The ecosystems in a significant proportion of the Boyne, Liffey and Suir river catchments are at risk from pollution, which may threaten "healthy and balanced" stocks of salmon and trout, a new report says.
The interim report of the Three Rivers Project, supported by the EU Cohesion Fund, says there is biological evidence of pollution at 72 per cent of monitoring stations in the Boyne catchment.
The figures for the Liffey and Suir were 60 per cent and 53 per cent respectively.
Phosphorus exceeded acceptable levels in over half the sites monitored in the three catchments.
There has, however, been some improvement in water quality in the Liffey since the Three Rivers project began in 1999, the report says. This is attributed to the upgrading of the waste-water treatment plants at Osberstown and Leixlip.
Thirty-six local authorities, statutory bodies and farming organisations are involved in the Three Rivers project, which will present its final report by the end of the year.
Mr Ciaran O'Keeffe, a spokesman for the project, warned that stocks of trout and salmon would not exist if water quality was poor. Local authorities as well as those contributing to pollution needed to commit resources and police the Three Rivers project's recommended management strategies, he said.
"In light of current conditions, this will take between five and 10 years to achieve a significant improvement, even with sustained effort and long-term funding."