Underground water is considered to be one of the most important natural resources in Azerbaijan. Due to the differences in chemical composition, they fall into several types, such as service water, drinkable, medical waters, and waters used in various industrial sectors. 
High heat energy underground waters which temperature varies in the range from 60 to 115 C have been discovered in our country. Different types of natural environments have caused the various origin of water type and their spatial distribution. Mesozoic-Quaternary sedimentary deposits of various lithology, pervasive within the plain areas contain tremendous resources of artesian and ground waters used for everyday needs and drinking. Groundwaters are usually met within Quaternary deposits throughout the country. Due to active water exchange observed within the foothill areas, those waters occur at relatively deeper ranges. That water mineralization measures 1gr/l. and their chemical composition is referred to as the calcium-hydro carbonate type. Waterhead artesian basins have been discovered under inclined plain areas encased within Quaternary, Absheron, and Akchagil deposits within Ganja, Gazakh, Guba-Khachmaz, Garabagh, Shirvan zones, as well as within Sarmatian deposits in Nakhchivan AR. Those water mineralization measures about 1gr/l and chemical composition are referred to as calcium-hydro carbonate, and therefore they are used to supply people's needs in towns and villages, and for service purposes.
Over 1000 cold and thermal springs have been discovered in the Azerbaijan Republic. Several sanatoriums (Istisu, Galaalty, Shih spit, Surakhany) and mineral water plants (Istisu, Sirab, Badamly, Vayhir, etc) have been built up around those water springs. Mineral water's gas composition in Republic varies from carbon dioxide to hydrogen sulfide, to methane, to nitrogen and radon. Mineral waters distribution due to their gas composition is as follows: mineral waters with carbon dioxide gases were encountered within both Minor Caucasus (Msimsu, Shirlan, Turshsu) and Nakhchivan AR (Sirab, Badamly, etc), with hydrogen sulfide gases within Absheron Peninsula (Surakhany, Shih spit), Talish zone (Istisu) as well as within Great Caucasus southeast foothills (Chukhuryurd, Altyaghaj), nitrogen waters have been discovered within Astara-Lankaran (Meshasu), Salyan (Babazanan), and Masally (Arkivan) regions. Mineral waters containing radon gases have been discovered within Kalbajar (Baghirsag) and in Nakhchivan AR (Gahab). The mineral composition of those waters contains basically potassium, sodium, calcium, and hydrocarbonate, sulfur, chlorine anions. Those waters' temperature varies in the range from 4 to 65 C.