Agriculture contributes about 60 per cent of phosphorus pollution in the Boyne, Liffey and Suir river catchments, according to the final report of the Three Rivers Project released in Waterford yesterday.
The report also found that forestry, urban development and septic tanks were significant contributors to poor water quality.
The Three Rivers Project has been under way for three years and has cost €6 million.
Its report, which was launched by the Minister for the Environment, Mr Cullen, makes radical recommendations for future water monitoring and enforcement.These include a review of all existing discharge licences affecting the three catchment areas, which stretch from Co Tipperary through Waterford and as far north as Co Louth.
The area contains one-fifth of the State's population.
The Minister emphasised its recommendations would have to be met to comply with obligations under the EU Water Directive.
Mr Cullen said he will bring proposals to Government early next year on measures to regulate and monitor phosphate use on farms, the installation and management of septic tanks and industrial discharges as well as urban waste water systems.
Although agriculture was responsible for almost 60 per cent of the phosphate pollution, the report pointed out it accounted for up to 91 per cent of land use in each river catchment.
Town sewerage systems contributed an estimated 15 to 19 per cent of the total, even though urban development accounts for only 1 to 7 per cent of land use.
Other major polluters include industrial discharges and septic tank owners. Urban run-off is also a significant pollutant in the Liffey catchment.
Overall, however, the project found water quality in the Boyne is improving and the decline in the Liffey has been halted. But water quality in the Suir continues to deteriorate.
Mr Cullen said waste water treatment plants had been built at Oberstown and Leixlip in Co Kildare serving the Liffey; Carrick-on-Suir and Templemore serving the Suir; and Navan and Trim serving the Boyne.
The Minister stressed the need for a consensus approach to the issue of water management and said he was "particularly impressed by the active participation of the farming community in the project".
He was having discussions with the Minister for Agriculture, Mr Walsh, on implementing the recommendations of the study.
According to Mr Jerry Grant, managing director of MC O'Sullivan and Associates, lead consultants, the project will require a clear commitment to funding.
"This is an ongoing issue for central and local authorities charged with effective management of water resources. It is clear that society aspires to clean rivers and lakes and coastal waters and this aspiration must be matched by the financial and other commitments needed to deliver on it," he said.
