Fears have been raised over the state of Northern Ireland's waterways after almost six pollution incidents a day were reported to, or discovered by, inspectors in 2013.
Latest figures show reports of 2,112 water pollution incidents in 2013, of which 1,310 (62%) had an impact on the water quality.
The total number of reported incidents has increased by 6% compared with the previous year, while the number of substantiated incidents has risen by 11%.
The figures, published in the 2015 Northern Ireland Environmental Statistics Report, show the number of substantiated incidents has fallen by 16% since 2001.
The indicators focus on eight main themes. The Green Party said public bodies should be setting the standard for good environmental protection.
The party's leader, Steven Agnew MLA, said: "In Northern Ireland we are reliant on both the agriculture and tourism sector for economic success and both these key areas are, in turn, reliant on clean water.
"We need more robust action to ensure the amount of pollution that is discharging into our water system is reduced.
"There are too many discharge licences which legally permit waste, pollution, chemicals and other damaging substances to pour into our waterways and this leads to fish kills and a reduction of the biodiversity in and around our water systems."
Environmental group Friends of the Earth said water pollution remained a persistent problem.
"In 2013, 48% of reported incidents (802) were not substantiated, but what does this mean?
"Did a pollution incident not occur in these cases, or did NIEA staff fail to react quickly enough, so whatever pollution there had been dissipated?" it said.
"Given the staffing and funding cuts NIEA has had to endure, the latter would seem to be a very real possibility, which puts the accuracy of these figures in doubt. The real level of water pollution is likely to be higher."