Long-term changes of nitrogen and phosphorus loadings to a large lake in North-West Ireland

Lower Lough Erne is a large (109.5 km2) eutrophic lake in north-west Ireland. Nutrient data from 14 years in the period 1974 to 1997 are analysed for temporal trends. Over the period of observation, soluble reactive phosphorus loadings have increased by approximately 2.0 tonnes SRP yr−1 so that between 1974 and 1997 the mean concentration of the inflow has increased from 15 to 33 μg SRP l−1. The increase is probably caused by diffuse agricultural sources. There is no temporal trend in inorganic nitrogen inputs, but the total nitrogen and total Kjeldhal N both show a weak upward trend with time.