Lough
Neagh is the UK's largest lake and a multi-purpose
resource. The
Lough is a major source of drinking water and one of the
most eutrophic lakes in the world due to high
phosphorus (P) inputs.
The P inputs to Lough Neagh have been measured and ascribed to sources.
Phosphorus from sewage works was shown to account for almost half the
amount entering the lake. To curtail this source, P reduction treatment
was introduced in 1981 at the ten major sewage disposal works in the
Lough Neagh Catchment. This was the first time P reduction treatment
had been employed in the UK and it led to a reduction in P loading and
improved water quality in the lake. Lough Neagh and its tributaries
have been sampled at least fortnightly since 1969 and the unbroken
record of nutrient inputs and water quality in the lake shows that in
the early 1990's, the effects of sewage P reduction were overtaken by
increasing diffuse P loads. What constitutes a point or diffuse nutrient source is not always obvious. For example, atmospheric deposition and agriculture are classed as diffuse sources, as is urban runoff, but sewage treatment works are classed as point sources, even though a proportion of the nutrient load to them is diffuse in origin. Human waste to rivers via sewage treatment works is regarded as a point source, but this is derived from a population that occupies the same area from which 'diffuse' urban runoff is derived. In agriculture, a significant proportion of the pollutant load is generated from small point sources, such as a farmyard. In an agricultural context, the categorisation of nutrient loads into point and diffuse sources is largely a scale issue, with small point sources regarded as diffuse pollution on a catchment scale, but increasingly as point sources as the spatial resolution of observation increases.
Nutrient enrichment of inland and tidal waters is considered by the European Environment Agency to be one of the most important issues to facing Europe. However this enrichment is heterogeneously distributed both throughout Europe and within the UK. On a national and European basis , diffuse source-derived P is typically estimated to constitute some 40-60% of the surface water nutrient budget, while diffuse source-derived N accounts for approximately 70-80% of the nitrogen load. In groundwater, a higher proportion (often >95%) of the nitrogen budget is derived from diffuse sources."
The above text has been derived from a review entitled 'Diffuse Pollution: Sources of N & P'. Copies of the full report are available from FWR Publications (£35.00 less 20% to FWR Members).
The Centre for Environment and Society and Department of Biological Sciences of the University of Essex have conducted a preliminary assessment for The Environment Agency of the environmental damage costs incurred in England and Wales because of the eutrophication of fresh waters. Visit their website for the latest details. A paper describing the results has now been published:-
Pretty, J. N., Mason, C. F., Nedwell, D.B., Hine, R. E., Leaf, S. and Dils,R. Environmental Costs of Freshwater Eutrophication in England and wales, Environmental Science and Technology, 37, 201-208, (2003).