A dairy farmer has been fined almost $73,000 for deliberately discharging effluent into his drains which then flowed into the Coromandel Peninsula's Tairua River.
The 11 years of illegal discharges is "quite staggering", the Waikato Regional Council says.
Peter Craig Darrah was convicted and sentenced by Judge Jeff in Thames District Court on Monday.
Last year, council inspectors found the effluent ponds at Darrah's Hikuai Settlement Rd farm, near Tairua, were overflowing to water.
Hoses appeared to be set up for the purpose of pumping effluent into farm drains.
Despite an abatement notice, Darrah continued the illegal pumping.
On one occasion, nine hours of pumping put more than 300,000 litres of effluent into the farm drain, which flowed a short distance to Boom Stream, which itself flows about 1.5 kilometres to the Tairua River.
"In some respects this is about as bad as it gets," said council investigations manager Patrick Lynch.
"The fact the discharges continued after the farmer was formally directed to cease is quite staggering."