Polluted water in Slovakia: worst sites, groundwater and treatment plants

Overview

How much water is within the standard and how much is not, and how we know

Surface water, 2025SHMÚ state monitoring sites on watercourses and reservoirs
- 69sites met all standards
- 91fails the standard only in indicators outside the score (mainly PAHs, salts, minerals)
- 203fails the standard for oxygen, nutrients, metals or harmful substances
Groundwater, 2025SHMÚ monitoring stations
- 298stations without an exceedance of the standard
- 289standard exceeded for other substances (often natural: iron, manganese, sulfates)
- 171substances from human activity (nitrates, pesticides, PFAS, solvents)
Treatment plants near the fishing districtstreatment plants within 2 km of the fishing district; problem = fails EU requirements or is overloaded above 100 %
- 230treatment plants with no fault found
- 35treatment plants with a problem (7 fail EU requirements, 29 overloaded)
Fishing districtsall assessed fishing districts
- 31fishing districts meet all the clean-water conditions
- 1 365others (a condition not met or data missing)

Overview of pollution of Slovak waters from public data: 294 of 363 SHMÚ state monitoring sites (81 %) failed the standard in at least one indicator in 2025. Of these, only 203 sites count towards the district scores, where oxygen, nutrients, metals or harmful substances are concerned; the rest are mainly PAHs from combustion, salts and minerals.

Details: groundwater, measured values and treatment plants

Groundwater: in 2025, 460 of 758 stations exceeded the standards, and in 171 of them it concerns substances from human activity (nitrates, pesticides, PFAS, solvents).

Namerané hodnoty podzemnej vody (2025): máme ich pre 758 staníc. Dusičnany sú nad normou 50 mg/l na 79 staniciach a ďalších 89 má 25 až 50 mg/l, škodlivé látky (kovy, pesticídy, PFAS, rozpúšťadlá) prekračujú normu na 151 staniciach. Tieto hodnoty používame pri každom revíri v skóre, vo filtroch a na mape.

Treatment plants near the fishing districts: of the 265 treatment plants we found within 2 km of the districts, 7 fail the requirements of the EU directive and 29 are overloaded above 100 % of capacity (some meet both conditions, 35 treatment plants with a problem in total).

River basins from most to least polluted

Share of SHMÚ sites that failed the standard in 2025

Map of fishing districts by pollution

Each fishing district by its nearest SHMÚ monitoring site

Detailed filtersregion, district, riverbed, depth, shading, satellites, water chemistry and pollution, fish, geology

Region

River basin

District and local SRZ organization

1445fishing districts

Pick a category to narrow the selection. Next to each option you can see how many fishing districts remain.

Map color

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Move the map with two fingers. In full-screen mode one finger is enough.

The color of the fishing district line shows the number of indicators that failed the standard at the nearest SHMÚ site (2025). Gray fishing districts have no site with the same watercourse name nearby. You can also switch the color to groundwater and treatment plants.

Worst sites on watercourses

Most failed indicators; recent years carry more weight

Zemplínske HradišteTrnávka, rkm 7.5 · Bodrog basin5 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
dissolved oxygen●standard not met●standard not met●standard not met●standard not met
COD (chemical oxygen demand)●standard not met●standard not met·standard met·standard met
Nutrients and nitrogen
ammonium●standard not met●standard not met●standard not met●standard not met
nitrites●standard not met●standard not met●standard not met●standard not met
total phosphorus●standard not met●standard not met●standard not met●standard not met
nitrates·standard met●standard not met·standard met·standard met
Harmful organic substances
AOX (adsorbable organic halogens)●standard not met●standard not met●standard not met●standard not met
petroleum substances (NEL)●standard not met·standard met·standard met·standard met
Salts, pH and minerals
calcium·standard met●standard not met·standard met·standard met
Biology and bacteria
saprobic index of biosestone●standard not met·standard met·standard met·standard met
The location of the site is only approximate (based on the water body).
Devínska Nová Ves, podMláka, rkm 0.5 · Morava basin7 indicators in 2025
Indicator2022202320242025
Nutrients and nitrogen
nitrites●standard not met●standard not met●standard not met●standard not met
total phosphorus●standard not met●standard not met●standard not met●standard not met
nitrates●standard not met●standard not met·standard met●standard not met
Harmful organic substances
AOX (adsorbable organic halogens)●standard not met●standard not met●standard not met●standard not met
octylphenol·standard met●standard not met·standard met·standard met
Salts, pH and minerals
aluminium·standard met●standard not met●standard not met●standard not met
calcium●standard not met●standard not met●standard not met·standard met
pH·standard met●standard not met·standard met·standard met
Biology and bacteria
saprobic index of biosestone●standard not met●standard not met●standard not met●standard not met
phytoplankton abundance·standard met●standard not met·standard met·standard met
chlorophyll a·standard met●standard not met·standard met·standard met
culturable microorganisms (22 °C)·standard met●standard not met·standard met·standard met
intestinal enterococci·standard met●standard not met·standard met·standard met
PAHs: 3 substances (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene·standard met●standard not met●standard not met●standard not met
benzo(ghi)perylene·standard met●standard not met·standard met·standard met
fluoranthene·standard met●standard not met·standard met·standard met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
Adamov, KopčanyUnínsky potok, rkm 2.7 · Morava basin8 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
COD (chemical oxygen demand)·standard met●standard not met●standard not met·standard met
dissolved oxygen·standard met·standard met·standard met●standard not met
Nutrients and nitrogen
nitrites·standard met●standard not met●standard not met●standard not met
total phosphorus·standard met●standard not met●standard not met●standard not met
ammonium·standard met●standard not met·standard met●standard not met
nitrates·standard met●standard not met●standard not met·standard met
total nitrogen·standard met●standard not met·standard met●standard not met
Harmful organic substances
AOX (adsorbable organic halogens)·standard met●standard not met●standard not met●standard not met
chlorpyrifos●standard not met·standard met·standard met·standard met
Salts, pH and minerals
conductivity·standard met●standard not met●standard not met●standard not met
calcium·standard met●standard not met●standard not met●standard not met
pH·standard met●standard not met·standard met·standard met
Biology and bacteria
chlorophyll a·standard met·standard met●standard not met·standard met
PAHs: 1 substance (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene·standard met·standard met●standard not met·standard met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
Nearest site for the fishing districts: Štrkovisko Unín
Topoľčny, cestný most na KrušovceBedziansky P., rkm 1.4 · Nitra basin7 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
BOD₅ (biochemical oxygen demand)–site not in the yearbook●standard not met●standard not met●standard not met
COD (chemical oxygen demand)–site not in the yearbook●standard not met●standard not met●standard not met
dissolved oxygen–site not in the yearbook●standard not met●standard not met·standard met
total organic carbon–site not in the yearbook●standard not met·standard met·standard met
Nutrients and nitrogen
total phosphorus–site not in the yearbook●standard not met●standard not met●standard not met
ammonium–site not in the yearbook●standard not met●standard not met·standard met
nitrites–site not in the yearbook●standard not met●standard not met·standard met
total nitrogen–site not in the yearbook●standard not met●standard not met·standard met
Harmful organic substances
heptachlor–site not in the yearbook●standard not met·standard met·standard met
Salts, pH and minerals
conductivity–site not in the yearbook●standard not met·standard met·standard met
calcium–site not in the yearbook●standard not met·standard met·standard met
PAHs: 4 substances (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene–site not in the yearbook●standard not met·standard met●standard not met
fluoranthene–site not in the yearbook●standard not met·standard met●standard not met
benzo(b)fluoranthene–site not in the yearbook·standard met·standard met●standard not met
benzo(k)fluoranthene–site not in the yearbook·standard met·standard met●standard not met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
The location of the site is only approximate (based on the water body).
PršaSuchá, rkm 3.1 · Ipeľ basin4 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
total organic carbon●standard not met●standard not met●standard not met·standard met
dissolved oxygen●standard not met·standard met●standard not met●standard not met
Nutrients and nitrogen
total phosphorus●standard not met●standard not met●standard not met●standard not met
nitrites●standard not met●standard not met·standard met·standard met
ammonium●standard not met·standard met·standard met·standard met
Metals
nickel●standard not met·standard met·standard met·standard met
Harmful organic substances
AOX (adsorbable organic halogens)●standard not met●standard not met●standard not met●standard not met
Salts, pH and minerals
calcium●standard not met●standard not met●standard not met●standard not met
PAHs: 1 substance (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene●standard not met●standard not met·standard met·standard met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
The location of the site is only approximate (based on the water body).
ČOV Jablonka, podČierna Orava, rkm 3.2 · Váh basin3 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
total organic carbon·standard met●standard not met●standard not met●standard not met
COD (chemical oxygen demand)·standard met●standard not met●standard not met·standard met
Nutrients and nitrogen
nitrites●standard not met●standard not met●standard not met●standard not met
Harmful organic substances
AOX (adsorbable organic halogens)●standard not met●standard not met·standard met●standard not met
Biology and bacteria
saprobic index of biosestone●standard not met●standard not met●standard not met·standard met
PAHs: 1 substance (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene●standard not met●standard not met●standard not met·standard met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
The location of the site is only approximate (based on the water body).
Kyjov, ústieKyjov, rkm 0.6 · Bodrog basin8 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
COD (chemical oxygen demand)●standard not met·standard met●standard not met·standard met
BOD₅ (biochemical oxygen demand)·standard met·standard met●standard not met·standard met
dissolved oxygen·standard met·standard met●standard not met·standard met
Nutrients and nitrogen
total nitrogen●standard not met●standard not met●standard not met●standard not met
organic nitrogen●standard not met●standard not met●standard not met●standard not met
nitrites●standard not met·standard met●standard not met●standard not met
nitrates●standard not met·standard met●standard not met●standard not met
ammonium●standard not met·standard met●standard not met·standard met
Harmful organic substances
AOX (adsorbable organic halogens)·standard met●standard not met●standard not met●standard not met
petroleum substances (NEL)·standard met●standard not met●standard not met●standard not met
total cyanides●standard not met·standard met●standard not met·standard met
Salts, pH and minerals
dissolved solids, ignited (550 °C)·standard met●standard not met●standard not met●standard not met
calcium·standard met●standard not met●standard not met●standard not met
dissolved solids (105 °C)·standard met●standard not met●standard not met·standard met
conductivity●standard not met·standard met●standard not met·standard met
chlorides●standard not met·standard met·standard met·standard met
sulfates·standard met●standard not met·standard met·standard met
Biology and bacteria
saprobic index of biosestone·standard met·standard met●standard not met·standard met
PAHs: 1 substance (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
fluoranthene●standard not met·standard met●standard not met·standard met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.
PohanskoDyje, rkm 17.0 · Morava basin9 indicators in 2025
Indicator2022202320242025
Oxygen and organic matter
COD (chemical oxygen demand)·standard met·standard met·standard met●standard not met
Nutrients and nitrogen
nitrites●standard not met●standard not met●standard not met●standard not met
total phosphorus●standard not met●standard not met●standard not met●standard not met
Harmful organic substances
AOX (adsorbable organic halogens)●standard not met●standard not met●standard not met●standard not met
Salts, pH and minerals
pH●standard not met●standard not met●standard not met●standard not met
manganese·standard met●standard not met·standard met·standard met
Biology and bacteria
phytoplankton abundance●standard not met●standard not met●standard not met●standard not met
chlorophyll a●standard not met·standard met●standard not met●standard not met
PAHs: 2 substances (not counted in the score)
Indicator2022202320242025
PAHs (combustion and deposition)
benzo(a)pyrene●standard not met●standard not met●standard not met●standard not met
fluoranthene·standard met·standard met●standard not met●standard not met
Polycyclic aromatic hydrocarbons. The standard for benzo(a)pyrene is extremely low (0.17 ng/l), so most streams exceed it; the main sources are combustion and atmospheric deposition.

standard not met
no unmet standard
site not in the yearbook

All surface waters and river basins

Worst groundwater stations

Most substances from human activity above the standard in 2025

Male RaskovceMichalovce district · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Manganese
- Total iron
- Ratio of NO3 to NO2
- Nitrates
- Conductivity at 20 °C
- TOC
- Sulfates
- Total pesticides
- Chlorides
- MCPB
- Acetochlor oxamic acid (µg/l)
- Alachlor OA
- Alachlor ESA
Measured values, year 2025, sampling 30 Oct 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates392 mg/l
- Ammonium0,28 mg/l
- Nitrites0,05 mg/l
- Iron0,21 mg/l
- Chlorides315 mg/l
- Aluminium95% of the standard
- sum of pesticides478% of the standard
Ipelsky SokolecLevice district · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Ratio of NO3 to NO2
- Ammonium
- Nitrates
- Conductivity at 20 °C
- Total pesticides
- Glyphosate
- MCPB
- Acetochlor oxamic acid (µg/l)
Measured values, year 2025, sampling 4 Nov 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates150 mg/l
- Ammonium6,19 mg/l
- Nitrites< 0.01 mg/l
- Iron0,003 mg/l
- Chlorides84,4 mg/l
- Selenium20% of the standard
- glyphosate9,000% of the standard
Moldava nad BodvouKošice district – surroundings · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Ratio of NO3 to NO2
- Nitrates
- PH
- Benzo(a)pyrene
- Sum of PCE (tetrachloroethene) and TCE (trichloroethene)
- Sum of PAHs
Measured values, year 2025, sampling 24 Sep 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates84,8 mg/l
- Ammonium0,03 mg/l
- Nitrites< 0.01 mg/l
- Iron0,034 mg/l
- Chlorides174 mg/l
- Antimony61% of the standard
- Methylbentazone60% of the standard
- sum of PCE (tetrachloroethene) and TCE (trichloroethene)727% of the standard
- benzo(a)pyrene460% of the standard
BlatneSenec district · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Ratio of NO3 to NO2
- Nitrates
- Total pesticides
- Methylbentazone
- MCPB
Measured values, year 2025, sampling 7 Oct 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates105 mg/l
- Ammonium< 0.01 mg/l
- Nitrites< 0.01 mg/l
- Iron0,012 mg/l
- Chlorides44,8 mg/l
- Aluminium85% of the standard
- Methylbentazone190% of the standard
Horna PotonDunajská Streda district · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Ratio of NO3 to NO2
- Nitrates
- Total pesticides
- Glyphosate
- Benzene
Measured values, year 2025, sampling 6 Oct 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates73,9 mg/l
- Ammonium< 0.01 mg/l
- Nitrites0,02 mg/l
- Iron0,02 mg/l
- Chlorides46 mg/l
- Chromium24% of the standard
- glyphosate8,000% of the standard
- benzene100% of the standard
ModranyKomárno district · borehole or well
substances from human activity
2017 to 2025
Exceeded in 2025:
- Ratio of NO3 to NO2
- Nitrates
- Total pesticides
- Glyphosate
- Desisopropylatrazine
Measured values, year 2025, sampling 10 Nov 2025 (2 samplings, the highest value of the year for each substance):
- Nitrates106 mg/l
- Ammonium< 0.01 mg/l
- Nitrites< 0.01 mg/l
- Iron0,013 mg/l
- Chlorides39,1 mg/l
- Chromium12% of the standard
- glyphosate15,000% of the standard

substances from human activity
natural substances only
no exceedance recorded

All groundwater and its trends

Treatment plants that cause a problem

Greatest overload and greatest discharged pollution near the fishing districts

Most overloadedload above the treatment plant's capacity

COV Podbanskecapacity 1,243 PEnear the district: Belá č. 1a267 %
COV Gabcikovocapacity 2,000 PEnear the fishing district: Dunaj č. 3 – waterworks tailrace canal, Dunaj č. 3 – waterworks feed canal and others (1)235 %
COV Tatranska Kotlina BTH1capacity 35 PEnear the fishing district: Biela č. 1, Beliansky potok and others (1)197 %
COV Hrabusicecapacity 2,500 PEpri revíre: Hornád č. 5c, Veľká Biela Voda (NP Slovenský raj) a ďalšie (2)185 %
COV Veselecapacity 1,440 PEnear the fishing district: Chtelnička, Dudváh č. 4175 %

Largest BOD₅ dischargeorganic pollution, tonnes per year

COV Ruzomberokcapacity 623,774 PEnear the fishing district: Váh č.18a, Čutkovo189 t
COV Vrakunacapacity 617,817 PEnear the district: Malý Dunaj č. 6115 t
COV Liptovsky Mikulascapacity 126,400 PEnear the fishing district: Váh č.20, Jalovecký potok and others (3)76 t
COV Koksov – Baksacapacity 175,104 PEnear the district: Hornád č. 1b72 t
COV Zilinacapacity 220,000 PEnear the fishing district: Váh č.12, Hričovský kanál č.2b and others (2)60 t

Fail EU requirementsDirective 91/271/EEC

COV Tlmacefails: BOD₅, CODnear the fishing district: Hron č. 3, VN Veľké Kozmálovce and others (2)
COV Trsticefails: BOD₅, CODnear the fishing district: Malý Dunaj č. 3, Malý Dunaj č. 2
COV Zavadka nad Hronomfails: BOD₅, CODnear the fishing district: Hron č.12, VN Závadka nad Hronom
COV Komjaticefails: BOD₅, CODnear the district: Nitra č. 2
COV Elektrosvit Vrakunfails: BOD₅, CODnear the district: Žitnoostrovské kanály č. 3

All treatment plants and polluters

What most often fails

Number of SHMÚ sites that failed the given indicator in 2025

benzo(a)pyrenePAHs (combustion and deposition)135
nitritesNutrients and nitrogen83
AOX (adsorbable organic halogens)Harmful organic substances71
total phosphorusNutrients and nitrogen66
pHSalts, pH and minerals51
fluoranthenePAHs (combustion and deposition)47
COD (chemical oxygen demand)Oxygen and organic matter43
conductivitySalts, pH and minerals32
total nitrogenNutrients and nitrogen31
nitratesNutrients and nitrogen28
dissolved oxygenOxygen and organic matter26
BOD₅ (biochemical oxygen demand)Oxygen and organic matter26

counted in the fishing district score
shown, not counted in the score

Where the data come from and what they do not say

Surface waters: yearbooks of the Slovak Hydrometeorological Institute (SHMÚ) Surface Water Quality for the years 2022 to 2025. We transcribed the list of sites and indicators that failed the standard under Government Regulation no. 269/2010 Coll. into a table in the plugin. Older yearbooks are in a different format and we did not include them.
Groundwater: SHMÚ yearbooks Groundwater Quality, stations and indicators exceeded in 2017 to 2025 according to the drinking-water limits. The connection to the fishing district is only indirect.
Groundwater, measured values: the public SHMÚ interface "Groundwater quality monitoring results". We have actually measured values (nitrates, ammonium, iron, chlorides, metals, pesticides, PFAS, solvents) for 758 stations; for each substance we take the highest value from the samples in 2025 (for stations without data for that year, from one of the two previous years). A value equal to the standard counts as an exceedance, as it does at SHMÚ.
Treatment plants: register of wastewater treatment plants (VÚVH, EEA) from the "Points near fishing districts" file, that is, only plants within 2 km of the fishing district line. There are considerably more treatment plants in Slovakia.

What this data does not say. The yearbook lists the sites that failed the standard. A site missing from it is not proof of clean water, so the score of a fishing district is only ever lowered and never raised. We did not include industrial polluters (the National Pollution Register) in the list because the register was unavailable when the data was collected, and for wastewater treatment plants we list only those we found near the fishing districts. Only 31% of SHMÚ sites have an exact location, 47% have only an approximate location (based on the water body, so they count less near the districts) and 22% have no location at all, so we do not assign them to any district. We determine the distance, the match of the watercourse name and the ranking ourselves; the assignment is indicative.