As a result of non-tectonic movements, intermountain depressions and mountain uplifts were formed. The depressions consist of weakly cemented and loose deposits, while the mountain uplifts, composed of Proterozoic and Paleozoic rocks, have undergone complex tectonic disturbances and are permeated by numerous various fractures. Groundwater is concentrated in the fractured zones, emerging as springs on the surface and being used for water supply. The main (predominant) groundwater resources in Kyrgyzstan are concentrated in the valleys. Here, groundwater is formed and utilized as a result of the infiltration of surface water flows. Unlike other mineral resources, groundwater is characterized by constantly replenished reserves, but the primary resources play a decisive role. Large intermountain depressions located in the northern regions of Kyrgyzstan are relatively rich in groundwater, while in the southern regions of the republic, the groundwater reserves are significantly smaller, which is related to less favorable conditions for groundwater accumulation in the peripheral parts of the Fergana artesian basin.
Fresh groundwater is of immense importance for the water supply of settlements, irrigation of agricultural lands, and meeting domestic, industrial, and other needs. The republic has mineral waters of all types and varieties. They are widely used for therapeutic purposes and for drinking.
Groundwater in Kyrgyzstan is used for various types of water supply, irrigation of lands, and also for balneological purposes. With the increasing practical use of groundwater, the scale of numerous hydrogeological studies has also increased. The formation of groundwater in Kyrgyzstan is determined by its location in the mountainous folded areas of the Tien Shan and Pamir-Alay. The features of hydrogeological conditions and groundwater resources of the republic are closely related to geological-structural factors, relief, and climate, as well as the influence of human engineering activities. In Kyrgyzstan, three main structural-hydrogeological levels are distinguished: the upper level, which includes pore groundwater in loose Quaternary deposits; the middle level, predominantly consisting of pore-fractured waters in semi-rock Neogene-Paleogene and Mesozoic rocks; and the lower level, consisting of fractured, less frequently fractured-vein and fractured-karst waters in Paleozoic and Proterozoic formations. Based on the combination of these levels in the latest structural forms in the modern relief, two main hydrogeological structures are distinguished — hydrogeological masses and artesian basins. In them, the features of groundwater formation and accumulation in the earth's crust, their territorial distribution, and internal redistribution along the flow path are most vividly manifested.
Hydrogeological masses represent protrusions on the surface of the lower structural-hydrogeological level, associated with folded-block uplifts — mountain ridges, where fractured groundwater (unconfined) predominates, circulating in scattered streams in the weathering zone at depths of several tens to 150-200 meters. According to structural-geological conditions within the republic, the following types of hydrogeological masses are distinguished: those composed predominantly of magmatic rocks (Küngöy, Teskey Ala-Too, Suusamyr ridges, etc.), those composed predominantly of metamorphic rocks (Talass, Zhetimbel ridges, etc.), those formed from terrigenous, carbonate, and volcanogenic rocks (At-Bashinsky, Kyrgyz, Kakshaalsky, Alai, Turkestan ridges, etc.), and those composed of sedimentary rocks (Fergana ridge). Hydrogeological masses have a deeply dissected relief, steep slopes of the talwegs, which means that the atmospheric precipitation falling here only slightly contributes to the replenishment of groundwater, with the majority flowing into river runoff. Due to this, the reserves of groundwater, both natural and operational, are relatively small here.
Artesian basins represent reservoirs of groundwater associated with complex folded-block depressions — intermountain depressions, where the upper and middle structural-hydrogeological levels are of primary importance, especially the upper one, which possesses significant resources of fresh water, most accessible for practical use. In Kyrgyzstan, several dozen basins of different levels with various accumulation conditions of the cover and different degrees of exposure of runoff are distinguished. Basins of stable subsidence have the most complete section of Paleogene-Neogene and Quaternary sediments. The thickness of the cover is 4-5 km. The thickness of only the Quaternary accumulations exceeds 300 meters. This structure of the cover creates favorable possibilities for the formation of groundwater resources. These include the Chui, Talas, Issyk-Kul, At-Bashinsky, Karavan-Kökjar, Nookat, Alai, Fergana, and Ortoalysh basins. Basins of unstable subsidence have a reduced section of Paleogene-Neogene accumulations, non-continuous distribution of Quaternary formations, with thickness rarely reaching 100 meters. These circumstances have led to limited favorable possibilities for groundwater resource formation in such basins. They include the Alabuga-Naryn, Suusamyr, Jumgal, Toguz-Toros, Toktogul, Chon-Kemin, Chatkal, Chatyr-Köl, and Ak-Sai basins. Inversion basins have a reduced section of Paleogene-Neogene deposits, with the thickness of Quaternary sediments rarely reaching 50 meters. This structure leads to unfavorable possibilities for groundwater resource formation. The basins of this type include the Son-Köl, Arpin, Kazhysay, Ara-Bel—Kum-Tör, Upper-Naryn, Sary-Jaz, Työlök, and Oktorkoy basins.
In total, about 50 artesian basins are distinguished in the territory of Kyrgyzstan, of which about 30 are large and medium-sized. As a rule, they have a three-tier structure and are divided into external, predominantly Mesozoic-Cenozoic, which developed during the latest stage against the background of folded-block subsidence, and internal-Cenozoic, which underwent a process of uplift during the Quaternary period along with hydrogeological masses. The largest resources are concentrated in external artesian basins: Chui, Issyk-Kul, Talas, Fergana (within the republic), and others. In internal basins, they are in most cases significantly smaller: Alabuga-Naryn, Toguz-Toros, Arpin, At-Bashinsky, Kochkor, Jumgal, and others.
The total volume of natural resources of fresh groundwater in the republic is 330 m3/sec. In addition, about 650 km3 of static (capacity) groundwater reserves are contained in the Quaternary water-bearing rocks, of which 300 km3 are associated with the Chui artesian basin. The percentage of utilization of explored reserves varies across different deposits. The total operational water withdrawal of groundwater is 5.2 million m3/day, of which 2.0 million is for domestic drinking consumption, 2.3 million for land irrigation, 0.8 million for industrial-technical consumption, and 0.1 million for pasture drainage. Among the groundwater of Kyrgyzstan, a large group of thermal mineral waters stands out due to their composition and temperature, which are suitable for use as therapeutic, energy, or industrial waters. The total number of occurrences and deposits of such waters in the republic is close to 150 (see article on Mineral Waters).
Mineral waters — underground (less frequently — surface) waters characterized by an increased content of biologically active mineral (less frequently — organic) components and possessing specific physicochemical properties (radioactivity, etc.), on which their effect on the human body and therapeutic application are based. Artificially prepared mineral waters are also used for therapeutic purposes.
Among Turkic-speaking peoples, natural waters with healing properties are called "arashan" or "arasan." They visually differ from the variety of natural waters by temperature and gas emissions. The people inhabiting the territory of Kyrgyzstan have used the healing properties of mineral waters since ancient times.
In Kyrgyzstan, there are more than 250 natural and artificial (well) occurrences of mineral waters. Of the 40 types of mineral waters identified in practical resortology, 30 have been found in Kyrgyzstan, as well as another 10 types that have no close analogs. Mineral waters containing an increased amount (compared to fresh waters) of salts and gases possess specific properties (temperature, radioactivity, etc.) that determine their therapeutic effect.
In accordance with the definition provided above, the following criteria for the evaluation of mineral waters have been developed and implemented in practice.
All mineral waters in Kyrgyzstan, depending on their chemical composition, properties, and therapeutic significance, are classified into the following balneological groups: saline waters and brines, carbonated, siliceous thermal, radon, sulfide, iron, and iodide-bromine.
Saline waters and brines. Mineral waters have an extremely wide range of mineralization (from 1 g/l to saturated brine salts of 500-600 g/l), with the gas composition mainly consisting of nitrogen and methane, while the ionic composition is dominated by SO4 2-, Cl-, Na+, and less frequently Ca2+ and Mg2+. The types belonging to this group are widespread in platforms and artesian basins, in the structure of which powerful layers of sedimentary rocks participate. They are especially abundant in artesian basins composed of salt-bearing formations. They are found in all intermountain artesian basins of Kyrgyzstan. They are associated with halogenic formations, predominantly with glauberite mineralization. The chemical composition is dominated by Na+, SO4 2-, and Cl-. Their mineralization ranges from 10 to 250-350 g/l. The main representatives of saline waters and brines are the mineral water deposits of certain areas along the shores of the Issyk-Kul artesian basin, uncovered by wells at depths of over 1000 m, with maximum mineralization (in Neogene deposits) of 64 g/l; the Bishkek mineral water deposit in the central part of the Chui depression with a mineralization of 50.0 g/l; Zhyrgalan — 138 g/l; Tuz — 253 g/l (Leilek district); Uch-Kashka — Chaar-Kuduk — 200 g/l; Uch-Terek (Ketmen-Tyobon valley) — 346 g/l, and others. Saline waters and brines have high therapeutic properties; they are used for drinking treatment (when diluted), baths, pools, and other balneological procedures, as well as for extracting useful components and their compounds (sodium chloride, iodine, bromine, sodium, etc.) and preparing a wide range of medicinal products.
Carbonated waters. Natural waters with various ionic compositions, mineralization, and temperatures, containing at least 0.75 g/l of carbon dioxide (CO2). Among the mineral waters used for therapeutic purposes, the group of carbonated waters is one of the most important and effective groups. For their use as drinking therapeutic and therapeutic-table waters, the CO2 content must be at least 0.5 g/l. Carbonated waters constitute one of the most extensive provinces of mineral waters, with a planetary distribution. In terms of geostructure, the occurrences of these waters are associated with areas of recent volcanism and intense mountain formation. Both shallow tectonic disturbances and large regional faults play a significant role in the formation of carbonated waters. Currently, about 30 deposits and occurrences of carbonated waters containing free carbon dioxide in amounts of 500 mg/l or more are known in Kyrgyzstan. Most of them are located in the Fergana ridge: in the basin of the river Jazy (areas of Arkar-Shoro, Baibiche, Zhol-Chabay, Kara-Shoro, Konur-Tyobon, Kök-Jar, Kulubek, Chon-Chabay, etc.), in the basin of the river Tar (areas of Kulun, Syok, Terek, Tyuz-Ashuu), in the basin of the river Arpa (Karakol, Kyzyl-Beles), in the basin of the river Kara-Kulja (Karakol, Kara-Kulja, Suuk-Tör, Sur-Tash, Shilbili), in the Ak-Sai valley and its mountainous surroundings (Besh-Belchir—Arashan, Köl-Suu, Usyolok, Chatyr-Köl), in the Jumgal valley (Kara-Keche, Chamyndy, Beyshen-Sai), in the Issyk-Kul valley (Tuura-Suu, Ulakol, Arabel). Mineralization ranges from 1.8 to 40 g/l. In terms of chemical composition, they are bicarbonate calcium, bicarbonate magnesium-calcium, and bicarbonate sodium waters. They have high therapeutic properties and are close analogs to the widely known therapeutic-table waters of Borjomi, Essentuki, Narzan, Arzni, and others. Currently, carbonated waters from Besh-Belchir—Arashan, Kara-Shoro, and Ak-Suu are bottled on an industrial scale. The industrial reserves of carbonated waters in Kyrgyzstan are classified as category B — 104 m3/day, C1— 69 m3/day, and C2— 50 m3/day.
Siliceous thermal waters. Natural warm and hot alkaline waters with low mineralization (from 0.4 to 2.0 g/l) with sodium predominating in the cation composition, with a high content of silicic acid (from 50 to 60 mg/l) and high alkalinity (pH more than 8.6). In addition to silicic acid, these waters often contain anomalous amounts of fluorine (up to 10-15 µg/l), as well as a number of other microcomponents. Their temperature ranges from 20 to 100°C. They are mainly distributed in the Southern, Central, and Northern Tien Shan. Thermal waters are found in the territories of sanatoriums and balneological clinics of the republic: Issyk-Ata, Alamyudun, Ak-Suu (Teploklyuchenka), Jalal-Abad, Altyn-Arashan, Boz-Uchuk, Juu-Kuchak, Keregetash, Zhoopai, Chayek, and others. A large number of occurrences of siliceous mineral waters are associated with regional faults in acidic Paleozoic intrusions, forming so-called "thermal lines." In the republic, two such hydrothermal lines are known: on the northern slopes of the Kyrgyz Ala-Too and Teskey Ala-Too ridges. On these thermal lines are located the occurrences of well-known deposits of siliceous thermal waters in Kyrgyzstan: Kara-Balta, Alamyudun, Issyk-Ata, Tuyuk (on the Kyrgyz Ala-Too ridge), Jeti-Oguz, Chon-Kyzyl-Suu, Keregetash, Ak-Suu (Teploklyuchenka), Boz-Uchuk (on the Teskey Ala-Too ridge). The most characteristic representative of siliceous thermal waters in Kyrgyzstan is the mineral water of Issyk-Ata. Here, nitrogen weakly mineralized siliceous thermal waters of chloride-sulfate sodium composition with a mineralization of 0.25 g/l are discharged. The water is colorless, alkaline, contains nitrogen, fluorine, and silicic acid. It is used for bathing and is also recommended for treatment. Indications for treatment include diseases of the musculoskeletal system, nervous system, and gynecological diseases. Siliceous thermal waters are also recommended for drinking treatment and as an unconventional natural mineral raw material for obtaining a wide range of medicinal products (for dentistry, gynecology, dermatology, etc.).
Radon waters. Waters with a radon concentration of more than 5 nCi/l (1 nCi/l = 10 eman = 2.8 Mache units) are classified as radon waters. They are widely distributed in nature and are distinguished as a separate province of mineral waters, in which the therapeutic action of radon is combined with the therapeutic properties of other components or properties (CO2, mineralization, temperature, pH, etc.). They are formed in zones of tectonic faults, characterized by the presence of radioactive mineralization. The surface occurrences of radon waters are controlled by deep faults. In the Chui depression, they are associated (Kara-Balta mineral waters) with the Karakol deep fault, in the Issyk-Kul basin (Jeti-Oguz, Keregetash mineral waters, etc.) — with the Central-Teskey fault. The main deposit is Jeti-Opuz, located on the northern slope of the Teskey Ala-Too ridge, 30 km southwest of the city of Karakol, 25 m from the shore of Lake Issyk-Kul. They are unique in hydrogeological and balneological indicators. The water temperature is 20-44°C. Mineralization is 0.9-13 g/l. In terms of chemical composition, they are chloride-sodium-calcium. The radon content ranges from 10 to 100 nCi/l or more. The approved reserves of radon waters amount to 43 m3/day, of which only about 90 m3/day or 20% are used for direct therapeutic purposes. They are effective in treating nervous, gynecological, and other diseases. According to some studies, the weak radon (5-14 nCi/l) thermal springs of Kyrgyzstan include the sources of Kara-Balta, Kökömeren, Tuura-Suu, and Ak-Suu (Teploklyuchenka).
Sulfide waters. Natural waters of various mineralization and ionic composition, containing more than 10 mg/l of hydrogen sulfide. They are used for therapeutic purposes. They are found in stratified Paleogene and Neogene deposits of the Fergana depression (Kairagach, Ak-Saray, Chon-Kara, Rishtan, Changyr-Tash, Mayluu-Suu, Kyzyl-Zhar) and in heavily displaced siliceous-mica schists of the Silurian (the Kara-Dyobyo area on the southwestern slope of the Fergana ridge). They are among the most valuable in balneology. The sulfide waters of Kyrgyzstan are analogous to those of Sochi's Matsesta (H2S = 50-400 mg/l). The waters of the Rishtan area with a mineralization of 3-6 g/l, having a chloride-sulfate calcium-sodium composition, contain 50-110 mg/l of total hydrogen sulfide (H2S). The flow rate of the source is more than 4 l/sec. The water from the Kyzyl-Zhar area is bicarbonate-chloride sodium with a mineralization of 4-5 g/l, containing 175-240 mg/l of H2S. The water from the Chon-Kara area is chloride-sodium with a mineralization of 24 g/l, with a hydrogen sulfide concentration of 480 mg/l. The water in the Changyr-Tash area is sulfate-chloride sodium-calcium with a mineralization of 10-31 g/l, characterized by a hydrogen sulfide content of 550 mg/l.
Iron waters. Waters of various ionic compositions, mainly weakly or moderately mineralized. From a balneological point of view, they are waters containing total iron (Fe2+ + Fe3+) in the amount of 20 mg/l. They are used for therapeutic purposes. In the upper reaches of the river Jazy, about a dozen groups of carbonated water sources containing an increased concentration of dissolved iron emerge over an area of about 3000 km2, along with several groups of purely iron springs. The highest iron content (45 mg/l) has been recorded in a natural occurrence located in the Sabay area, Arkar-Shoro (at an altitude of 2870 m above sea level), 2 km northeast of the confluence of the rivers Chytty and Jazy. A group of small streams of iron water from the Tuyuk formation of Lower Jurassic age. The water temperature is 7.6°C. In terms of chemical composition, it is bicarbonate calcium-iron, with a mineralization of 180 mg/l and a dissolved carbon dioxide content of 88 mg/l. Many sources with increased iron content are found in the valleys of Chon-Chabay, Zhol-Chabay, Chon-Agatan (iron concentration reaches 10-20 mg/l), Maks, and iron content in the groundwater of Kyrgyzstan has been noted during the testing of well No. 7 at the Kara-Shoro deposit (depth 80 m). In terms of composition, it is chloride sodium with a mineralization of about 25 g/l. Bitter-salty in taste. The iron content is 120 mg/l. In the basin of the river Chamyndy (Jumgal depression), three groups of springs are distinguished, in which the iron content is 3 mg/l. In terms of chemical composition, they are sulfate calcium.
Currently, none of the iron springs are used, although they could be a means for treating anemia, which is widespread among the population of the republic.
Iodide-bromine waters. Mineral waters containing at least 5 mg/l of iodine and at least 25 mg/l of bromine with varying mineralization and temperature; used for therapeutic purposes. In Kyrgyzstan, these waters are associated with oil-bearing structures of the foothills of the Fergana depression. They have been found in mineral waters uncovered by deep wells in the Issyk-Kul and Naryn valleys. The largest amounts of these waters have been recorded near the town of Mayluu-Suu and the village of Kochkor-Ata in the Jalal-Abad region, with iodine content of 6-25 mg/l and bromine of 3-390 mg/l. They are characterized by a mineralization of 115 g/l. The water temperature is above 50°C (at a depth of 3-4 km). In the hydrotherapy clinic of the village of Kochkor-Ata (Jalal-Abad region), water from well No. 14 is used. The waters are chloride sodium with a mineralization of 55 g/l; they contain more than 10 mg/l of iodine and 160 mg/l of bromine. The water temperature is 44°C. In terms of composition, the water is analogous to the widely known Maikop therapeutic water. Well No. 200 was drilled to a depth of 3000 m. It is located north of the village of Kochkor-Ata. The temperature is 55°C, and in terms of chemical composition, it is chloride sodium. The water contains bromine (204 mg/l) and iodine (5.76 mg/l). During testing, the well produced more than 1200 m3/day.
