There have been almost 200 pollution incidents at livestock farms in Norfolk and Suffolk over the last six years, including animal waste leaking into rivers.
But the overall number of incidents is going down and most have not caused serious damage to the environment, according to research from The Bureau of Investigative Journalism.
Figures from the Environment Agency obtained by The Bureau show livestock farms are responsible for serious pollution incidents every week on average in the country.
But in Norfolk and Suffolk the number of pollution incidents is falling, from a high of 38 in 2012, to just five last year.
And there have been just three serious pollution incidents in the region since 2014.
Environmental experts warned bad practices can mean chemicals in pesticides, animals waste or fertilisers cause harm to ecosystems.
But farming leaders said an increase in the “professionalism of the industry” and better awareness of risks means there are “constant” checks against pollution.
Rob Wise, East Anglia’s environment advisor for the National Farmers’ Union, said most farms went “above and beyond” the minimum requirements and many had Red Tractor Assurance accreditation.
“The potential for the pollution to have a significant impact on people is very small,” he added. “The potential to damage aquatic life is somewhat greater, but again the chance of significant harm being done is relatively minor.”
None of the incidents recorded by the Environment Agency fell under the most serious category, in which a “major environmental impact” was deemed to have happened.
But three were ranked as the second most serious category of “significant environmental impact”.
In the most recent serious incident in Norfolk dairy farmers were prosecuted for polluting the River Tud at North Tuddenham.
FS Dann and Son Ltd at Pound Farm were fined £1,000 by Norwich Magistrates in June for the leak in January last year.
Dirty water leaked from the farm into the river through a pipe and high levels of ammonia were then found in the river.
Farmer Simon Dann said the accidental leak happened because there was a delay in building a system to take the dirty water away from his new dairy.
It meant water drained from a field into an open pipe which took it to the river. “We put too much (dirty water) in the wrong place,” he said.
In January 2016 there was also a “containment and control failure” at Great Common Farm, Ilketshall St Andrew, near Beccles.
FJ Godfrey & Son, the farm’s owner, said: “Sadly a field became flooded as a result of a mechanical failure and material managed to reach the field ditch. In cooperation with the Environment Agency we completed all appropriate environmental measures and payments to ensure there is no lasting damage and that an incident of this type cannot recur.”
A serious incident was also found at Bowling Green Farm in Badingham in 2014. Great Lodge Farms Limited, the farm’s owner, was ordered to pay more than £10,000 after pig muck from the farm polluted a 10 kilometre stretch of the River Yox at Sibton.
The company told investigators staff had not been able to spread the slurry because the fields were too wet so it had to be stored. The lagoon was full of what was thought to be rainwater and was discharged into the ditch to free up space.
To reduce pollution, Environment Agency inspectors visit large intensive livestock farms across the country.
They have found almost 650 non-compliances at these farms in the East Anglia region in the last three years
But almost all were classed as having a minor or no foreseeable environmental impact.
Two serious non-compliances were found in Norfolk at Bernard Matthews farms in February 2015 at Briston and Haveringland.
Bernard Matthews has been contacted for comment.
Peter Melchett, who is a Norfolk farmer and policy director with the Soil Association, said pollution incidents were just one part of the problem.
“The real underlying story is the continuous drip, drip of nitrogen and phosphates from fertilisers and pesticides, which leave waterways in a poor condition, particularly in this region,” he added.
Mr Melchett said farmers should seek biological alternatives to fertilisers, using nitrogen fixing plants such as beans and clover.
Environmental experts say all farming practices have the potential to pollute making good management key.
David Santillo, a senior scientist with Greenpeace, said the risk was greatest near water where run off from fertilizers, muck-spreading, pesticides or leakages from slurry tanks could cause pollution.
“Bad practice, such as fertilizing at the wrong times, or too close to water, poor slurry management or animal husbandry, can lead to more serious incidents,” he said.
“Some water pollution events are down to deliberate bad practice, others to a combination of poor weather, poor maintenance and bad luck.
“The more intensive the farm, especially the higher the density of livestock, the more critical pollution control measures become.”
Dr Santillo said the figures may not give the full extent of farm-related pollution, as there were potentially many that go unreported or unnoticed.
There have been serious pollution incidents at livestock farms every week on average in England and Wales, according to the data gathered by The Bureau of Investigative Journalism.
The Bureau obtained the data from the Environment Agency through the Freedom of Information Act. It found there were 683 serious incidents at dairy, poultry and pig farms from 2010 to 2016.
Incidents include slurry and agricultural waste leaking and contaminating fields and rivers, animal carcasses being illegally buried and waste being illegally dumped. The EA ranks pollution incidents from one to four, with one being the most serious. Most of the 3,700 incidents are the less serious categories.
The Bureau also obtained data on Environment Agency inspections of large intensive livestock farms in England. Inspectors found hundreds of non compliances each year, with 1,265 in 2016. Again the majority are not serious breaches.