0 m3/sec.

Particularly should be stressed the presence of trough-shaped reservoir of ground-water downstream waters situated within the Mukhrani depression area and containing high quality drinking water with approximate statistical operating supplies up to 2 billion cubic meters. Mineralization of the waters varies between 0, 2-0, 3 g/l, temperature – 9-110C.

Within the area of Kartli artesian basin in the water-bearing horizon at the depth of 50-250 meters boreholes (wells) of downstream sub-artesian waters with the piezometric (pressure gradient) level from – 12 to + 10 meters have been bored.

Chemical content of the water predominantly is hydro-carbonate, calcium and sodium with the mineralization up to 1 g/l.

Old Quaternary alluvial and proluvial deposits are mostly spread in the Alazani valley within the area of the Alazani artesian basin. Here the formations of debris cones of the Alazani river tributaries make (compose) high-capacity water-bearing layer (30-500 meters) on the both banks of the river, particularly large-scale being on the left embankment and the central part of the valley (fig. 2, 3).

Presence in the section of these sediments with the facial replacing each other water-proof and non-water-tight layers create conditions for the formation of hydraulically inter-related water-bearing strata. At the tops of debris cones, mainly in the left inflows of the AlazaniRiver, where the river water and atmospheric precipitation is intensively absorbed, ground waters lie down at the depth of 10 to 60 meters. As moving the one (single) flow of ground waters become divided forming several downstream strata, however, as a whole – one so called Kvareli water-bearing horizon.

This horizon, containing about 11 water-bearing strata (layers) with the total capacity up to 90 meters, is observed, mainly along the left bank of the Alazani river and partially getting across to the right bank, lying down to the depth of 5 to 200 meters.

The debit of self flowing wells varies from 0, 2 to 165 l/sec, specific debit – 0, 1-5 l/sec, debit factor (coefficient) of water conductivity – 500-1500 m2/24 h.

Chemical water contain is hydrocarbon-sulphate-calcium-magnesium; hydrocarbon-calcium-magnesium and sodium-calcium. Mineralizationhere equals 0, 2-1, 0 g/l, hardness – 1, 8-6, 5mg/equiv,temperature – 13-16,50C, pH – 6, 5-7, 2.

The basic feeding area of Kvareli horizon is situated along the foothills of the South slope of the Main Caucasus ridge and encompasses the tops (peaks, crests) of debris cones of the AlazaniRiver left inflows.

Feeding sources of this horizon are rivers (8, 8 m3/sec), fissure and karst inflow from the southern slope of the Big Caucasus ridge, atmospheric precipitation, (3,1 m3/sec) and downstream waters underlying Apsheron-Akchagil deposits. For the assessment of the amount of feeding resources at the expense of the inflow of fissure and karst anddownstream waters of the Apsheron-Akchagil deposits, it is necessary to undertake special testing and hydro-geological and thematic work.

Within the horizon two zones of the ground water movement are distinguished: 1) zone of active movement – the area of supply characterised by sharp decrease of piezometric level of water (inclination – from 0, 006 to 0,15) and 2) zone of slow movement, occupying the central part of the basin with the inclination of the ground water surface – 0, 0001.

The area of Kvareli water-bearing horizon unloading is located in the Alazani river valley. The horizon is unloaded into the ground water through the hydro-geological openings and relatively waterproof roofing at the expense of excess pressure. This causes, on the one hand, swamping of rather big territories, and on the other – soil salination at the right bankof the Alazani river (area of Milari steppe (fig. 2) at the border with Azerbaijan.

The amount of drained water of the Alazani river equals 14 m3/sec. For the assessment of the amount of water unloaded due to the excess pressure to the direction of Azerbaijan, it is necessary that special filtration testing and thematic workis carried out.

Operational resources of ground waters of Kvareli water-bearing horizon amount to 29, 46 m3/sec. Particularly, it should be mentioned that at the boarder with Azerbaijan within the area of the right bank of the Alazani river to the depth of 50 meters the ground water of this water-bearing horizon is mineralised, with the content of salts mostly over 1, 0 g/l and, thus, useless for industrial and drinking purposes. At the same time, mineralization is increasing upstream along the strip and reaches 30-35 g/l..Chemically, the waters mostly contain chloride sodium-magnesium.

Old quaternary alluvial-proluvial sediments are widely spread also within Iori-Shiraki artesian basin in the region of Sagaredjo-Mtsvane Mindori (left bank of the Iori river).

Here within the debris cones of the Iori tributaries (Sagaredjos Khevi and Lakbe rivers) power (capacity) of pebbles with the sandy and sandy clay filler and sands reaches 100 meters.

Within the debris cones of the Sagaredjos-Khevi old quaternary alluvial and proluvial sediments are filling up the synclinal structure, the axis of which extends along the right-bank of the Iori river almost in parallel with the river-bed. They are rather abundant in water.

In the upper part of the debris cone proluvial sediments are represented by pebbles characterised with high water permeability. This is the main part of the area of ground waters feeding at the expense of precipitations and absorption of river water. Ground waters here have free surface. In the same area the main intake facility of economic and drinking water supply of Sagaredjo city is situated.

To the southwards comes the zone within which occurs gradual facial replacement of boulder-pebble sediments by sandy filler and pebbles with loamy and sand-loamy filler by clay. Thanks to this the water acquires pressure and there occurs their partial unloading in the form of group ascending springs here and there causing the soil swamping. With the help of wells it has been defined that in this strip the capacity of the described horizon varies within 37 and 72 meters, the average capacity amounting to 61,5. The waters are mainly self-emitting with the debit from 1,5 to 8,5 and specific debit from 1,5 to 13,0 l/sec. Average water conductivity value – 270 m2/24 h, filtration factor – 3,9 m/24 h, average gradient of piezometricsurface – 0,01, using (operational) resources – 27950 m3/24 h, piezometric level – from minus 3 to +4 m.

Chemical contents of the horizon waters include hydrocarbon-calcium-sodium. Mineralization does not exceed 0, 7 g/l; common hardness – 1, 8-6, 5mg/equiv., temperature – 13-140C, pH – 6, 8-7, 1. The water is suitable for economic and drinking purposes.

The horizon under the consideration is widely spread also within Marneuli-Gardabani valley, as well as in its peripheral parts and in all places is represented by weakly (feebly) sintered conglomerates with the lenses of loam and pebbles. They mainly compose plinth terraces and are characterised by rather weak sporadic watering.

In the central, submerged part of the valley in these sediments at the depth of 20 meters are circulating rather powerful Tamari, Gardabani, Kodi, Tselaskuri flows of ground waters with the total natural resources amounting to 36802 m3/24 h.The most powerful out of them are Tselaskuri and Gardabani flows with the debit of 7242 and 25258 m3/24 h respectively.

By chemical composition the waters are hydro-carbon-sulphate and sulphate-hydro carbonic calcic with the mineralization up to 1, 0 g/l and totalhardness 7-10 mg/equiv. The least mineralization (0,3-0,4 g/l) is observed in Tamari flow which is fed by the Khrami river.

1.3. Water-bearing horizon of middle-quaternary- upper-Pliocene lava cover is widely spread mainly within Samtskhe-Djavakheti volcanic plateau – hydro-geological body of interstitial waters. It is represented by dolerites, basalt, andesite, dacites; in the upper part – by interlayer and lenses of lake sands, clay sand and clay, and mellow (porous) tufa formations between the cover, and volcanic ashes. Capacity of these sediments exceeds 1000 meters. They are developed on small areas also within The Greater Caucasus at the upper reaches of the rivers Terek, Aragvi and Liakhvi, while min Adjara-Trialeti – in the canyons of the rivers Gujaretis-tskali and Borjomula.

Lava layers are characterised by high fissuring cooling and weathering, here and there being tectonic which conditions its abundance in water. Atmospheric precipitation (600-1000 mm per year) and favourable morphological conditions for leakage and condensation contribute to this as well, particularly at the central strips of lava flow.

Manifestation of ground waters at the surface of the plateau is insignificant. Powerful interstitial sources (particularly – formation) are belonging to the cornices of canyon-type gorges or to the contacts of outcrop relatively waterproof formations. The following sources belong to the last: Bejano with the debit of 390 l/sec, Ablari – 924, Ikhtila – 440, Ozni – 1085, Dashbash – 3760 l/sec and others. High debits of these sources and their stable regimes within Djavakheti plateau are conditioned by the presence of underground reservoirs of significant size, by all means playing the regulating role.

In the eastern part of Tsalki depression so called Beden lava stream goes descends towards Marneuli valley of the Khrami river occupying its middle course. Here this andesite-basalt stream submerges under the quaternary alluvial-prolluvial sediments and forms two downstream layers with the significant debit of interstitial ground waters.

Lava areas of the Kels Plateau-Kazbegi descending as far as 10-12 kilometres along the gorges of the rivers Terek, Ksani, Aragvi and Liakhvi, in the contact with underlying waterproof shale clay of Jurassic age are forming the outlet of big sources (Gudarekhi, Khorisari) with the debit of several hundred of litters per second.

Lava formations of the gorges of the Borjomula and Gujaretis-tskali, originating in Bakuriani-Gudjareti area, are stretched along 20-25 kilometres and are deposited on the old quaternary alluvial sediments having the capacity up to 100 m. To these streams are belonging big interstitial sources – so called “Melnichni” and many others.