An unacceptable level of polluted waterways and the number of fish kills in rivers require remedial measures if valuable resources are to be protected, the Environmental Protection Agency (EPA) has warned.
A new EPA report, Water Quality in Ireland 2005, shows that water quality continues to be of a high standard.
However, EPA programme manager Dr Jim Bowman said: "While these data are encouraging there remains an unacceptable level of polluted water bodies in the country, with 30 per cent of rivers, 10 per cent of lakes and 22 per cent of estuaries and coastal waters in a condition that will require remedial measures if we are to protect our valuable water resources and comply with the requirements of the water framework directive."
Dr Bowman said the report showed that the number of fish kills in rivers and the level of bacterial contamination in ground waters remained at unacceptable levels.
It showed a satisfactory water quality in 70.2 per cent of rivers, 90 per cent of lakes and 78 per cent of estuaries and coastal waters.
However, 30 per cent of the ground water samples showed bacteriological (faecal coliform) contamination, with some 11 per cent of all samples being grossly contaminated.
In Ireland ground water was a significant source of drinking water supply. Approximately 23 per cent of the ground water locations examined exceeded the national guidelines value for nitrate concentration for drinking water and 2 per cent breached the mandatory limit.
While almost 90 per cent of the lakes examined in 2003 to 2005 were in a satisfactory condition, this represented a slight deterioration compared to the 2001 to 2003 period.
Of the 421 lakes assessed, water quality in 68 was less than satisfactory.
Thirteen of the lakes were classified as being highly polluted, seven of them in Co Monaghan.
The overall quality of the 131 bathing waters in Ireland remained very good, although the number of sites complying with the EU mandatory values in 2005 showed a reduction of 2 per cent compared with 2004.
The report said there were 45 fish kills recorded in 2005. These were attributed largely to activities associated with agriculture, industry and local authority services.
The overall quality in 67 water bodies from estuarine and coastal areas examined in 2001 to 2005 showed improvement, with a decline from 12 to 10 in the number of water bodies being classified as over-enriched.
The quality of shellfish waters also improved in 2005, with a notable increase in those waters assessed to be of the highest quality for shellfish production.
A reduction was recorded in the number of reported incidents of pollution at sea from 59 in 2004 to 46 in 2005.
These were attributed mainly to oil spillages, with diesel and gas oils the most frequently identified pollutants.