Rivers suffering 'dramatic' decline as pollution and population grow
Worrying trend: Number of pristine waterways falls from 500 to just 20
The country's rivers have suffered a dramatic decline in health in recent years with pollution and fish kills on the increase.
Where there were more than 500 river sites classified 'pristine' in the late 1980s, the number has plummeted to just 20 today, while the number of seriously polluted rivers has increased.
Overall, just 53pc of rivers are classified as being in good health and tentative improvements made in the quality of the waters in the earlier part of this decade have reversed.
Fish kills had reduced year on year to just 14 in 2017, but that number rocketed to 40 last year. The number of seriously polluted rivers rose from six to nine.
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The Environmental Protection Agency (EPA), which conducted a five-year assessment of the national waterways, said the trend was disappointing.
"Not only are we failing to improve water quality, we are also failing to prevent further deterioration of our rivers," said Matt Crowe, EPA director.
The blame is placed chiefly on the expansion of farming and the residues of fertiliser and waste that run off the land, in particular excess levels of nutrients - namely nitrogen and phosphorous from fertilisers and detergents.
They encourage excessive growth of plants and algae that monopolise the oxygen supply, choking off other plant and animal life.
Population growth and the associated rise in untreated waste water discharges from poorly installed connections and overflowing treatment plants is also a major issue.
Poorly managed forestry and industrial emissions are also factors, as are man-made changes to waterways through dredging, straightening and the construction of dams, weirs and other obstructions.
The EPA's report found that only 50pc of lakes were in good health, although that was an improvement on previous years, while just 38pc of estuaries were in good health which was down from the previous assessment.
The amount of phosphorous found in the estuaries jumped by a third from 2013, while nitrogen concentrations were up by 16pc.
Mary Gurrie, water programme manager for the EPA, said it was essential that trend was halted.
"The overall increase in nutrients is a worrying development for our water quality," she said. "We need to address the sources and the pathways by which these nutrients make their way into our rivers and lakes."
Healthy waterways are given a 'high' or 'good' status, while those considered unsatisfactory are ranked 'moderate', 'poor' or 'bad'.
The report describes the loss of high status waters as "one of the most worrying trends".
"These near pristine unpolluted water are vital for the survival of sensitive aquatic species and the protection of aquatic biodiversity," it stated.
It said that the numbers have fallen by a third since 2009 alone.
Coastal waters fared better with 80pc in good health, along with 87pc of canals and 92pc of groundwater.