{
  "url": "https://openlegislation.uk/surface-waters-fishlife-classification-regulations-1997/schedule/part-I",
  "json_url": "https://openlegislation.uk/surface-waters-fishlife-classification-regulations-1997/schedule/part-I.json",
  "legislation": "uksi/1997/1331",
  "legislation_title": "The Surface Waters (Fishlife) (Classification) Regulations 1997",
  "legislation_url": "https://openlegislation.uk/surface-waters-fishlife-classification-regulations-1997",
  "path": "schedule/part/I",
  "kind": "part",
  "number": "I",
  "heading": "CRITERIA FOR CLASSIFICATION OF WATERS AS SALMONID AND CYPRINID WATERS",
  "text": "No. in Annex I to 78/659/EEC\nParameter\nRequirements to be satisfied for salmonid waters\nRequirements to be satisfied for cyprinid waters\nMethods of analysis or inspection\nMinimum sampling and measuring frequency\nObservations\n1\nTemperature (°C)\n1 Temperature measured downstream of a point of thermal discharge (at the edge of a mixing zone) must not exceed the unaffected temperature by more than 1.5°C for salmonid waters and 3°C for cyprinid waters\nDerogations limited in geographical scope may be decided by the Environment Agency if the Agency can show that there are no harmful consequences for the balanced development of the fish population\n2 Thermal discharges must not cause the temperature downstream of the point of thermal discharge (at the edge of the mixing zone) to exceed—\n(a) 10°C (0) during the breeding season in the case of waters which contain species which need cold water for reproduction;\n(b) at other times or in the case of waters which do not contain such species, 21.5°C (0) for salmonid waters and 28°C (0) for cyprinid waters\nTemperature limits may, however, be exceeded for 2% of the time\nThermometry\nWeekly, both upstream and downstream of the point of thermal discharge\nOver-sudden variations in temperature must be avoided\n2\nDissolved oxygen (mg/l O2)\n50%>=9\nWhen the oxygen concentration falls below 6 mg/l, the Environment Agency shall comply with regulation 4(6) and the Agency must prove that this situation will have no harmful consequences for the balanced development of the fish population\n50%>=7\nWhen the oxygen concentration falls below 4 mg/l, the Environment Agency shall comply with regulation 4(6) and the Agency must prove that this situation will have no harmful consequences for the balanced development of the fish population\nWinkler’s method or specific electrodes (electro-chemical method)\nMonthly,minimum one sample representative of low oxygen conditions on the day of sampling\nHowever, where major daily variations are suspected, a minimum of two samples in one day shall be taken\n3\npH\n6 to 9 (0)\nArtificial pH variations with respect to the unaffected values shall not exceed ±0.5 of a pH unit within the limits falling between 6 and 9 provided that these variations do not increase the harmfulness of other substances present in the water\nElectrometry calibration by means of two solutions with known pH values, preferably on either side of, and close to the pH being measured\nMonthly\n8\nPhenolic compounds (mg/l C6 H5 OH)\nPhenolic compounds must not be present in such concentrations that they adversely affect fish flavour\nBy taste\nAn examination by taste shall be made only where the presence of phenolic compounds is presumed\n9\nPetroleum hydrocarbons\nPetroleum products must not be present in the water in such quantities that they—\n(a) form a visible film on the surface of the water or form coatings on the beds of water-courses and lakes;\n(b) impart a detectable “hydrocarbon” taste to fish;\n(c) produce harmful effects on fish.\nVisual and by taste\nMonthly\nA visual examination shall be made regularly once a month, with an examination by taste only where the presence of hydrocarbons is presumed\n10\nNon-ionised ammonia (mg/l NH3)\n<=0.025\nMolecular absorption spectrophotometry using indophenol blue or Nessler’s method associated with pH and temperature determination\nMonthly\nValues for non-ionised ammonia may be exceeded in the form of minor peaks in the daytime\n11\nTotal ammonium (mg/l NH4)\nIn order to diminish the risk of toxicity due to non-ionised ammonia, of oxygen consumption due to nitrification and of eutrophication, the concentrations of total ammonium should not exceed 1 mg/l\nIn particular geographical or climatic conditions and particularly in cases of low water temperature and of reduced nitrification or where the Environment Agency can show that there are no harmful consequences for the balanced development of the fish population, the Agency may fix a value higher than 1 mg/l\nMolecular absorption spectrophotometry using indophenol blue or Nessler’s method associated with pH and temperature determination\nMonthly\n12\nTotal residual chlorine (mg/l Zn)\n<=0.005\nDPD-method (diethyl-p-phenylenediamene)\nMonthly\nThe value corresponds to pH = 6\nHigher concentrations of total chlorine can be accepted if the pH is higher\n13\nTotal Zinc (mg/l Zn)\n<=0.3\n<=1.0\nAtomic absorption spectrometry\nMonthly\nThe values correspond to a water hardness of 100 mg/l CaCO3\nFor hardness levels between 10 and 500 mg/l corresponding limit values can be found in the Table in Part II of this Schedule",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [
    {
      "type": "words substituted",
      "affecting": "wsi/2013/755",
      "affecting_title": "The Natural Resources Body for Wales (Functions) Order 2013"
    }
  ],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1997/1331/schedule/part/I",
    "retrieved_at": "2026-10-29T12:08:21.146177+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}