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Groundwater

Groundwater pollution

Monitoring stations
758
With an exceedance, 2025 (61 %)
460
Substances from human activity (23 %)
171
Years in the yearbooks
9

Groundwater

SHMÚ monitoring, 2017 to 2025

  • 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)

Groundwater is a source of drinking water and, in dry periods, also the main source of water in watercourses. Of 758 SHMÚ monitoring stations, 460 exceeded the standard in at least one indicator in 2025. Natural substances (iron, manganese, sulfates, conductivity) are often a result of geology. For pollution, nitrates, pesticides, PFAS and chlorinated solvents that got into the water from human activity are more important.

The link to the fishing district is indirect: groundwater reaches watercourses as baseflow. That is why it counts only weakly towards the district score: a typical value from stations within 10 km (nitrates, harmful substances, ammonium, iron, chlorides) multiplied by data reliability is used. Where measured values are missing, the yearbook is used, i.e. whether most of the surrounding stations exceed limits for substances from human activity.

Measured values, 2025

Actual figures from SHMÚ stations, not just exceedances

The yearbooks list only the indicators that exceeded the standard. Besides these, SHMÚ also publishes the actual measured values, so you can also see how far a site is from the standard. We have them for 758 of 758 stations (last year with measurements: 2025; for stations without data for the last year, one of the two preceding years is used).

Nitrates are above the standard of 50 mg/l at 79 stations (10 %), and a further 89 (12 %) have 25 to 50 mg/l. Harmful substances (metals, pesticides, PFAS, solvents) exceed the standard at 151 stations, ammonium or nitrites at 86. 363 stations (48 %) are within the standard for everything that counts towards the district scores.

For each fishing district we take a typical value from stations within 10 km (a closer station has more weight) and use it in the score, in the “Water pollution” filter, in the ordering of districts and in the map colours. A value equal to the standard counts as an exceedance, as in SHMÚ.

Nitratesnumber of stations by measured value

  1. below 25 mg/l590 from 75878 %
  2. 25 to 50 mg/l89 from 75812 %
  3. from 50 mg/l (standard)79 from 75810 %

Nitrates by regionshare of stations from 25 mg/l

  1. Bratislava14 from 8117 %
  2. Trnava33 from 12626 %
  3. Trenčín15 from 7021 %
  4. Nitra49 from 11742 %
  5. Žilina7 from 759 %
  6. Banská Bystrica12 from 9712 %
  7. Prešov5 from 707 %
  8. Košice33 from 11928 %
  • nitrates above the standard (from 50 mg/l)
  • nitrates from 25 mg/l

What exceeds the standardnumber of stations out of 758

  1. Iron from 1 mg/l138
  2. Ammonium or nitrites86
  3. Pesticides74
  4. Metals and metalloids55
  5. Solvents and benzene32
  6. Chlorides from 230 mg/l17
  7. PAHs (combustion, petroleum substances)11
  8. PFAS (“forever chemicals”)2
  • counted in the fishing district score
  • shown, not counted in the score

Map of fishing districts by nitrates in groundwater

Typical value from stations within 10 km of the fishing district

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

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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The colour of the district line shows typical nitrates in groundwater within 10 km of the fishing district (mg/l, SHMÚ measurement from 2025). The drinking water standard is 50 mg/l. You can also switch the colour to harmful substances in groundwater, surface water and treatment plants.

Stations with the highest nitrates

Highest value measured in 2025 (ranked by mg/l)

  • KiarovVeľký Krtíš district · borehole or well
    nitrates above the standard and more (2)

    Measured values, year 2025, sampling 23 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates640 mg/l
    • Ammonium0,11 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,003 mg/l
    • Chlorides433 mg/l
    • Aluminium20 % of standard
    • glyphosate18,000 % of standard
  • TupaLevice district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampled 10 Jul 2025:

    • Nitrates461 mg/l
    • Ammonium0,03 mg/l
    • Nitrites0,02 mg/l
    • Iron0,089 mg/l
    • Chlorides45 mg/l
    • Arsenic19 % of standard
    • glyphosate11,000 % of standard
  • Male RaskovceMichalovce district · borehole or well
    nitrates above the standard and more (2)

    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 standard
    • sum of pesticides478 % of standard
  • TonKomárno district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampling 22 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates374 mg/l
    • Ammonium0,2 mg/l
    • Nitrites0,08 mg/l
    • Iron0,065 mg/l
    • Chlorides167 mg/l
    • Nickel25 % of standard
    • glyphosate9,000 % of standard
  • Streda nad BodrogomTrebišov district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampling 8 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates285 mg/l
    • Ammonium14,2 mg/l
    • Nitrites0,05 mg/l
    • Iron0,11 mg/l
    • Chlorides134 mg/l
    • Nickel50 % of standard
  • Palarikovo-ludovitovNové Zámky district · borehole or well
    nitrates above the standard

    Measured values, year 2025, sampled 6 May 2025:

    • Nitrates277 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,02 mg/l
    • Iron0,002 mg/l
    • Chlorides161 mg/l
    • Arsenic5 % of standard
  • OravkaRimavská Sobota district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampling 21 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates249 mg/l
    • Ammonium0,03 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,014 mg/l
    • Chlorides120 mg/l
    • Aluminium15 % of standard
    • atrazine130 % of standard
  • JatovNové Zámky district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampled 6 May 2025:

    • Nitrates246 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,07 mg/l
    • Iron0,007 mg/l
    • Chlorides271 mg/l
    • Nickel15 % of standard
  • DiakovceŠaľa district · borehole or well
    nitrates above the standard

    Measured values, year 2025, sampling 9 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates244 mg/l
    • Ammonium0,03 mg/l
    • Nitrites0,12 mg/l
    • Iron0,006 mg/l
    • Chlorides47,8 mg/l
    • Aluminium85 % of standard
  • Velke LudinceLevice district · borehole or well
    nitrates above the standard

    Measured values, year 2025, sampling 8 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates206 mg/l
    • Ammonium0,01 mg/l
    • Nitrites0,01 mg/l
    • Iron0,005 mg/l
    • Chlorides105 mg/l
    • Chromium14 % of standard
  • SvodinNové Zámky district · borehole or well
    nitrates above the standard

    Measured values, year 2025, sampled 12 May 2025:

    • Nitrates205 mg/l
    • Ammonium0,03 mg/l
    • Nitrites0,05 mg/l
    • Iron< 0.002 mg/l
    • Chlorides148 mg/l
    • Aluminium10 % of standard
  • MuzlaNové Zámky district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampling 30 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates175 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,01 mg/l
    • Iron0,006 mg/l
    • Chlorides82,7 mg/l
    • Aluminium70 % of standard
    • glyphosate6,000 % of standard
  • above the standard: nitrates from 50 mg/l, harmful substances or ammonium
  • nitrates from 25 mg/l, iron or chlorides high
  • within the standard

For each substance the value is the highest of the samples in the given year. A value equal to the standard counts as an exceedance, as in SHMÚ.

Stations with harmful substances above the standard

Metals, pesticides, PFAS or solvents above the standard, the most groups of substances at the top

  • Bratislava – Vlcie HrdloBratislava II district · borehole or well
    harmful substances above the standard

    Measured values, year 2025, sampling 15 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates< 1 mg/l
    • Ammonium0,06 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,033 mg/l
    • Chlorides101 mg/l
    • Aluminium15 % of standard
    • Methylbentazone110 % of standard
    • chloroethene (vinyl chloride)2,560 % of standard
  • Dvorniky na OstroveDunajská Streda district · borehole or well
    harmful substances above the standard

    Measured values, year 2025, sampling 30 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates15,1 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,018 mg/l
    • Chlorides17,6 mg/l
    • Aluminium15 % of standard
    • glyphosate6,000 % of standard
    • chloroethene (vinyl chloride)300 % of standard
  • HoliceDunajská Streda district · borehole or well
    harmful substances above the standard and more (1)

    Measured values, year 2025, sampling 16 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates25,5 mg/l
    • Ammonium0,03 mg/l
    • Nitrites0,02 mg/l
    • Iron0,026 mg/l
    • Chlorides31,8 mg/l
    • Aluminium15 % of standard
    • glyphosate9,000 % of standard
    • chloroethene (vinyl chloride)360 % of standard
  • Horna PotonDunajská Streda district · borehole or well
    nitrates above the standard and more (1)

    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 standard
    • glyphosate8,000 % of standard
    • benzene100 % of standard
  • Jasenie – Zo StolyBrezno district · source
    harmful substances above the standard

    Measured values, year 2025, sampled 24 Jul 2025:

    • Nitrates3,7 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron< 0.002 mg/l
    • Chlorides< 1 mg/l
    • Arsenic144 % of standard
    • chloroethene (vinyl chloride)300 % of standard
  • JelkaGalanta district · borehole or well
    harmful substances above the standard

    Measured values, year 2025, sampling 6 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates11,4 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,02 mg/l
    • Iron0,024 mg/l
    • Chlorides42,2 mg/l
    • Aluminium20 % of standard
    • glyphosate5,000 % of standard
    • chloroethene (vinyl chloride)1,280 % of standard
  • KalinkovoSenec district · borehole or well
    harmful substances above the standard and more (2)

    Measured values, year 2025, sampling 17 Nov 2025 (4 samplings, the highest value of the year for each substance):

    • Nitrates3 mg/l
    • Ammonium1,29 mg/l
    • Nitrites< 0.01 mg/l
    • Iron1,58 mg/l
    • Chlorides19,2 mg/l
    • Arsenic412 % of standard
    • MCPB100 % of standard
    • Sum of PFAS (20 selected indicators)40 % of standard
  • KomarnoKomárno district · borehole or well
    harmful substances above the standard and more (1)

    Measured values, year 2025, sampling 27 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates37 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,11 mg/l
    • Chlorides21 mg/l
    • Arsenic153 % of standard
    • chloroethene (vinyl chloride)3,520 % of standard
  • Opatovce nad NitrouPrievidza district · borehole or well
    harmful substances above the standard and more (2)

    Measured values, year 2025, sampling 30 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates< 1 mg/l
    • Ammonium0,58 mg/l
    • Nitrites0,01 mg/l
    • Iron12,4 mg/l
    • Chlorides14,1 mg/l
    • Arsenic193 % of standard
    • clopyralid20 % of standard
    • chloroethene (vinyl chloride)2,660 % of standard
  • RybnikLevice district · borehole or well
    nitrates above the standard and more (1)

    Measured values, year 2025, sampling 29 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates92,8 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,02 mg/l
    • Iron0,002 mg/l
    • Chlorides34,6 mg/l
    • Arsenic100 % of standard
    • chloroethene (vinyl chloride)3,400 % of standard
  • Ulany nad Zitavou – D. OhajNové Zámky district · borehole or well
    harmful substances above the standard and more (1)

    Measured values, year 2025, sampling 14 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates< 1 mg/l
    • Ammonium0,2 mg/l
    • Nitrites0,01 mg/l
    • Iron8,09 mg/l
    • Chlorides58,4 mg/l
    • Arsenic268 % of standard
    • desisopropylatrazine120 % of standard
  • Vysne ValiceRimavská Sobota district · borehole or well
    harmful substances above the standard and more (3)

    Measured values, year 2025, sampled 16 Jul 2025:

    • Nitrates2,4 mg/l
    • Ammonium10 mg/l
    • Nitrites0,02 mg/l
    • Iron1,37 mg/l
    • Chlorides447 mg/l
    • Arsenic134 % of standard
    • benzene230 % of standard

The value for a substance is the highest share of the standard in its group. The standards are set for drinking water and are stricter than the limits harmful to fish; metals can also come from rocks.

Trend since 2017

Share of stations exceeding the standard

  1. 201779 from 27510 %
  2. 201876 from 27110 %
  3. 201994 from 30112 %
  4. 2020111 from 31215 %
  5. 202186 from 28911 %
  6. 2022112 from 42215 %
  7. 2023178 from 47023 %
  8. 2024157 from 46521 %
  9. 2025171 from 46023 %
  • stations with substances from human activity
  • stations with any exceedance (including natural substances)

By region

Stations with substances from human activity above the standard in 2025

  1. Bratislava25 from 8131 %
  2. Trnava48 from 12638 %
  3. Trenčín7 from 7010 %
  4. Nitra51 from 11744 %
  5. Žilina10 from 7513 %
  6. Banská Bystrica14 from 9714 %
  7. Prešov2 from 703 %
  8. Košice14 from 11912 %

Worst 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 standard
    • sum of pesticides478 % of 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 standard
    • glyphosate9,000 % of 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 standard
    • Methylbentazone60 % of standard
    • sum of PCE (tetrachloroethene) and TCE (trichloroethene)727 % of standard
    • benzo(a)pyrene460 % of 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 standard
    • Methylbentazone190 % of 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 standard
    • glyphosate8,000 % of standard
    • benzene100 % of 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 standard
    • glyphosate15,000 % of standard
  • Dvorniky na OstroveDunajská Streda district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Total pesticides
    • Glyphosate
    • Chloroethene (vinyl chloride)
    • Chlormequat

    Measured values, year 2025, sampling 30 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates15,1 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,018 mg/l
    • Chlorides17,6 mg/l
    • Aluminium15 % of standard
    • glyphosate6,000 % of standard
    • chloroethene (vinyl chloride)300 % of standard
  • Calovec – KamenicnaKomárno district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Total iron
    • Ammonium
    • Conductivity at 20 °C
    • TOC
    • Sulfates
    • Total pesticides
    • Glyphosate
    • Hydroxyterbuthylazine

    Measured values, year 2025, sampling 14 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates< 1 mg/l
    • Ammonium0,68 mg/l
    • Nitrites0,02 mg/l
    • Iron4,45 mg/l
    • Chlorides241 mg/l
    • Aluminium20 % of standard
    • glyphosate9,000 % of standard
  • KiarovVeľký Krtíš district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Ratio of NO3 to NO2
    • Nitrates
    • Conductivity at 20 °C
    • Sulfates
    • Total pesticides
    • Glyphosate
    • Chlorides
    • Magnesium

    Measured values, year 2025, sampling 23 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates640 mg/l
    • Ammonium0,11 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,003 mg/l
    • Chlorides433 mg/l
    • Aluminium20 % of standard
    • glyphosate18,000 % of standard
  • BrestovanyTrnava district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Total iron
    • Conductivity at 20 °C
    • TOC
    • Sulfates
    • Total pesticides
    • Terbutryn
    • Prometryn

    Measured values, year 2025, sampling 9 Sep 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates< 1 mg/l
    • Ammonium0,27 mg/l
    • Nitrites0,02 mg/l
    • Iron4,99 mg/l
    • Chlorides139 mg/l
    • Arsenic59 % of standard
    • prometryn220 % of standard
  • TonKomárno district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Ratio of NO3 to NO2
    • Nitrates
    • Conductivity at 20 °C
    • TOC
    • Sulfates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampling 22 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates374 mg/l
    • Ammonium0,2 mg/l
    • Nitrites0,08 mg/l
    • Iron0,065 mg/l
    • Chlorides167 mg/l
    • Nickel25 % of standard
    • glyphosate9,000 % of standard
  • TupaLevice district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Ratio of NO3 to NO2
    • Nitrates
    • Conductivity at 20 °C
    • Sulfates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampled 10 Jul 2025:

    • Nitrates461 mg/l
    • Ammonium0,03 mg/l
    • Nitrites0,02 mg/l
    • Iron0,089 mg/l
    • Chlorides45 mg/l
    • Arsenic19 % of standard
    • glyphosate11,000 % of standard
  • TonKomárno district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Conductivity at 20 °C
    • TOC
    • Sulfates
    • Total pesticides
    • Glyphosate
    • Methylbentazone

    Measured values, year 2025, sampling 20 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates18,6 mg/l
    • Ammonium0,11 mg/l
    • Nitrites0,03 mg/l
    • Iron0,048 mg/l
    • Chlorides46,3 mg/l
    • Nickel20 % of standard
    • glyphosate9,000 % of standard
  • OravkaRimavská Sobota district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Ratio of NO3 to NO2
    • Nitrates
    • Conductivity at 20 °C
    • TOC
    • Chlormequat
    • Atrazine

    Measured values, year 2025, sampling 21 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates249 mg/l
    • Ammonium0,03 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,014 mg/l
    • Chlorides120 mg/l
    • Aluminium15 % of standard
    • atrazine130 % of standard
  • MuzlaNové Zámky district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Ratio of NO3 to NO2
    • Nitrates
    • Conductivity at 20 °C
    • Sulfates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampling 30 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates175 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,01 mg/l
    • Iron0,006 mg/l
    • Chlorides82,7 mg/l
    • Aluminium70 % of standard
    • glyphosate6,000 % of standard
  • MocaKomárno district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Ratio of NO3 to NO2
    • Nitrates
    • Sulfates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampling 3 Dec 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates107 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,03 mg/l
    • Iron0,008 mg/l
    • Chlorides49,3 mg/l
    • Aluminium65 % of standard
    • glyphosate11,000 % of standard
  • Dvorniky N.o.-kele Mj.Dunajská Streda district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Total iron
    • Total pesticides
    • Glyphosate
    • Chlormequat

    Measured values, year 2025, sampling 6 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates1,4 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,01 mg/l
    • Iron0,21 mg/l
    • Chlorides30,7 mg/l
    • Aluminium15 % of standard
    • glyphosate5,000 % of standard
  • OldzaDunajská Streda district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Ratio of NO3 to NO2
    • Nitrates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampling 18 Nov 2025 (4 samplings, the highest value of the year for each substance):

    • Nitrates62,9 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,034 mg/l
    • Chlorides51,4 mg/l
    • Aluminium20 % of standard
    • glyphosate7,000 % of standard
    • sum of PCE (tetrachloroethene) and TCE (trichloroethene)59 % of standard
  • OldzaDunajská Streda district · borehole or well
    substances from human activity
    2017 to 2025

    Exceeded in 2025:

    • Ratio of NO3 to NO2
    • Nitrates
    • Total pesticides
    • Glyphosate

    Measured values, year 2025, sampling 18 Nov 2025 (4 samplings, the highest value of the year for each substance):

    • Nitrates112 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron0,023 mg/l
    • Chlorides46,8 mg/l
    • Aluminium15 % of standard
    • glyphosate5,000 % of standard
    • sum of PCE (tetrachloroethene) and TCE (trichloroethene)14 % of 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

    Measured values, year 2025, sampling 6 Oct 2025 (2 samplings, the highest value of the year for each substance):

    • Nitrates73,7 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites0,01 mg/l
    • Iron0,017 mg/l
    • Chlorides44 mg/l
    • Aluminium15 % of standard
    • glyphosate7,000 % of standard
  • substances from human activity
  • natural substances only
  • no exceedance recorded

SHMÚ gives station names without diacritics and in capital letters; we show them as it gives them.

What most often fails

Number of stations that exceeded the given indicator in 2025

  1. ManganeseNatural composition, standard 0.05 mg/l300
  2. Total ironNatural composition, standard 0.2 mg/l202
  3. AmmoniumNatural composition, standard 0.5 mg/l84
  4. Conductivity at 20 °CNatural composition, standard 125 mS/m83
  5. Ratio of NO3 to NO2Natural composition, standard 180
  6. NitratesNitrates and nitrites, standard 50 mg/l79
  7. TOCNatural composition, standard 3 mg/l77
  8. SulfatesNatural composition, standard 250 mg/l65
  9. Total pesticidesPesticides and their breakdown products, standard 0.5 µg/l53
  10. GlyphosatePesticides and their breakdown products, standard 0.1 µg/l48
  11. ArsenicNatural composition, standard 10 µg/l32
  12. Chloroethene (vinyl chloride)Chlorinated solvents and benzene, standard 0.5 µg/l27
  13. PHNatural composition, standard 6.5 – 9.523
  14. COD-MnNatural composition, standard 3 mg/l22
  15. AluminiumNatural composition, standard 0.2 mg/l15
  16. ChloridesNatural composition, standard 250 mg/l12
  • substances from human activity
  • natural substances and geology

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.