Lack of drinking water and water scarcity in general is at present enhanced by climate change impact. It is namely felt by people in those areas of the Slovak Republic where their own natural groundwater resources are limited by geological settings. In 2018, a regional hydrogeological research project was approved in the country, targeting those areas that are the most deficient in terms of groundwater resources so far. The aim is to help the inhabitants of regions critically threatened by water shortages to face the impact of climate change. The way in which the most deficient territories within the state are to be objectively determined is based on the history of the previous balancing of water resources and hydrogeological surveys that have been carried out in the country since the 1960s.
Since 1975, regional determination of natural groundwater resources and available/utilizable groundwater resources is carried out for territorial “hydrogeological units”. These are geographically, geologically, hydrogeologically and geomorphologically defined territorial units, specially delineated for the purposes of groundwater balancing. In Slovakia, 141 such hydrogeological units were defined at that time.
The size of total natural groundwater resources at national average is currently estimated to be about 3.0 l/s/km2 in terms of specific groundwater runoff. However, as a result of environmental, technical and geological reasons combination, such a quantity cannot be sustainably used. Therefore, utilizable groundwater resources are legally defined as that part of natural groundwater resources, which can be exploited by the use of technical means (such as wells, spring sinks, drains…) on a long-term basis. Accurate calculations of utilizable groundwater resources are subjected to critical review by the Groundwater Approval Commission on the Ministry of Environment. Currently, available/utilizable groundwater resources are estimated to be approximately 55% of the total natural resources.
Approximately 83% of all available groundwater quantities in Slovakia come from 36 hydrogeological units: those where extensive accumulations of Quaternary gravelly sediments in large river valleys are found, or those formed by karstifying Triassic limestones and dolomites. Such hydrogeological units occupy 44.7% of the whole country area; second-class groundwater resources suitable only for local water supply are found in the rest of the country.
The balance sheet of utilised and utilisable groundwater resources in hydrogeological units is annually published in the Groundwater Balance Yearbook (by Slovak Hydrometeorological Institute). The spatial distribution of available groundwater resources and demands for its use is based on data collection from about 18,000 water abstraction points. For many years, the greatest unmet need of water resources in comparison to available groundwater amounts is felt in the southernmost part of central Slovakia, area mostly built by marine Miocene sediments. Therefore, the currently implemented hydrogeological surveys funded by EU cohesion funds were targeted into these areas.