Lakes and Watercourses

More documents

Recommendations

Info

In lakes, Secchi depth is classified using seasonal mean values (May – October) over one year, based on monthly readings using a Secchi disk in the offshore area of the lake. Underwater binoculars should be used to ensure that accurate readings can be taken in different weather conditions. The assessment scale is intended to group concentration levels typical of Swedish lakes and watercourses and is not related to biological or microbial effects. Comments Classifications must be based on samples taken and analyses made in accordance with the Swedish EPA Environmental Monitoring Handbook. If assessments are made on the basis of more limited data, this should be stated. The variables to be used for classification should be decided from case to case. As a rule, it is not necessary to use all the given variables. The scales should be used bearing in mind the wide natural variation between individual lakes and from year to year. All the given variables vary from season to season, in running water often depending on the flow rate. Periods of high flow are frequently associated with high colour and turbidity. Sampling should therefore ensure that periods with highest flow are also represented. Algal production has a very powerful influence on both turbidity and Secchi depth in lakes, particularly eutrophic ones. References Anonymous (1989): Vannkvalitetskriterier for ferskvann (”Quality criteria for fresh water”). Norwegian EPA. US EPA (1986): Quality criteria for water. – EPA 440/5-86-001. Wiederholm, T. (1989): Bedömningsgrunder för sjöar och vattendrag. Bakgrundsrapport 1. Näringsämnen, syre, ljus, försurning. (”Environmental Quality Criteria for Lakes and Watercourses. Background report 1 – Nutrients, oxygen, light, acidification”). Swedish EPA Report 3627. 35
Acidity / acidification Introduction The acidity of water is significant to aquatic organisms because it affects a number of important biotic and abiotic processes. Indirectly, acidity is also important to aquatic organisms because it governs the chemical form in which metals occur. Dissolved aluminium is particularly important, since this may occur in toxic form at high concentrations under acid conditions. Most waters have a buffering capacity, ie, they are able to neutralise the input of acidic substances. Buffering capacity is principally determined by hydrocarbonate; only when this is nearly exhausted can water become severely acidified. Alkalinity is used here as a measure of buffering capacity. The lower the alkalinity, the greater the effect of acidic input on the acidity. An alternative measure of buffering capacity is ANC (acid neutralising capacity), which, in addition to hydrocarbonate, also includes organic anions. The difference between ANC and alkalinity is fairly small in clear waters, but in brown (humic) waters, ANC may be substantially higher than alkalinity. ANC has become more widely used internationally for acidification assessments in recent years, although alkalinity has a simpler and clearer correlation to the acidity of water. When alkalinity approaches zero pH falls most rapidly, regardless of the ANC level at that point. The water’s natural content of organic anions may have an appreciable effect on its acidity and sensitivity to acidification. However, the fact that alkalinity rather than ANC has been chosen as the measure of buffering capacity does not mean that this natural effect is assumed to be non-existent, nor that it is confused with anthropogenic impact. The calculation below showing how present buffering capacity differs from that during the pre-industrial era, solely refers to the change caused by the sulphur deposition of recent years, regardless of the original acidity of the water. In practice, this change in buffering capacity will be equally great, whether it is measured as the difference in alkalinity or the difference in ANC. However, the estimated correlation between present and pre-industrial alkalinity is easier to use than the equivalent ANC correlation as the basis for an assessment of whether the pH of the water has been affected by acid deposition. 36
Page 1 and 2: Environmental Quality Criteria - La
Page 3 and 4: TO ORDER Swedish Environmental Prot
Page 5 and 6: Reference Group Mats Bengtsson, Swe
Page 7 and 8: Summary This report on lakes and wa
Page 11 and 12: included. In addition to a large nu
Page 13 and 14: ased estimates are used. Given that
Page 15 and 16: TABLE 1. SUMMARY of parameters incl
Page 17 and 18: 16 The current conditions scale in
Page 19 and 20: (in Swedish with English summary).
Page 21 and 22: conditions for watercourse flora an
Page 23 and 24: show the availability of nitrogen i
Page 25 and 26: Mean concentration of total phospho
Page 27 and 28: TABLE 9. DEVIATION from reference v
Page 29 and 30: Comments Classifications must be ba
Page 31 and 32: winter/spring, i.e. ice-covered per
Page 33 and 34: Light conditions Introduction Light
Page 35: TABLE 13. CURRENT CONDITIONS: turbi
Page 39 and 40: industrial pH). The change in acidi
Page 41 and 42: The pre-industrial concentration of
Page 43 and 44: very high degree of reliability and
Page 45 and 46: TABLE 19. CURRENT CONDITIONS: metal
Page 47 and 48: TABLE 22. DEVIATION from reference
Page 49 and 50: TABLE 24. (continued) Cu Zn Cd Pb C
Page 51 and 52: Swedish EPA (1993): Metals and the
Page 53 and 54: Assessment of current conditions TA
Page 55 and 56: TABLE 29. CURRENT CONDITIONS: poten
Page 59 and 60: References Cronberg, G., Lindmark,
Page 61 and 62: (see Appendix 1). If submerged and
Page 63 and 64: References Andersson, B. (1998): Va
Page 65 and 66: The genera in question and their tr
Page 67 and 68: Benthic fauna Introduction Benthic
Page 69 and 70: TABLE 41. CURRENT CONDITIONS: botto
Page 71 and 72: Comments The assessment must be bas
Page 73 and 74: has yielded better results than did
Page 75 and 76: TABLE 45. CURRENT CONDITIONS: fish,
Page 81 and 82: TABLE 48. (Contd.) Proportion of al
Page 84 and 85: Presentation of data When using the
Page 86 and 87:
APPENDIX 1 Ceratophyllum demersum 1
Page 88 and 89:
APPENDIX 2 Calculation of index and
Page 90 and 91:
APPENDIX 2 Table 1b. Indicator gene
Page 92 and 93:
Genus Indicator value -------------
Page 94 and 95:
APPENDIX 2 45 Planorbis sp. 46 Anis
Page 96 and 97:
APPENDIX 2 214 Leuctra hippopus 215
Page 98 and 99:
APPENDIX 2 384 Tinodes waeneri 385
Page 100 and 101:
APPENDIX 2 (6) O/C index (Wiederhol
Page 102 and 103:
APPENDIX 3 Dace Stäm Leuciscus leu
Page 106:
REPORT 5050 Environmental Quality C
show all

Lakes and Watercourses

Create successful ePaper yourself

Delete template?

Save as template?