76 / 234
Ireland’s Environment – An Assessment 2016
72
A recent assessment found that there continues to
be a very clear spatial pattern of elevated nitrate and
phosphorus concentrations in groundwater (Figure 5.7),
rivers, lakes and estuarine waters, giving rise to
water quality problems across Ireland (EPA, 2016b).
Concentrations of both nitrate and phosphorus tend to
be elevated in the north-east, south-east and south of
the country and lower towards the west, north-west and
south-west. There is a clear correlation between the areas
with the highest nitrate and phosphorus concentrations in
waters and areas with the most intensive agriculture and
highest human population densities.
Drivers and Pressures
Eutrophication
Eutrophication caused by excessive nutrients is the
main threat to the quality of our waters.
Eutrophication, which is caused by nutrient enrichment,
remains the most significant issue for surface waters.
Excessive nutrient concentrations can lead to eutrophication
impacts, including accelerated growth of algae and plants,
leading to ecological impacts in rivers, lakes and marine
waters, such as reduced oxygen levels and loss of sensitive
aquatic species. Phosphorus tends to drive eutrophication
impacts in freshwaters, while nitrogen tends to drive
eutrophication impacts in coastal waters, although there
are exceptions. Eutrophication remains the most significant
pollution issue for surface waters in Ireland.
Excessive loads of nitrogen and phosphorus can arise
from a number of sources. The two most important
suspected causes of pollution in rivers are agriculture and
municipal sources, accounting for 53% and 34% of cases,
respectively (EPA, 2015b).
Levels of nitrogen and phosphorus in groundwater
and rivers have been mostly stable and decreasing
since 2007. Riverine inputs to transitional waters and
coastal waters have also shown declines. Nutrient
inputs to rivers, particularly from the agriculture sector,
have fallen: nitrogen levels have fallen by 18.7% and
phosphorus levels by 37.7%. Anticipated increases in
pressures due to human population growth and increase
in agricultural output will need to be carefully managed
to build on these trends.
Figure 5.7
Nitrate Concentrations in Groundwater in
2014 (Source: EPA, 2016b)