Km. Stronge et al., PREDICTING NITRATE CONCENTRATIONS IN NORTHERN-IRELAND RIVERS USING TIME-SERIES ANALYSIS, Journal of environmental quality, 26(6), 1997, pp. 1599-1604
Lough Neagh is an important natural resource, being the largest single
source of potable water for Belfast. Its catchment area covers about
one-third of the land area of Northern Ireland. Six inflow rivers drai
n 88% of the total catchment, which has a land usage of grassland and
rough grazing that is similar to Northern Ireland as a whole. This rep
ort examines the causes of the year-to-year variation in river NO3- co
ncentrations that have been the focus of European Community (EC) legis
lation. A multiple regression model has been developed which explains
74% of the variation in NO3- concentrations for the time period 1974 t
o 1994. Based on a knowledge of the Northern Ireland annual utilized m
etabolizable energy (UME) for grazing livestock and N fertilizer sales
, the model employs the efficiency of fertilizer usage as an independe
nt variable. Additional independent variables are climatic: previous s
ummer rainfall, sun hours in the winter and rainfall for the period Ja
nuary to June. Based on a worst case scenario, employing the extreme v
alues for these climatic variables and the least fertilizer efficiency
ratio, the predicted NO3- concentration is only 4.4 mg N L-1, which i
s well below the EC maximum admissible level of 11.3 mg N L-1 for drin
king water.