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ANNEX 2: SURFACE WATER QUALITY - PROPOSED STANDARDS FOR PHOSPHORUS IN FRESHWATER AND BRACKISH LOCHS

1. To determine the appropriate total phosphorus standard to apply to a freshwater or brackish loch or any part thereof and subject to paragraphs 2, 3 and 5, SEPA shall classify-

(i) all brackish lochs as being of the geological category; "high alkalinity";

(ii) a freshwater lochs as being of the geological category specified in Column 1 of Table A which corresponds with the annual mean alkalinity range specified in Column 2 of that Table which is applicable to the loch; and

(iii) the depth characteristics of the loch as being of the depth category specified in Column 1 of Table B which corresponds with the depth range specified in Column 2 of that Table which is applicable to the loch.

2. For freshwater lochs with an annual mean alkalinity of greater than 1000 micro-equivalents per litre, SEPA shall classify the loch as being of the geological category specified in Column 1 of Table A which corresponds with the description of the solid geology of the catchment of the loch specified in Column 4 of that Table which is applicable to the loch.

3. Subject to paragraph 4, where SEPA has insufficient data to classify the geological characteristics of a freshwater loch in accordance with the procedure set out in sub-paragraph (ii) of paragraph 1, it shall classify the geological characteristics of the loch as being of the geological category specified in Column 1 of Table A which corresponds with the annual mean conductivity range specified in Column 3 of that Table which is applicable to the loch.

4. eshwater lochs with an annual mean conductivity of > 250 - 1,000 micro Siemens per centimetre, SEPA shall classify the loch as being of the geological category specified in Column 1 of Table A which corresponds with the description of the solid geology of the catchment of the loch specified in Column 4 of that Table which is applicable to the loch.

5. Where SEPA has insufficient data to classify the geological characteristics of a freshwater loch using the criteria set out in paragraphs 1 to 4 above, it shall classify the geological characteristics of the loch as being of the geological category specified in Column 1 of Table A which corresponds with the description of the solid geology of the catchment of the loch specified in Column 4 of that Table which is applicable to the loch.

Table A: Geological characteristics used to identify geological categories to which the loch total phosphorus standards apply

Table B: Depth characteristics used to identify depth categories to which the loch phosphorus standards apply

Environmental standards for total phosphorus in [lakes]

6. Subject to paragraphs 7, 8 and 9, SEPA shall apply, as applicable to the loch or part thereof, the "high", "good", "moderate" or "poor" total phosphorus standard calculated in accordance with the formulae specified in Columns 1, 2, 3 and 4, respectively, of Table C, where in relation to those formulae:

"R" represents the annual mean total phosphorus concentration expected for the loch in the absence of more than very minor phosphorus inputs to the loch resulting from human activities and, where a reliable estimate of 'C' is available, shall have the value given by the formula; Antilog ₁₀ [1.36 - (0.09 &×A) + (0.24 &× B); or 35, whichever is the smaller value;

"A" = Log ₁₀ of the altitude in metres above mean sea level of the loch;

"B" = Log ₁₀(C ÷ D);

"C" = the mean alkalinity of the loch in milli-equivalents per litre estimated for the loch when:

(i) in accordance with paragraphs 7 and 8 of Part B of Schedule 1 of the Scotland River Basin District (Surface Water Typology and Environmental Standards) (Scotland) Directions 2007, its acid neutralising capacity is at least good; and

(ii) its alkalinity has not been otherwise altered as a result of point or diffuse pollution;

"D" = the mean depth of the loch in metres;

"H" = 0.755 + (0.012 × C) - (0.001 × D); or 0.7, whichever is the larger value; and

"G" = 0.506 + (0.023 × C) - (0.002 × D); or 0.46, whichever is the larger value.

7. If, in accordance with paragraphs 1 to 5, SEPA has classified the geological characteristics of a loch as being of the geological category "Marl", it shall apply, as applicable to the loch or part thereof, the "high", "good", "moderate" or "poor" total phosphorus standard specified in Columns 2, 3, 4 and 5, respectively, of Table D which corresponds with the combination of geological and depth categories specified in Column 1 of that Table that is applicable to the loch in accordance with paragraphs 1 to 5.

8. If the value of "C" in paragraph 6 cannot be reliably estimated for the purpose of calculating the value "R" in accordance with that paragraph, SEPA shall:

(i) use an alternative method for estimating the value "R", provided that, for other lochs for which the value "C" can be reliably estimated, that alternative method produces an equivalently unbiased estimate of the value "R" to that produced by the application of the formula specified in paragraph 6; or

(ii) apply the procedure specified in paragraph 9 below.

9. If SEPA does not have the necessary data to calculate the total phosphorus standard applicable to a loch or part in accordance with paragraph 6 or sub-paragraph (i) of paragraph 8, as applicable, it shall apply, as applicable to the loch or part, the "high", "good", "moderate" or "poor" total phosphorus standard specified in Columns 2, 3, 4 and 5, respectively, of Table D which corresponds with the combination of geological and depth categories specified in Column 1 of that Table that is applicable to the loch in accordance with paragraphs 1 to 5.

Table C: Total phosphorus standards for freshwater and brackish lochs

Table D: Type-specific total phosphorus standards for freshwater and brackish lochs where the standards specified in Table C do not apply

New Definitions:

"Brackish loch" means lochs with an annual mean conductivity of > 1,000 micro Siemens per centimetre.

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