# The Surface Waters (Fishlife) (Classification) Regulations 1997, Part II: ZINC CONCENTRATIONS (mg/l Zn) FOR DIFFERENT WATER HARDNESS VALUES BETWEEN 10 AND 500 mg/l CaCO3


Classification of waters
Water hardness (mg/l CaCO3)
10
50
100
500
Salmonid waters (mg/l Zn)
0.03
0.2
0.3
0.5
Cyprinid waters (mg/l Zn)
0.3
0.7
1.0
2.0

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Source: https://www.legislation.gov.uk/uksi/1997/1331/schedule/part/II (the official version)
Page: https://openlegislation.uk/surface-waters-fishlife-classification-regulations-1997/schedule/part-II
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.