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Groundwater quality

Last update of indicator 13.12.2021

Indicator definition

The indicator describes the groundwater quality within the basic and operational monitoring.




Related policy documents and targets

Strategy of the environmental policy of the Slovak Republic - Greener Slovakia (2019)
Sustainable Use and Effective Protection of Natural Resources
Goals: A good condition and water potential of all water bodies through the restoration of river ecosystems will be accomplished.

1. Enough clean water for everyone

1.1 The prevention of water pollution

  • Illegally discharged waste water from households, commerce and services, but also from the industry or leakage from environmental burdens and agricultural activity, significantlypollute surface and ground water. Strengthening and streamlining of controls, documentation of legal waste water disposal and a threat of real effective sanctions will help limit these actions.

1.3. Elimination of adverse impacts on water courses

  • In terms of the impact on water status, there are three main groups of significant hydromorphological changes: a disruption of longitudinal connection of the rivers and the habitats, a disruption of transverse connection of wetlands and inundation with sewer and other morphological changes and hydrological changes. It is therefore essential to focus on the revitalization and re-naturalization of water courses and the adjacent riverine landscapes and to ensure the coherence of water courses, which is one of the basic conditions for the functioning of river ecosystems.
  • The prioritization of renewal of land improvement channels will be set, depending on their function and use. Land improvement channels can also drain water from areas, where it is necessary. For this reason, it will be important to assess where the operation and maintenance of channels is needed and where it is environmentally harmful.

Orientation, Principles and Priorities of the Slovak Republic Water Management Policy by 2027 (2016)


With a view to water status improvement:

  • Ensure systematic and comprehensive monitoring of waters which is necessary to obtain data and knowledge about the real status of waters, long-term development and trends for the preparation of analysis and creation of development planning and concept documents, for the evaluation of taken measures effectiveness, and the setting of new measures necessary to achieve the objectives;

In order to ensure the efficient use of water resources:

  • Identify alternative sources of groundwater. These resources should be of good quality properties, long residence time and low vulnerability. Where there are not enough good-quality groundwater resources, it is necessary to look for alternative solutions within the surface waters, for example through water supply of available water systems;

Slovak Water Plan (2016)

6.2.1. Environmental target for underground water bodies is to perform measures aimed at:

  • Preventing or limiting entry of pollutants into underground water and at preventing deterioration of the condition of underground water bodies;
  • Protection, improvement and renewal of underground water bodies and at ensuring the balance between underground water takings and completing their quantity in order to achieve the good condition of underground water until 22 December 2015 and 2021, respectively;
  • Reversing the important increasing trend of the pollutant concentration that is caused by human activities in order to decrease the underground water pollution gradually.


Strategy of SR adaptation to adverse impacts of climate change (2018)


5. Strategy objectives


To propose appropriate set of proactive adaptation measures and mechanisms to their implementation within the framework of sectoral policies, development strategies and action plans at all levels of the process;

8. Proposed adaptation measures in individual areas

8.5.3. Water management

Adaptation measures in our country should be directed to the compensation of drought manifestations, i.e. the decrease of flows and water resource yields, as well as to minimization of adverse consequences of flooding, particularly of flash floods in mountain and foothill areas. Adapting to the climate change in water management area should be focused on the implementation of measures leading to the creation of conditions for the better management of runoff in the river basin.

Water is becoming a critical strategic resource of the country which must be protected, and its efficient and effective use must be managed, in accordance with an objective to ensure the sustainable development. Rightly, the biggest attention is paid to water resources, their conservation and the need for more efficient use.

Measures to prevent degradation of water by contamination

- reducing contaminants in water bodies in accordance with the Slovak Water Plan

Key question

Have the requirements for underground water quality been met?

Key messages

  • Monitoring of groundwater chemical status in 2020 took place within the basic monitoring (175 objects) and operational monitoring (220 objects). For both types of monitoring exceedances of the set limits of pollution were recorded.
  • In order to evaluate the chemical status of groundwater bodies all quaternary and pre- quaternary bodies of groundwater were covered by the monitoring objects, with the exception of two pre-quaternary bodies. In 2020, in all quaternary water bodies there was at least one object not satisfying the requirements set out in the government regulation, where manganese and total iron were the most common non-compliant parameters, indicating the persistence of unfavourable oxidation-reduction conditions. In the 10 pre-quaternary sites, exceedances occurred for only one indicator most commonly nitrate, pH and naphthalene.
Change since 2005 Change since 2015 Last year-on-year change
emo_smile Neutralny trend Neutralny trend
Since 2007, the groundwater quality has been monitored in quaternary and pre-quaternary groundwater bodies within the basic and operational monitoring. The evaluation of the condition of underground water bodies is performed by evaluating their chemical and quantitative status.
In both types of monitoring the issues of adverse oxidation-reduction conditions. The percentage of oxygen saturation was the most frequent unsatisfactory indicator in all quaternary water bodies.
In both types of monitoring the issues of adverse oxidation-reduction conditions (increased concentrations of  Fe, Mn) stand  out.


Summary assessment

Frequency of exceeded selected indicators in the basic monitoring objects in 2020

Red - number of exceedances
Blue - number of determinations
Source: SHMI

Frequency of exceeded selected indicators in the operational monitoring objects in 2020

Red - number of exceedances
Blue - number of determinations
Source: SHMI

Frequency of exceeded selected indicators in the operational monitoring objects in 2020

Red - number of exceedances
Blue - number of determinations
Source: SHMI

Detailed assessment

Monitoring of groundwater chemical status was divided into:

  • basic monitoring,
  • operational monitoring.
Within the basic monitoring all ground water bodies were covered at least by one sampling point, with the exception of 2 bodies in which it is necessary to complete the objects of monitoring network. In 2020, the groundwater quality was monitored in 176 objects of basic monitoring. These are the objects of SHMI´s state monitoring network or the springs not affected by point sources of pollution. In 2020, the groundwater samples were collected depending on the ground type, once in 75 pre-quaternary objects, 2 times in 6 pre-quaternary objects and 41 quaternary objects, and 4 times in 54 pre-quaternary karst-fissure objects.

Frequency of breaches of permissible concentration (the highest permissible concentration) defined by the Decree of the Slovak Republic Ministry of Health (MZ SR) 247/2017 Coll., in the year 2020 in basic monitoring facilities is shown in graph no. 1. pH values were within the limits, with the exception of 16 samples, conductance exceeded the indication values 26 times out of the total of 385 assessments. Graph no. 1 implies that in ground water of basic monitoring facilities, the question of adverse redox conditions comes to the fore, of which the exceeding of total permissible concentrations of Fe (39 times), bivalent Fe (28 times), Mn (58 times), a NH4+ (13 times) are suggestive. Apart from these indicators, there was also an excess of SO42- (22 times), NO3- (13 times), Na (7 times),  CODMn (9 times), Cl- (3 times) a TOC (13 times). The concentrations of trace elements were Sb (5 times), As (4 times), Pb (6 times), Al (2 times),Ni (1 times) and Hg (1 times). Pollution by organic matters in basic monitoring facilities was only of a local character, in 2020, values exceeding the established limits in the polyaromatic hydrocarbon group were discovered for naphthalene (4 times) and acenafthen (1 time). In the aliphatic hydrocarbon group vinylchloride (3 times) and benzene (2 times). Among pesticides, in the year 2020, higher concentrations were measured of desetylatrazine (1 times). Other specific organic matters were measured to be within the limit established by the Decree of the Slovak Republic Ministry of Health (MZ SR) 247/2017 Coll.
In the operational monitoring facilities, including the area of Žitný ostrov, the values of the permissible concentration (highest permissible concentration) as defined by the Decree of the Slovak Republic Ministry of Health (MZ SR) 247/2017 Coll. in 2020 were exceeded by indicators as show in graph no. 2. The values of conductivity exceeded the indication value established by government regulation 62 times out of a total of 687 assessments, pH, with the exception of 4 samples, was within the limits. Among the most frequently exceeded indicators were Mn, total Fe, bivalent Fe, which suggests a lasting adverse state of redox conditions. Apart from these indicators, the impact of anthropogenic pollution of ground water is indicated by exceeded limits of Cl- and SO42-. The nature of land use (agriculturally utilised lands) is reflected in higher content of oxidized and reduced forms of nitrogen in ground water, the most highly contributing towards these exceeded values were NH4+ (66 times) and NO3- (60 times). In the operational monitoring facilities, in 2020, the permissible values as per the governmental decree ware exceeded in the trace element group for As (29 times), Sb (7 times), Se (3 times) and Hg (3 times). The presence of specific organic matters in ground water indicates the impact of human activity. In the operational monitoring facilities, in 2020, a wider scale of specific organic matters was recorded. The most frequent instances of exceeded limits were found among the polyaromatic hydrocarbons group (acenaphthene, naphthalene, phenanthrene, pyrene, benzo(a)pyrene (BZP)), in the deciduous aliphatic hydrocarbon group the limits were exceeded by these indicators – tetrachloroethene (PCE), the sum of PCE and TCE (trichlorethen), chlorethen and 1,2-dichloroethane (1,2 DCA). The highest concentrations of tetrachloroethene (PCE), which exceeded the limits of the decree were recorded in facility 309390 Moldava nad Bodvou in both sample collection cycles. Further in the deciduous aromatic hydrocarbons group, the limits were exceeded by dichlorobenzenes (1.2, 1.3 a 1.4). The most common pesticides above the limit values were terbutryn, desethylatrazine, prometryn, atrazine (ATZ), propikonazol, tebukonazol and the sum of pesticides (PLs represents the sum of actually recorded values of all monitored pesticides in a single analysis). The impact of anthropogenic activity on ground water quality is also expressed by higher concentrations of CODMn (16 times). In the common organic matters group the values of total organic carbon were exceeded 51 times and the limit value of the NEL index was exceeded 2 times in 2020.
As per the purpose of the monitoring program, the monitoring facilities of basic monitoring are situated in areas not impacted by human activity which is why ground water shows better quality compared to the facilities of operational monitoring which are designed so as to capture the impact of significant sources of ground water pollution.


Assessment of groundwater quality on the territory of Žitný ostrov (2019 - 2020)

The issue of unfavourable oxidation-reduction conditions comes to the fore in the monitoring of the groundwater in Žitný ostrov, as indicated by frequent elevated concentrations of total iron, manganese and ammonium ions.

The predominant nature of land use in the monitoring area (urbanised and agricultural land use) translates into elevated levels of oxidised and reduced forms of nitrogen in the waters. In addition to these indicators, the influence of anthropogenic pollution on groundwater quality is indicated by the exceeded threshold limit values of Cl- and SO42-. Exceedances of the SO42- (sulphates) threshold limit value were recorded in a total of 15 cases.

Increased concentrations of arsenic (20 times) and lead (1 time) were recorded in the trace element group in the 2019 and 2020 monitoring period. For the other monitored trace elements, no exceedance of the threshold limit values given by the Decree of the Ministry of Health of the Slovak Republic 247/2017 Coll. was recorded.

Of the pesticides, atrazine exceeded the limit concentration in 2019 (1x) in object 7215 Malinovo. In 2020, atrazine (6 times) and desethylatrazine (5 times) were the most frequent contributors to groundwater contamination. Other pesticides that exceeded the limit in 2020 include promethrin, terbutryn and tebuconazole.

Of the polyaromatic hydrocarbons, naphthalene was the most frequently exceeded concentration in both years (2019 and 2020). In 2019 - 62 times (with a maximum measured concentration above 0.700 µg/l) and in 2020 - 22 times (with a maximum concentration above 0.160 µg/l on the premises). Of the other monitored indicators in this group, the limit values for phenanthrene were exceeded (2 times in 2019). In 2019, an above-limit concentration was recorded at 605990 Čalovec - Kameničná for the parameters acenaphthene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, phenanthrene, fluoranthene, fluorene, naphthalene, pyrene and sum of polyaromatic hydrocarbons (PAHs represents the sum of the real measured values of benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene and indeno(1,2,3-c,d)pyrene).

In the group of volatile aliphatic hydrocarbons, vinyl chloride (chloroethylene) exceeded the threshold limit value set by Decree 247/2017 Coll. of the Ministry of Health of the Slovak Republic, especially in 2020.

Most of the specific  organic substances monitored were determined below the detection limit of the analytical method used.


Evaluation of the condition of underground water bodies

The evaluation of the condition of underground water bodies is performed by evaluating their chemical and quantitative conditions.
Out of the total number of 75 underground water bodies, the following bodies have been evaluated:

  • 11 underground water bodies in the bad chemical condition – 7 quaternary and 4 pre-quaternary
  • 64 underground water bodies in the good chemical condition

The good chemical condition was indicated in 85.3% of underground water bodies, i.e. 77.9% of the total area of bodies. The bad condition was indicated in 14.7% of underground water bodies, i.e. 22.1% of the total area of units.

The evaluation of the quantitative condition of underground water bodies is the assessment of the influence of documented impacts on the underground water bodies as a whole. The basic indicator of the quantitative condition of underground water bodies was determined to be the stabilized regime of the underground water level (or abundance of springs); the others included the balance evaluation of quantities of underground water and changes in the underground water regime based on the monitoring programme results. In the Slovak Republic, four underground water bodies were included in the bad quantitative condition.


Ing. Ľubica Koreňová, SAŽP,

Related definitions:

The groundwater quality is the analysis of groundwater samples, which are determined for a set of indicators listed in the Government Regulation no. 496/2010 Coll.

The groundwater body is a defined amount of ground water of hydrological collector or hydrogeological collectors.

The groundwater chemical status expresses the extent within which the water quality is affected by pollutants and it is expressed in two status classes, a good status and bad status.

Monitoring of groundwater quality constitutes a systematic monitoring and evaluation of the quality and condition of groundwater.

The basic monitoring of groundwater is carried out in the river basin districts, based on the characterization and evaluation of human activity effects and their impacts on ground water quality. The basic monitoring of the groundwater lasts at least one year during the period covered by the Slovak Water Plan. In case of  groundwater bodies in which the previous monitoring showed a good chemical status, and which at the same time are not exposed to influences that could change their chemical status to unsatisfactory, the basic monitoring of groundwater lasts at least one year during the period to which three consecutive Slovak Water Plans apply.

The operational monitoring of groundwater is conducted in all bodies or groups of groundwater bodies that are, based on their characterization, evaluation of the impacts and results of basic monitoring, identified as being at risk of failure to achieve the environmental objectives. When selecting the monitoring points, ensuring the representativeness of obtained monitored data for the whole groundwater body or group of groundwater bodies is taken into account.
(section 14 of the Decree of SR MoAERD no. 418/2010 Coll.)


Slovak Hydrometeorological Institute has been monitoring the quality of underground waters within the national monitoring program since 1982.

In the years 1995 - 2006, the quality of groundwater was assessed under STN 75 7111 in 26 important water management areas (alluvial sediments, Mesozoic, neo-volcanic complexes), created by the objects of the SHMI basic network, supplemented with drillings and springs of used and unused resources. The quality monitoring plan was annually specified in terms of water management needs and with regard to capacity possibilities and defined funds.

Sampling of groundwater along with the basic field measurements are carried out according to operating procedures for groundwater sampling and in situ measurements of parameters that have been prepared for Water Quality Testing Laboratory (SL KV), and they meet the requirements defined by the technical standards applicable in Slovakia and EU. The actual sampling within the monitoring of Slovakia´s groundwater is carried out by sampling groups of the Slovak Hydrometeorological Institute (SL KV Bratislava, Banská Bystrica, Košice and Žilina), and in Bratislava and western Slovakia by an accredited Skúšobné laboratórium Perútka s.r.o., under the instructions of geoanalytical laboratories that analyse groundwater samples.

The selection of parameters for the quality of the groundwater evaluation has been adapted to the requirements of the WFD and SR Government Regulation no.496/2010 Coll., amending and supplementing SR Government Regulation no. 354/2006 Coll., laying down requirements on water intended for human consumption and quality control of water intended for human consumption, in which the Directive 98/83/ EC is incorporated.

Chemical analyses are carried out by the accredited geoanalytical laboratories of State Geological Institute of Dionýz Štúr in Spišská Nová Ves. The overview of analytical methods with detection limits is shown in the table.

Data sources:


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