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Paragraph 3

Northern Ireland

The Department must apply, as applicable, the “high”, “good”, “moderate”, “poor” or “bad” reactive phosphorus standard to that river or part thereof, calculated in accordance with the formula specified in sub paragraph (a)—

(a)

RP standard = 10^((1.0497 x log10(A)+1.066) x (log10(reference condition RP)- log10(3,500)) + log10(3,500));

(b)

In relation to the above formula—

  • “RP standard” is the annual mean concentration of reactive phosphorus in ug/l estimated for the lower class boundary of high, good, moderate and poor ecological status, depending on the value of “A” used;

  • “A” has the value 0.702 when calculating the standard for high; 0.532 when calculating the standard for good; 0.356 when calculating the standard for moderate; and 0.166 when calculating the standard for poor;

  • “reference condition RP” = 10^(0.454 (log10alk) – 0.0018 (altitude) + 0.476) and represents the annual mean concentration of reactive phosphorus at near natural conditions. If the predicted value of reference condition RP is <7ug/l, reference condition RP is set to 7ug/l;

  • “log10alk” means log10(alkalinity), where alkalinity is the concentration of CaCO3 in mg/l. For sites with an alkalinity greater than 250, alkalinity is set to 250. For sites with an alkalinity less than 2, it is set to 2;

  • “altitude” means the site's altitude above sea level in metres. For sites with an altitude greater than 355 metres, altitude is set to 355 metres.